Chemical Compositions Of Polygonum Posumbu And Their Bioactivities

Polygonum posumbu is a member of the Polygonum from Polygonaceae family.There are many species in the Polygonum used as traditional medicine resource of all countries in the world,among which Polygonum aviculare L,Polygonum cuspidatum,Polygonum bistorta L,Polygonum tinctorium Lour and others are famous Chinese herbal medicines.They were included in the Chinese Pharmacopoeia,and some of the plants in the genus were folk medicine.It was found that polygonum plants mainly contain flavonoids,terpenoids,phenylpropanoids,steroids and other chemical components.Most of Polygonum showed good biological activities in antimicrobial activity,antioxidant activity,antitumor and other aspects.However,the chemical composition and main active ingredients of Polygonum posumbu are not clearly understood at present,and the medicinal value can not be fully used.Therefore,this study focus on chemical constituents in antimicrobial activities and antioxidant activities of Polygonum posumbu in Xunyang county,Shaanxi Province.The air-dried whole herb of Polygonum posumbu?14.2 kg?were soaked with95%ethanol and reflowed extraction for 6 times.The crude ethanol extract was obtained by distillation under reduced pressure.After the extract was suspended in water,the organic solvents petroleum ether,ethyl acetate,n-butanol with different polarities were successively used as extraction.The three-phase extracts were separated by silica gel column chromatography,Sephadex LH-20,TLC and other chromatographic techniques to obtain 14 compounds.Compounds 1-4 were isolated from the petroleum ether phase,compounds 5-11 were isolated from the ethyl acetate phase,and compounds 12-14 were isolated from the n-butanol phase.Combining the physicochemical characteristics of each compound with the analysis of nuclear magnetic and mass spectral data,these 14 pure compounds were identified as:n-hexacosanol?1?,n-tetradecanoic acid?2?,?-sitosterol?3?,?-sitosterol-3-O-?-D-glucoside?4?,gallic acid?5?,quercetin-3-O-?2??-O-galloyl?-?-D-glucopyranoside?6?,quercetin-3-O-?-D-glucoside?7?,quercetin?8?,o-phthalic acid bis-?2-ethyl decyl?-ester?9?,inositol?10?,sucrose?11?,succinic acid?12?,n-butyl-?-D-fructofuranoside?13?,?-D-glucose?14?.Compounds 1-14 were isolated from this plant for the first time and compounds 1,2,9 and 10 were isolated for the first time from Polygonum plants.Antimicrobial activities of 11 compounds?1-8,10,12,13?were tested against4 strains of bacteria and 7 strains of plant pathogenic fungi by MIC method.The results showed that flavonoids 6,7 and 8 had good inhibitory activity against 4bacteria and 7 fungi.The differences in the structure of compounds resulted in different antimicrobal activities,especially the minimum inhibitory concentrations of compounds 6 and 8 reached 31.2?g.mL^-1,which was comparable to that of the positive control.This result indicated that Polygonum posumbu had antimicrobal activity.Antioxidant activities of 7 compounds?3-8,13?were tested by the DPPH method,and Vitamin C was selected as a positive sample.The results showed that quercetin-3-O-?2??-O-galloyl?-?-D-glucopyranoside(IC₅₀=4.57?g.mL^-1),gallic acid(IC₅₀=5.38?g.mL^-1)and quercetin(IC₅₀=5.79?g.mL^-1)had stronger antioxidant effect than Vc(IC₅₀=7.60?g.mL^-1).Compound 7(IC₅₀=8.44?g.mL^-1)also had slightly weaker antioxidant activity than Vc.The different structure results in antioxidant activity results.This experiment also showed that the antioxidant activity was another activity of Polygonum posumbu.By studying the chemical composition and biological activity in the Polygonum posumbu,it was shown that the compound species were relatively abundant and diverse.Similarly,bacteriostatic and antioxidant properties were also prominent of Polygonum posumbu.Therefore,this plant can be a natural source of non-toxic,natural,low-cost antibacterial agents and antioxidants,and has good potential for exploitation and utilization.