Green tea polyphenols in the amelioration of osteoarthritis: Memoir on the preclinical observations

Green tea prepared from the plant Camellia sinensis is globally one of the highly consumed beverages. In addition to its use as a beverage, green tea has a long history of medicinal use, especially in the traditional Chinese system of medicine, and is used as a stimulant, a diuretic, an astringent, wound-healing agent, and to improve heart function. Other traditional uses of green tea include treating gas, regulating body temperature, regulating blood glucose, improving digestion, and improving the mental processes. Scientific studies carried out in the recent past have validated many of the ethnomedicinal observations and observations indicate that the validated properties are mediated predominately by the polyphenols epicatechin (EC), epigallocatechin (EGC), epicatechin-3-gallate (ECG), and epigallocatechin-3-gallate (EGCG). Of these, EGCG has been highly investigated and shown to be useful in mitigating numerous ailments. Preclinical studies have also shown green tea and its principal polyphenol EGCG to be useful in mitigating osteoarthritic and to mediate this by modulating multiple molecular pathways and end points responsible for the ailment. The current review compiles the validated observations by focusing on the mechanism responsible for the beneficial effects.