Ontogenetic variability of Vitex pseudo-negundo essential oil and its phytotoxic activity

Abstract

In the present study, variations were examined in the content and compositions of Vitex-pseudo-negundo leaf essential oil (EO). These evaluations were carried out at 2 different ontogenetic stages, i.e. before and during flowering. Fresh leaves of vitex were harvested and analyzed at these two stages. The EOs of air-dried samples were extracted by hydrodistillation. The yield of EOs (w/W%) significantly increased (P ≤ 0.05) in the leaves at the flowering stage (0.43%), compared to the stage before it (0.25%). The EOs were analyzed by gas chromatography (GC) and by GC–mass spectrometry (GC–MS). The main EO components in the leaves at these 2 stages were α-pinene (25.4–30.2%), limonene (11.9–12.5%), α-terpinyl acetate (22.6–29.5%) and (E)-caryophyllene (7.6–11.6%). Moreover, α-terpinyl acetate had its strongest presence at the flowering stage (29.5%), while α-pinene, limonene and (E)-caryophyllene showed their highest contents before the flowering stage (30.2, 12.5 and 11.6%, respectively). The phytotoxic activities of EOs were examined at the full flowering stage. These EOs were employed in concentrations of 0, 400, 800, 1200, 1600, 2000 and 2400 μL/L and were used on a crop, Lepidium sativum, and on two weeds, Amaranthus retroflexus and Taraxacum officinale. The EOs of vitex showed inhibitory effects on these species. The efficiency of inhibition depended on the type of species being treated with EO and on the concentration of EO being used.