Mycotoxigenic fungi and multimycotoxin contamination in medicinal plants sold in the Free State province, South Africa.

Abstract

South Africa has a long history and extensive use of medicinal plants in traditional medicine, but relatively few studies have been conducted on their contamination with moulds and mycotoxins. The purpose of the present study was to characterise medicinal plant trade and determine the extent of fungal and mycotoxin contamination among frequently sold medicinal plants in the Free State Province not yet reported before. A market survey was conducted using semi-structured interviews across 29 locations with 48 respondents. Fungi species were isolated as single colonies morphologically and identified using molecular techniques. Mycotoxin analysis of samples was done using Ultra High-Pressure Liquid Chromatography-Tandem Mass Spectrometry (UPLC-ESI-MS/MS) for the simultaneous detection of AFB1, DON, FB1, FB2, FB3, NIV, OTA, and ZEN. The trade in medicinal plants was mainly dominated by street vendors and muthi shops made up mainly of Sotho, Zulu, Ndebele ethnicities. Traders were mostly men who worked full time with no other income sources and had been in business for 0.5 years up to 26 years. The mean monthly income for men was ZAR 1 825, and for women was ZAR 760. A total of 165 ethno-species belonging to 48 families were the most frequently sold medicinal plants. Salient families for the medicinal plant trade in the province were Asteraceae, with 13 species, followed by Liliaceae (5) and Fabaceae (3). The dominant species were Hypoxis latifolia, Dicoma anomala, Helichrysum odoratissimum, Elephantorrhiza elephantina, Tulbaghia alliacea, and Pentanisia prunelloides. Thirty-four medicinal plant samples were purchased from street vendors and muthi shops in the Free State Province. Approximately 26% of the samples had no fungi contamination, whilst 74% were only contaminated by one or more fungal species. The fungal load in positive samples purchased from street vendors ranged from 1 × 106 to 8.4 × 107 with a mean of 2.55 × 107 CFU/g. Whereas for muthi shops, the study reported a mean fungal load of 2.33 ×107 , ranging from 1 × 106 to 8.4 × 107 CFU/g. For all positive samples, the fungal load was above 1 × 106 CFU/g (above the WHO limit). A total of 54 fungal isolates were recovered, comprising of 17 species. Species belonging to Penicillium, Aspergillus, Fusarium, and Purpureocillium were the most dominant in the medicinal plant samples. About 59% of the fungal isolates screened for their ability to produce mycotoxins were toxigenic, whilst 41% did not produce any detectable quantities of mycotoxins under investigation. All fungal isolates did not produce, nivalenol, ochratoxin A and zearalenone in culture. Ten out of 34 samples tested positive for mycotoxins as follows; AFB1(10%); OTA (10%), FB1 (30%), FB2 (50%), FB3 (20%) and ZEN (30%). Mean concentration levels ranged from AFB1 (15 µg/kg), OTA (4 µg/kg) FB1 (7-12 µg/kg), FB2 (1-18 µg/kg), and FB3 (1-15 µg/kg), ZEN (7-183 µg/kg). Multimycotoxin contamination was observed in 30% of the positive samples with fumonisin derivatives. The concentration of AFB1 reported in this study is above the South African permissible limit for AFB1 (5 µg/kg). Fumonisin concentration did not exceed the South African limit set for raw maize grain (4000 µg/kg of FB1 and FB2). ZEN and OTA are not regulated in South Africa but reported concentrations were below EU Commission-set limits. The study findings indicate the prevalence of mycotoxin contamination in frequently traded medicinal plants, mycotoxins pose a significant health risk to consumers due to their additive or synergistic health effects. Routine monitoring of multiple mycotoxin contaminations, human exposure assessments using biomarker analysis, and establishing regulations and standards.is essential. Therefore, strategies to mitigate mycotoxin contamination should be enacted at major markets, traditional healers, local suppliers, muthi shops and street vendors.