Antibacterial Potential of a New Endiandric Acid From <i>Beilschmiedia acuta</i> (Lauraceae) Against Drug‐resistant Bacteria

A previously unidentified endiandric acid derivative named beilschmiedic acid P (1), together with eight (2-9) known compounds including four pentacyclic triterpenoids (3-6), one amide (2) and, three steroids (7-9) were isolated from Beilschmiedia acuta stem barks. Chromatographic techniques were used for these isolations while their characterization was based on their one-/two-dimensional nuclear magnetic resonance and mass spectrometry experiments. The antibacterial activity of the new compound (1) was tested via INT colourimetric assay against nine bacterial strains all expressing multidrug-resistant phenotypes including Klebsiella pneumoniae (KP55), Escherichia coli (AG102 and ATCC8739), Pseudomonas aeruginosa (PA124 and PA01), Enterobacter aerogenes (EA27 and ATCC13048) and Providencia stuartii (PS2636 and ATCC29916). The activity was categorised based on the scale described by Kuete (2010), as significantly active for minimal inhibitory concentration (MIC) ≤ 10 µg/mL, moderately active for 10 µg/mL < MIC ≤ 100 µg/mL and weakly active for MIC > 100 µg/mL. The results showed a moderately active antibacterial activity of compound 1 at a rate of 77.78% (7/9) on the tested strains that is, seven out of the nine bacteria were sensitive to the action of the tested compound. Among the tested strains, E. coli (ATCC8739) showed the most efficient MIC value of 16 µg/mL.