Optimising steroid saponins extraction from Costus pictus leaves using response surface methodology and investigating antibacterial properties of extracts obtained under optimised conditions

Abstract

The aim of the study was to optimise the extraction of steroid saponins from Costus pictus leaves and investigate the
antibacterial activity of the obtained C. pictus leaf extract. The influence of major single factors, including ethanol
concentration, ratio of raw materials to solvent, and extraction time, were investigated, and the use of the response surface methodology provided optimal extraction conditions. The results of the study showed that the optimal conditions for steroid saponins extraction were as follows: ethanol solvent concentration (79%), material/solvent ratio (1/31 g/ml), and extraction time (60 hours), resulting in 7.62% steroid saponin content. The C. pictus leaf extract obtained under these optimised conditions exhibited effective inhibition against all four bacterial strains: Bacillus subtilis, Vibrio sp., E. coli, and Salmonella sp.. Among them, the inhibitory effect on Vibrio sp. was the highest, while the inhibitory effect on Salmonella sp. was the lowest.