Antioxidant activities and chemical composition of various crude extracts of Lepidagathis keralensis

Lepidagathis keralensis (Acanthaceae), a plant mainly used as a preventive medicine against malnutrition was studied for the evaluation of in vitro antioxidant activity. Petroleum ether, acetone, methanol and aqueous extract of the stem and leaves of the plant were analyzed. The Total Phenolic Content (TPC) and Total Flavonoid Content (TFC) were quantitatively estimated for correlation studies. DPPH radical scavenging assay, Reducing power assay and Phosphomolybdenum method were employed for the evaluation of antioxidant activity. Chemical components of the extracts showing higher antioxidant properties were subjected to Gas chromatography-mass spectrometry (GC-MS) analysis. Potent antioxidant activities were shown by the methanol extract of leaf and acetone extract of the stem in all the assays, with the methanol extract of leaf showing highest DPPH scavenging activity(94.78%), reducing power(1.226 ) and total antioxidant activity(656.89±1.68 mg/g AAE). Highest TPC and TFC were obtained for the methanol extract of leaf (139.76±0.41 and 258.33±1.47) and acetone extract of stem (102.00±1.40 and 240.00±2.42). Positive correlations were obtained for TPC and TFC with the observed antioxidant activity. GC-MS analysis of the extracts revealed the presence of 13 phytocomponents in the methanol extract of leaf. Cyclopentaneundecanoic acid methyl ester (27.4%), Benzene, (ethenyloxy)-(17.3%), n-Hexadecanoic acid (palmitic acid) (13.93%) and 10-Undecynoic acid, methyl ester (11.67%) were the major components identified in the extract. 25 components were identified in the acetone extract of stem with Cyclopentaneundecanoic acid (29.6%), 1,6-Octadiene,3,7-dimethyl-(17.17%), 10-Undecyn-1-ol(9.54%) and 3-Hydroxy-4-methoxybenzoic acid(6.79%) as the major components. The study confirms that the plant is rich source of natural antioxidants.