Antibacterial and antioxidant activities of aqueous extract of soapnuts (Sapindus mukorossi)

As an alternative to chemical surfactants, the biosurfactants obtained from plants are renewable, biocompatible, biodegradable, less toxic and less expensive. In the present report, the aqueous extract prepared from the pericarps of soapnuts fruits is employed, which are known to exhibit a myriad of biological properties. The extract was characterized using Fourier transform infrared spectroscopy (FTIR) and zeta analyzer for identifying the functional groups and surface charge, respectively. The extract showed abundance of saponins, triterpenoids, flavonoids and negative charge of-8.9 mV. The free radical scavenging and antibacterial activities of the extract were evaluated with DPPH scavenging and well diffusion assays. The DPPH scavenging (%) increased with an increase in extract concentration and showed a significant radical scavenging potential of 85.3% at a concentration of 250 μg/mL. The extract didn't show antibacterial action on Gram-negative bacteria at the selected concentrations. But, it demonstrated significant inhibitory action on Gram-positive bacteria; Bacillus subtilis and Micrococcus luteus with inhibition zones of 4.0 mm and 12.5 mm at 43.75 mg of crude saponins, respectively. Thus, the green extract used in the present study finds its application as a natural, antibacterial and antioxidant biosurfactant in cosmetic and food industries, as a substitute to chemical surfactants.