Phytochemical and antimicrobial study of Pilocarpus pennatifolius Lemaire

Abstract

The investigation of the crude extract of leaves and bark of Pilocarpus pennatifolius Lemaire allowed isolated of a not yet described coumarin, together with three known coumarins (bergapten, xanthotoxin and dimethyl allyl xanthyletin), and a not yet described imidazole alkaloid. All structures were established by means of spectral analysis, including extensive 2D NMR studies. In addition, the alkaloid had its absolute stereochemistry determined by X-ray diffraction. Meanwhile, extracts and pure compounds were tested against various strains of bacteria and fungi, showing promising antimicrobial activities. We highlight the activities of crude bark methanol extract (CBME), of the leaf basic acetate fraction (LBAcF), and of compound 2 against the Gram negative bacteria Shigella flexneri (MICs = 7.8, 7.8 and 3.12 μg·mL−1, respectively), of compound 5 against the Gram positive Enterococcus fecalis (MIC = 1.56 μg·mL−1), and against two Gram negative bacteria Salmonella enteritidis (MIC = 1.56 μg·mL−1), and Pseudomonas aeruginosa (MIC = 6.25 μg·ml−1). On the other hand, CBME and compounds 3–5 showed excellent activity against the fungus Candida krusei with MICs of 15.6, 1.56, and 3.12 μg·mL−1 respectively, as actives or better than the antifungal standard fluconazole (MIC = 3.12 μg·mL−1).