Secondary Metabolite Profiling and Biological Activities of Leaf Extract of Cestrum nocturnum

Abstract

This study investigated the chemical composition and biological effects of leaf extracts from Cestrum nocturnum L., an ornamental plant, prepared with methanol and hexane. Phytochemical screening showed that the methanolic extract contained alkaloids, flavonoids, terpenoids, and polyphenols, whereas the hexane extract contained glycosides, steroids, and saponins. Antimicrobial properties were evaluated using the agar disc diffusion technique against three reference strains: The Gram-positive bacterium Bacillus subtilis (ATCC 6051), the Gram-negative bacterium Escherichia coli (ATCC 8739), and the fungus Candida albicans (ATCC 2091). Each extract was tested at 50 mg/mL and 100 mg/mL. The hexane extract outperformed the methanolic extract in antibacterial activity against both bacterial strains, producing zones of inhibition of 8 mm and 10 mm against B. subtilis and 6 mm and 9 mm against E. coli at the low and high concentrations, respectively. The methanolic extract showed weaker antibacterial effects overall but displayed notable antifungal activity against C. albicans, with inhibition zones of 3 mm and 6 mm at the two concentrations tested. The methanolic extract’s antioxidant capacity was also examined via the DPPH free radical-scavenging assay, which showed a promising ability to neutralise free radicals with an IC50 of 98.46 μg /mL. Its total phenolic and flavonoid contents were found to be 63.3 mg/g GAE and 21.607 mg/g QE, respectively.