Antifungal Activity of Cymbopogon citratus Essential Oil on Toxigenic Fungal Strains Isolated from Cameroonian Rice

Abstract

With a view to finding alternative compounds to the synthetic chemicals used in food preservation, a study was initiated to evaluate the antifungal activity of C. citratus essential oil on toxigenic molds isolated from Cameroonian rice. To this end, 12 rice samples of one kilogram each was taken in October 2019 in four cities in Cameroon: Tonga, Ndop, Yagua and Maga. Water activity in the rice samples collected was measured using an electronic hygrometer; mycotoxins were determined by HPLC. The isolation and identification of fungal strains were done on the basis of macroscopic and microscopic characteristics, and the identity of the strains was confirmed by PCR-sequencing. The extraction of the essential oil was done using a Clevenger by hydrodistillation, and the analysis of its chemical composition by GC/MS. From these analyses, it appears that all samples tested are contaminated with at least one mycotoxin, and that the three mycotoxins tested (AFB1, CIT and OTA) are indeed present in our rice samples, but at values not exceeding the limits set by European Commission Regulation N0 1881/2006. Seven cases of co-contamination have been identified. On the other hand, 9 fungal genera have been identified and the dominant genera being Aspergillus, Penicillium and Fusarium, all of which are involved in the synthesis and excretion of mycotoxins in cereals. The essential oil of C. citratus has been shown to be effective in inhibiting the growth of A. carbonarius, A. versicolor, F. graminaerum, F. moniliform and P. citrinum; and the main compounds of this oil are geranial (42.4%), neral (33.5%) and myrcene (10.8). A. carbonarius was the most sensitive strain to the essential oil, and F. moniliform was the most resistant strain.