Publications by authors named "Yau Yan Lim"

23 Publications

  • Page 1 of 1

Choices of chromatographic methods as stability indicating assays for pharmaceutical products: A review.

Heliyon 2021 Mar 27;7(3):e06553. Epub 2021 Mar 27.

School of Science, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, 47500 Petaling Jaya, Selangor Darul Ehsan, Malaysia.

Stability indicating assay describes a technique which is used to analyse the stability of drug substance or active pharmaceutical ingredient (API) in bulk drug and pharmaceutical products. Stability indicating assay must be properly validated as per ICH guidelines. The important components in a stability indicating assay include sensitivity, specificity, accuracy, reliability, reproducibility and robustness. A validated assay is able to measure the concentration changes of drug substance/API with time and make reliable estimation of the quantity of the degradation impurities. The drug substance is separated and resolved from the impurities. Pros and cons of HPLC, GC, HPTLC, CE and SFC were discussed and reviewed. Stability indicating assay may consist of the combination of chromatographic separation and spectroscopic detection techniques. Hyphenated system could demonstrate parallel quantitative and qualitative analysis of drug substances and impurities. Examples are HPLC-DAD, HPLC-FL, GC-MS, LC-MS and LC-NMR. The analytes in the samples are separated in the chromatography while the impurities are chemically characterised by the spectroscopy in the system. In this review, various chromatographic methods which had been employed as stability indicating assays for drug substance and pharmaceutical formulation were systematically reviewed, and the application of hyphenated techniques in impurities characterisation and identification were also discussed with supporting literatures.
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http://dx.doi.org/10.1016/j.heliyon.2021.e06553DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8027279PMC
March 2021

Dietary phytochemicals that influence gut microbiota: Roles and actions as anti-Alzheimer agents.

Crit Rev Food Sci Nutr 2021 Feb 9:1-27. Epub 2021 Feb 9.

Department of Applied Biology and Chemical Technology, Hong Kong Polytechnic University, Hong Kong Special Administrative Region, China.

The last decide has witnessed a growing research interest in the role of dietary phytochemicals in influencing the gut microbiota. On the other hand, recent evidence reveals that dietary phytochemicals exhibit properties of preventing and tackling symptoms of Alzheimer's disease, which is a neurodegenerative disease that has also been linked with the status of the gut microbiota over the last decade. Till now, little serious discussions, however, have been made to link recent understanding of Alzheimer's disease, dietary phytochemicals and the gut microbiota together and to review the roles played by phytochemicals in gut dysbiosis induced pathologies of Alzheimer's disease. Deciphering these connections can provide insights into the development and future use of dietary phytochemicals as anti-Alzheimer drug candidates. This review aims at presenting latest evidence in the modulating role of phytochemicals in the gut microbiota and its relevance to Alzheimer's disease and summarizing the mechanisms behind the modulative activities. Limitations of current research in this field and potential directions will also be discussed for future research on dietary phytochemicals as anti-Alzheimer agents.
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http://dx.doi.org/10.1080/10408398.2021.1882381DOI Listing
February 2021

Anti-dengue virus serotype 2 activity of tannins from porcupine dates.

Chin Med 2020 20;15:49. Epub 2020 May 20.

1Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Jalan Lagoon Selatan, 47500 Bandar Sunway, Selangor Darul Ehsan Malaysia.

Background: Dengue fever is currently endemic in tropical and subtropical countries worldwide and effective drug against DENV infection is still unavailable. Porcupine dates, which are traditionally used to treat dengue fever, might contain potential anti-dengue compounds. Two porcupine dates, black date (BD) and powdery date (PD) from Himalayan porcupine (), were investigated for their antiviral activities against DENV-2 in vitro.

Methods: The methanol crude extracts (MBD and MPD) were prepared from the raw material of porcupine dates. The tannin-rich fractions (BDTF and PDTF) were isolated from their methanol crude extracts using column chromatography. The presence of tannins in BDTF and PDTF extracts was determined by fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses. The cytotoxicity and anti-DENV-2 activities including virus yield inhibition, virucidal, virus attachment and pre-treatment assays of the extracts were examined in Vero cells.

Results: Our findings revealed that all the extracts of porcupine dates exhibited antiviral activity against DENV-2 in Vero cells. The IC of BDTF and PDTF were 25 µg/mL and 11 µg/mL respectively, while their methanol crude extracts demonstrated lower antiviral efficacy (IC ≈ 101-107 µg/mL). BDTF and PDTF also exerted a similar higher virucidal effect (IC of 11 µg/mL) than methanol crude extracts (IC ≈ 52-66 µg/mL). Furthermore, all the extracts inhibited the attachment of DENV-2 by at least 80%. Pre-treatments of cells with BDTF and PDTF markedly prevented DENV-2 infection when compared to methanol crude extracts.

Conclusion: This study suggests that porcupine dates possess antiviral properties against DENV-2, which is attributed to its tannin compounds.
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http://dx.doi.org/10.1186/s13020-020-00329-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238553PMC
May 2020

Electrospun cellulose acetate butyrate/polyethylene glycol (CAB/PEG) composite nanofibers: A potential scaffold for tissue engineering.

Colloids Surf B Biointerfaces 2020 Apr 9;188:110713. Epub 2019 Dec 9.

