Characterization of Antibacterial Proanthocyanidins ofDalbergia monetaria, an Amazonian Medicinal Plant, by UHPLC-HRMS/MS

Dalbergia monetariais an Amazonian plant whose bark is widely used to treat urinary tract infections. This paper describes a bio-guided study of ethanolic extracts from the bark and leaves ofD. monetaria, in a search for metabolites active against human pathogenic bacteria.In vitroassays were performed against 10 bacterial strains, highlighting methicillin-sensitiveStaphylococcus aureusand methicillin-resistantStaphylococcus aureusandPseudomonas aeruginosa. Fractioning of the extracts was performed using instrumental and classical techniques, and samples were characterized by UHPLC-HRMS/MS. Ethyl acetate fractions from bark and leaves showed similar antibacterial activities. EAFB is enriched in isoflavoneC-glucosides and EAFL enriched in proanthocyanidins. Subfractions from EAFL presented higher activity and showed a complex profile of proanthocyanidins constructed by (epi)-cassiaflavan and (epi)-catechin units, including dimers, trimers and tetramers. The fragmentation pattern emphasized the neutral loss of cassiaflavan units by quinone-methide fission. Fraction SL7-6, constituted by (ent)-cassiaflavan-(ent)-cassiaflavan-(epi)-catechin isomers, showed the lowest MIC against theS. aureusandP. aeruginosawith values corresponding to 64 and 32 mu g/mL, respectively. Cassiaflavan-proanthocyanidins have not been found previously in another botanical genus, except inCassia,and the traditional medicinal use ofD. monetariamight be related to the antibacterial activity of proanthocyanidins characterized in the species.