Antioxidant activity, phenols and flavonoids contents and antibacterial activity of some Moroccan medicinal plants against tomato bacterial canker agent

Abstract

Medicinal and aromatic plants (MAP) belonging to 16 species, currently used in southern Moroccan traditional medicine, were evaluated here, firstly, for the action of their aqueous extracts against the bacterial canker agent of tomato in vitro. Then the phenolic contents, flavonoids contents and antioxidant capacities of these MAP extracts were estimated. Results obtained show that tested species exhibited biological activity toward the pathogen studied here; the inhibition zone diameter was between 0.5 and 4.88 cm. Furthermore, tested species exhibited a board range of phenolic contents varying from 55.58 ± 5.07 to 3.98 ± 0.16 mg of Cafeic acid equivalents (CAE) per gram of dry weight (DW). The flavonoids contents varied from 19.82 ± 0.65 to 1.74 ± 0.34 mg of Rutine equivalents (RE) per g of DW. Significant and positive linear correlations were found between total phenolic contents (R = 0.87 and R² = 0.76), flavonoids contents (R = 0.96 and R² = 0.93) and the biologic activity (IZ diameters) of the aqueous extracts. The antioxidant capacity expressed as Trolox equivalents antioxidant capacity (TEAC) varied from 550.67 to 1.18 mM per 100 g dry weight. Significant and positive linear correlation was found also between antioxidant capacities and both phenolic and flavonoids contents. These results proved that the richness of MAP with phenols and flavonoids was involved in there antibacterial activity and there antioxidant capacity. This finding is useful and can contribute to the development of potent and natural bio pesticides in the future for the control of bacterial canker of tomato as well as other phytopathogens by exploiting MAP compounds accepted by consummators and environmentalists.

Keywords: Bacterial canker, tomato, medicinal plants, biological control, flavonoids, Trolox equivalents antioxidant capacity (TEAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH).

African Journal of Biotechnology, Vol 13(49) 4515-4522