Phytotoxic potential of Vitex pseudo-negundo leaf and flower extracts and analysis of phenolic compounds

Abstract In the present study, aqueous extracts were obtained from the leaves and flowers of Vitex pseudo-negundo. The effects of these extracts were examined on the germination percentage and several developmental factors of three plant species, namely, Lepidium sativum, Amaranthus retroflexus and Taraxacum officinale. The major phenolic compounds of the leaf extract were Trans-ferulic acid (913.71 mg/L), Chloregenic acid (235 mg/L) and Hesperedin (115.68 mg/L), while those of the flower were Chloregenic acid (333 mg/L), p-Coumaric acid (256.04 mg/L) and Hesperedin (185.72 mg/L), as recognized by HPLC. The stock extract had a concentration of 10% (w/v) and was made from dried powders of the Vitex flower and leaf. The extract at 2.5% had a stimulatory effect on the seed germination of Lepidium sativum. A substantial increase (P ≤ 0.05) was observed in the germination percentage (98.3 and 96.6%, when using flower and leaf extract, respectively). The 7.5% extract (either leaf or flower) reduced root length to zero in A. retroflexus and T. officinale. However, in Lepidium sativum, there was a significant difference between leaf and flower extracts. At the same concentration (2.5%), leaf extract reduced fresh weight (0.43 g) more than the flower extract did (0.68 g). Taraxacum officinale and Amaranthus retroflexus showed a significant increase in the fresh weight of seedlings (0.2 g and 0.06 g, respectively) in response to the leaf extract (2.5%), compared to the control treatment, which indicates a stimulatory effect. In contrast, the highest concentration (7.5%) caused a significant inhibition (P ≤ 0.05%).