In vitro anti-yeast activity, kinetics and mechanism of action of essential oils from two cameroonian medicinal plants.

BACKGROUND: Treatment of Candida infections have become increasingly difficult due to antifungal drug resistance, which has drawn attention toward the search for innovative and effective drugs. This study aimed to assess the activity of essential oils (EOs) from Pentadiplandra brazzeana Baillon (PB) root and Drypetes gossweileri S. Moore (DG) stem bark against Candida albicans and Candida parapsilopsis strains, and determine their antifungal mechanism when tested alone or combined. METHODS: The anticandidal activity of the EOs using the checkerboard format was assessed using the broth micro-dilution technique. The checkerboard microtiter test was performed to evaluate the interaction of the EOs. The in vitro pharmacodynamics of the EOs alone or combined, using time-kill assays, following the chequerboard technique were evaluated. The anticandidal mode of action of these EOs, combined or not, was investigated using the sorbitol protection assay, and the ergosterol binding assay. Differences (p < 0.05) between the experimental and the control groups were evaluated using one way analysis of variance (ANOVA) followed by Tukey's test for multiple comparisons. RESULTS: Essential oils (EOs) from Drypetes gossweileri (DG) stem bark showed activity with MIC value of 62.5 µg/mL against Candida albicans and Candida parapsilopsis, whereas EOs from Pentadiplandra brazzeana (PB) root exhibited MICs of 125 µg/mL and 250 µg/mL against the respective yeasts. The EOs were fungicidal with synergism on C. parapsilopsis and additivity on C. albicans, with 2 to 64-fold drop in MIC values. The MIC combination of 31.25/7.81 µg/mL and 1.95/31.25 µg/mL (DG/PB EOs) required 20 and 18 h of exposure, respectively to effectively kill 99.9% of the inoculum. This fungicidal effect was accompanied by alteration of the cell walls and membranes of yeasts. CONCLUSION: The potency of the EOs combinations indicates further directions in their investigation as potential anticandidal agents.

Potent and Synergistic Extract Combinations from Terminalia Catappa, Terminalia Mantaly and Monodora tenuifolia Against Pathogenic Yeasts.

Mycoses caused by Candida and Cryptococcus species, associated with the advent of antifungal drug resistance have emerged as major health problems. Improved control measures and innovative therapies are needed. This paper describes results from the screening of bio-guided fractionated extracts alone and combinations of Terminalia catappa, Terminalia mantaly and Monodora tenuifolia harvested in Cameroon. Crude ethanolic, hydro-ethanolic and aqueous extracts and bio-guided fractions were screened for antifungal activity against isolates of C. albicans, C. glabrata, C. parapsilosis and Cr. neoformans and the reference strain C. albicans NR-29450. Minimal inhibitory concentrations (MIC) were determined using a broth micro dilution method according to the Clinical & Laboratory Standards Institute (CLSI). Time kill kinetics of extracts alone and in combination were also evaluated. Extracts from T. mantaly stem bark were the most active with the best MIC values ranging from 0.04 mg/mL to 0.16 mg/mL. Synergistic interactions were observed with combinations of sub-fractions from M. tenuifolia, T. mantaly and T. catappa. Combination of sub-fractions from M. tenuifolia and T. mantaly (C36/C12) showed synergistic interaction and fungicidal effect against four out of five tested yeasts. These results support further investigation of medicinal plant extracts alone and in combination as starting points for the development of alternative antifungal therapy.