Mycotoxins Associated with Fungal Pathogens and Their Impact on the Phytochemical Composition of Kola Nut (Cola nitida) in Yola, Adamawa State, Nigeria

Abstract

Kola nut (Cola nitida) is a vital cash crop in Nigeria, significantly impacting socio-economic conditions. This study investigated the fungi associated with kola nut rot, their potential for mycotoxin production, and the implications of fungal infection on the nut’s phytochemical composition. Thirty samples of infected and uninfected kola nuts were collected from wholesalers in Jimeta Modern Market, Yola, and analyzed in the Department of Plant Science at Modibbo Adama University, Yola. Fungal isolation was conducted using Potato Dextrose Agar, and mycotoxins were detected via thin-layer chromatography (TLC), with extraction performed using Potato Dextrose Broth. Data were analyzed using ANOVA and means were separated with LSD. Four pathogenic fungal species were identified: Aspergillus parasiticus, Aspergillus flavus, Fusarium oxysporum, and Rhizopus stolonifer. TLC analysis indicated that A. parasiticus and A. flavus produced aflatoxins (Rf = 0.398 and 0.709), while F. oxysporum produced metabolites resembling zearalenone or trichothecenes (Rf = 0.695), and R. stolonifer produced compounds suggestive of rhizoxin (Rf = 0.179 and 0.571). Qualitative phytochemical screening revealed the presence of various bioactive compounds, while quantitative analysis showed significant reductions in key constituents due to fungal infection (P≤0.05). Saponins decreased from 0.836% in uninfected nuts to below 0.046% in infected nuts, with similar declines noted in flavonoids, tannins, and other compounds. Overall, fungal colonization caused severe phytochemical degradation and contamination with harmful mycotoxins, emphasizing the need for improved post-harvest handling and effective measures to prevent fungal infestation in kola nuts.