Phytochemical composition, enzyme inhibitory potential, antioxidant and antibacterial activities of Pisonia grandis R.Br. (lettuce tree) leaves

Lettuce tree (Pisonia grandis R.Br.) leaves are underutilized vegetables with diverse nutritional and medicinal properties. Herein, P. grandis leaves (PGL) were explored for biological potentiality and chemical profiling using different solvents of varied polarity. The enzyme inhibitory property was evaluated by α-amylase, α-glucosidase, and tyrosinase inhibitory assays. Antioxidant property of PGL was done using five assays and minimum inhibitory concentration (MIC) required to inhibit the growth of six bacterial strains was tested. GC-MS analysis revealed the presence of 43 constituents. Phytol (27.5 and 12.3%) and squalene (14.6 and 4.9%) are identified as major compounds in petroleum ether (PEE) and ethyl acetate extracts (EAE). The EAE (IC50 of 29.04 ± 0.16 µg/mL) exhibited strong α-amylase inhibitory activity. Whereas, aqueous (IC50 of 53.41 ± 0.50 µg/mL) and methanolic (IC50 of 60.20 ± 0.38 µg/mL) extracts showed moderate α-glucosidase and tyrosinase inhibitory effects respectively. Methanolic extract of PGL showed better free radical scavenging activity in ABTS, DPPH and FRAP assays with an IC50 of 44.58 ± 0.42, 34.80 ± 0.21, and 61.51 ± 0.10 µg/mL respectively. The concentration (MIC) of PGL extract at 23.4 µg/mL is sufficient for the inhibition of the bacterial strains like Staphylococcus epidermidis and Vibrio cholera. The phytochemicals present in the PGL extract could be the basis for its promising biological properties. The results revealed the efficacy of this underutilized vegetable for use as a dietary supplement and other applications in food and pharmaceutical industries.