Green tea extract by virtue of its content of catechins, particularly epigallocatechin gallate (EGCG) is valued as a topical antioxidant. The stability of epigallocatechin gallate in dermatological and cosmetic formulations, prepared as creams and gels, determines its functionality as an antioxidant.1

A recent study sponsored by Sabinsa Corporation, explored the compatibility of EGCG with selected excipients that are commonly used in creams and gels. For the gel base, Carbopol 934 P at pH 3.5 (gelling agent) along with propylene glycol (vehicle) and isopropyl palmitate (emollient) were found to be compatible with EGCG. Based on stability studies in this system, the recommended level of EGCG in gel formulations for antioxidant skin care is 1.5%. Such formulations would remain shelf stable, with negligible loss in biological activity, for a period of twelve months at room temperature.

Source: 

D’Amelio, F.S. (1999) Botanicals:
A Phytocosmetic Desk Reference. CRC Press: Boca Raton, Fl.
pgs. 122-123.

Sabinsa Corporation supplies a cosmetic grade 75% Green Tea Extract standardized for epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate.