Antimicrobial and antioxidant activities of extracts and ten compounds from three Cameroonian medicinal plants : Dissotis perkinsiae (Melastomaceae), Adenocarpus mannii (Fabaceae) and Barteria fistulosa (Passifloraceae)

BACKGROUND : We decided to investigate the antimicrobial and the antioxidant activities of extracts and compounds
isolated from Dissotis perkinsiae, Adenocarpus mannii and Barteria fistulosa, three Cameroonianmedicinal
plants used for the treatment of skin diseases, wounds, fever, rheumatism, malaria and/or infectious diseases.
METHODS : Standard chromatographic and spectroscopic methods were used to isolate and identify ten compounds
from the three plant species [1–5 (from D. perkinsiae), 2, 6–8 (from A. mannii) and 2, 4, 9, and 10
(fromB. fistulosa)]. A two-fold serial microdilutionmethod was used to determine the minimuminhibitory concentration
(MIC) against a panel of fungal and bacterial species. The radical scavenging capacity using 2,2-
diphenyl-1-picryhydrazyl (DPPH) was determined to evaluate the antioxidant activity of the samples.
RESULTS : The compounds isolated were: ursolic acid (1), oleanolic acid (2), quercetin 3-O-(6″-O-galloyl)-
β-galactopyranoside (3), 3-O-β-D-glucopyranoside of sitosterol (4), ellagic acid (5), isoprunetin (6), chrysin 7-O-
β-D-glucopyranoside (7), isovitexin (8), hederagenin (9) and shanzhiside methyl ester (10). The ethanol extract
of D. perkinsiae had good antibacterial activity against Enterococcus faecalis (MICs 0.04 and 0.08 mg/ml),
Escherichia coli (MIC 0.08 mg/ml) and Staphylococcus aureus (MIC 0.08 mg/ml). The extract of B. fistulosa had significant
antifungal activity against Cryptococcus neoformanswith an MIC of 0.08 mg/ml. Other extracts hadmoderate
to poor antimicrobial activities with the MIC ranging from 0.16 to 2.50 mg/ml. The isolated compounds
were generally more active against bacteria (MIC ranging from 16 to 250 μg/ml) than fungi (MIC between 31
and 250 μg/ml). Moderate antibacterial activity was obtained with compound 3 against E. faecalis and E. coli
(MIC of 16 μg/ml in both cases), compounds 6 and 10 against E. faecalis (MIC of 16 μg/ml), and compound 9
against E. faecalis (MIC 31 μg/ml) and S. aureus (MIC 31 μg/ml). The B. fistulosa extract had the greatest radical
scavenging activity (IC50 100.16 μg/ml) followed by extracts of D. perkinsiae (IC50 130.66 μg/ml), and A. mannii
(IC50 361.30 μg/ml). Compounds 3 and 5 had significant antioxidant activities with the IC50 of 9.84 and
9.99 μg/ml as compared to that of ascorbic acid (IC50 2.41 μg/ml).
CONCLUSION : The results obtained support the traditional use of the three plant species (D. perkinsiae, A. mannii and
B. fistulosa) in traditional medicine for the treatment of infections. Some extracts and isolated compounds could
be useful in development of antimicrobial agents.We are currently investigating the toxicity and other pharmacological
activities with the potential use as topical antimicrobial agents.University of Dschang. The NRF and the University of Pretoria for the Postdoctoral Fellowship awarded to work at the Phytomedicine Programme, Department of Paraclinical Sciences, Faculty of Veterinary Science.http://www.elsevier.com/locate/sajbhb201