Phytochemical Analysis, GC-MS Profiling, and In Vitro Evaluation of Biological Applications of Different Solvent Extracts of Leonotis nepetifolia (L.) R.Br. Flower Buds.

Leonotis nepetifolia (L.) R.Br. is a medicinally important herb belonging to the family Lamiaceae. The plant is typically found in tropical regions, and its leaf and root extracts are renowned for their ethno-botanical and therapeutic applications. This study was designed to determine the presence of various bioactive components, and to evaluate antibacterial, antifungal, antioxidant, and anti-proliferative activities. The preliminary phytochemical screening and gas chromatography-mass spectrometry (GC-MS) analysis of different solvent extracts revealed the presence of various bioactive compounds, of which methanol extract showed 24 compounds, petroleum ether extract revealed 26 compounds, and 24 compounds in hexane extracts. The major bioactive components including λ-sitosterol (16.20 %) in methanol extract, 1-nonadecanol (15.48 %) in petroleum extract, and eicosane (13.22 %) in hexane extract have been reported with various bio-therapeutic applications. In addition, the flower bud methanolic extract of L. nepetifolia exhibited inhibitory potential against all tested bacterial and fungal pathogens. The DPPH radical scavenging assay revealed that methanolic extract possessed the highest antioxidant activity. The scavenging activity increased in a concentration-dependent manner, as indicated by a 74 % inhibition rate at 1000 µg/ml. Furthermore, the in vitro cytotoxic effects of the methanolic extract on the HepG2 cell line were evaluated. The IC 50 value of methanolic extract against HepG2 cells was determined to be 83.28 µg/ml. The findings reveal that different solvent extracts of L. nepetifolia flower buds contain a significant amount of various bioactive phytochemicals with antioxidant and anticancer activities; and thus, the plant could serve as a potential source of pharmacological applications.