Publications by authors named "Dejian Huang"

136 Publications

The inhibitory mechanism of chlorogenic acid and its acylated derivatives on α-amylase and α-glucosidase.

Food Chem 2021 Oct 5;372:131334. Epub 2021 Oct 5.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China; International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, Jiangsu 214122, China. Electronic address:

Due to the poor lipophilicity of chlorogenic acid (CA), five CA derivatives (C2-CA, C4-CA, C6-CA, C8-CA, and C12-CA) with different lipophilicities were synthesized using acylation catalyzed by lipase in present study. The inhibitory activities and mechanisms of CA and its derivatives on α-amylase and α-glucosidase were then determined. Results showed that the inhibitory activities of CA derivatives on α-amylase and α-glucosidase were enhanced as lipophilicity increased, and the inhibitory activities of C12-CA were stronger than those of CA. IC values of C12-CA were 13.30 ± 0.26 μmol/mL for α-amylase and 3.42 ± 0.10 μmol/mL for α-glucosidase. C12-CA possessed the smallest K and K values, and its inhibitory actions on α-amylase and α-glucosidase were stronger than those of CA and the other derivatives. Effects of C12-CA on microenvironments of amino acid residues and secondary structures of α-amylase and α-glucosidase were greater than those of CA and the other derivatives.
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http://dx.doi.org/10.1016/j.foodchem.2021.131334DOI Listing
October 2021

Inhibition Effect of Extract of Stem on α-Amylase and α-Glucosidase and Its Application in Lowering the Digestibility of Noodles.

Front Nutr 2021 12;8:701114. Epub 2021 Aug 12.

Department of Food Science and Technology, National University of Singapore, Singapore, Singapore.

A collection of tropical medicinal plants from East Malaysia's rainforests are used by indigenous tribes for their curative properties. Despite their purported healing properties, these forest plant species are largely unexplored and hence remain virtually unknown to the outside world. In this study, antidiabetic properties of , a plant used to treat diabetes by a local community in Sarawak, Malaysia were investigated. Ethyl acetate (EA) extract of stem was found to exhibit high starch hydrolase inhibition activity with an IC value of 15.4 ± 2.1 μg/ml against porcine α-amylase and an IC value of 32.4 ± 3.7 μg/ml against rat intestinal α-glucosidase. A complex mixture of A-type oligomeric proanthocyanidins containing (epi)fisetinidol, (epi)afzelechin, (epi)guibourtinidol, and (epi)catechin were found. These compounds may be responsible for the starch hydrolase inhibition activity. Ethyl acetate (EA) extract of stem was incorporated into wheat and rice flour to reformulate noodles with slow digestibility and was assessed under simulated gastrointestinal conditions. A dose-dependent effect on digestibility was observed for both noodles upon incorporation of 1-6% (w/w) of EA extract, with noodles containing 6% (w/w) extract exhibiting the greatest reduction in digestibility. As compared to rice noodles containing 6% extract (31.16% inhibition), wheat noodles with the same extract concentration had a smaller decline in digestibility (27.25% inhibition) after 180 min. Overall, our findings highlight the potential of in the prevention of postprandial hyperglycaemia.
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http://dx.doi.org/10.3389/fnut.2021.701114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8387799PMC
August 2021

The degradation kinetics and mechanism of moringin in aqueous solution and the cytotoxicity of degraded products.

Food Chem 2021 Dec 19;364:130424. Epub 2021 Jun 19.

Department of Food Science and Technology, Science Drive 2, Faculty of Science, National University of Singapore, Singapore 117542, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Lin Quan Street, Suzhou Industrial Park, Jiangsu 215123, China. Electronic address:

In this work, we investigated the degradation of moringin (4-[(α-l-rhamnosyloxy)benzyl]-isothiocyanate), a major bioactive isothiocyanate (ITC) found in moringa seeds (Moringa oleifera Lam), at various food processing conditions. Moringin degrades rapidly to several water-soluble products via a pseudo-first-order kinetics. By analyzing the reaction products, the degradation mechanism was found to be through hydrolyzing to (A) 1-O-(4-hydroxymethylphenyl) α-l-rhamnopyranoside (rhamnobenzyl alcohol RBA) or (B) rhamnobenzylamine. The formed amine further reacts with moringin to form N,N'-bis{4-[(α-l-rhamnosyloxy)benzyl]}thiourea (di-rhamnobenzyl thiourea, DRBTU). In addition, moringin isomerizes to 4-[(α-l-rhamnosyloxy)benzyl]thiocyanate (RBTC), which further reacts with moringin to form S,N-bis{4-[(α-l-rhamnosyloxy)benzyl]}-dithiocarbamate (DRBDTC). Furthermore, pH was found to have an effect on the degradation of moringin. RBA and RBTC were major degraded products in neutral and acidic conditions while thiourea (DRBTU) was in alkaline condition. Although moringin showed higher cytotoxicity to cancer cells, its degraded products showed very weak or no activities, suggesting that the isothiocyanate group of ITCs is essential for their cancer chemoprevention activities.
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http://dx.doi.org/10.1016/j.foodchem.2021.130424DOI Listing
December 2021

Anti-Inflammation Activity of Flavones and Their Structure-Activity Relationship.

J Agric Food Chem 2021 Jul 23;69(26):7285-7302. Epub 2021 Jun 23.

Department of Food Science and Technology, National University of Singapore, 2 Science Drive 2, Singapore, 117542.