School of Science, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway 47500, Subang Jaya, Selangor Darul Ehsan, Malaysia; Advanced Engineering Platform, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia; Monash-Industry Palm Oil Education and Research Platform (MIPO), Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, 47500 Selangor Darul Ehsan, Malaysia. Electronic address:

Electrospinning is a common method to prepare nanofiber scaffolds for tissue engineering. One of the common cellulose esters, cellulose acetate butyrate (CAB), has been electrospun into nanofibers and studied. However, the intrinsic hydrophobicity of CAB limits its application in tissue engineering as it retards cell adhesion. In this study, the properties of CAB nanofibers were improved by fabricating the composite nanofibers made of CAB and hydrophilic polyethylene glycol (PEG). Different ratios of CAB to PEG were tested and only the ratio of 2:1 resulted in smooth and bead-free nanofibers. The tensile test results show that CAB/PEG composite nanofibers have 2-fold higher tensile strength than pure CAB nanofibers. The hydrophobicity of the composite nanofibers was also reduced based on the water contact angle analysis. As the hydrophilicity increases, the swelling ability of the composite nanofiber increases by 2-fold with more rapid biodegradation. The biocompatibility of the nanofibers was tested with normal human dermal fibroblasts (NHDF). The cell viability assay results revealed that the nanofibers are non-toxic. In addition to that, CAB/PEG nanofibers have better cell attachment compared to pure CAB nanofibers. Based on this study, CAB/PEG composite nanofibers could potentially be used as a nanofiber scaffold for applications in tissue engineering.
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http://dx.doi.org/10.1016/j.colsurfb.2019.110713DOI Listing
April 2020

Approach to preserve phenolics in Thunbergia laurifolia leaves by different drying treatments.

J Food Biochem 2019 07 17;43(7):e12856. Epub 2019 Apr 17.

School of Science, Monash University Malaysia, Bandar Sunway, Malaysia.

Different drying methods and blanching were investigated as to their effects on antioxidant and oxidase activities of Thunbergia laurifolia leaves. Results showed that oven-drying had the highest degradation of total phenolic content (TPC) and antioxidant activity at >85%, while freeze-drying had the lowest at <20%. However, inactivation of oxidase enzymes by blanching at 100°C resulted in a lesser decrease in TPC for oven-drying at 50 and 100°C (51% and 65%, respectively), indicating the importance of inactivating the oxidase enzymes for lower degradation of phenolics on drying. The high-performance liquid chromatography analysis showed that its major antioxidant, rosmarinic acid, degraded tremendously in the presence of oxidase enzymes, but only degraded slightly upon inactivation of oxidase enzymes. Hence, this work showed that by controlling the enzymatic activity, the preservation of phenolics with specific bioactivity in herbal tea leaves can be achieved. PRACTICAL APPLICATIONS: Thunbergia laurifolia leaves have been frequently consumed in the form of a tea or pill due to its medicinal properties. Processing of fresh herbal plant leaves by drying is required to preserve antioxidant phenolic compounds and quality of the plant leaves. Although the drying effects on the antioxidant properties have been studied, the factors that cause the change in properties have not been investigated in-depth. Controlling the factors that affect the phenolic content can help to preserve the beneficial antioxidants when processing the leaves by drying. The result of this study will be of relevance and beneficial to the herbal tea industry.
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http://dx.doi.org/10.1111/jfbc.12856DOI Listing
July 2019

Current anti-biofilm strategies and potential of antioxidants in biofilm control.

Expert Rev Anti Infect Ther 2018 11 17;16(11):855-864. Epub 2018 Oct 17.

a School of Science , Monash University Malaysia , Bandar Sunway , Selangor , Malaysia.

Introduction: Biofilm formation is a strategy for microorganisms to adapt and survive in hostile environments. Microorganisms that are able to produce biofilms are currently recognized as a threat to human health. Areas covered: Many strategies have been employed to eradicate biofilms, but several drawbacks from these methods had subsequently raised concerns on the need for alternative approaches to effectively prevent biofilm formation. One of the main mechanisms that drives a microorganism to transit from a planktonic to a biofilm-sessile state, is oxidative stress. Chemical agents that could target oxidative stress regulators, for instance antioxidants, could therefore be used to treat biofilm-associated infections. Expert commentary: The focus of this review is to summarize the function and limitation of the current anti-biofilm strategies and will propose the use of antioxidants as an alternative method to treat, prevent and eradicate biofilms. Studies have shown that water-soluble and lipid-soluble antioxidants can reduce and prevent biofilm formation, by influencing the expression of genes associated with oxidative stress. Further in vivo work should be conducted to ensure the efficacy of these antioxidants in a biological environment. Nevertheless, antioxidants are promising anti-biofilm agents, and thus is a potential solution for biofilm-associated infections in the future.
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http://dx.doi.org/10.1080/14787210.2018.1535898DOI Listing
November 2018

Recycling of phenolic compounds in Borneo's tropical peat swamp forests.

Carbon Balance Manag 2018 Feb 7;13(1). Epub 2018 Feb 7.

Tropical Medicine and Biology Multidisciplinary Platform, School of Science, Monash University, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia.

