Chemical Composition and Efficacy of Ocimum basilicum L. Essential Oil against Stored Rice (Oryza sativa L.) Molds Sold in Ngaoundere (Cameroon)

The aimed of this study to evaluate the antifungal activity of essential oils of Ocimum basilicum L. on some fungi isolated from commercial rice sold in Cameroon. Fungal isolates were primarily identified based on morphological characteristics, while representative isolates were identified using PCR-based methods. Essential oils were extracted by hydro-distillation, chemical composition was analyzed by gas chromatography coupled with mass spectrometry (GC-MS) and antifungal activity against isolated fungi were assessed using the micro-atmospheric method. The percentage of frequency and abundance varied with the sample analyzed and the fungi detected. A total of 85 fungal isolates of eight genera including Aspergillus, Fusarium, Penicillium, Rhizopus, Cladosporum, Mucor Alternaria and Acremonium in decreasing order of predominance were identified. The most fungal species identified were Aspergillus flavus, A. fumgatis, A. niger, A. carbonarius, Fusarium oxysporum, F. graminarum, F. moniliforme, Penicillium citrinum, P. expansum, Rhizopus oryzea, Cladosporum sp, Mucor hiemalis, Alternaria solani, Acremonium murorum. More than 61% (A. flavus, A. niger, P. citrinum) and 44% (M. hiemalis, A. flavus, A. niger) of analyzed samples contain respectively aflatoxin B1, AFB1 (0 - 17.3 µg/kg) and ochratoxin A, OTA (0 - 5.2 µg/kg). Citrinin was not detected. The main compounds identified in O. basilicum EO are eugenol (30.6), linalool (29.5), cineole (14.4), Terpinen-4-ol (5.6), 2-norpinen (4.1), Cadinen (3.3), Limonen (2.4) and (E)-β-Ocimene (2.2). The O. basilicum EO exhibit antifungal activity with the MIC range from 750-2000 ppm. This activity varies with the strains and the concentration of EO. The increased prevalence of mycotoxigenic fungi in rice, a highly consumed food grain in Africa, poses serious health concerns to the general public. The O. basilicum EO can therefore be used as alternatives to synthetic pesticide in rice storage.