Flavones are an important class of bioactive constituents in foods, and their structural diversity enables them to interact with different targets. In particular, flavones are known for their anti-inflammatory activity. Herein, we summarized commonly applied , , and clinical models in testing anti-inflammatory activity of flavones. The anti-inflammatory structure-activity relationship of flavones was systematically mapped and supported with cross comparisons of that with flavanones, flavanols, and isoflavones. Hydroxyl groups (-OH) are indispensable for the anti-inflammatory function of flavones, and -OH at the C-5 and C-4' positions enhance while -OH at the C-6, C-7, C-8, and C-3' positions attenuate their activity. Moreover, the C2-C3 single bond, -OH at the C-3 and B-ring positions undermine flavone aglycones' activity. Most of the flavone aglycones function through NF-κB, MAPK, and JNK-STAT pathways, and their possible cell binding targets are kinase, aryl hydrocarbon receptor (AhR), G-protein coupled receptors, and estrogen receptors. However, the structure and anti-inflammatory activity relationship of flavones were unclear, and further research shall be conducted to close the gap in order to guide development of evidence-based functional foods.
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http://dx.doi.org/10.1021/acs.jafc.1c02015DOI Listing
July 2021

Modulating storage stability of binary gel by adjusting the ratios of starch and kappa-carrageenan.

Carbohydr Polym 2021 Sep 28;268:118264. Epub 2021 May 28.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; School of Food Science and Technology, Jiangnan University, Wuxi 214122, China. Electronic address:

This study aimed to investigate the interaction mechanism of the waxy starch and kappa carrageenan (KC) gel with different ratios during co-gelatinization and storage. Water distributions, mobilities and rheological properties of the mixture gels were studied. When KC concentration was low (0.5%KC and 4% starch), the starch dominated the system, and the gel strength was the lowest. When KC concentration increased to 0.75%, the gel had the lowest change rate of fracture force, and the most homogeneous network of the freeze-dried gel was observed. When KC concentration increased to 1.0%, the gel strength was high, but the uneven structure led to the instability of the gel. Overall, the gel with 0.75%KC and 4% starch was the most stable during storage, and the exclusion of the two components to each other was the weakest, resulting in the uniform structure of the gel.
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http://dx.doi.org/10.1016/j.carbpol.2021.118264DOI Listing
September 2021

Physicochemical and functional properties of red lentil protein isolates from three origins at different pH.

Food Chem 2021 Oct 8;358:129749. Epub 2021 Apr 8.

Department of Food Science and Technology, National University of Singapore, Science Drive 2, Singapore 117542, Singapore; National University of Singapore (Suzhou) Research Institute, 377 Linquan Street, Suzhou 215123, China. Electronic address:

Red lentils (Lens culinaris) present an attractive raw material for meat mimics due to its red-coloured proteins, abundance, high protein and low cost. However, data on its functional properties at various pH remain scarce. In this study, the physicochemical and functional properties of red lentil proteins (RLP) from three origins (USA, Nepal and Turkey), isolated by isoelectric precipitation, were evaluated. Amino acid profiles, water holding (ranging from 3.1 to 3.5 g/g) and oil absorption (ranging from 5.8 to 7.3 g/g) capacities of RLP samples were significantly different (p < 0.05). RLP consisted of legumin and vicilin, and comprised predominantly glutamine/glutamic acid (ranging from 8.72 to 10.55 g/100 g). Surface charge, protein solubility, foaming and emulsifying properties were the lowest and poorest at pH 5.2 (isoelectric point). Overall, good functional properties of RLP under high acidity and alkalinity conditions make it a promising protein for mimicking a wide range of meats.
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http://dx.doi.org/10.1016/j.foodchem.2021.129749DOI Listing
October 2021

Antioxidant activities of chlorogenic acid derivatives with different acyl donor chain lengths and their stabilities during in vitro simulated gastrointestinal digestion.

Food Chem 2021 Apr 20;357:129904. Epub 2021 Apr 20.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu 214122, China; International Joint Laboratory on Food Safety, Jiangnan University, Wuxi, Jiangsu 214122, China. Electronic address:

In this study, chlorogenic acid (CA) was acylated with vinyl esters of different carbon chain lengths under the action of the lipase Lipozyme RM. Five CA derivatives (C2-CA, C4-CA, C6-CA, C8-CA, and C12-CA) with different lipophilicities were obtained, and their digestive stabilities and antioxidant activities were evaluated. The lipophilicities were positively correlated with the digestive stabilities of CA derivatives. The antioxidant activities of CA derivatives did not change with the reduction of phenolic hydroxyl groups, and their capacity to scavenge 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS•) and 1,1-diphenyl-2-picrylhydrazyl (DPPH•) were similar to those of CA. In cellular antioxidant activity (CAA) tests, it was found that the capacity of these derivates to cross cell membranes were enhanced upon enhancing lipophilicity, and their antioxidant activities were improved. C12-CA showed the best antioxidant activity with a median effective dose (EC) of 9.40 μg/mL, which was significantly lower than that of CA (i.e., 29.08 μg/mL).
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http://dx.doi.org/10.1016/j.foodchem.2021.129904DOI Listing
April 2021

Facile mitochondria localized fluorescent probe for viscosity detection in living cells.

Talanta 2021 Apr 22;225:121996. Epub 2020 Dec 22.

Department of Food Science and Technology, National University of Singapore, 3 Science Drive 2, 117542, Singapore. Electronic address:

Fluorescent probes act as a powerful tool to understand the function of intracellular viscosity, which are closely associated with many functional disorders and diseases. Herein we report a boron-dipyrromethene (4,4-difluoro-4-borata-3a,4a-diaza-s-indacene, BODIPY) group based new fluorescent probe (BV-1), which was synthesized facilely by a one-step Knoevenagel-type condensation reaction, to detect viscosity in living cells with high selectivity and sensitivity. DFT calculation demonstrated that the unsaturated moiety at the meso-position of BODIPY suppressed the fluorescence via twisted intramolecular charge transfer (TICT) mechanism in low viscosity media. By restricting the rotation of the molecular rotor, the fluorescence would be enhanced significantly with redshift in emission wavelength in high viscosity conditions. The fluorescence intensity ratio (log (I/I)) at 570 nm showed a good linearity (R = 0.991) with the viscosity (log η) in the range of 2-868 cP. And the limit of detection (LOD) and limit of quantification (LOQ) for viscosity were calculated to be 0.16 cP and 0.54 cP, respectively. BV-1 was demonstrated to be mitochondria localized with low cytotoxicity. Utilizing the new probe BV-1, the changes in mitochondrial viscosity caused by monensin or nystatin have been monitored successfully in real time. This work will provide new efficient ways for the development of viscosity probes, which are expected to be used for the study of intracellular viscosity properties and functions.
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http://dx.doi.org/10.1016/j.talanta.2020.121996DOI Listing
April 2021

Using Plant Proteins to Develop Composite Scaffolds for Cell Culture Applications.