Background: Tropical peat swamp forests (TPSF) are globally significant carbon stores, sequestering carbon mainly as phenolic polymers and phenolic compounds (particularly as lignin and its derivatives) in peat layers, in plants, and in the acidic blackwaters. Previous studies show that TPSF plants have particularly high levels of phenolic compounds which inhibit the decomposition of organic matter and thus promote peat accumulation. The studies of phenolic compounds are thus crucial to further understand how TPSF function with respect to carbon sequestration. Here we present a study of cycling of phenolic compounds in five forests in Borneo differing in flooding and acidity, leaching of phenolic compounds from senescent Macaranga pruinosa leaves, and absorption of phenolics by M. pruinosa seedlings.

Results: The results of the study show that total phenolic content (TPC) in soil and leaves of three species of Macaranga were highest in TPSF followed by freshwater swamp forest and flooded limestone forest, then dry land sites. Highest TPC values were associated with acidity (in TPSF) and waterlogging (in flooded forests). Moreover, phenolic compounds are rapidly leached from fallen senescent leaves, and could be reabsorbed by tree roots and converted into more complex phenolics within the leaves.

Conclusions: Extreme conditions-waterlogging and acidity-may facilitate uptake and synthesis of protective phenolic compounds which are essential for impeded decomposition of organic matter in TPSF. Conversely, the ongoing drainage and degradation of TPSF, particularly for conversion to oil palm plantations, reverses the conditions necessary for peat accretion and carbon sequestration.
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http://dx.doi.org/10.1186/s13021-018-0092-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5803172PMC
February 2018

Antioxidant and Intracellular Reactive Oxygen Species/Reactive Nitrogen Species Scavenging Activities of Three Porcupine Bezoars from .

Pharmacognosy Res 2017 Oct-Dec;9(4):366-371

School of Science, Monash University Malaysia, Jalan Lagoon Selatan, Bandar Sunway, 47500 Subang Jaya, Selangor, Malaysia.

Background: Porcupine dates are phytobezoar stones that are used in Traditional Chinese Medicine (TCM) treatments against cancer, postsurgical recovery, dengue fever, etc. The medicinal values have not been scientifically investigated due to the availability and high pricing of the dates.

Objectives: This paper represents the first report on the phytochemical content, antioxidant and intracellular reactive oxygen species (ROS)/reactive nitrogen species (RNS) scavenging properties of the extracts of three porcupine dates: grassy date (GD), black date (BD), and powdery date (PD).

Materials And Methods: Dried samples were extracted with methanol and lyophilized. Samples were screened for phytochemical constituents, antioxidant assays based on total phenolic content (TPC), free radical scavenging, and ferric reducing power (FRP) as well as intracellular ROS and RNS scavenging properties.

Results: Phytochemical screening and total tannins assay revealed that tannins, cardiac glycosides, and terpenoids were found in all porcupine dates with tannins forming the major portion of the TPC. In comparison to GD, BD and PD were found to contain significantly high TPC, radical scavenging activity, and FRP. At 200 μg/ml, BD and PD remarkably scavenged 2, 2-azobis (2-amidinopropane) dihydrochloride-induced ROS in RAW264.7 cells and significantly reduced nitric oxide in lipopolysaccharide-stimulated cells.

Conclusion: Overall, BD and PD exhibited promising antioxidant as well as intracellular ROS/RNS scavenging properties.

Summary: Tannins, cardiac glycoside, and terpenoids were found in all three types of porcupine dates with tannins being the major compoundsAntioxidant contents and properties of three dates were in the order black date (BD) > powdery date (PD) > grassy dateBD and PD extracts showed significant intracellular reactive oxygen species and reactive nitrogen species scavenging properties. TCM: Traditional Chinese Medicine, BD: Black date, GD: Grassy date, PD: Powdery date, TPC: Total phenolic content, FRS: Free radical scavenging, FRP: Ferric reducing power, NO: Nitric oxide, ROS: Reactive oxygen species, RNS: Reactive nitrogen species, GAE: Gallic acid equivalent, AAE: Ascorbic acid equivalent, PVPP: Polyvinylpolypyrrolidone, DCFH-DA: Dichloro-dihydro-fluorescein diacetate, AAPH: 2, 2-azobis (2-amidinopropane) dihydrochloride, LPS: Lipopolysaccharide.
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http://dx.doi.org/10.4103/pr.pr_145_16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5717789PMC
December 2017

Isolation and Characterisation of a Proanthocyanidin With Antioxidative, Antibacterial and Anti-Cancer Properties from Fern .

Pharmacogn Mag 2017 Jan-Mar;13(49):31-37

Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.

Background: Linn. (Blechnaceae), a fern, is traditionally used in the treatment of various ailments, such as skin diseases, stomach pain, urinary bladder complaints, and also as a female contraceptive. Previously, we reported a strong radical scavenging activity, antibacterial activity and cytotoxicity against HT29 colon cancer cells by aqueous extract of .

Objective: In this study, we attempted to isolate and identify the active compound from the aqueous extract of .

Materials And Methods: Aqueous extract of was subjected to repeated MCI gel chromatography, Sephadex-LH-20, Chromatorex C18 and semi-preparative high performance liquid chromatography and was characterized using nuclear magnetic resonance and electrospray ionization mass-spectrometry spectroscopic methods. Antioxidant activity was determined using 2, 2-diphenyl-1-picrylhydrazyl radical scavenging assay. Antibacterial assays were conducted using disc diffusion whereas the minimum inhibitory concentration (MIC) and minimum bactericidal concentration were determined using the broth microdilution assay. Cytotoxicity was assessed using thiazolylblue tetrazoliumbromide.

