HIGH-INCIDENCE OF ASPERGILLUS-FLAVUS AND AFLATOXINS IN STORED GROUNDNUT IN GHANA AND THE USE OF A MICROBIAL ASSAY TO ASSESS THE INHIBITORY EFFECTS OF PLANT-EXTRACTS ON AFLATOXIN SYNTHESIS

Groundnut samples from 21 selected markets in the 10 regions of Ghana yielded high levels of the aflatoxigenic fungus Aspergillus flavus on half-strength potato dextrose agar. The fungus was associated with 31. 7 and 12.8%, respectively, of all damaged and undamaged kernels assaye d. Only 0.24% of total kernels assayed yielded A. parasiticus. Other f ungi detected from total kernels assayed were A. niger (34%), A. candi dus (1.45%), A. tamarii (3.93%), A. ochraceous (5.26%), Fusarium spp. (1.7%) Penicillium spp. (5.19%), a Mucor sp. (2.3%), a Trichoderma sp. (0.2%), Rhizopus stolonifer (12%) and certain unidentifiable fungi (1 1.72%). Total aflatoxin levels ranging from 5.7 to 22, 168 ppb were id entified with damaged kernel samples. The mycotoxin was not detected i n 50% of undamaged kernel samples tested and very low levels mostly ra nging from 0.1 to 12.2 ppb were associated with the undamaged samples that tested positive for aflatoxins. Tn a novel in vitro microbial ass ay to determine the effectiveness of certain plant extracts against af latoxin synthesis, extracts from Xylopia aethiopica, Monodera myristic a, Cinnamomum verum and Piper nigrum permitted fungal growth in 1.5% p otato-dextrose broth while completely suppressing NOR formation. These extracts, however, could not suppress NOR formation in a yeast extrac t sucrose medium.