Abstract
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.
Keywords – Plectranthus mollis; essential oils; antioxidants; cytotoxicity; lipid peroxidation; DNA
protection; human cancer cells.
- Introduction
Various plant extracts and phytochemicals including essential oils are considered strong antioxidative
agents and have been advocated as potent lead-compounds for these products. Essential oils are
natural, volatile, complex secondary metabolites produced by aromatic plants and are characterized
by their strong odour [1]. They are known for their broad-spectrum medicinal and commercial
values. Plectranthus mollis (family Lamiaceae) is an annual erect herb, locally called Lal aghada,
found throughout India and is used extensively as a vasoconstrictor, cardiac depressant, respiratory
stimulant, fever-reducer, besides being also used for rheumatism, hemorrhage, mental retardation,
snakebites as well as a general tonic