Isolation and structural elucidation of anthocyanidin 3,7-β-O-diglucosides and caffeoyl-glucaric acids from calafate berries.

Calafate (Berberis microphylla G. Forst) is an edible wild berry growing in South Patagonia that is very rich in anthocyanins and hydroxycinnamic acid derivatives. Calafate contains unusual phenolic compounds compared to other berries, such as anthocyanidin dihexosides, different from the common 3,5-diglucosides, and isomeric esters of caffeic acid with hexaric acids. After isolation, their structures have been elucidated by UV-vis, MS/MS, and NMR spectroscopies. The anthocyanidin dihexosides constitute the complete series of 3,7-β-O-diglucosides of the five anthocyanidins usually found in calafate, the structures of which were completely elucidated in the cases of delphinidin, petunidin, and malvidin derivatives and tentatively suggested in the cases of cyanidin and peonidin, and their occurrence seems to be characteristic of calafate among other wild berries from South Patagonia. With regard to caffeoyl-hexaric acids, two of four isomers have been assigned as 3- and 4-trans-caffeoyl-glucaric acids, but the determination of the linkage position for each isomer was not possible. A third isomer was also isolated, but it easily degraded and was suggested to be the 2- or 5-trans-caffeoyl-glucaric acid. The caffeoyl-glucaric acids account for around half of the pool of hydroxycinnamic acid derivatives in calafate.