Chemico-biological aspects of (−)- epigallocatechin- 3 -gallate (EGCG) to improve its stability, bioavailability and membrane permeability: Current status and future prospects

Natural products have been a bedrock for drug discovery for decades. (-)-Epigallocatechin-3-gallate (EGCG) is one of the widely studied natural polyphenolic compounds derived from green tea. It is the key component believed to be responsible for the medicinal value of green tea. Significant studies implemented in in vitro, in cellulo, and in vivo models have suggested its anti-oxidant, anti-cancer, anti-diabetic, anti-inflammatory, anti-microbial, neuroprotective activities etc. Despite having such a wide array of therapeutic potential and promising results in preclinical studies, its applicability to humans has encountered with rather limited success largely due to the poor bioavailability, poor membrane permeability, rapid metabolic clearance and lack of stability of EGCG. Therefore, novel techniques are warranted to address those limitations so that EGCG or its modified analogs can be used in the clinical setup. This review comprehensively covers different strategies such as structural modifications, nano-carriers as efficient drug delivery systems, synergistic studies with other bioactivities to improve the chemico-biological aspects (e.g., stability, bioavailability, permeability, etc.) of EGCG for its enhanced pharmacokinetics and pharmacological properties, eventually enhancing its therapeutic potentials. We think this review article will serve as a strong platform with comprehensive literature on the development of novel techniques to improve the bioavailability of EGCG so that it can be translated to the clinical applications.