Changes in Composition and Antioxidant and Antimicrobial Activities of Essential Oil of Fennel (Foeniculum vulgare Mill.) Fruit at Different Stages of Maturity

Abstract

The chemical composition and antioxidant and antimicrobial activities of the hydro-distilled essential oils from the fruit of sweet fennel (Foeniculum vulgare Miller) were investigated at three stages of maturity (immature, intermediate, and mature). Maximum essential oil content (3.5%) was observed in the mature, and the minimum oil content (2.8%) was observed in immature fruit. GC–MS analysis of the fennel essential oils from the plants revealed the presence of trans-anethole (65.2%, 69.7%, 72.6 %); fenchone (8.8%, 10.0%, 11.0%); estragole (6.9%, 6.9%, 7.2 %); and limonene (7.8%, 4.7%, 3.5 %) as the main components at immature, intermediate, and mature stages, respectively. Both the essential oils and trans-anethole, the principal constituent, exhibited appreciable antioxidant and antimicrobial activities as assessed by 2,2-diphenyl-1-picrylhydrazyl free radical-scavenging ability, bleaching β-carotene in linoleic acid system, inhibition of linoleic acid oxidation, disc diffusion, and microdilution broth assays. The variations in the content of most components with antioxidant and antimicrobial activities in the essential oils as the fruit matured were significant (p < 0.05).