Theasinensin A is polyphenol flavonoid from black tea (Camellia sinensis) created during fermentation, by oxidation of epigallocatechin gallate.
One important take-home is that theasinensin A is only poorly soluble in water & to get the best possible extraction must employ an alcoholic medium.
While it is known that EGCG has enjoyed use as a topical skincare product, a limitation of its use is that it is not very stable and has poor solubility in water. A recent patent states substituting EGCG for theasinensin A "provides wrinkle-reducing or skin elasticity-enhancing benefits, and skin-brightening benefits".
Its atropisomer is theasinensin D.
See also Theasinensin B Theasinensin C Theasinensin D Theasinensin E Theasinensin F Theasinensin G
References