Seasonal variation in chemical compositions and biological activities of essential oils extracted from Ageratum conyzoides L. - grown in Western Ghats Region-South India

The study aimed to characterize the influence of seasonal variation on the chemical composition and biological activities of essential oils extracted from the leaves of Ageratum conyzoides L. (A. conyzoides). Essential oils were extracted in summer (May), winter (January), and autumn (September) by hydrodistillation. GC/MS identified the volatiles compounds. The major compounds present in the essential oils across the three different seasons were Precocene II (29.44, 39.8 and 43.90%), Precocene I (32.17, 22.8 and 20.14%), and Caryophyllene oxide (9.09, 11.50 and 10.2%), followed by Carvone Hydrate (4.39, 4.65 and 3.65%) and Germacrene D (2.42, 2.25 and 2.76%). Biological activities such as in-vitro antioxidant, anti-cancer, and anti-bacterial activities were evaluated. The essential oil from A. conyzoides leaves exhibited strong antioxidant activity with IC50 values of 34.17 µg/mL for DPPH and 33.47 µg/mL for ABTS assays in summer; 99.92 µg/mL for DPPH and 26.40 µg/ mL for ABTS in winter; and 96.47 µg/mL for DPPH and 78.59 µg/mL for ABTS in autumn. The essential oil showed significant anticancer activity against the MDA-MB-231 breast cancer cell line with IC50 value of 122±0.05 µg/mL in summer, 86.50±0.05 µg/mL in winter, and 148.38 ± 1.15 µg/mL in autumn, compared to and Etoposide at 30 µg/mL. The antibacterial activity against two gram-positive and four Gram-negative bacteria is moderate to good.