Natural occurrence of fungi and mycotoxins in some selected South African medicinal plants with some antifungal properties

M.Tech. (Food Technology)Abstract: The importance of medicinal plants for the treatment of different diseases has stimulated their widespread utilization in South Africa, particularly considering that these plants are readily available and affordable. Although some of these plants may have antifungal properties, they could be contaminated with fungi under conditions in which they find themselves and thereafter produce secondary metabolites including mycotoxins known to cause severe health problems in both animals and humans. It could be assumed that since such medicinal plants have high contents of phytochemicals, such phytochemicals may hinder the proliferation of mycotoxigenic fungi and subsequent mycotoxin production. There is therefore, a need to establish the mycoflora and mycotoxin profile of these plants in South Africa as there are a number of reports elsewhere on increased fungal and mycotoxin contamination of medicinal plants. This study was aimed at investigating the presence of fungi and mycotoxins in South African medicinal plants and to assess the antifungal properties of these plants. Thirty-six (36) samples of various medicinal plants were randomly purchased from Faraday Muthi market in the Johannesburg metropolis. Using conventional methods and DNA sequencing thereafter, a mycological screening of samples revealed the identities of a total of 164 fungi that were recovered. Accordingly, Alternaria alternata, Aspergilus niger, A. parasiticus, A. flavus, A. ochraceus, A. nidulans, Cladosporium sp., Chaetomium sp., Emericella nidulans, Epicoccum sp., Fusarium oxalicum, F. proliferatum, F. graminearum, P. aurantiogriseum, P. expansum, Mucor sp. and Rhizopus sp. with A. niger occurring most frequently. Over 39% of withal recovered isolates were identified as Aspergillus spp. with fungal load above the 1 x 103 CFU/g permissible limit set by World Health Organization (WHO). Of all the medicinal plants, Acacia karoo had the lowest fungal load of 1.8 × 104 CFU/g of sample, whereas Putranjiva roxburgii, Schotia brachypetata and Elephantorriza elephantine both had the highest fungal contamination level of 2 × 107 CFU/g sample. Mycotoxicological investigation for some economically important mycotoxins including total aflatoxins (AFs) [aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1) and G2 (AFG2)], ochratoxin A (OTA) and zearalenone (ZEA) was carried out following the multi-mycotoxin extraction method and quantification thereafter performed on a high performance liquid chromatography (HPLC) instrument. The analysis showed that AFs, OTA and ZEA occurred in most of the samples..