Study On Chemical Constituents Of Ophiorrhiza Japonica

Ophiorrhiza Linn.plants,a kind of traditional Chinese material medica,are dicotyledonous herbs belonging to Rubiaceae.As reported,these plants furniture an array of alkaloids,as well as flavonoids,steroids,anthraquinones,terpenoids and other chemical components.These chemical compositions exhibit anti-cancer,anti-inflammatory,antibacterial and other properties.The diverse,complex chemical compositions and their significant activities of Ophiorrhiza has made it become one of the research hotspots.In this paper,the sencondary metabolites of Ophiorrhiza japonica were systematically studied,and DPPH and ABTS radical scavenging methods were used to screen the antioxidant activity of the obtained compounds,which could give an evidence of the antioxidant compounds’ composition,and a basis for further exploration of the title plants and the Ophiorrhiza genus.In this experiment,the whole plant of Ophiorrhiza japonica was extracted with anhydrous ethanol,and the crude extract was obtained after evaporation.Then this extract was dispersed with water,and extracted with petroleum ether.The left water layer was acidulated,followed was the extraction with ethyl acetate.Subsequently,the alkalization of the left water was conducted,and then extraction with chloroform was performed.All the three crude extracts were isolated and purified by column chromatography using silica gel and Sephadex LH-20 under the detection of thin layer chromatography.A total of forty-five monomer compounds were obtained.Among them,eleven compounds were identified by extensive spectroscopic analysis including MS and NMR.Three alkaloids,deppeaninol(1),6-hydroxyharman(2)and harman(3),were identified as the chemical composition of the chloroform extract.Five compounds,3-hydroxy-2-methoxymethylanthraquinone(4),p-hydroxy benzaldehyde(5),scopoletin(6),3-O-α-alcohol(7)and loliolide(8),were isolated from the ethyl acetate extract.Three compounds,β-sitosterol(9),pomolic acid(10)and glyceryl monooleate(11),were purified from the petroleum ether layer.It is worthy to point out that compound 4 is a new compound and compounds 1,5,7,8,10 and 11 were discovered from this genus for the first time.The antioxidant activities of compounds 1-3,9 and 10 were screened by DPPH and ABTS radical scavenging methods.The results showed that compound 2 has the strongest scavenging effect on the two kinds of free radicals,and both IC50 are 0.041 mg/mL,wheares compound 1 was a bit weaker with IC50 of 2.8,3.5 mg/mL,respectively.Preliminary structure-relationship study revealed that the hydroxyl group at C-6 could significantly increase the antioxidant activity.