Results: A polymeric proanthocyanidin consisting of 2-12 epicatechin extension units and epigallocathecin terminal units linked at C4-C8 was elucidated. Bioactivity studies showed strong radical scavenging activity (IC = 5.6 ± 0.1 µg/mL), antibacterial activity (MIC = 31.3-62.5 µg/mL) against five gram-positive bacteria and selective cytotoxicity against HT29 colon cancer cells (IC = 7.0 ± 0.3 µg/mL).

Conclusion: According to our results, the proanthocyanidin of demonstrated its potential as a natural source of antioxidant with antibacterial and anti-cancer properties.

Summary: A bioactive proanthocyanidin was isolated from the aqueous extract of medicinal fern Linn and the structure was elucidated using NMR and ESI-MS spectral studies.The proanthocyanidin compound possessed strong radical scavenging activity (IC 5.6 ± 0.1 µg/mL)The proanthocyaniding compound showed bactericidal activity against five gram-positive bacteria inclusive of MRSA (minimum inhibitory concentration, MIC and minimum bactericidal concentration, MBC 31.3-62.5 µg/mL).The proanthocyanidin compound is strongly cytotoxic towards cancer cells HT29 (IC 7.0 ± 0.3 µg/mL), HepG2 (IC 16 µg/mL) and HCT116 (IC 20 µg/mL) while weakly cytotoxic towards the non-malignant Chang cells (IC 48 µg/mL). CC: Column chromatography, DP: degree of polymerization, DPPH: 2,2-diphenyl-1-picrylhydrazyl, ESI-MS: electronsprayionisation mass-spectrometry, MBC: Minimum bactericidal concentration, MIC: Minimum inhibitory concentration, MTT: Thiazolyl Blue Tetrazolium Bromide, MRSA: methicillin-resistant , NMR: nuclear magnetic resonance, TLC: thin layer chromatography, PD: prodelphinidin.
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http://dx.doi.org/10.4103/0973-1296.197659DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5307911PMC
February 2017

Enzymatic synthesis of quercetin oleate esters using Candida antarctica lipase B.

Biotechnol Lett 2017 Feb 3;39(2):297-304. Epub 2016 Nov 3.

School of Science, Monash University Malaysia, Jalan Lagoon Selatan, 47500, Bandar Sunway, Selangor, Malaysia.

Objectives: To investigate the lipase-catalyzed acylation of quercetin with oleic acid using Candida antarctica lipase B.

Results: Three acylated analogues were produced: quercetin 4'-oleate (CHO), quercetin 3',4'-dioleate (CHO) and quercetin 7,3',4'-trioleate (CHO). Their identities were confirmed with UPLC-ESI-MS and H NMR analyses. The effects of temperature, duration and molar ratio of substrates on the bioconversion yields varied across conditions. The regioselectivity of the acylated quercetin analogues was affected by the molar ratio of substrates. TLC showed the acylated analogues had higher lipophilicity (152% increase) compared to quercetin. Partition coefficient (log P) of quercetin 4'-oleate was higher than those of quercetin and oleic acid. Quercetin 4'-oleate was also stable over 28 days of storage.

Conclusions: Quercetin oleate esters with enhanced lipophilicity can be produced via lipase-catalyzed reaction using C. antarctica lipase B to be used in topical applications.
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http://dx.doi.org/10.1007/s10529-016-2246-5DOI Listing
February 2017

Antioxidant and tyrosinase inhibition activity of the fertile fronds and rhizomes of three different Drynaria species.

BMC Res Notes 2015 Sep 22;8:468. Epub 2015 Sep 22.

School of Science, Monash University Malaysia, Bandar Sunway, 46150, Petaling Jaya, Selangor, Malaysia.

Background: For generations, the rhizomes of Drynaria ferns have been used as traditional medicine in Asia. Despite this, the bioactivities of Drynaria rhizomes and leaves have rarely been studied scientifically.

Methods: This study evaluates the antioxidant properties of the methanolic extracts of the fertile fronds and rhizomes from three species in this genus: Drynaria quercifolia, Drynaria rigidula and Drynaria sparsisora. The phenolic and flavonoid contents of the samples were respectively quantified with the total phenolic content (TPC) and total flavonoid content (TFC) assays, while the antioxidant activities were determined via measuring the DPPH radical scavenging activity (FRS), ferric reducing power (FRP), ferrous ion chelating (FIC) activity and lipid peroxidation inhibition (LPI). The tyrosinase inhibition activity of all three species was also reported.

Results: The fertile fronds of D. quercifolia were found to exhibit the highest overall TPC (2939 ± 469 mg GAE/100 g) and antioxidant activity amongst all the samples, and the fertile fronds of D. quercifolia and D. rigidula exhibited superior TPC and FRP compared to their rhizomes, despite only the latter being widely used in traditional medicine. The fronds of D. quercifolia had high tyrosinase inhibition activity (56.6 ± 5.0 %), but most of the Drynaria extracts showed unexpected tyrosinase enhancement instead, particularly for D. sparsisora's fronds.

