Bio-guided investigation of a Cameroonian medicinal plant with anticandidal activity: Monotes kerstingii (Dipterocarpaceae)

Background: Fungal diseases including ringworms, vaginal candidiasis and infections of the mouth, throat, and esophagus kill million of people every year and affect over a billion people. This situation has increased the worries of the health authorities and the WHO which urgently recommends the search for new antifungal therapy to face this threat (Chen et al. 2020). The main objective of this work is bio-guided study of Monotes kerstingii, a plant used in the traditional folk medicine for the treatment of fungal infections.
Methods: The root of the plant was air dried, crushed and extracted using DCM/MeOH (1:1) and the extract obtained was screened for its antifungal activity against three Candida strains: C. albicans, C. parapsilosis and C. krusei using fluconazole as positive control to confirm its activity. The extract was then fractionated and the fractions submitted to anticandidal activity as well and further purified by the mean of usual chromatographic method. Their structures were determined using HRESIMS, 1D and 2D-NMR and their activities assessed as well.
Results: The root extract showed anticandidal activity against all the three tested strains with a MIC of 250 µg/mL. After fractionation, the ethyl acetate fraction was twice active than the crude extract. From this fraction, eight compounds were isolated among which: two phytosterols; one triterpene, one ellagic acid, one stilbene and three stilbene-coumarins. The stilbene 5-[(1E)-2-(4-hydroxyphenyl) ethenyl]-4-methoxyphenyl}-2-methyl-1-propanone showed the best activity against all the tested strains with MICs of 7.81, 15.56 and 15.56 µg/mL against C. albicans, C. parapsilosis and C. krusei respectively.
Conclusion: This study revealed that a bio-guided investigation of a medicinal plant can lead to the formulation of an effective standardized phytomedicine that can be integrated into the Cameroonian health care system for sustainable development.
Keywords: Candidiasis, Monotes kerstingii, stilbene, anticandidal activity, phytomedicines