In vitro antimicrobial activity of triterpenoid saponin from Tephrosia purpurea seeds extract

Abstract

A novel oleanen type triterpenoid glycoside has been isolated from the butanolic extract of the seeds of Tephrosia purpurea. Its structure was elucidated as 3-O-{β-D-glucopyranosyl-(1→6)-[α-L-rhamnopyranosyl-(1→2)]-β-D-glucopyranosyl-(1→4)-[β-D-glucopyranosyl-(1→2)]-β-D-xylopyranosyl}-2,16-dihydroxy-23,29-dihydroxymethylolean-11,13(18)-diene-28-oic acid on the basis of spectral evidences, i.e. FT-IR, ¹H NMR, ¹³C NMR and FAB-MS data. The isolated saponin was tested for its antimicrobial activity. Significant results were obtained by evaluating the antibacterial activity by “Disc diffusion method” and antifungal activity by “Spore dilution method”. Maximum inhibition was recorded in gram positive bacterium- Streptococcus pneumoniae, while complete inhibition on the growth of fungus-Alternaria alternata was observed at a concentration of 200 μg/mL. The potency of the extract was quantitatively assessed by determining the minimum inhibitory concentration values against selected bacteria. The minimum inhibitory concentration values were in agreement with antibacterial results where minimum value was recorded to be 23 μg/mL for Streptococcus pneumoniae.