Cai Y  et. al. (1991) “”Biological and Chemical Investigations of Dragon’s Blood from Croton Species of South America” Part 1. Polyphenolic compounds from C. lecheri.” Phytochemistry 30(6), 2033-40.

Abstract: The blood-red sap of Croton lechleri was found to contain proanthocyanidins as major constituents which accounted for up to 90% of the dried weight. In addition to (+)-catechin, (−)-epicatechin, (+)-gallocatechin, (−)-epigallocatechin and dimeric procyanidins B-1 and B-4, five novel dimers and trimers were isolated and characterized as catechin-(4small alpha, Greek→8)- epigallocatechin, gallocatechin-(4small alpha, Greek→8)-epicatechin, gallocatechin-(4small alpha, Greek→6)-epigallocatechin, catechin-(4small alpha, Greek→8)- gallocatechin-(4small alpha, Greek→8)-gallocatechin and gallocatechin-(4small alpha, Greek→8)-gallocatechin-(4small alpha, Greek→8)-epigallocatechin. Higher oligomers were also obtained. A new procedure combining chemical degradation with 1H NMR spectroscopy has been developed for determination of the composition and molecular size of oligomeric/polymeric proanthocyanidins. The oligomers of the sap were shown to have the mean degree of polymerization of 4,5–6 and 6–7, respectively, and Mr up to 2130. The heterogeneity of the oligomers was clearly indicated by the presence of a variety of flavan-3-ols as extension and terminal units. An exceptionally high content of gallocatechin and epigallocatechin in the oligomers was observed.