Antimicrobial activity of flavanoid sulphates and other fractions of Argyreia speciosa (Burm.f) Boj.

Antimicrobial activity of flavanoid sulphates and different fractions of A. speciosa root was studied against bacteria, fungi and Mycobacterium tuberculosis H37 Rv sensitive strain by in vitro and in vivo assays. Flavanoid sulphates such as quercetin 3'7 di-O methyl 3- sulphate and kaempferol 7-O methyl 3-sulphate were isolated from the n-butanol fraction of 80% methanolic extract of the plant. The structures of the isolated flavanoids were confirmed by spectral studies. Ethyl acetate (EAAS) fraction and flavanoid sulphates inhibited the growth of M. tuberculosis Rv sensitive strain at MIC values 50 and 25 microg/ml, respectively. Ethanolic fraction (EtAS) showed significant inhibition of gram positive organism with a MIC of 31.25 microg/ml. More inhibition was observed with a less MIC (2 microg/ml) for flavanoid sulphates against Klebsiella pneumoniae, a gram negative organism and it is almost comparable with the standards. Interestingly, chloroform fraction alone exhibited significant antifungal activity with a MIC of 100 microg/ml. A synergistic effect between flavanoids sulphates and commercially available antitubercular drugs was observed with FIC index of 0.443 +/- 0.245, 0.487 +/- 0.247 for isoniazid and 0.468 +/- 0.333, 0.417 +/- 0.345 for rifampicin, whereas EAAS fraction showed partial synergistic effect. A synergistic effect was observed for EAAS fraction and flavanoids sulphates with FIC index < 0.5 with antibiotics. Hemolysis assay on RBCs suggested that EAAS and flavanoids sulphates exhibited least cellular toxicity to erythrocytes as compared to chloramphenicol. In vivo studies in mice infected with K. pneumoniae demonstrated that on day 10 post treatment of different fractions and isolated compounds of A. speciosa, about 60% of the animals treated with EAAS, 70% of animals treated with flavanoids sulphates and 40% of animals treated with EtAS were survived.