Conclusion: The high bioactivity of the fertile fronds in the fern species indicate that there is value in further research on the fronds of ferns which are commonly used mostly, or only, for their rhizomes.
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http://dx.doi.org/10.1186/s13104-015-1414-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4580379PMC
September 2015

Antioxidant and antibacterial activity of Rhoeo spathacea (Swartz) Stearn leaves.

J Food Sci Technol 2015 Apr 22;52(4):2394-400. Epub 2013 Dec 22.

School of Science, Monash University Sunway Campus, Bandar Sunway, 46150 Petaling Jaya, Selangor Malaysia.

The decoction and infusion of Rhoeo spathacea (Swartz) Stearn leaves have been recognized as a functional food particularly in South America, but has not yet gained international popularity as a beverage. The primary aim of this study was to establish the viability of R. spathacea aqueous leaf extracts as a beverage, in terms of its antioxidant activity and antibacterial activity. The antioxidant contents of aqueous and methanol leaf extracts were evaluated by the total phenolic content (TPC) and total flavonoid content (TFC) assays. The antioxidant activities measured were DPPH radical scavenging activity (FRS), ferric reducing power (FRP) and ferrous ion chelating (FIC) activity. The aqueous leaf extracts in the forms of decoction and infusion, were found to have comparable TPC and antioxidant activity with other herbal teas previously reported by our research group. Both decoction and infusion also exhibited antibacterial activity against six species of Gram positive and four species of Gram negative bacteria, notably methicillin-resistant Staphylococcus aureus and Neisseria gonorrhoeae. A total of four different known phenolic compounds were identified by HPLC and MS, three of which have not been previously reported to be found in this plant. Both the decoction and infusion of the leaves R. spathacea have potential to be popularized into a common beverage.
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http://dx.doi.org/10.1007/s13197-013-1236-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4375197PMC
April 2015

Critical analysis of current methods for assessing the in vitro antioxidant and antibacterial activity of plant extracts.

Food Chem 2015 Apr 2;172:814-22. Epub 2014 Oct 2.

School of Science, Monash University Malaysia, Bandar Sunway, 46150 Petaling Jaya, Selangor, Malaysia.

Natural product research is an active branch of science, driven by the increased value placed on individual health and well-being. Many naturally-occurring phytochemicals in plants, fruits and vegetables have been reported to exhibit antioxidant and antibacterial activity; often touted as being beneficial for human health. In vitro screening is a common practice in many research laboratories as a means of rapidly assessing these properties. However, the methods used by many are not necessarily optimal; a result of poor standardization, redundant assays and/or outdated methodology. This review primarily aims to give a better understanding in the selection of in vitro assays, with emphasis placed on some common assays such as the total phenolic content assay, free radical scavenging activity, disc-diffusion and broth microdilution. This includes a discussion on the reasons for choosing a particular assay, its strengths and weaknesses, ways to improve the accuracy of results and alternative assays.
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http://dx.doi.org/10.1016/j.foodchem.2014.09.141DOI Listing
April 2015

Bioactivity-guided isolation of anticancer agents from Bauhinia kockiana Korth.

Afr J Tradit Complement Altern Med 2014 3;11(3):291-9. Epub 2014 Apr 3.

School of Science, Monash University Sunway Campus, Selangor, Darul Ehsan Malaysia.

Background: Flowers of Bauhinia kockiana were investigated for their anticancer properties.

Methods: Gallic acid (1), and methyl gallate (2), were isolated via bioassay-directed isolation, and they exhibited anticancer properties towards several cancer cell lines, examined using MTT cell viability assay. Pyrogallol (3) was examined against the same cancer cell lines to deduce the bioactive functional group of the phenolic compounds.

Results: The results showed that the phenolic compounds could exhibit moderate to weak cytotoxicity towards certain cell lines (GI50 30 - 86 µM), but were inactive towards DU145 prostate cancer cell (GI50 > 100 µM).

Conclusion: It was observed that pyrogallol moiety was one of the essential functional structures of the phenolic compounds in exhibiting anticancer activity. Also, the carboxyl group of compound 1 was also important in anticancer activity. Examination of the PC-3 cells treated with compound 1 using fluorescence microscopy showed that PC-3 cells were killed by apoptosis.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4202451PMC
http://dx.doi.org/10.4314/ajtcam.v11i3.40DOI Listing
July 2015

Antiproliferative activity of Vallaris glabra Kuntze (Apocynaceae).

Pharmacogn Mag 2014 Apr;10(Suppl 2):S232-9

Faculty of Applied Sciences, UCSI University, 56000 Cheras, Kuala Lumpur, Malaysia.

Background: Our earlier study on the antiproliferative (APF) activity of leaf extracts of ten Apocynaceae species showed that leaves of Vallaris glabra possessed strong and broad-spectrum properties.

Materials And Methods: In this study, sequential extracts of leaves, flowers and stems, and fractions and isolated compounds from dichloromethane (DCM) leaf extract of V. glabra were assessed for APF activity using the sulphorhodamine B (SRB) assay. Apoptotic effect of MDA-MB-231 cancer cells treated with DCM leaf extract of V. glabra was studied using Hoechst 33342 dye and caspase colorimetry.

