Chemical Composition, Antioxidant, Cytotoxic and DNA Damage Protective Activities of Plectranthus mollis Essential Oils

The essential oils were obtained by hydro-distillation from Plectranthus mollis and subjected to phytochemical screening and gas chromatography-mass spectroscopy (GC-MS) to establish their qualitative and quantitative compositions. Phytochemical investigations confirmed that the essential oils are rich-source of phenols, flavonoids, ascorbic acid and carotenoids. The essential oils were evaluated for their antioxidant and lipid-peroxidation inhibition activities besides their oxidative DNA damage protection potentials. GC-MS data revealed a total of 40 compounds identified, which accounted 98.4% of the total constituents. The major constituents were: Fenchone (31.43%) followed by Piperitone oxide (17.79%), 3-Cyclopenten-1-one, 2-hydroxy-3-(3-methyl-2-butenyl) (8.19%), Ζ-β-Farnesene (5.98%) and α-Humulene (5.86%). These essential oils exhibited broad-spectrum, dose-dependent antioxidant potencies as evidenced by total-antioxidant-activity (TAA), 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging, and ferric reducing antioxidant power (FRAP) assays. They showed significant inhibition of lipid peroxidation rate measured in terms of malondialdehyde (MDA) content. These results hold significance, as lipid-peroxidation is considered as biological end-point of oxidative damage and its inhibition as the most important index for antioxidant potential. The oils successfully protected the DNA from Fenton's reagent induced DNA damage. The essential oils of P. mollis showed good anti-proliferative activity in a dose-dependent manner against human melanoma cancer M-16 cell line, with only ∼10% cell survival at 2 μL concentration.