Characterization of crude saponins from stem bark extract of Parinari curatellifolia and evaluation of its antioxidant and antibacterial activities

Abstract Saponins are surface active glycosides which occur in plants as one of the secondary products of primary metabolism. Saponins have been reported to demonstrate antimicrobial, antioxidant and other biological activities. This study was designed to characterize the crude saponins extracted from stem bark of Parinari curatellifolia and to study the antibacterial and antioxidant activities. The saponin was extracted using standard protocol and was subjected to physicochemical characterization. Foaming and haemolysis tests as wells as determination of foaming index were conducted to confirm the presence of saponins. The solubility of the crude saponins was tested in various organic solvents at room temperature. The nature of the aglycone moiety was identified using Salkowski’s and Liebermann–Burchard’s tests. The glycone moiety was identified using Fehling’s test. Fluorescence test was conducted using UV light at 254 and 366 nm. The TLC separation profile was determined in suitable solvent system. The saponin was subjected to UV and FTIR finger printings using standard methods. Silver nanoparticles were synthesized and characterized using standard method. The saponins were evaluated for antioxidant and antibacterial activities using standard procedures. The foaming index was found to be 1666.6. The crude saponin showed different degrees of solubility in the solvents tested and was found to be highly soluble in methanol, ethanol and DMSO. Generally, the saponins were found to be insoluble in non-polar solvents. The aglycone moiety was found to be triterpenoidal in nature and the glycone was found to be a reducing sugar. The crude saponin produced fluorescence at 254 nm which indicated the presence of some chromophores. The TLC showed the presence of some metabolites with varying Rf values. The UV analysis revealed two absorption peaks at 480 nm and 580 nm. The FTIR finger printing showed absorptions characteristic of some functional groups at different frequencies. The crude saponin and silver nanoparticles demonstrated free radical activity against DPPH free radical with IC50 of 5.878 mg/mL and IC50 0.2477 mg/mL, respectively while the H2O2 radical had IC50 of 5.750 mg/mL. The saponin inhibited the growth of Staphylococcus aureus with zone diameter of inhibition between 2 and 3 mm. The saponins are triterpenoidal in nature and demonstrated antioxidant and antibacterial activity.