Results: Both DCM extracts of leaves and flowers possessed broad-spectrum APF activity against HT-29, MCF-7, MDA-MB-231 and SKOV-3 cancer cells. From DCM leaf extract, stearic acid (SA) and ursolic acid (UA) were isolated by column chromatography, and identified by NMR and MS analyses. APF activity of SA from DCM leaf extract displayed weak inhibitory activity and scientific literature showed UA has anticancer properties against those cancer cells used in this study. MDA-MB-231 cancer cells treated with DCM leaf extract and stained with Hoechst 33342 dye provided evidence that the extract had an apoptotic effect on the cells. Caspase colorimetry showed that the apoptotic effect involved activation of caspase-8, -9 and -3, but not caspase-6.

Conclusion: The potential of V. glabra as a candidate species for anticancer drugs warrants further investigation.
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http://dx.doi.org/10.4103/0973-1296.133238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4078344PMC
April 2014

Caffeoylquinic acids in leaves of selected Apocynaceae species: Their isolation and content.

Pharmacognosy Res 2014 Jan;6(1):67-72

Faculty of Applied Sciences, UCSI University, 56000 Cheras, Kuala Lumpur, Malaysia.

Background: Three compounds isolated from the methanol (MeOH) leaf extract of Vallaris glabra (Apocynaceae) were those of caffeoylquinic acids (CQAs). This prompted a quantitative analysis of their contents in leaves of V. glabra in comparison with those of five other Apocynaceae species (Alstonia angustiloba, Dyera costulata, Kopsia fruticosa, Nerium oleander, and Plumeria obtusa), including flowers of Lonicera japonica (Japanese honeysuckle), the commercial source of chlorogenic acid (CGA).

Materials And Methods: Compound were isolated by column chromatography, and identified by NMR and MS analyses. CQA content of leaf extracts was determined using reversed-phase HPLC.

Results: From the MeOH leaf extract of V. glabra, 3-CQA, 4-CQA, and 5-CQA or CGA were isolated. Content of 5-CQA of V. glabra was two times higher than flowers of L. japonica, while 3-CQA and 4-CQA content was 16 times higher.

Conclusion: With much higher CQA content than the commercial source, leaves of V. glabra can serve as a promising alternative source.
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http://dx.doi.org/10.4103/0974-8490.122921DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3897013PMC
January 2014

Antioxidant Content, Antioxidant Activity, and Antibacterial Activity of Five Plants from the Commelinaceae Family.

Antioxidants (Basel) 2014 Nov 17;3(4):758-69. Epub 2014 Nov 17.

School of Science, Monash University Sunway Campus, Bandar Sunway 46150, Malaysia.

Commelinaceae is a family of herbaceous flowering plants with many species used in ethnobotany, particularly in South America. However, thus far reports of their bioactivity are few and far between. The primary aim of this study was to quantify the antioxidant and antibacterial activity of five Commelinaceae methanolic leaf extracts. The antioxidant content was evaluated by the total phenolic content (TPC), total tannin content (TTC), and total flavonoid content (TFC) assays. The antioxidant activities measured were DPPH free radical scavenging (FRS), ferric reducing power (FRP), and ferrous ion chelating (FIC); of the five plants, the methanolic leaf extract of Tradescantia zebrina showed the highest antioxidant content and activity, and exhibited antibacterial activity against six species of Gram-positive and two species of Gram-negative bacteria in a range of 5-10 mg/mL based on the broth microdilution method.
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http://dx.doi.org/10.3390/antiox3040758DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4665499PMC
November 2014

Standardised herbal extract of chlorogenic acid from leaves of Etlingera elatior (Zingiberaceae).

Pharmacognosy Res 2011 Jul;3(3):178-84

Faculty of Applied Sciences, UCSI University, Cheras, Kuala Lumpur, Malaysia.

Background: Chlorogenic acid (CGA) or 5-caffeoylquinic acid, was found to be the dominant phenolic compound in leaves of Etlingera elatior (Zingiberaceae). The CGA content of E. elatior leaves was significantly higher than flowers of Lonicera japonica (honeysuckle), the commercial source. In this study, a protocol to produce a standardised herbal CGA extract from leaves of E. elatior using column chromatography was developed.

Materials And Methods: Freeze-dried leaves of E. elatior were extracted with 30% ethanol, and sequentially fractionated using Diaion HP-20 and Sephadex LH-20.

Results: The CGA fractions, which yielded extracts of 10% and 40% w/w purity, possessed antioxidant, tyrosinase inhibition, and antibacterial properties. The entire fractionation process took only 6.5 hours, using gravity flow. From 50 g of leaves, the final yield of CGA extract was 0.2 g (0.4%). The CGA content of the standardised herbal extract from leaves of E. elatior (40%) is 1.6 times that of commercial extracts from honeysuckle flowers (25%).

Conclusion: With high CGA content, the standardised herbal extract has a great potential to be developed into functional food and other health products. Leaves of E. elatior, which currently have no economic value, could serve as an alternative source of CGA. Leaves are large, available in abundance, and harvesting is non-destructive to the plants.
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http://dx.doi.org/10.4103/0974-8490.85003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3193618PMC
July 2011

Potential dermal wound healing agent in Blechnum orientale Linn.

BMC Complement Altern Med 2011 Aug 12;11:62. Epub 2011 Aug 12.