Int J Bioprint 2021 30;7(1):298. Epub 2020 Oct 30.

National University of Singapore (Suzhou) Research Institute, Suzhou, Jiangsu 215123, China.

Electrohydrodynamic printing (EHDP) is capable of fabricating scaffolds that consist of micro/nano scale orientated fibers for three-dimensional (3D) cell culture models and drug screening applications. One of the major hurdles that limit the widespread application of EHDP is the lack of diverse biomaterial inks with appropriate printability and desired mechanical and biological properties. In this work, we blended plant proteins with synthetic biopolymer poly(ε-caprolactone) (PCL) to develop composite biomaterial inks, such as PCL/gliadin and PCL/zein for scaffold fabrication through EHDP. The tensile test results showed that the composite materials with a relatively small amount of plant protein portions, such as PCL/gliadin-10 and PCL/zein-10, can significantly improve tensile properties of the fabricated scaffolds such as Young's modulus and yield stress. These scaffolds were further evaluated by culturing mouse embryonic fibroblasts (NIH/3T3) cells and proven to enhance cell adhesion and proliferation, apart from temporary inhibition effects for PCL/gliadin-20 scaffold at the initial growth stage. After these plant protein nanoparticles were gradually released into culture medium, the generated nanoporous structures on the scaffold fiber surfaces became favorable for cellular attachment, migration, and proliferation. As competent candidates that regulate cell behaviors in 3D microenvironment, such composite scaffolds manifest a great potential in drug screening and 3D model development.
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http://dx.doi.org/10.18063/ijb.v7i1.298DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7875055PMC
October 2020

Formation, structural characteristics and physicochemical properties of beeswax oleogels prepared with tea polyphenol loaded gelators.

Food Funct 2021 Mar;12(4):1662-1671

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China. and School of Food Science and Technology, Jiangnan University, Wuxi 214122, China and International Joint Laboratory on Food Safety, Jiangnan University, Wuxi 214122, China.

In this study, a tea polyphenol (TP) loaded beeswax gelator (TP gelator) was constructed and incorporated into soybean oil to improve the oxidative stability of oleogels. The effects of TP on the structure and storage stability of oleogels were investigated. The TP gelator prepared by embedding TP into beeswax improved the dispersity of TP in lipids. The thermal characteristics and X-ray diffraction analysis showed that the components of the TP gelator coexisted homogeneously and TP was well dispersed in beeswax. The Fourier-transform infrared spectra indicated that the phenolic hydroxyl group of TP had intermolecular force with the quaternary ammonium nitrogen in the choline portion of soybean lecithin. The formation of needle-like crystals by beeswax restricted the flow of liquid oil, and TP did not participate in the construction of the internal network structure of the oleogel. In the accelerated storage experiment at 60 °C, the peroxide value of the TP loaded oleogel decreased by 60.6% at the end of the storage period compared with soybean oil. TP was successfully embedded in the oleogel without changing its structure, which not only solved the problem of poor dispersion of TP in oil, but also showed a significant inhibitory effect on lipid oxidation.
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http://dx.doi.org/10.1039/d0fo02772cDOI Listing
March 2021

Enzymatic treatment, unfermented and fermented fruit-based products: current state of knowledge.

Crit Rev Food Sci Nutr 2020 Nov 30:1-22. Epub 2020 Nov 30.

Department of Food Science and Technology, National University of Singapore, Singapore, Singapore.

In recent years, food manufacturers are increasingly utilizing enzymes in the production of fruit-based (unfermented and fermented) products to increase yield and maximize product quality in a cost-effective manner. Depending on the fruits and desired product characteristics, different enzymes (e.g. pectinase, cellulase, hemicellulase, amylase, and protease) are used alone or in combinations to achieve optimized processing conditions and improve nutritional and sensorial quality. In this review, the mechanisms of action and sources of different enzymes, as well as their effects on the physicochemical, nutritional, and organoleptic properties of unfermented and fermented fruit-based products are summarized and discussed, respectively. In general, the application of enzymatic hydrolysis treatment (EHT) in unfermented fruit-based product helps to achieve four main purposes: (i) viscosity reduction (easy to filter), (ii) clarification (improved appearance/clarity), (iii) better nutritional quality (increase in polyphenolics) and (iv) enhanced organoleptic characteristic (brighter color and complex aroma profile). In addition, EHT provides numerous other advantages to fermented fruit-based products such as better fermentation efficiency and enrichment in aroma. To meet the demand for new market trends, researchers and manufacturers are increasingly employing non- yeast (with enzymatic activities) alone or in tandem with to produce complex flavor profile in fermented fruit-based products. Therefore, this review also evaluates the potential of some non- yeasts with enzymatic activities and how their utilization helps to tailor wines with unique aroma profile. Lastly, in view of an increase in lactose-intolerant individuals, the potential of fermented probiotic fruit juice as an alternative to dairy-based probiotic products is discussed.
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http://dx.doi.org/10.1080/10408398.2020.1848788DOI Listing
November 2020

Neural evidence of dysfunction of reward processing in women with premenstrual syndrome.

Neuropsychologia 2020 12 5;149:107669. Epub 2020 Nov 5.

