Proanthocyanidins from Lotus corniculatus

The chemical structure of the purified proanthocyanidin polymers of Lotus corniculatus was analysed by C-13 NMR and by mild acid catalysed degradation in the presence of excess of phloroglucinol. The NMR data showed that the polymer was partially glycosidated with a number average M(r) in the range 1800-2100 (six to seven flavanoid units). The products from phloroglucinol scission reaction indicated the extender flavan units to consist mostly of epicatechin (67%) and epigallocatechin (30%), with minor amounts of catechin and epiafzelechin units, which were linked together predominantly by C-4/C-8 interflavanoid bonds. The polymer chains were terminated mostly by catechin (83%) and, to a lesser extent, by epicatechin (16%).