Antibacterial activity of native plants from Northwest Argentina against phytopathogenic bacteria.

Extracts from aerial parts of medicinal plants from northwest Argentina were screened for antibacterial activity against the phytopathogenic strains namely CECT 124 ( Pseudomonas corrugata ), CECT 126 ( P. syringae pv. tomato ), CECT 225 ( Erwinia carotovora var. carotovora ), CECT 472 ( Agrobacterium tumefaciens ) and CECT 792 ( Xanthomonas campestres pv. vesicatoria ). Leaves and stems of Aspidosperma quebracho-blanco , Schinus fasciculatus , S. gracilipes , Amphilophium cynanchoides and Tecoma stans were separately extracted with solvents of increasing polarity to obtain the dichloromethane (fCH ₂ Cl ₂ ), ethyl acetate (fEtAc) and methanol extracts (fMeOH), respectively. Among the thirty extracts tested, only fEtAc from leaves and stems of S. fasciculatus reached the IC ₅₀ against the five bacterial strains tested (IC ₅₀  = 0.9 mg/ml). The fEtAc from the leaves contained kaempferol, quercetin and agathisflavone which had moderate to strong antibacterial activity. This extract and its identified flavonoids showed synergic (CECT 124,126 and 792) or additive effects (CECT 472 and 225) in mixtures with Kocide 3000.