Antifungals from native Schinopsis: natural growth inhibitors on toxigenic Fusarium species.

ME ARISTIMUÑO FICOSECO, MA VATTUONE, CA CATALÁN, DA SAMPIETRO

Buenos Aires

Congreso; XI Congreso Latinoamericano de Microbiología e Higiene de Alimentos. VI Congreso Argentino de Microbiología de Alimentos y III Simposio Argentino de Conservación de Alimentos (MICROAL 2012).; 2012

Asociación Argentina de Microbiología

Fusarium verticillioides and F. graminearum are the main ethiological agents of ear rots in argentinian wheat and maize. They reduce yields and contaminate the grains with mycotoxins which constitute a risk for national food safety. Chemical control of ear rots is restricted to application of fungistatics during grain storage (i.e. sorbates,benzoates) or fungicides during floral antesis (i.e. azoles,azoles+strobilurins). The cost and lack of sustainability in the use of these chemical agents require the development of more readily available and enviromentally friendly antifungals. In this context, native Anacadiaceae are a source of bioactive compounds potentially useful for control of these Fusarium species. The aim of this work was to search and identify antifungals in leaf extracts of native Anacardiaceae species useful for control of F. verticillioides and F. graminearum. Leaves of Schinus (S. molle, S. fasciculatus, S. gracilipes) and Schinopsis (S. lorentzii, S. haenkeana) native from northwest Argentina were sequentially extracted with dichloromethane, ethyl acetate and methanol. The obtained extracts were evaporated to dryness, suspended in 50 ml of methanol and filtered. The antifungal activity of the filtrated methanolic fractions from dichloromethane (fDCl), ethyl acetate (fEtAc) and methanol extracts (fMeOH) were evaluated by disc diffusion and microdilution methods. Minimum inhibitory dose (DIM), diameters of inhibition (DI) and concentration needed for growth inhibition of 50% of mycelial growth (IC50) were calculated. Then, components of the most bioactive extracts were separated using silica gel columns and hexane:ethyl acetate as (7:1) as mobile phase. Components of the bioactive fractions were followed by thin layer chromatography and bioautography. Then, they were identified by GC-MS. The lowest DIMs (~125 ìg dry matter/disc) and highest DIs (~1.5 cm) were obtained for fDCl and fEtAc of Schinopsis species on F. graminearum. The same methanolic fractions were less inhibitory on F. verticillioides. Comparison of the  IC50s and DIMs showed that the fDCl and fEtAc of Schinopsis species were the most inhibitory on Fusarium. Bioguided separation of the components from these fractions indicated the presence of taraxasterol and long chain alk(en)ylcatechols. The efficiency of the isolated compounds in the control of toxigenic Fusarium species on cereal grains under a broad range of environmental factors is currently under research.