Rapid Detection of ACTG- and AK-Toxins inAlternaria alternataby LC-ESI-MS/MS Analysis and Antifungal Properties of Citrus Compounds

Kátia R Prieto,Marsele M Isidoro,Marcos A Machado,Lívia S De Medeiros,Rodrigo M Stuart,Leonardo Toffano,Maria Fátima G F Da Silva,Edson Rodrigues-Filho,Moacir R Forim,Paulo C Vieira,João B Fernandes

doi:10.5935/0103-5053.20160195

Kátia R Prieto, Marsele M Isidoro + Show 9 more

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https://doi.org/10.5935/0103-5053.20160195

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A methanol-soluble fraction of the dichloromethane extract from the culture broth of A. alternata AT4303 strain afforded the following five known mycotoxins: alternariol, alternariol monomethyl ether, altenusin, altenuene and altertoxin I. A hexane-soluble fraction of the dichloromethane extract yielded the steroids ergosterol and ergosterol peroxide, and alternariol monomethyl ether. The concentrated ethyl acetate extract afforded the nucleoside uridine, uracil and inosine. The micro-extracts obtained from this strain in solid media were analyzed using liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS), and the following five known toxins were identified: ACTG-C, D, E and F and AK-toxin II. The major toxins produced by the tangerine pathotype ACT-toxins appear to be absent in strain AT4303. However, the low concentration of ACT-toxins appears to be responsible for their lack of detection in this study. Some compounds isolated from citrus plants were tested for in vitro activity against this strain. The results indicated that 17.3 µM apigenin-7-O-rutinoside inhibited by 80% conidial germination and appressorium development.

Highlights

The fungi of the Alternaria genus Nees ex Wallr. are well known to be a source of many bioactive substances with vastly differing structures, many of which are phytotoxic, acting as either host-specific or non-specific toxins
To determine the specific toxins of the tangerine pathotype of A. alternata, this study has further investigated the AT4303 strain previously obtained from severely infected Murcott tangor leaves
Inoculations were performed using the AT4303 strain of the tangerine pathotype of A. alternata, which was previously obtained from severely infected Murcott tangor fruit collected in Campo Alegre Farm, Aguaí, SP, Brazil

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Introduction

The fungi of the Alternaria genus Nees ex Wallr. are well known to be a source of many bioactive substances with vastly differing structures, many of which are phytotoxic, acting as either host-specific or non-specific toxins. To determine the specific toxins of the tangerine pathotype of A. alternata, this study has further investigated the AT4303 strain previously obtained from severely infected Murcott tangor leaves.

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