Department of Psychology, Nanjing University, Nanjing, 210023, China. Electronic address:

Background: Most studies on the mechanism behind premenstrual syndrome (PMS) have focused on negative emotional overreaction, but little evidence exists regarding the weakening of positive emotions. Given the close relationship between positive emotions and reward processing, the aim of this study is to investigate the dysfunction of reward processing in women with PMS.

Method: Seventeen women with PMS and seventeen healthy women were scanned during a card guessing task in the late luteal phase. By selecting bilateral caudate and orbitofrontal cortex (OFC) as seed regions, region-of-interest (ROI) analysis and functional connectivity (psycho-physiological interaction [PPI]) analysis were conducted to compare the difference between two groups. Exploratory whole brain analysis was also conducted to examine the group differences in other reward-related brain regions.

Results: ROI analysis revealed that healthy women showed stronger activation at the bilateral caudate and OFC when gains were contrasted to losses feedback, whereas women with PMS showed no significant difference between these two conditions. Whole brain analysis indicated that healthy women showed stronger activation at the right middle frontal gyrus (MFG) when gains were contrasted to losses feedback, whereas women with PMS showed no significant difference between these two conditions. Furthermore, separate analysis on healthy women revealed significant clusters of greater activation to gains minus losses that included the bilateral caudate, right middle temporal gyrus, and left inferior occipital gyrus; conversely, no significant clusters of activations to gains minus losses were observed in women with PMS. PPI analysis results revealed that women with PMS exhibited lower functional connectivity between the right caudate and the right cerebellum than healthy women when experiencing gains versus losses.

Conclusions: Our findings provide one of the first evidence that PMS is related to dysfunction in reward processing, which could be associated with the weakening of positive emotions.
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http://dx.doi.org/10.1016/j.neuropsychologia.2020.107669DOI Listing
December 2020

Room temperature cupric halides mediated olefin alkoxylation of BODIPYs with methanol: mechanisms and scope.

Org Biomol Chem 2020 Oct;18(39):7916-7921

Department of Chemistry, College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot, 010021 China.

We disclose an efficient methodology for olefin alkoxylation of fluorescent BODIPYs (boron-dipyrromethene) at the 3,5-styryl group with methanol by cupric halide (chloride or bromide) at room temperature. Mechanistic studies provide evidence for the alkoxylation reaction firstly initiated by a radical cation, that is, halide promotes the oxidizing ability of the Cu(ii) center to an extent that the single electron transfer (SET) from BODIPYs to the cupric ion and results in the production of a BODIPYs radical cation and Cu(i), then the BODIPYs radical cation subsequently reacts with methanol to afford the alkoxylated product. As the dialkoxylated product complexes with cuprous halide and further decreases its reducing ability, which is supported by DFT calculations, only strongly oxidative cupric bromide can mediate tetraalkoxylation and give rise to the tetraalkoxylated product. In addition, the expanded scope studies suggest that this method is also well suited for the alkoxylation of electron-rich conjugated olefins. The active benzyl bromide derivative may be another intermediate in the presence of cupric bromide. Therefore, the reaction is highly dependent on the anions of cupric salts; Cu(OAc)2, CuSO4 and Cu(NO3)2 containing weakly nucleophilic anions show no activity in alkoxylation.
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http://dx.doi.org/10.1039/c9ob02590aDOI Listing
October 2020

Interactions in starch co-gelatinized with phenolic compound systems: Effect of complexity of phenolic compounds and amylose content of starch.

Carbohydr Polym 2020 Nov 21;247:116667. Epub 2020 Jun 21.

State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; School of Food Science and Technology, Jiangnan University, Wuxi 214122, China. Electronic address:

Maize starches of different amylose contents were co-gelatinized with caffeic acid (CA), quercetin (Qu) and epigallocatechin gallate (EGCG), respectively. The decomposition temperature of waxy maize starch (WS)-CA blends was increased compared to WS, while that of normal maize starch (MS) and high amylose starch (HS) was decreased. The more complex of the phenolic compounds, the lower the decomposition temperature of the MS. The results of Fourier-transform infrared spectroscopy suggested that CA increased short range ordered structure of gelatinized WS but decreased that of gelatinized MS and HS. Hydrogen bonds associated with CA and starch led to the arrangement of ordered structures in different starch. Nuclear magnetic resonance (NMR) indicated that all hydroxyl groups of CA and EGCG formed hydrogen bonds, while hydroxyl group at C-4' of quercetin had priority to form hydrogen bonds. During co-gelatinization process, more single helixes were induced in MS by CA than Qu or EGCG did.
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http://dx.doi.org/10.1016/j.carbpol.2020.116667DOI Listing
November 2020

Moringin and Its Structural Analogues as Slow HS Donors: Their Mechanisms and Bioactivity.

J Agric Food Chem 2020 Jul 29;68(27):7235-7245. Epub 2020 Jun 29.

Department of Food Science and Technology, Science Drive 2, Faculty of Science, National University of Singapore, 117542 Singapore.

Moringin (rhamnobenzyl isothiocyanate) is a major bioactive compound in moringa seeds, which have been used as a healthy food. However, its bioactivity mechanisms are not well understood. We investigated moringin and its structurally similar analogues, including benzyl isothiocyanate and 4-hydroxylbenzyl isothiocyanate, for their hydrogen sulfide (HS)-releasing activity triggered by cysteine. These isothiocyanates rapidly formed cysteine adducts, which underwent intramolecular cyclization followed by slowly releasing (a) organic amine and raphanusamic acid and (b) HS and 2-carbylamino-4,5-dihydrothiazole-4-carboxylic acids. The product distributions are highly dependent on para-substituents on the phenyl group. Moringin has higher cytotoxicity to cancer cells and is a more potent anti-inflammatory agent than benzyl and hydroxybenzyl analogues, while benzyl isothiocyanate is a better antibacterial agent. Taken together, their bioactivity may not be directly related to their HS donation activity. However, other metabolites alone do not have cytotoxicity and anti-inflammatory activity. These findings indicated that their activity may be the combination effects of different metabolites via competitive pathways as well the para-substituent groups of benzyl ITCs.
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http://dx.doi.org/10.1021/acs.jafc.0c02358DOI Listing
July 2020

Cranberry Polyphenolic Extract Exhibits an Antiobesity Effect on High-Fat Diet-Fed Mice through Increased Thermogenesis.

