Abstract:
BACKGROUND: Plants of the genus Maytenus belong to the family Celastraceae and are widely used in folk medicine
as anti-tumour, anti-asthmatic, analgesic, anti-inflammatory, antimicrobial and anti-ulcer agents, and as a treatment
for stomach problems. The aim of this study was to isolate and identify active compounds with antifungal activity
from Maytenus undata after a preliminary study highlighted promising activity in crude extracts.
METHODS: Sequential extracts of M. undata leaves prepared using hexane, dichloromethane (DCM), acetone and
methanol (MeOH) were tested for activity against Cryptococcus neoformans, a fungal organism implicated in
opportunistic infections. Bioassay-guided fractionation of the hexane extract using C. neoformans as test organism
was carried out to isolate antifungal compounds. The cytotoxicity of compounds isolated in sufficient quantities
was evaluated using a tetrazolium-based colorimetric cellular assay (MTT) and a haemagglutination assay (HA).
RESULTS: The hexane extract was most active with an MIC of 20 μg/ml against C. neoformans. The triterpene
compounds friedelin (1), epifriedelanol (2), taraxerol (3), 3-oxo-11α-methoxyolean-12-ene-30-oic acid (4), 3-oxo-11α-
hydroxyolean-12-ene-30-oic acid (5) and 3,11-dihydroxyolean-12-ene-30-oic acid (6) were isolated. Compound 6 was
isolated for the first time from a plant species. The antimicrobial activity of compounds 1, 3, 5 and 6 was
determined against a range of bacteria and fungi implicated in opportunistic and nosocomial infections.
Compounds 5 and 6 were the most active against all the tested microorganisms with MIC values ranging between
24 and 63 μg/ml, except against Staphylococcus aureus which was relatively resistant. Compounds 1 and 3 had a
low toxicity with an LC50 > 200 μg/ml towards Vero cells in the MTT assay. Compounds 5 and 6 were toxic with
LC50 values of 6.03±0.02 and 2.98±0.01 μg/ml, respectively. Compounds 1 and 3 similarly were not toxic to the red
blood cells (RBCs) but compounds 5 and 6 were toxic, showing HA titer values of 1.33 and 0.67 respectively.
CONCLUSIONS: Compounds 5 and 6 were the most active but were also relatively cytotoxic to monkey kidney cells
and red blood cells, while the other isolated compounds were less active and less cytotoxic.
