Comprehensive analysis of antibacterial and antioxidant properties in Calotropis gigantean leaf extracts

Calotropis gigantea Linn., commonly known as arka, is a wild tropical plant from the Asclepiadacea family with various medicinal properties. Previous studies have stated its antioxidant and antibacterial properties. For this purpose, leaf extracts of C. gigantea were prepared using a variety of solvents: ethanol, methanol, and n-hexane. For phytochemical bioactive compounds identification LC-MS analysis was performed, and to evaluate antibacterial activity against different gram positive (Bacillus subtilis, Bacillus muralis) and gram negative (E. coli, Acetobactor rhizospherensis) bacterial strains well diffusion method was applied. Antioxidant activity was observed using ABTS (2,2′-azino-bis-(3-ethylenebenzothiazoline)-6-sulfonic acid assay) and DPPH (2,2-diphenylpicrylhydrazyl assa) assays. The LC-MS (liquid chromatography-mass spectrometry) analysis revealed that ethanol leaf extract contained the highest number of compounds (14), while a 50% ethanol-methanol mixture had the fewest. In antimicrobial activity tests, methanol leaf extract exhibited the greatest inhibition zone against Bacillus subtilis (8 mm), and n-hexane the smallest (2 mm). Ethanol leaf extract had the highest inhibition against E. coli (9.5 mm), with methanol showing the lowest (4 mm). For Acetobacter rhizopherensis, ethanol extract demonstrated the largest inhibition zone (7.75 mm), while n-hexane showed the smallest (6 mm). Against Bacillus muralis, n-hexane showed the highest inhibition (5.75 mm), and methanol the lowest (3.5 mm). The ABTS assay indicated that ethanol extract had the highest inhibition activity (9.73%), and n-hexane the lowest (5.64%). The DPPH assay revealed that methanol extract had the highest radical remaining activity (99.68%), with n-hexane having the lowest (97.19%). C. gigantea is a prospective source of antioxidant and antibacterial agent.