Croatian barberry (Berberis croatica Horvat): a new source of berberine—analysis and antimicrobial activity

By using HPLC/UV–VIS, Croatian barberry (Berberis croatica Horvat) was found to be a new source of the bioactive alkaloid berberine. Comparison of berberine content in roots, leaves, and twigs between wild specimens of B. croatica and B. vulgaris collected in Croatia showed that the roots of both species contained the highest berberine content (B. croatica 1.120–1.217%; B. vulgaris 0.805–1.424%), followed by twigs (B. croatica 0.049–0.216%; B. vulgaris 0.077–0.112%). While the berberine content in the leaves of both species was very low (between 0.002% and 0.044%), they were found to be rich in phenols and flavonols. The Student’s t-test showed a significant difference at P < 0.05 for phenol and flavonol content in the plant organs, both between species and within species. Leaf samples were most variable, while root samples were the least. Extracts from the roots of both barberry species expressed antimicrobial activity against Bacillus subtilis NCTC 8236, Staphylococcus aureus ATCC 6538, Escherichia coli ATCC 10535, Pseudomonas aeruginosa ATCC 27853 and Candida albicans ATCC 10231. Antimicrobial activity of leaf extracts was species-dependent. Root extracts of both species also showed lower MIC values than other extracts (MIC ≤ 87.5 mg/ml).