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

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 R 6 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. [Display omitted] • Three phenolic compounds were isolated and characterized from Phyllanthus emblica. • The phenolic compounds showed promising antibacterial activity against S. scabies. • SAR study showed carboxyl substituents of gallic acid affected bactericidal activity. • Gallic acid analog pyrogallol showed the strongest bactericidal activity. • Gallic acid and analogs damaged membrane integrity and permeability of S. scabies. [ABSTRACT FROM AUTHOR]