Antimicrobial activity and total content of polyphenols of Rheum L. species growing in Poland

Abstract

In the crude ethanol extracts obtained from the rhizome and roots of Rheum palmatum L., Rheum undulatum L. and Rheum rhaponticum L. growing in Poland concentration of polyphenols ranged from 46.11 to 76.45 mg/g. Concentration of tannins ranged from 7.07% to 8.67%, while anthracene derivatives and anthraquinones varied by species - R. palmatum measured 36.3 and 34 mg/g, while R. undulatum or R. rhaponticum did not exceed 20.4 and 18.1 or 19.8 mg/g and 16.6 mg/g, respectively. Using a broth microdilution method it was found that all of the Rheum spp. extracts were more active against reference strains of Gram-positive bacteria (Staphylococcus spp.) than against those of Gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Proteus mirabilis). The strongest inhibitory effect against Staphylococcus spp. was exerted by R. undulatum extract with MIC = 125–250 μg/mL. The moderate in vitro antibacterial activity of R. undulatum suggests that this plant, often used in the European cuisine to improve flavour, may be also important and useful as an alternative or auxiliary medicine remedy in the treatment of uncomplicated superficial infections caused especially by clinically important staphylococci, potentially pathogenic S. aureus or opportunistic S. epidermidis.