J Nutr 2020 08;150(8):2131-2138

College of Food Science and Nutritional Engineering, Beijing Key Laboratory of Viticulture and Enology, China Agricultural University, Beijing, China.

Background: Although polyphenol-rich cranberry extracts reportedly have an antiobesity effect, the exact reason for this remains unclear.

Objectives: In light of the reported health benefits of the polyphenolic compounds in cranberry, we investigated the effects and mechanism of a cranberry polyphenolic extract (CPE) in high-fat diet (HFD)-fed obese mice.

Methods: The distributions of individual CPE compounds were characterized by HPLC fingerprinting. Male C57BL/6J mice (4 wk old) were fed for 16 wk normal diet (ND, 10% fat energy) or HFD (60% fat energy) with or without 0.75% CPE in drinking water (HFD + CPE). Body and adipose depot weights, indices of glucose metabolism, energy expenditure (EE), and expression of genes related to brown adipose tissue (BAT) thermogenesis, and inguinal/epididymal white adipose tissue (iWAT/eWAT) browning were measured.

Results: After 16 wk, the body weight was 22.5% lower in the CPE-treated mice than in the HFD group but remained 17.9% higher than in the ND group. CPE treatment significantly increased EE compared with that of the ND and HFD groups. The elevated EE was linked with BAT thermogenesis, and iWAT/eWAT browning, shown by the induction of thermogenic genes, especially uncoupling protein 1 (Ucp1), and browning-related genes, including Cd137, a member of the tumor necrosis factor receptor superfamily (Tnfrsf9). The mRNA expression and abundance of uncoupling protein 1 in BAT of CPE-fed mice were 5.78 and 1.47 times higher than in the HFD group, and 0.61 and 1.12 times higher than in the ND group, respectively. Cd137 gene expression in iWAT and eWAT of CPE-fed mice were 2.35 and 3.13 times higher than in the HFD group, and 0.84 and 1.39 times higher than in the ND group, respectively.

Conclusions: Dietary CPE reduced but did not normalize HFD-induced body weight gain in male C57BL/6J mice, possibly by affecting energy metabolism.
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http://dx.doi.org/10.1093/jn/nxaa163DOI Listing
August 2020

Development of a Fluorescent Probe for Measurement of Singlet Oxygen Scavenging Activity of Flavonoids.

J Agric Food Chem 2019 Sep 11;67(38):10726-10733. Epub 2019 Sep 11.

Department of Food Science and Technology , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Republic of Singapore.

A turn-on fluorescent probe, HOCD-RB, for monitoring singlet oxygen (O) was developed by linking rhodamine B as fluorophore with dimethylhomoocoerdianthrone (HOCD) as O reaction site and fluorescence quencher due to the intramolecular energy transfer (ET) between rhodamine B and HOCD moieties. Upon exposure to O it rapidly forms endoperoxide with HOCD and turns on the fluorescence of rhodamine B by 18-fold. Taking advantage of the HOCD-RB probe that shows fast response, high sensitivity, and selectivity for O, it is applied for imaging of endogenous O in living cells and the fluorometric assay for evaluating O quenching activity of selected common flavonoids found in our daily diets. The results show that the O scavenging activity of flavonoids depends on not only the structure of individual flavonoid but also the competitive interactions between mixed flavonoids. The best antioxidant capacity for individual and mixed flavonoids is epigallocatechin gallate and the mixture of catechin gallate with kaempferol, respectively. Overall, this work provided a new tool for detection and imaging of singlet oxygen activity in a biological system as well as an efficient fluorometric assay of O scavenging activity.
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http://dx.doi.org/10.1021/acs.jafc.9b04025DOI Listing
September 2019

Conditional survival analysis of four treatment strategies for patients with stage I non-small cell lung cancer.

Oncol Lett 2019 Aug 30;18(2):1089-1098. Epub 2019 May 30.

Department of Thoracic Surgery, First Hospital of China Medical University, Shenyang, Liaoning 110001, P.R. China.

Conditional survival (CS) is used to describe dynamic survival possibility, taking account of the change in the survival risk that occurs with longevity. The present study aimed to explore the CS of four treatment strategies for stage I non-small cell lung cancer (NSCLC), staged according to the eighth edition of the American Joint Committee on Cancer/Union for International Cancer Control NSCLC staging system. Using the Surveillance, Epidemiology and End Results Program cohort obtained between 2004-2014, the current study first extracted data for 27,116 patients with stage I NSCLC. The actuarial cancer-specific survival rates (ACSs) and conditional cancer-specific survival rates of four treatment strategies were then compared. ACS was assessed using the Kaplan-Meier method and a log-rank test. The 3-year conditional cancer-specific survival (CCS3) of patients who had already survived for n years was calculated as CCS3=ACS(n+3)/ACS(n). Cox regression and propensity-score matching (PSM) was applied to adjust confounding factors. The 5-year ACS of patients who underwent lobectomy, sublobar resection, radiation and observation was 80.3, 72.0, 40.8 and 19.6%, respectively. The 5-year CCS3 of patients who underwent lobectomy, sublobar resection, radiation and observation was 91.7, 86.4, 77.0 and 58.2%, respectively. CCS3 increased with an increase in survival time and patients who underwent lobectomy had the highest CCS3 estimates and flattest growth, with the smallest survival gap between CCS3 and ACS. The results were similar in the PSM analysis. In conclusion, CS estimates may provide a more accurate survival prediction for patients with stage I NSCLC, and may assist with treatment decisions and surveillance strategies. In addition, the current study provided evidence that suggests lobectomy may be the optimal treatment strategy for stage I NSCLC compared with sublobar resection.
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http://dx.doi.org/10.3892/ol.2019.10413DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6607325PMC
August 2019

Isothiocyanates as HS Donors Triggered by Cysteine: Reaction Mechanism and Structure and Activity Relationship.

