Volatile Fraction Composition and Total Phenolic and Flavonoid Contents of Elionurus hensii— Antioxidant Activities of Essential Oils and Solvent Extracts

Abstract

The objective of this study was to characterize Elionurus hensii in terms of the chemical composition of its essential oil and volatile fractions, the total phenolic and flavonoid contents of solvent extracts and antioxidative activity. Analysis of E. hensii essential oil samples from Congo was carried out using Gas Chromatography (GC) and Gas Chromatography-Mass Spectrometry (MS). The essential oil of the aerial parts consisted predominantly of oxygenated monoterpene compounds, of which the main components were menthane alcohol stereoisomers, whereas the essential oil of the root was characterized by a high content of oxygenated sesquiterpenes, the main component of which was aristolone. The amounts of total phenolics and flavonoids in the solvent extracts (dichloromethane, ethyl acetate and methanol) were determined spectrometrically. The essential oil did not exhibit significant antioxidant activity in terms of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid (ABTS^•+) scavenging ability, and exhibited only slight Fe³⁺ reducing ability. In contrast, the antioxidant activity of the solvent extracts of the aerial parts increased in the order ethyl acetate > methanol > dichloromethane, and that of the solvent extracts of the root increased in the order methanol > ethyl acetate > dichloromethane. Finally, a relationship was observed between the antioxidant activity and the total phenolic and flavonoid levels of the extract.