Phytochem Anal 2020 May 27;31(3):297-305. Epub 2019 Nov 27.
Bioscreening Unit, Department of Pharmaceutical Chemistry and Pharmacognosy, Faculty of Pharmaceutical Sciences and Centre of Excellence for Innovation in Chemistry, Phitsanulok, Thailand.
Introduction: Chromatographic techniques coupled with bioassays are popularly used for the detection of bioactive compounds in natural products. In this study phytochemicals responsible for showing Phosphodiesterase type 5 (PDE5) inhibitory activity in Derris scandens were studied using at-line method.
Objective: The objective of this study was to develop an at-line liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) micro-fractionation method for rapid separation and identification of PDE5A1 inhibitors in 95% ethanolic extract of D. scandens.
Methodology: Initially, the correlation between LC-MS and PDE5A1 inhibitory activity was studied using three concentrations of 1:1 mixture of sildenafil and derrisisoflavone A; PDE5A1 inhibitors. The mixture was separated by high-performance liquid chromatography (HPLC) column and the eluent was split into two flows in the ratio of 1:9. The major part was collected in a 96-well plate, in each well consecutively every 30 s. The minor part was fed into an electrospray ionisation (ESI)-QTOF-MS system. After subsequent solvent removal, the collected micro-fractions were subjected to radioassay to determine PDE5A1 inhibition.
Results: The result showed, PDE5A1 inhibitory activities of the micro-fractions were observed in a dose response manner and found to be in agreement with an off-line study. Similarly, 95% ethanolic extract of D. scandens was subjected to the at-line LC-QTOF-MS micro-fractionation developed, resulting in separation and tentative identification of 25 compounds with PDE5A1 inhibitory activity. Most of the compounds contained prenylated isoflavone skeleton. Additionally, the active micro-fractions also showed selectivity on PDE5A1 over PDE6 and PDE1B.
Conclusion: Our results demonstrated that the at-line coupled LC-QTOF-MS micro-fractionation with PDE5A1 inhibitory assay is a valuable tool for identifying PDE5A1 inhibitors from complex extracts.