Antibacterial activity of native plants from Northwest Argentina

ZAREATH TERÁN BAPTISTA; PEDRO AREDES FERNANDEZ; CESAR CATALAN ; SYLVIE MICHEL ; MARINA KRITSANIDA; RAPHAËL GROUGNET; DIEGO SAMPIETRO

Lille

Congreso; Trends in Natural Product Research ? PSE Young Scientists? Meeting Lille 2017; 2017

Phytochemical Society of Europe

Copper compounds and antibiotics are often worldwide used for the control of phytopathogenic bacteria. They have a preventive more than a curative action and have showed adverse environmental impacts. New antibacterial constituents are needed. This work aims to: 1) assay the antibacterial activity of extracts from native plants of northwest Argentina on several phytopathogenic bacteria, and 2) elucidate the structure of antibacterial agents found in the most bioactive extracts. Stems and leaves from Aspidosperma quebracho-blanco, Schinus fasciculatus, S. gracilipes, Amphilophium cynanchoides and Tecoma stans were sequentially extracted with dichloromethane, ethyl acetate and methanol, yielding fCH2Cl2, fAcet and fMeOH extracts respectively, from stems orleaves. The antibacterial activity of the extracts was assayed by the microdilution method (4000-2.9 ppm) and dot blot bioautography (50 μg) on Pseudomonas corrugata (Pc), P. syringae (Ps), Xanthomonas campestris (Xc), Erwinia carotovora (Ec) and Agrobacterium tumefaciens (At). The concentration needed for 50% of bacterial growth inhibition (IC50) and the diameter of growthinhibition (D) were calculated.The fAcet and fMeOH of S. fasciculatus and S. gracilipes significantly inhibited the growth of Ps, Xc, Ec and At with IC50 = 800-1700 ppm and D = 1.90-4.79 cm. The fCH2Cl2 of S. fasciculatus inhibited Xc(IC50: 900-1100 ppm; D = 2.10-3.45 cm). The fAcet of A. cynanchoides inhibited Pc (IC50: 1600 ppm; D = 2.35 cm) and At (IC50: 2100 ppm; D = 2.60 cm). A principal component analysis indicated that the fAcet from leaves and stems of S. fasciculatus were the most active extracts. Antibacterial constituents were isolated from the fAcet of the S. fasciculatus leaves by silica gel chromatography and identified by NMR as kaempferol, quercetin and a dimer of luteolin. Further investigations are inprogress to determine which other metabolites are responsible for the observed antibacterial activity.