Effects of tannins and related polyphenols on methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) often acquires multi-drug resistance and is involved in many cases of disease in hospitals. We investigated natural substances directly effective against MRSA or that influence antibiotic resistance. Aloe-emodin, an anthraquinone, and several licorice flavonoids showed potent antibacterial effects against MRSA. Like some hydrolysable tannins (corilagin and tellimagrandin 1) and a tea polyphenol [(-)-epicatechin gallate], the licorice flavonoid licoricidin also restored the effects of oxacillin, a beta-lactam antibiotic against MRSA. Further study revealed that theasinensin A, a polyphenol formed from (-)-pigallocatechin gallate, proanthocyanidins obtained from fruits of Zizyphus jujuba var. inermis, and polymeric proanthocyanidins from fruit peels of Zanthoxylum piperitum also suppressed the antibiotic resistance of MRSA. (c) 2005 Elsevier Ltd. All rights reserved.