Transdermal delivery of (-)-epigallocatechin-3-gallate, a green tea polyphenol, in mice

Epigallocatechin-3-gallate (EGCG) is the most studied catechin in green tea (Camellia sinensis). EGCG and green tea are cancer preventive in many animal models, and numerous mechanisms have been proposed in cell lines. EGCG is poorly bioavailable in man and rodents. We hypothesized that transdermal delivery of EGCG could result in improved bioavailability. Following application of EGCG transdermal gel (50 mg kg^-1, t.d.) to SKH-1 mice, EGCG was observed in the epidermis (1365.7-121.0 ng g^-1) and dermis (411.2-42.6 ng g^-1). The maximum plasma concentration (C_max) of EGCG was 44.5 ng mL^-1. The t1/2 (94.4 h) and AUC_0→24h (881.5 ng mL^-1 h) of EGCG were greater than values previously reported for oral EGCG. The t1/2 and area under the concentration-time curve up to 24h (AUC_0→24h) in the liver, small intestine and colon were 21.3-74.6 h and 715-2802 ng g^-1 h, respectively. Stability studies showed that the transdermal formulation was stable at 4°C and had a half-life (t1/2) of 47.1 and 20.2 h at 25°C and 37°C, respectively. These data indicate that transdermal EGCG is useful for delivering prolonged levels of EGCG to plasma and tissues, and may provide an alternative to tea consumption as a dosage form of EGCG.