Chemical characterization, biological assessment and molecular docking studies of essential oil of Ocimum viride for potential antimicrobial and anticancer activities

Ocimum viride (family: Lamiaceae) is a medicinally important aromatic plant that grows widely in north western Himalayan range of Indian subcontinent. Essentials oils (EOs) and purified aromatic compounds derived from plants of genus Ocimum have long been used in traditional system of medicine to treat various chronic disorders. In this study we made an attempt to assess the chemical composition of essential oil (EO) obtained from Ocimum viride for potential antimicrobial and anticancer properties. Gas chromatography-mass spectrometry (GCMS) analysis revealed that EOs of aerial parts (leaves) of Ocimum viride contain high amounts of oxygenated monoterpenes, thymol and gamma terpinene. Notably, thymol (~50%) and γ-terpinene (~18%) were identified as the most abundant components of the oil. EOs showed most prominent antibacterial effect against Bacillus subtilis and in silico molecular docking analyses of antibacterial action against bacterial cell wall of Bacillus subtilis showed interaction of thymol with Sec A protein of Bacillus subtilis (binding energy of - 15 kcal/mol) with active site Lys284, Trp275, Leu269, Arg19, Glu277, pro270. While, in vitro cytotoxic effect of EO against six human cancer cell lines showed maximum effect with IC 50 value of ~0.034 ± 0.001μL/ mL against HT-29 colon cancer cell line. DNA fragmentation analysis and cell cycle analysis revealed that EO inhibits the growth of HT-29 colon cancer cells probably through induction of unrepairable DNA damage and subsequent cell death. Taken together, our results indicate that EO possesses potent antimicrobial and anticancer properties, and may find applications in bacterial growth inhibition and cancer therapeutics.