Role of phenolic compounds release by Peganum harmala L. on germination and growth suppression of Convolvulus arvensis L.

Peganum harmala L. (Zygophyllaceae) is a medicinal herb with a wide range of pharmacological properties [1]. In traditional medicine, various parts of the plant are used to treat several diseases [2]. In order to search for new integrated strategies to improve weed management, we investigated potential herbicidal activity of P. harmala against Convolvulus arvensis. Sixteen g of fresh P. harmala leaves were soaked in 100ml distilled water for 24h. After filtering and centrifuging, the extract was diluted with sterile distilled water to concentrations of 4, 8, 12 and 16% (w/v). Fifteen seeds of C. arvensis were placed in Petri dishes containing 5ml of each P. harmala extract (or distilled water for control). Results indicate that in 8, 12 and 16% extract concentrations, a significant reduction in germination, seedling length, seedling dry weight and total chlorophyll content of C. arvensis was obtained when compared to control. In general, the effect was concentration-dependent whereas there was a significant correlation between each parameter and extract concentration. The adverse effect on C. arvensis indicates the presence of some water-soluble inhibitory substances in P. harmala aqueous extract. Upon HPLC analysis, seven phenolic compounds were identified in the extract. Between these phenolics, 4- hydroxybenzoic was present in maximum amount followed by caffeic acid and ferulic acid. The study concluded that P. harmala aqueous extract exerted phytotoxicity effect on germination and growth of C. arvensis, possibly by releasing water-soluble phenolic acids.

Acknowledgements: This research was supported by project MSM 6046070901.

References: [1] Kartal, M. et al. (2003)J. Pharm. Biomad. Anal. 31:263–269.

[2] Agedilova, M.T. et al. (2006) Chem. Nat. Comp. 42:226–227.