Isolation, Characterization, and Assessment of the In Vitro Antibacterial and Antifungal Properties of Methanol Extracts and Friedelan-3-one from Uapaca ambanjensis (Leandri)

Abstract

Uapaca ambanjensis Leandri (Phyllanthaceae) is a largely un-researched plant whose crushed stem bark, leaf, and fruit infusions are ethno-medicinally claimed to cure typhoid fever, other fevers, skin diseases, and stroke. This work aimed at the isolation, characterization, and determination of antimicrobial potency of the methanol stem-bark extracts of Uapaca ambanjensis.  Phytochemical screening revealed the presence of alkaloids, glycosides, flavonoids, tannins, saponins, steroids and triterpenes in the methanol extract. The antimicrobial assessment of the extract against Salmonella typhi, Staphylococcus aureus, Streptococcus pyogenes, Klebisiela pneumoniae, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger showed the diameter of zones of inhibition (ZOI) ranging from 11 to 18 mm at a concentration of 12.5mg/mL to 100mg/mL, with most prominent activities against S. aureus, S. typhi and P. aeruginosa. Chromatographic fractionation and purification led to the isolation of a pentacyclic triterpenoid (friedelan-3-one) labeled G23f-9. The compound showed antimicrobial potency evidenced by zones of inhibition against S. aureus (20 mm), S. typhi (16 mm), S. pyogenes (14 mm), K. pneumoniae (13 mm), and P. aeruginosa (13 mm) at a concentration of 100 µg/mL while the values for the standard drug, Ciprofloxacin, at 10 µg/mL are respectively 24 mm, 20 mm, 27 mm`1,20mm and 18mm. The Minimum Inhibitory Concentrations (MIC) were 12.5 µg/mL for S. aureus, 25 µg/mL for S. typhi and 100 µg/mL for the rest while the Minimum Bactericidal Concentrations (MBC) were 50 µg/mL for S. aureus and 100 µg/mL for S. typhi. The isolated compound showed some antifungal activity against C. albicans with ZOI of 11 mm at 100µg/mL while the antifungal drug, Terbinafine, gave 30 mm at 30 µg/mL. Phytochemical and antimicrobial results lay credence to some ethnomedicinal claims on the plant including its use to treat typhoid fever and some skin diseases. The biological assessment of the methanol extract and isolated compound reveals that the plant could have antibacterial and antifungal potentials. The isolation of Friedelan-3-one is reported for the first time from the plant U. ambanjensis Leandri.