Collagen and polyphenols: new relationships and new outcomes. Part 1. Flavanoid reactions for new tanning processes

The process of vegetable tanning is hindered by the astringency of the tannins, which affects the development of their use as organic tanning agents for modern purposes. The use of non tans, either from natural sources such as green tea or by degrading tannins into non tannins, avoids the problem of hindered penetration through pelt due to the high reactivity of the polyphenols. Both tannins and non tannins are capable of engaging in combination tannage with aldehydic agents, to confer high hydrothermal stability to collagen. The use of prodelphinidin or prorobinetinidin polyphenols, characterized by the presence of a pyrogallol B-ring, is preferred in this context. Also, the use of non tannins provides a practical route to modem organic tanning.