Antibacterial and cytotoxic activity of compounds isolated from Flourensia oolepis

JORAY M.B.; TRUCCO L.D.; GONZÁLEZ M.L.; DIAZ NAPAL, G.N.; PALACIOS S. M.; BOCCO J.L.; CARPINELLA M. C.

EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2015 vol. 2015 p. 1 - 11

1741-427X

In our ongoing effort to identify therapeutic agents of plant origin, we evaluated the antibacterial and cytotoxic effects of metabolites isolated from an antibacterial extract of Flourensia oolepis, a bush native to Argentina, the therapeutic properties of which have not yet been thoroughly explored.Bioguided fractionation of this extract led to the isolation of five flavonoids, identified as 2´,4´-dihydroxychalcone (1), isoliquiritigenin (2), pinocembrin (3), 7-hydroxyflavanone (4) and 7,4´-dihydroxy-3´-methoxyflavanone (5). The susceptibility of reference and clinical strains of Enterococcus faecalis, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa and Staphylococcus aureus to the isolated compounds was evaluated by agar and broth dilution methods. Compound 1 showed the highest antibacterial effect, with minimum inhibitory concentration (MIC) values ranging from 31 to 62 and 62 to 250 g/mL, against Gram-positive and -negative bacteria, respectively.On further assays, the cytotoxic effect of compounds 1-5 was determined by MTT assay on the leukemia cell lines CCRF-CEM and K562, and their respective multidrug resistant (MDR) counterparts, CEM/ADR5000 and Lucena 1, as well as on HEK293T and peripheral blood mononuclear cells (PBMC). Compound 1 was the most potent, inducing considerable cytotoxic activity toward CCRF/CEM and CEM/ADR5000 (IC50 = 6.6 and 9.9 M, respectively) and a lower effect against K562 and Lucena 1 (IC50 = 27.5 and 30.0 M, respectively). These results were confirmed by trypan blue exclusion test. The lower antiproliferative activity of 1 observed in HEK293T and PBMC (IC50 = 67.0 and 82.8 M, respectively) evidenced a selective effect, based on the selectivity indexes calculated (SI = IC50 in non-target cells/IC50 tumor cells). In order to elucidate the underlying mechanism of compound 1-induced antiproliferative activity, flow cytometry was used to analyze cell cycle distribution and cell death by PI-labeled cells and by Annexin V/PI staining, respectively.Upon treatment at two-fold IC50, 1 induced cell cycle arrest in the G2/M phase in both CCRF-CEM and K562 cells, accompanied by a strong induction of apoptosis. The present results describe for the first time the metabolites responsible for the antibacterial effect of F. oolepis extract, with 1 being the most effective. This chalcone also emerges as a selective cytotoxic agent against sensitive and resistant leukemic cells, highlighting its potential as a lead compound.