Antimicrobial and Antioxidant Activity of the Essential Oil and Methanol Extract of Nepeta cataria

Catnip (Nepeta cataria) is an important medicinal herb belonging to the mint family, Lamiaceae. In this study, the in vitro antimicrobial and antioxidant activities of the essential oil and methanol extract from Nepeta cataria. and its essential oil composition were investigated. The essential oil, which has 4a alpha,7 alpha,7a beta-nepetalactone (70.4%), 4a alpha,7 alpha,7a beta-nepetalactone (6.0%), thymol (2.3%), and 4a alpha,7 alpha, 7a beta-nepetalactone (2.5%), as main components, exhibited activity against eleven bacteria, and twelve fungi and a yeast, C. albicans; with Minimum Inhibitory Concentrations (MIC) values ranging from 12.50 to 250 mu l/ml; the methanol extract showed weaker activity. The samples were also subjected to a screening for their possible antioxidant activities by using 2.2-diphenyl-1-picrylhydrazyl (DPPH) and beta-carotene/linoleic acid assays. In DPPH assay, the extract showed slight antioxidant activity whereas the essential oil remained inactive. In the latter case, both the extract and the essential oil exerted weak activity having inhibiton ratios of linoleic acid oxidation at 16.4% and 27.0%, respectively. The weak antioxidative nature of the extract could be attributed to the low phenolic content, estimated as gallic acid equivalent at 22.6 +/- 2.07 mu g/ml or 2.26%. In both systems, antioxidant capacity of BHT was determined in parallel experiments.