Changes in composition and antioxidant activities of essential oils in Phlomis anisodonta (Lamiaceae) at different stages of maturity

The composition of hydro-distilled essential oils of Phlomis anisodonta Boiss. subsp. occidentalis Jamzad in vegetative, flowering and post flowering stages were investigated using GC and GC-MS, leading to identification of 41, 26 and 23 compounds, respectively. In all three samples, sesquiterpenes were the main components. In vegetative stage the main components of the oil were germacrene-D (14.3%), bicyclogermacrene (12.4%) and α-pinene (6.8%); in flowering stage, germacrene-D (52.6%) and β-caryophyllene (15.9%); and in fruiting stage, germacrene-D (27.9%), bicyclogermacrene (17.6%), caryophyllene oxide (14.7%) and β-caryophyllene (11.3%). The samples were also subjected to screening for their possible antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and β-carotene-linoleic acid assays. In the first experiment, the free radical scavenging activity of polar subfraction of methanol extract in fruiting stage was superior to all other extracts (IC50= 41±0.4 μg/ml). When using linoleic acid system, oxidation of the linoleic acid was effectively inhibited by the non-polar subfraction of methanol extract in different stages. The results of this study show that the composition of essential oils varies considerably both in different parts of the plants and at different stages of development. When using the plants for medicinal purposes, it is important to be aware of the effective developmental phase, i.e. when the most effective components reach their peak volume, as well as the most useful parts.