Seasonal Variation in Essential Oil Compositions and Antioxidant Properties of Acorus calamus L. Accessions

Background: Acorus calamus (Sweet flag) is a known herbal drug commonly used in traditional medicine. Our aim was to perform seasonal and altitudinal phytochemical screening to assess the antioxidant activity of the essential oils in the rhizome and leaves of A. calamus from three different altitudes. Methods: Phytochemical screening was performed using GC/MS analysis and in vitro antioxidant assay was done by different methods. Results: The essential oils mainly contained α-asarone, β-asarone (35.3–90.6%), and Z-isoelemicin (1.7–7.3%) as the major constituents, besides linalool, Z-methyl isoeugenol, shyobunone, kessane, etc. All the oils exhibited vast molecular diversity in terms of quantitative ingredients. All essential oils were studied for their antioxidant activity by different methods, including their effect on the DPPH radical-scavenging activity, reducing power, and chelating properties of Fe(2+). The oils isolated in all the different seasons exhibited antioxidant activity as a function of concentration, with IC(50) values ranging from 475.48 ± 0.08 to 11.72 ± 0.03 compared to standards. Conclusion: From the results obtained it can be inferred that the herb may be a good source of bioactive compounds and can work as an antioxidant to prevent oxidative deterioration in food. The data provide a basis for its in-situ investigation for judicious exploitation.