School of Biosciences, Taylor’s University Lakeside Campus, No. 1, Jalan Taylor’s, 47500 Subang Jaya, Selangor, Malaysia.

Background: Blechnum orientale Linn. (Blechnaceae) is used ethnomedicinally to treat wounds, boils, blisters or abscesses and sores, stomach pain and urinary bladder complaints. The aim of the study was to validate the ethnotherapeutic claim and to evaluate the effects of B. orientale water extract on wound healing activity.

Methods: Water extract of B. orientale was used. Excision wound healing activity was examined on Sprague-Dawley rats, dressed with 1% and 2% of the water extract. Control groups were dressed with the base cream (vehicle group, negative control) and 10% povidone-iodine (positive control) respectively. Healing was assessed based on contraction of wound size, mean epithelisation time, hydroxyproline content and histopathological examinations. Statistical analyses were performed using one way ANOVA followed by Tukey HSD test.

Results: Wound healing study revealed significant reduction in wound size and mean epithelisation time, and higher collagen synthesis in the 2% extract-treated group compared to the vehicle group. These findings were supported by histolopathological examinations of healed wound sections which showed greater tissue regeneration, more fibroblasts and angiogenesis in the 2% extract-treated group.

Conclusions: The ethnotherapeutic use of this fern is validated. The water extract of B. orientale is a potential candidate for the treatment of dermal wounds. Synergistic effects of both strong antioxidant and antibacterial activities in the extract are deduced to have accelerated the wound repair at the proliferative phase of the healing process.
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http://dx.doi.org/10.1186/1472-6882-11-62DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3170243PMC
August 2011

Antiproliferative and phytochemical analyses of leaf extracts of ten Apocynaceae species.

Pharmacognosy Res 2011 Apr;3(2):100-6

School of Science, Monash University Sunway Campus, 46150 Petaling Jaya, Selangor, Malaysia.

Background: The anticancer properties of Apocynaceae species are well known in barks and roots but less so in leaves.

Materials And Methods: In this study, leaf extracts of 10 Apocynaceae species were assessed for antiproliferative (APF) activities using the sulforhodamine B assay. Their extracts were also analyzed for total alkaloid content (TAC), total phenolic content (TPC), and radical scavenging activity (RSA) using the Dragendorff precipitation, Folin-Ciocalteu, and 1,1-diphenyl-2-picrylhydrazyl (DPPH) assays, respectively.

Results: Leaf extracts of Alstonia angustiloba, Calotropis gigantea, Catharanthus roseus, Nerium oleander, Plumeria obtusa, and Vallaris glabra displayed positive APF activities. Extracts of Allamanda cathartica, Cerbera odollam, Dyera costulata, and Kopsia fruticosa did not show any APF activity. Dichloromethane (DCM) extract of C. gigantea, and DCM and DCM:MeOH extracts of V. glabra showed strong APF activities against all six human cancer cell lines. Against breast cancer cells of MCF-7 and MDA-MB-231, DCM extracts of C. gigantea and N. oleander were stronger than or comparable to standard drugs of xanthorrhizol, curcumin, and tamoxifen. All four extracts of N. oleander were effective against MCF-7 cells. Extracts of Kopsia fruticosa had the highest TAC while those of Dyera costulata had the highest TPC and RSA. Extracts of C. gigantea and V. glabra inhibited the growth of all six cancer cell lines while all extracts of N. oleander were effective against MCF-7 cells.

Conclusion: Extracts of C. gigantea, V. glabra, and N. oleander therefore showed great promise as potential candidates for anticancer drugs. The wide-spectrum APF activities of these three species are reported for the first time and their bioactive compounds warrant further investigation.
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http://dx.doi.org/10.4103/0974-8490.81957DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3129018PMC
April 2011

Assessment of phytochemical content, polyphenolic composition, antioxidant and antibacterial activities of Leguminosae medicinal plants in Peninsular Malaysia.

BMC Complement Altern Med 2011 Feb 10;11:12. Epub 2011 Feb 10.

School of Science, Monash University Sunway Campus, Bandar Sunway, Petaling Jaya, Selangor, Malaysia.

Background: Many medicinal plants from Leguminosae family can be found easily in Malaysia. These plants have been used as traditional medicines by local ethnic groups, where they are prepared as decoction, pastes for wound infections, and some have been eaten as salad. This paper focused on the assessment of antioxidant potential, antibacterial activity and classes of phytochemicals of nine plants from the Leguminosae family.

Methods: Acacia auriculiformis, Bauhinia kockiana, Bauhinia purpurea, Caesalpinia pulcherrima, Calliandra tergemina, Cassia surattensis, Leucaena leucocephala, Peltophorum pterocarpum, and Samanea saman were extracted with aqueous methanol and dichloromethane:methanol mixture to test for antioxidant and antibacterial activities. The Folin-Ciocalteu assay was conducted to quantify the total phenolic content and 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay was used to determine the free radical quenching capacity. Antibacterial activity was assessed using disc diffusion (Kirby-Bauer) assay. Screening for major classes of phytochemical was done using standard chemical tests.

