Characterization of anthocyanins and proanthocyanidins in wild and domesticated Mexican blackberries (Rubus spp.)

This study was designed to characterize and compare wild, commercial, and noncommercial cultivated blackberry genotypes grown in Michoacan, Mexico. Six genotypes, including WB-3, WB-7, WB-10, and WB-11 (all wild blackberry types), Tupy (a commercial cultivar), and UM-601 (a cultivated breeding line), were selected and profiled for anthocyanins and proanthocyanidins by separating extracts over Amberlite XAD-7 resin and Sephadex LH-20 columns. Subsequent high-performance liquid chromatography (HPLC) and liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) analyses revealed that the major anthocyanin for all genotypes was cyanidin 3-O-glucoside. The proanthocyanidins (condensed tannins) were present in mono- to hexamer forms. Also, hydrolyzable tannins, ellagitannins, were characterized in the blackberry fruits. The average anthocyanin concentration in Sephadex LH-20 fractions was 49.2 mg/g in the commercial cultivar Tupy, while in the wild genotypes and the breeding line, the range was 361.3-494.9 mg/g (cyanidin 3-O-glucoside equivalent). The proanthocyanidin concentration varied widely among wild genotypes (417.5-1343.6 mg/g, catechin equivalent). This study demonstrated that the use of Amberlite XAD-7 followed by Sephadex LH-20 chromatography, with subsequent HPLC and LC-ESI-MS analyses, was able to effectively separate and characterize the diverse polyphenolics in blackberry genotypes. These results suggest that recommendations for dietary intake of blackberries for human health benefits need to take into account the source, because of the wide inherent variation in bioactive polyphenolic content in different blackberry genotypes.