Stryphnodendron adstringensstem bark is used to producetannins of the prorobinetinidins or prodelphinidins type. These are robinetinidol-(4β → 8)-epigallocatechin, robinetinidol-(4α → 8)-epigallocatechin, robinetinidol-(4β → 8)-epigallocatechin 3-O-gallate, robinetinidol-(4α → 8)-epigallocatechin 3-O-gallate, robinetinidol-(4α → 6)-gallocatechin and robinetinidol-(4α → 6)-epigallocatechin, in addition to the tentatively characterized, robinetinidol -gallocatechin and robinetinidol--gallocatechin.