Org Lett 2019 08 18;21(15):5977-5980. Epub 2019 Jul 18.

Food Science and Technology Programme, Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore.

Isothiocyanates are reported as HS donors, yet the mechanisms are not clear. Herein, we reported that isothiocyanates (ITCs, R-NCS) rapidly formed adducts with cysteine. These adducts underwent intramolecular cyclization followed by releasing organic amine R-NH and raphanusamic acid (RA) as major products with formation of HS and 2-carbylamino-4,5-dihydrothiazole-4-carboxylic acids as minor products. The ratios of the two groups of products are dependent on the R groups which have strong impact on HS releasing rates.
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http://dx.doi.org/10.1021/acs.orglett.9b02117DOI Listing
August 2019

Non-Linear Quantitative Structure⁻Activity Relationships Modelling, Mechanistic Study and In-Silico Design of Flavonoids as Potent Antioxidants.

Int J Mol Sci 2019 May 10;20(9). Epub 2019 May 10.

Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore.

In this work, we developed quantitative structure-activity relationships (QSAR) models for prediction of oxygen radical absorbance capacity (ORAC) of flavonoids. Both linear (partial least squares-PLS) and non-linear models (artificial neural networks-ANNs) were built using parameters of two well-established antioxidant activity mechanisms, namely, the hydrogen atom transfer (HAT) mechanism defined with the minimum bond dissociation enthalpy, and the sequential proton-loss electron transfer (SPLET) mechanism defined with proton affinity and electron transfer enthalpy. Due to pronounced solvent effects within the ORAC assay, the hydration energy was also considered. The four-parameter PLS-QSAR model yielded relatively high root mean square errors (RMSECV = 0.783, RMSEE = 0.668, RMSEP = 0.900). Conversely, the ANN-QSAR model yielded considerably lower errors (RMSEE = 0.180 ± 0.059, RMSEP1 = 0.164 ± 0.128, and RMSEP2 = 0.151 ± 0.114) due to the inherent non-linear relationships between molecular structures of flavonoids and ORAC values. Five-fold cross-validation was found to be unsuitable for the internal validation of the ANN-QSAR model with a high RMSECV of 0.999 ± 0.253; which is due to limited sample size where resampling with replacement is a considerably better alternative. Chemical domains of applicability were defined for both models confirming their reliability and robustness. Based on the PLS coefficients and partial derivatives, both models were interpreted in terms of the HAT and SPLET mechanisms. Theoretical computations based on density functional theory at ωb97XD/6-311++G(d,p) level of theory were also carried out to further shed light on the plausible mechanism of anti-peroxy radical activity. Calculated energetics for simplified models (genistein and quercetin) with peroxyl radical derived from 2,2'-azobis (2-amidino-propane) dihydrochloride suggested that both SPLET and single electron transfer followed by proton loss (SETPL) mechanisms are competitive and more favorable than HAT in aqueous medium. The finding is in good accord with the ANN-based QSAR modelling results. Finally, the strongly predictive ANN-QSAR model was used to predict antioxidant activities for a series of 115 flavonoids designed combinatorially with flavone as a template. Structural trends were analyzed, and general guidelines for synthesis of new flavonoid derivatives with potentially potent antioxidant activities were given.
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http://dx.doi.org/10.3390/ijms20092328DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6539043PMC
May 2019

Dietary Flavonoids Scavenge Hypochlorous Acid via Chlorination on A- and C-Rings as Primary Reaction Sites: Structure and Reactivity Relationship.

J Agric Food Chem 2019 Apr 8;67(15):4346-4354. Epub 2019 Apr 8.

Food Science and Technology Programme, Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Republic of Singapore.

Dietary flavonoids are known as scavengers of reactive oxygen species such as hypochlorous acid. In spite of the abundant scavenging capacity data reported, few reports have addressed the relationship between the scavenging capacity and structures of different flavonoids. We characterized the reaction products of five flavonoids (apigenin, quercetin, naringenin, ampelopsin, and epicatechin) with hypochlorous acid and found that primary chlorination reaction occurred on the A-ring (C6 or C8) and/or C-rings but not on B-rings. Correlation of the hypochlorous acid scavenging capacity (IC values) and the structural features of flavonoids revealed that the hydroxyl groups in the A-ring and B-ring can enhance the scavenging capacity, whereas the C(2)C(3) double bond has a negative impact on the HClO scavenging capacity. Combining the SAR analysis and chemical study, we proposed that the reaction mechanism between flavonoids and HClO should be an electrophilic substitution reaction. Density functional theory (DFT) results are consistent with the selectivity of chlorination on the flavonoids. Our findings highlight the importance of considering specific reactive oxygen species when measuring radical scavenging capacity of dietary antioxidants.
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http://dx.doi.org/10.1021/acs.jafc.8b06689DOI Listing
April 2019

Durian Fruits Discovered as Superior Folate Sources.

Front Nutr 2018 28;5:114. Epub 2018 Nov 28.

Chair of Analytical Food Chemistry, Technical University of Munich, Freising, Germany.

