Studies On The Anti-bacterial Constituents Of Carex Siderosticta Hance

Carex siderosticta Hance,perennial herb,belongs to the genus Carex within the Cyperaceae family.Previous studies have shown that ethanol extracts of C.siderosticta Hance have strong antimicrobial activity,but studies of the active compounds are rare.In this study,we assessed the antibacterial activity of C.siderosticta Hance extracts and then systematically isolated,purified and analyzed the active ingredients by activity-guided fractionations.The results were as follow:1.Eleven compounds were subsequently isolated and identified for first time from C.siderosticta Hance,including stilbenes: Curcusionol(Y1),Kobophenol A(Y2),Resveratrol(Y7),Hopeanolin(Y9),Miyabenol C(Y10);Phenylpropanosides: Smiglasides A(Y3)、Smiglasides B(Y4)and Smiglasides C(Y11);flavonoids: Taxifolin(Y5)and Quercetin(Y8);phenols: 6-Prenylquercetin-3-Methyl Ether(Y6).2.The results of bioassay in vitro showed that the ethanol extract from the stem of C.siderosticta Hance had strong antimicrobial activity against Pseudomonas syringae pv.actinidiae(PSA),with an minimum inhibitory concentration(MIC)value of 100 μg/m L.The ethanol extract of C.siderosticta Hance was dissolved with distilled water,extracted with petroleum ether,chloroform,ethyl acetate and n-butanol sequentially.The ethyl acetate extract and the chloroform extract showed the high antimicrobial activity,with MIC value of50 μg/m L and 100 μg/m L.Ten compounds were isolated from the ethyl acetate extract by activity-guided fractionations.Four compounds were isolated from the chloroform.Compounds Y1,Y2,Y5,Y6,Y7 and Y10 showed antibacterial activity with MIC values lower than 200 μg/m L against pathogens.Among these compounds,compound Y1 has most antibacterial activity against PSA and Ralstonia solanacearum,with the same MIC values of12.5 μg/m L.Compound Y5 shown to be active against Bacillus subtilis,with the MIC value of 200 μg/m L.Compound Y6 has antibacterial activity against five kinds of bacteria.Among these bacterias,the inhibitory effect was significant against Ralstonia solanacearum,with an MIC value of 12.5 μg/m L.Compound Y7 shown antibacterial activity against six kinds of bacteria,and the most antibacterial activity against PSA,with MIC value of 50 μg/m L.Compound Y10 also has the inhibitory activity against five kinds of bacteria,and the most antibacterial activity against PSA,with the MIC value of 12.5 μg/m L.Compounds Y3,Y4,Y8 and Y9 have the weak antibacterial activity.3.The pot experiment results of compound Y1 and Y2 on Ralstonia solanacearum showed that compound Y1 had a better protective effect on tobacco bacterial wilt,which was is equivalent to the treatment of streptomycin sulfate.The control effect of compound Y1 at14 days and 21 days was 61.15% and 57.36%,respectively.The protective effect of compound Y2 on tobacco bacterial wilt was far lower than that of compound Y1 and streptomycin sulfate.The control effect on 14 days and 21 days was 34.07% and 22.51%,respectively.In summary,it was preliminarily determined that the main antibacterial active substance in C.siderosticta Hance was stilbene.Compound Y1 showed significant antibacterial activity against PSA and Ralstonia solanacearum in vitro,and had a good protective effect against tobacco bacterial wilt in pot experiment.Thus,compound Y1 is worthy of further research.