Alternaria toxins in South African sunflower seeds: cooperative study

摘要

Sunflower seed samples (N = 80) from different sunflower cultivars originating from different localities in South Africa were analyzed for 15 toxins produced by fungi of the genus Alternaria by means of a simple one-step extraction dilute-and-shoot HPLC-MS/MS approach. References for valine-tenuazonic acid (Val-TeA), altenusin (ALTS), and altenuisol (ALTSOH) were isolated from fungal culture extracts and spectroscopically characterized. Additionally, valine-tenuazonic acid was tested regarding its cytotoxicity in comparison with tenuazonic acid (TeA) and showed less activity on HT-29 cells. Furthermore, alternariol monomethyl ether-3-O-beta-D-glucoside (AME-3G) was produced by fermentation of alternariol monomethyl ether (AME) with the fungus Rhizopus oryzae. The seed samples were analyzed both with and without hulls. The method covers the AAL toxins TA_1 and TA_2, altenuene (ALT) and iso-altenuene (iso-ALT), altenuisol, altenusin, altertoxin I (ATX-I) and altertoxinII (ATX-II), alternariol (AOH) and alternariol monomethyl ether, alternariol monomethyl ether-3-O-beta-D-glucoside, tenuazonic acid, allo-tenuazonic acid (allo-TeA) and valinetenuazonic acid, and tentoxin (TEN). More than 80% of the samples were positivefor one or more analytes above the respective limit of detection (0.2-23 mug/kg). Alternariol, its monomethyl ether, tentoxin, tenuazonic acid, altenuisol, and valine-tenuazonic acid were found in quantifiable amounts. The highest prevalences were foundfor tentoxin (73% positive, mean content 13.2 mug/kg, maximum level 130 ± 0.9 mug/kg) followed by tenuazonic acid (51 % positive, mean content 630 mug/kg, maximum level 6300 ± 560 mug/kg). The obtained data were further analyzed statistically to identify quantitative or qualitative relationships between the levels of Alternaria toxin in the samples.