Durian () is a tropical fruit grown in Southeast Asia and highly appreciated by consumers throughout Asia. Folates are a group of vitamins and are essential nutrients for humans. Here we present the folate analysis of different durian cultivars as well as diverse durian products. An LC-MS/MS method and the application of a stable isotope dilution assay (SIDA) was used for quantitation of the folate vitamers 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, 10-formylfolate, tetrahydrofolate, and pteroylmonoglutamic acid by using [C]-labeled internal standards. Total folates varied from 175 to 440 μg/100 g for durian arils and from 15.0 to 417 μg/100 g for durian products. These contents are extraordinarily high compared to other fruits and may be correlated to the upregulated methionine biosynthesis pathway reported recently. In summary, the tropical fruit durian can be considered as a very rich dietary source of natural folates.
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http://dx.doi.org/10.3389/fnut.2018.00114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6279852PMC
November 2018

Rapid and Visual Detection and Quantitation of Ethylene Released from Ripening Fruits: The New Use of Grubbs Catalyst.

J Agric Food Chem 2019 Jan 12;67(1):507-513. Epub 2018 Dec 12.

Food Science and Technology Program, Department of Chemistry , National University of Singapore , 3 Science Drive 3 , Singapore 117543 , Singapore.

Herein, we report on fluorophore-tagged Grubbs catalysts as turn-on fluorescent probes for the sensitive detection and quantitation of ethylene, a plant hormone that plays a critical role in many phases of plant growth and fruit ripening. The ruthenium-based weak fluorescent probes were prepared handily through the metathesis reaction between the first-generation Grubbs catalyst and selected fluorophores that have high quantum yields and contain terminal vinyl groups. Upon exposure to ethylene, fluorescence enhancement was observed via the release of fluorophore from the probe. Our probe shows an excellent limit of detection for ethylene at 0.9 ppm in air and was successfully applied for monitoring ethylene released during the fruit-ripening process. Our work opens up a new avenue of application of Grubbs catalysts for bioanalytical chemistry of ethylene, which is critically important in plant biology, agriculture, and food industry.
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http://dx.doi.org/10.1021/acs.jafc.8b05874DOI Listing
January 2019

Synthesis and Biological Evaluation of Rhein-Based MRI Contrast Agents for in Vivo Visualization of Necrosis.

Anal Chem 2018 11 9;90(22):13249-13256. Epub 2018 Nov 9.

Laboratories of Translational Medicine , Jiangsu Province Academy of Traditional Chinese Medicine , Nanjing 210028 , Jiangsu Province , P. R. China.

Early and accurate assessment of therapeutic response to anticancer therapy plays an important role in determining treatment planning and patient management in clinic. Magnetic rseonance imaging (MRI) of necrosis that occurs after cancer therapies provides chances for that. Here, we reported three novel MRI contrast agents, GdL, GdL, and GdL, by conjugating rhein with gadolinium 2-[4,7,10-tris(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl]acetic acid (Gd-DOTA) through different linkers. The T1 relaxivities of three probes (7.28, 7.35, and 8.03 mM s) were found to be higher than that of Gd-DOTA (4.28 mM s). Necrosis avidity of GdL was evaluated on the rat models of reperfused liver infarction (RLI) by MRI, which showed an increase of T1-weighted contrast between necrotic and normal liver during 0.5-12 h. Besides, L was also labeled with Cu to assess its necrosis avidity on rat models of RLI and muscle necrosis (MN) by a γ-counter. The uptakes of CuL in necrotic liver and muscle were higher than those in normal liver and muscle ( P < 0.05). Then, the ability of GdL to assess therapeutic response was tested on rats bearing Walker 256 breast carcinoma injected with a vascular disrupting agent CA4P by MR imaging. The signal intensity of tumoral necrosis was strongly enhanced, and the contrast ratio between necrotic and viable tumor was 1.63 ± 0.11 at 3 h after administration of GdL. Besides, exposed DNA in necrosis cells may be an important mechanism of three probes targeting to necrosis cells. In summary, GdL may serve as a promising MRI contrast agent for accurate assessment of treatment response.
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http://dx.doi.org/10.1021/acs.analchem.8b01868DOI Listing
November 2018

The Possible Reduction Mechanism of Volatile Sulfur Compounds during Durian Wine Fermentation Verified in Modified Buffers.

Molecules 2018 Jun 15;23(6). Epub 2018 Jun 15.

Food Science and Technology Program, Department of Chemistry, National University of Singapore, Science Drive 3, Singapore 117543, Singapore.

Durian fruit is rich in volatile sulfur compounds (VSCs), especially thiols and disulfides, which contribute to its onion-like odor. After fermentation, these VSCs were reduced to trace or undetectable levels in durian wine. The possible reduction mechanism of these VSCs (especially diethyl disulfide and ethanethiol) was investigated in a modified buffer in the presence of sulfite at different pH. An interconversion between diethyl disulfide and ethanethiol was found to be dependent on the pH: the higher the pH, the higher production of ethanethiol. It is suggested that, during durian wine fermentation, disulfides endogenous to durian pulp might be firstly converted into their corresponding thiols in the presence of reductant sulfite formed by yeast. The produced thiols as well as the thiols endogenous to the durian pulp were then removed by the mannoproteins of yeast lees.
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http://dx.doi.org/10.3390/molecules23061456DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6100591PMC
June 2018

I-Evans blue: evaluation of necrosis targeting property and preliminary assessment of the mechanism in animal models.

Acta Pharm Sin B 2018 May 19;8(3):390-400. Epub 2017 Sep 19.

Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210028, China.

