Polyphenol content and serine-protease inhibitory activities from selected medicinal plants

Abstract

Proteinase inhibitors play a crucial role in the regulation of metabolism and the development of living beings. This research deals with proteinase inhibitory activity (PIA) and polyphenol contents from 20 Vietnamese medicinal plants, which have been used to cure infection, pimples and rash. The relationship between PIA and polyphenol content and their bioavailability were investigated. Among the 26 aqueous fresh samples of the 20 medicinal plants that belong to 17 different families, we found 21 samples from 16 plants possess inhibitory activity against trypsin (TIA), chymotrypsin (ChIA) and extracellular proteases from Pseudomonas aeruginosa (PsIA), of which ChIA is found to be highest in this respect. In the same connection, Syzygium resinosum Gagnep has the highest PIA (TIA, PsIA, ChIA about 11631, 8195, 33332 mIU/g fresh sample, respectively). There have been found that the samples with high PIA also possess high content of polyphenol. PIA of ethanol extracts is higher than that of aqueous extracts. An investigation of inhibitory activity against PA of P. aeruginosa and Staphylococcus aureus by zymography has indicated that ethanol extracts of sappan heartwood and dormant seed coat can put an end to or partially reduce all three proteinase bands from these microbes. For further study, heartwood flavonoid is fractionated on silicagel column chromatography. All obtained fractions exhibit PIA, and the major fraction is taken for subsequent purification and then subjected to a NMR analysis. The result of the analysis shows that the fraction appears to be protosappanin A.