Biflavonoids from Allanblackia floribunda pods: Antibacterial activity and molecular docking analysis

A phytochemical investigation of the aqueous-MeOH extract of Allanblackia floribunda (Guttifereae) pods was conducted to isolate five compounds (1-5). The structures were established based on the interpretation of their HRMS-ES, HRMS-LD⁺ and NMR data. The absolute configurations of 1-3 were determined using DFT-based ECD (electronic circular dichroism) data. To explore the therapeutic potential of this plant for microbial diseases, the inhibitory and cytotoxic activities of the extract and the isolated compounds were evaluated against a panel of human pathogens. An in silico molecular docking study was performed on isolated compounds using the DNA gyrase-bound crystal structures 7C7N and 5CDP, enzymes implicated against E. coli and S. aureus resistance. Three unreported compounds i.e. (+)-nlongboflavone A (1), (+)-nlongboflavone B (2) and florinone (3), together with two known compounds: morelloflavone (4) and morelloflavone-7"-O-β-glucopyranoside (5) were identified. Potent activity against Staphylococcus aureus NR 46003 was observed for the crude extract, ethyl acetate and residual fractions, with MICs of 12.5, 10.60 and 16.34 μg/mL as well as (+)-nlongboflavone A (1), also exhibited activity at 17.5 μM. Compound (1) exhibited a favorable binding energy (ΔG = -11.7 kcal/mol) against S. aureus DNA gyrase, suggesting that its antibacterial activity may be mediated through DNA gyrase inhibition. This research supports the traditional use of Allanblackia floribunda to treat microbial ailments.