Necrosis is a form of cell death, which is related to various serious diseases such as cardiovascular disease, cancer, and neurodegeneration. Necrosis-avid agents (NAAs) selectively accumulated in the necrotic tissues can be used for imaging and/or therapy of related diseases. The aim of this study was to preliminarily investigate necrosis avidity of I-evans blue (I-EB) and its mechanism. The biodistribution of I-EB at 24 h after intravenous administration showed that the radioactivity ratio of necrotic to viable tissue was 3.41 in the liver and 11.82 in the muscle as determined by counting in model rats. Autoradiography and histological staining displayed preferential uptake of I-EB in necrotic tissues. nuclear extracts from necrotic cells exhibited 82.3% of the uptake in nuclei at 15 min, as well as 79.2% of the uptake at 2 h after I-EB incubation. The DNA binding study demonstrated that evans blue (EB) has strong binding affinity with calf-thymus DNA (CT-DNA) (=5.08×10 L/(mol/L)). Furthermore, the accumulation of I-EB in necrotic muscle was efficiently blocked by an excess amount of unlabeled EB. In conclusion, I-EB can not only detect necrosis by binding the DNA released from necrotic cells, but also image necrotic tissues generated from the disease clinically.
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http://dx.doi.org/10.1016/j.apsb.2017.08.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5989829PMC
May 2018

Zein Increases the Cytoaffinity and Biodegradability of Scaffolds 3D-Printed with Zein and Poly(ε-caprolactone) Composite Ink.

ACS Appl Mater Interfaces 2018 Jun 25;10(22):18551-18559. Epub 2018 May 25.

National University of Singapore (Suzhou) Research Institute , 377 Linquan Street , Suzhou , Jiangsu 215123 , China.

Electrohydrodynamic printing (EHDP) has attracted extensive interests as a powerful technology to fabricate micro- to nano-scale fibrous scaffolds in a custom-tailored manner for biomedical applications. A few synthetic biopolymer inks are applicable to this EHDP technology, but the fabricated scaffolds suffered from low mechanical strength, biocompatibility, and biodegradability. In this study, a series of poly(ε-caprolactone) (PCL)/zein composite inks were developed and their printability was examined on a solution-based EHDP system for scaffold fabrication. Multilayer grid scaffolds were manufactured by PCL, PCL/zein-10, and PCL/zein-20 inks, respectively and characterized. The mechanical strength of scaffolds printed by PCL/zein composite inks was remarkably enhanced in terms of Young's modulus and yield stress. The enzyme-accelerated in vitro degradation study demonstrated that zein-containing scaffolds exhibited dose-responsive improvement on the degradation rate as evidenced by surface morphological change of fibers. Moreover, the biocompatibility of PCL/zein scaffolds, tested on mice embryonic fibroblast (NIH/3T3) and human nonsmall lung cancer cell (H1299), manifested better cell affinity. Our findings suggest that scaffolds fabricated by the solution-based EHDP with PCL/zein composite inks can significantly improve Young's modulus, yield stress, biocompatibility, and biodegradability and have potential applications in drug delivery systems, 3D cell culture modeling, or tissue engineering.
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http://dx.doi.org/10.1021/acsami.8b04344DOI Listing
June 2018

Profiling of Phenolic Compounds and Antioxidant Activity of 12 Cruciferous Vegetables.

Molecules 2018 05 10;23(5). Epub 2018 May 10.

NUS Environmental Research Institute, National University of Singapore, 5A Engineering Drive 1, Singapore 117411, Singapore.

The phenolic profiles of 12 cruciferous vegetables (pakchoi, choysum, Chinese cabbage, kailan, Brussels sprout, cabbage, cauliflower, broccoli, rocket salad, red cherry radish, daikon radish, and watercress) were studied with UHPLC-MS/MS. Antioxidant activity and total phenolic content (TPC) were also evaluated. A total of 74 phenolic compounds were identified, including 16 hydroxycinnamic acids and derivatives, and 58 flavonoids and derivatives. The main flavonoids identified were glycosylated quercetin, kaempferol and isorhamnetin, and the main hydroxycinnamic acids were ferulic, sinapic, caffeic and -coumaric acids. Principal component analysis (PCA) revealed that the distribution of phenolic compounds in different genera of cruciferous vegetables was in accordance with their conventional taxonomy. The DPPH, ORAC and TPC values ranged from 1.11 to 9.54 µmoles Trolox equivalent/g FW, 5.34 to 32.92 µmoles Trolox equivalent/g FW, and 0.16 to 1.93 mg gallic acid equivalent/g FW respectively. Spearman’s correlation showed significant ( < 0.05) positive correlations between TPC, flavonoids and antioxidant activity.
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http://dx.doi.org/10.3390/molecules23051139DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6100362PMC
May 2018

Preclinical Evaluation of Radioiodinated Hoechst 33258 for Early Prediction of Tumor Response to Treatment of Vascular-Disrupting Agents.

Contrast Media Mol Imaging 2018 26;2018:5237950. Epub 2018 Feb 26.

Affiliated Hospital of Integrated Traditional Chinese and Western Medicine, Nanjing University of Chinese Medicine, Nanjing 210028, China.

This study aimed to explore the use of I-Hoechst 33258 (I-H33258) for early prediction of tumor response to vascular-disrupting agents (VDAs) with combretastatin-A4 phosphate (CA4P) as a representative. Necrosis avidity of I-H33258 was evaluated in mouse models with muscle necrosis and blocking was used to confirm the tracer specificity. Therapy response was evaluated by I-H33258 SPECT/CT imaging 24 h after CA4P therapy in W256 tumor-bearing rats. Radiotracer uptake in tumors was validated ex vivo using -counting, autoradiography, and histopathological staining. Results showed that I-H33258 had predominant necrosis avidity and could specifically bind to necrotic tissue. SPECT/CT imaging demonstrated that an obvious "hot spot" could be observed in the CA4P-treated tumor. Ex vivo -counting revealed I-H33258 uptake in tumors was increased 2.8-fold in rats treated with CA4P relative to rats treated with vehicle. Autoradiography and corresponding H&E staining suggested that I-H33258 was mainly localized in necrotic tumor area and the higher overall uptake in the treated tumors was attributed to the increased necrosis. These results suggest that I-H33258 can be used to image induction of cell necrosis 24 h after CA4P therapy, which support further molecular design of probes based on scaffold H33258 for monitoring of tumor response to VDAs treatment.
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http://dx.doi.org/10.1155/2018/5237950DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5846351PMC
July 2019
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