Structure-activity relationships of antimicrobial phenolic derivatives from Phyllanthus emblica against Streptomyces scabies

Abstract

Potato common scab is a soil-borne bacterial disease caused by Streptomyces scabies, which is ubiquitous and difficult to control. In this study, the issue of developing antimicrobial agents derived from plant extracts against S. scabies was addressed. Three bioactive phenolic compounds, named gallic acid, 1-O-galloyl-β-d-glucose, and corilagin, were isolated and identified from Phyllanthus emblica pomace through bioassay-guided fractionation. The antibacterial effects of these compounds on S. scabies were evaluated with MIC values of 0.63, 0.31, and 1.25 mg/mL, respectively. Furthermore, Structure-activity relationship analyses of 17 gallic acid and its structural analogs revealed that the R6 position of the benzene ring was a key factor to their antibacterial activity against S. scabies, among which pyrogallol had the best antibacterial effect. Scanning electron microscopy showed that when S. scabies was exposed to this gallic acid and its structural analogs, the cell membranes of which was damaged. The results will help promote the development and structural modification of plant-derived bacteriostatic agents.