Sonja Stockenström

A preliminary survey of mycological and fumonisin and aflatoxin contamination of African traditional herbal medicines sold in South Africa.

Traditional medicine is an important aspect of healthcare delivery in South Africa and is used by at least 70% of the country’s population. The trade in medicinal plants is a multi-million rand business which is a major driver for rural economies. However, the conditions in which these plant products are transported and stored make them prone to fungal contamination which results in economic losses to the traders and pose potential health hazards to consumers. Of major concern is the possible presence of toxigenic fungi and mycotoxins. This study assessed fungal and mycotoxin contamination of African herbal products sold in Cape Town and Tshwane (formerly Pretoria) in South Africa. Of the 16 samples analyzed, 15 were contaminated with at least one of these three fungal genera: Aspergillus, Fusarium, and Penicillium. Fumonisin B1 was present in 13 of the samples in quantities ranging from 14 to 139 μg/kg (detection limit 5 μg/kg). None of the samples was contaminated with aflatoxigenic fungi or aflatoxin (detection limit 0.5 μg/kg). This is the first study to report on mycological and mycotoxin contamination of commercial traditional African medicines in South Africa. There is a need to expand the study to other urban centers to gain enough insight into this problem and then to intervene with measures that can protect the public from potential harm.

Polyclonal Antibody-Based ELISA and HPLC Methods for the Determination of Fumonisins in Corn: A Comparative Study

The performance of an experimental polyclonal antibody (PAb)-based competitive direct enzyme-linked immunosorbent assay (CD-ELISA) developed for the analysis of fumonisins in corn was assessed by comparison with an established high-performance liquid chromatography (HPLC) method. The comparative study was conducted using a series of 20 corn samples naturally contaminated with combined fumonisin levels ranging from <0.05 to >5 μg/g (ppm). Linear regression analysis between the results generated by HPLC and CD-ELISA provided correlation coefficients (r) and regression slopes (b) of r = 0.960, b = 1.493 (P < 0.001); r = 0.865, b = 3.903 (P < 0.001); and r = 0.832, b = 0.107 (P < 0.001) for the individual fumonisins B1 (FB1), B2 (FB2) and B3 (FB3), respectively, while corresponding values of r = 0.967, b = 1.059 (P < 0.001) were obtained for the combined FB1, FB2, and FB3 concentrations. In 3 of 18 fumonisin-positive corn samples, combined fumonisin levels determined by CD-ELISA were between 85 and 100% higher than those determined in the same extracts by HPLC, while in 13 other samples, CD-ELISA results were between 1.8 and 53% higher than those determined by HPLC. Conversely, in 2 of 18 samples, CD-ELISA results were lower than those determined by HPLC. The differences recorded between HPLC and the experimental PAb-based CD-ELISA were far less than those previously recorded for other mono- and polyclonal antibody-based CD-ELISA systems. The results indicate that the experimental PAb-based CD-ELISA may be effectively applied for the initial screening for fumonisins in corn.

Determination of fumonisins in corn: Evaluation of two purification procedures.

The performance of two solid phase extraction (SPE) purification procedures, used in the determination of fumonlsin B1 (FB1), B2 (FB2) and B3 (FB2) In corn, was evaluated using both thin-layer chromatography (TLC) and high performance liquid chromatography (HPLC). Fewer interferences were observed In extracts prepared using the strong anion exchange (SAX) media, in contrast to those purified on C18 media, where on occasions, visual discernment of the TLC bands was hampered by the presence of interfering compounds. Precipitate formation, resulting In the blocking of SPE cartridges was also encountered when using the C18 procedure. HPLC analyses of extracts prepared by both media indicated that they gave comparable fumonlsin recoveries from naturally contaminated corn samples. The results suggest that the C18 procedure, originally developed for the TLC analyses of FB1 in mixed feeds, may also be applied to the determination of FB2 and FB2. However, where TLC is used quantitatively for fumonlsin levels <1 μg/g, purification of sample extracts on SAX media is recommended.

Investigation of patulin contamination in apple juice sold in retail outlets in Italy and South Africa

A study of apple juice products sold in Italy and South Africa was initially carried out on 20 samples bought in Cesena, Italy, and Tygerberg in Cape Town, South Africa. The samples were bought at random and analysed for patulin contamination. All 12 of the Italian samples had no detectable levels of patulin, except one, which was just slightly above the lowest regulatory limit of 10 ng ml−1. On the other hand, five of the eight South African samples were all contaminated with patulin levels above 10 ng ml−1, with one showing a concentration of 75 ng ml−1, well above the highest regulated limit of 50 ng ml−1. This latter result led to a more targeted investigation with 14 samples being purchased in the low-income areas of Tygerberg where the initial samples were sourced. These samples confirmed that there might be a problem of mycotoxin contamination in apple juices products sold to low-income consumers because half of the samples showed patulin contamination of which four had levels well above the acceptable limits. This is the first study in South Africa to look at apple juice products in low-income areas and it points to a need to intervene and introduce quality systems in the supply chain of the manufacture and packaging of apple juice products by independent small business.

Fumonsin B1, B2, and B3 content of commercial unprocessed maize imported into South Africa from Argentina and the USA during 1992

The widespread occurrence of F. moniliforme and the toxic effects of its secondary metabolites, the fumonisins B1(FB1), B2(FB2) and B3(FB3), make it imperative that fumonisin contamination of maize, a major constituent of animal feed as well as the staple diet of many populations, be closely monitored to reduce the risk of fumonisin exposure. Equine leukoencephalomalacia and porcine pulmonary oedema have been associated with the intake of feed heavily contaminated with fumonisins. In addition, high levels of fumonisins in the maize-based staple diets of certain populations have been linked to a high incidence of oesophageal cancer in the Transkei region of South Africa and in Linxian and Cixian Counties, China. Bulk shipments of maize imported into South Africa from the USA and Argentina during 1992 were sampled at the port of entry to determine fumonisin levels. Of the 79 samples from two US shipments, all were positive for fumonisins, with FB1 constituting approximately 71% of the total fumonisins with an overall mean of 2.35 micrograms/gFB1. The maximum FB1 level observed was 3.9 micrograms/g. These levels contrast with those obtained from two Argentinian bulk shipments, which also were all positive for fumonisins, but had a mean FB1 level of 0.31 microgram/g and a maximum observed level of 0.7 microgram/g FB1 measured over 47 composite samples.