Results: B. kockiana flowers and C. pulcherrima leaves contained high total phenolic content (TPC) and strong DPPH radical scavenging ability with TPC of 8280 ± 498 mg GAE/100 g, IC(50) of 27.0 ± 5.0 μg/mL and TPC of 5030 ± 602 mg GAE/100 g, IC(50) of 50.0 ± 5.0 μg/mL respectively. Positive correlation was observed between TPC and free radical scavenging ability. Most extracts showed antibacterial activity against Gram positive bacteria at 1 mg, while none showed activity against Gram negative bacteria at the same dose. All extracts (except Samanea saman flower) showed antibacterial activity against two strains of methicillin resistant Staphylococcus aureus (MRSA) with MID values ranging between 100 μg/disc and 500 μg/disc.

Conclusion: The potential source of antioxidant and antibacterial agents, especially for MRSA infection treatments were found in B. kockiana, C. pulcherrima, C. tergemina and P. pterocarpum. These preliminary results would be a guide in the selection of potential candidates for further pharmacological study and in search of new drug candidate in treating MRSA infections.
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http://dx.doi.org/10.1186/1472-6882-11-12DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3045388PMC
February 2011

Assessment of antiproliferative and antiplasmodial activities of five selected Apocynaceae species.

BMC Complement Altern Med 2011 Jan 14;11. Epub 2011 Jan 14.

School of Science, Monash University Sunway Campus, Bandar Sunway, 46150 Petaling Jaya, Selangor, Malaysia.

Background: Studies have shown that the barks and roots of some Apocynaceae species have anticancer and antimalarial properties. In this study, leaf extracts of five selected species of Apocynaceae used in traditional medicine (Alstonia angustiloba, Calotropis gigantea, Dyera costulata, Kopsia fruticosa and Vallaris glabra) were assessed for antiproliferative (APF) and antiplasmodial (APM) activities, and analysed for total alkaloid content (TAC), total phenolic content (TPC) and radical-scavenging activity (RSA). As V. glabra leaf extracts showed wide spectrum APF and APM activities, they were further screened for saponins, tannins, cardenolides and terpenoids.

Methods: APF and APM activities were assessed using the sulphorhodamine B and lactate dehydrogenase assays, respectively. TAC, TPC and RSA were analysed using Dragendorff precipitation, Folin-Ciocalteu and DPPH assays, respectively. Screening for saponins, tannins, cardenolides and terpenoids were conducted using the frothing, ferric chloride, Kedde and vanillin-H2SO4 tests, respectively.

Results: Leaf extracts of A. angustiloba, C. gigantea and V. glabra displayed positive APF activity. Dichloromethane (DCM) extract of C. gigantea, and DCM and DCM:MeOH extracts of V. glabra showed strong APF activity against all six human cancer cell lines tested. DCM extract of A. angustiloba was effective against three cancer cell lines. Against MCF-7 and MDA-MB-231 cell lines, DCM extract of C. gigantea was stronger than standard drugs of xanthorrhizol, curcumin and tamoxifen. All five species were effective against K1 strain of Plasmodium falciparum and three species (C. gigantea, D. costulata and K. fruticosa) were effective against 3D7 strain. Against K1 strain, all four extracts of V. glabra displayed effective APM activity. Extracts of D. costulata were effective against 3D7 strain. Selectivity index values of extracts of A. angustiloba, C. gigantea and V. glabra suggested that they are potentially safe for use to treat malaria. Extracts of K. fruticosa had the highest TAC while D. costulata had the highest TPC and RSA. Phytochemical screening of extracts of V. glabra also showed the presence of terpenoids, tannins and saponins.

Conclusions: Leaf extracts of C. gigantea and V. glabra showed great promise as potential candidates for anticancer drugs as they inhibited the growth of all six cancer cell lines. Against K1 strain of P. falciparum, all four extracts of V. glabra displayed effective APM activity. The wide spectrum APF and APM activities of V. glabra are reported for the first time and this warrants further investigation into its bioactive compounds.
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http://dx.doi.org/10.1186/1472-6882-11-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3032759PMC
January 2011

Antioxidative, tyrosinase inhibiting and antibacterial activities of leaf extracts from medicinal ferns.

Biosci Biotechnol Biochem 2009 Jun 7;73(6):1362-6. Epub 2009 Jun 7.

School of Science, Monash University Sunway Campus, Selangor, Malaysia.

Leaf extracts of five medicinal ferns, Acrostichum aureum L. (Pteridaceae), Asplenium nidus L. (Aspleniaceae), Blechnum orientale L. (Blechnaceae), Cibotium barometz (L.) J. Sm. (Cyatheaceae) and Dicranopteris linearis (Burm.) underwood var. linearis (Gleicheniaceae), were investigated for their total phenolic content (TPC), and antioxidative, tyrosinase inhibiting and antibacterial activities. The antioxidative activity was measured by assays for radical scavenging against 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric ion reducing power (FRP), beta-carotene bleaching (BCB) and ferrous ion chelating (FIC). The results revealed B. orientale to possess the highest amount of total polyphenols and strongest potential as a natural antioxidative, tyrosinase inhibiting and antibacterial agent as demonstrated by its strong activities in all related bioassays. The other ferns with antioxidative potential were C. barometz and D. linearis. Except for A. aureum, all ferns showed antibacterial activity which may justify their usage in traditional medicines.
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http://dx.doi.org/10.1271/bbb.90018DOI Listing
June 2009