The Effect of Epigallocatechin gallate (EGCG) on Mycobacterium tuberculosis and Mycobacterium smegmatis

Objectives/Research questions: Epigallocatechin gallate (EGCG) is a major catechin (antioxidant) component of green tea. Recent studies have shown that it possesses many health benefits, including antimicrobial activity against some bacteria and viruses. Due to its known antimicrobial activity, this study focused on exploring the effects of EGCG on the growth of Mycobacterium tuberculosis, the causative agent of tuberculosis, as it remains a major public health concern. Through the use of a model mycobacterial species, Mycobacterium smegmatis, the experiments investigated the effects of varying concentrations of EGCG on mycobacteria.Methods: The effects of EGCG on the growth of M. tuberculosis and M. smegmatis were explored by setting up serial dilutions and carrying out cell counts over certain time periods. High Pressure Liquid Chromatography (HPLC) was used to fractionate the EGCG in order to better understand its behavior in the media.Results: The study has found that medium containing EGCG has anti-mycobacterial activity, but it is not EGCG itself that carries it out but a degradant molecule. This observation was achieved following experiments showing that a 3-day pre-incubation of EGCG in the medium strengthens its anti-mycobacterial activity. However, the HPLC showed that EGCG is fully degraded by day 1. Therefore, by day 3, there are only degradant molecules in the medium. Findings were consistent with an experiment which found that a pre-incubated green tea extract has more activity against the cells than a fresh one.Conclusions: A three day pre-incubation of green tea extract at 37°C enhances anti-mycobacterial activity, which may have implications in using green tea as a prophylactic agent.Implications for public health: If EGCG has antimicrobial activity green tea could be used as a prophylactic agent against Mycobacterium tuberculosis.