Bioprospecting the pharmacological potential of endophytic bacteria associated with medicinal plants

Endophytic bacteria, which inhabit internal plant tissues without causing disease, have increasingly been recognized as valuable sources of pharmacologically active compounds. This present study explored the bioactive potential of endophytic bacteria isolated from four medicinal plants viz., Sesbania grandiflora, Senna auriculata, Tabernaemontana divaricata, and Artemisia pallens, collected from Nilambur, Tamil Nadu, India. Healthy leaves were surface-sterilized, homogenized and serially diluted before being cultured on nutrient agar. Pure bacterial isolates were screened for non-toxicity using blood agar, and one non-haemolytic isolate from S. grandiflora and was selected for further analysis. The isolate was found to be Gram-negative and exhibited positive results in methyl red, TSI, and starch hydrolysis tests, indicating acid production and enzymatic activity. In vitro toxicity assessment using RBC haemolysis confirmed the sample's non-toxic nature. The bacterial extract was evaluated for pharmacological activities, which revealed significant antioxidant potential through hydrogen peroxide scavenging, FRAP and reducing power assays. Anti-inflammatory activity was demonstrated via. albumin denaturation and RBC membrane stabilization, while anti-obesity potential was shown through pancreatic lipase inhibition. Anticancer activity was assessed against the B16 melanoma cell line using MTT assays, which showed dose-dependent cytotoxicity. GC-MS analysis identified several bioactive compounds such as eicosane, isopropyl myristate, triacontane, phenol derivatives, and butanoic acid which were associated with antioxidant, anti-inflammatory, anti-obesity and anticancer properties. These findings highlighted the multifaceted pharmacological capabilities of endophytic bacteria and their promise as sustainable, natural alternatives to synthetic drugs. The study supported bioprospecting of plant-associated microbiota as an innovative, ecofriendly approach to drug discovery and development, integrating microbiology, pharmacology, and analytical chemistry.