Antibacterial Proanthocyanidins of Dalbergia monetaria, an Amazonian Medicinal Plant.
A team of chemists from the IPB and the University of Rio de Janeiro (Brazil) recently published a bioassay-guided study (de Moura et al., 2020) of ethanolic extracts from Dalbergia monetaria, in a search for metabolites active against human pathogenic bacteria. D. monetaria is an Amazonian plant whose bark is widely used to treat urinary tract infections. Such infections can be caused by different bacteria, including Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus.
Building on this ethnobotanical knowledge, the researchers performed in vitro assays with D. monetaria extracts against ten bacterial strains, fractioned the extracts, and characterized the samples by UHPLC-HRMS/MS. While subfractions from both leaves and bark exhibited antibacterial activities, that of leaves was higher and its characterization revealed a complex profile of proanthocyanidins made up of (epi)-cassiaflavan and (epi)-catechin units, including dimers, trimers and tetramers. The researchers were able to identify a specific fraction consisting of (ent)-cassiaflavan-(ent)-cassiaflavan-(epi)-catechin isomers with a minimum inhibitory concentration in the low micromolar range (64 and 32 µg/mL, respectively) against S. aureus and P. aeruginosa.
Cassiaflavan-proanthocyanidins have not been found previously in another botanical genus, except in Cassia, and the authors conclude that the traditional medicinal use of D. monetaria might be related to the antibacterial activity of proanthocyanidins characterized in the species.
Original publication:
de Moura PHB, de Sousa AA, Porzel A, Wessjohann LA, Leal ICR, Martins RCC. Characterization of Antibacterial Proanthocyanidins of Dalbergia monetaria, an Amazonian Medicinal Plant, by UHPLC-HRMS/MS. Planta Med. 2020;86(12):858-866. doi:10.1055/a-1170-8016