Antibacterial potential assessment of Nalca ( Gunnera tinctoria Mol.) ethanolic extracts

Nalca is an edible rhubarb-type plant from the southern of Chile; with studies focussing on petiole chemical and biological properties. This work evaluated for the first time the antibacterial capacities of three organs of nalca against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Petiole (P), root (R) and flower (F) ethanolic extracts at three different concentrations (25, 50, 100 mg/mL) were evaluated by means of agar diffusion assay and MIC. The result showed that antibacterial activities are bacteria and concentration dependent, with root having the highest antimicrobial activity of the organs plant studied. Compared to commercial antibiotics, nalca extracts show promising control over Ps. aeruginosa. The main polyphenolics of the extracts were identified by UPLC-MS/MS, observing for the first time caffeic, coumaric and gallic acids presence in all samples, with quercetin and rutin determined in petiole and flower extracts only. Our results contribute to better understanding of nalca attributes as potential source of antibacterial compounds to be used in nutraceutical, cosmetic and food industry.

Keywords: Gunnera tinctoria Mol.; agar diffusion; antimicrobial activity; bioactive extracts; minimum inhibitory concentration.