Structural Identification Of Antimicrobial Tompounds Against Microbes In White Loropetalum Chinese

Loropetalum chinense which belongs to the genus Loropetalum of Hamamelidaceae, is a constant shrub and widely grown in east of India and south of China. Its leaves, flowers and roots are traditional medicines in China, which has been used to treat diarrhea, coughs, hemorrhaging, burn and various diseases.Researches showed the plant contains tannin,flavonoid and Polyphenols,these maybe the main components of drug efficacy.But the antimicrobial activity of the extraction of the plant by ethanol was studied rarely.In this research,the test of antimicrobial activity of the extract of the Loropetalum chinense was performed by agar cup method,antimicrobial activity was found in the extract by Et OAc.Then this extract was performed further extraction and purification.Several compound were obtained by various column chromatography methods,the structural identifications were performed by mass spectroscopy, ultraviolet spectroscopy,infrared spectroscopy and nuclear magnetic resonance method.The bio-active ingredient was found by antimicrobial test.This research illuminated material base for antimicrobial activity in Loropetalum chinense and provided a gist for further exploration and utilization of Loropetalum chinense.In this research,the crude extract was obtained from stems and leaves as raw material by digestion with 90% ethanol.Then petroleum ether,Et OAc and n-Bu OH was used in sequence for extraction.Antimicrobial activity was found in the component of the extract in Et OAc by trial of antimicrobial activity of agar cup method.Seven fractions were obtained by separation on chromatography columns.Antimicrobial activity was found in the two fractions,F5 and F6 by method of bio-activity-guided isolation.Further purification was performed for the two fractions.Seven compound were isolated and purified by various separation methods of column chromatography and TCL monitoring.Structural identifications of these compound were performed with mass spectrum, ultraviolet spectrum,infrared spectrum and nuclear magnetic resonance spectrum.These compounds are 8-[1-(3,4-dihydroxyphenyl)-3-methoxy-3-oxopropyl]-catechin(loropetaliside A)(1),a lignan glucoside,1-(5-hydroxy-3-methoxyphenyl)-2-(2-β-glucopyranosyl-4-hydroxy-5-(1-(E)propen-3-ol)-phenyl)-propane-3-ol(loropetaliside B)(3) and several known compounds, manglieside D(2),quercetin(4),kaempferol- 3-O-D-glucopyranoside(5), quercetin-3-O-β-L-rhamnoside(6) and tiliroside(7).Antimicrobial activity was found in the extract in Et OAc against microorganisms, Candida albicans,Escherichia coli and Bacillus subtilis and confirmed the quercetin was the active compound.Quercetin exhibited the strongest inhibitive activity against C.albicans and moderate inhibitive activity against B.subtilis and E.coli.This result is according with the literature about antibacterial activity of quercetin on E.coli and antifungal activity on Candida tropicalis,and consider it a inhibitive substance preliminary. However compounds 1–3and5–7, which had a sugar group in C-3 of quercetin or kaempferol showed no activity against all tested bacterial and fungal strains.