Thiophene occurrence in different Tagetes species: agricultural biomasses as sources of biocidal substances

BACKGROUND: Tagetes species produce thiophenes, polyacetylenic compounds that possess strong biocidal activity, thus making Tagetes plants very useful for suppressing nematode populations in the soil and as sources of natural pesticides. In the present study, Tagetes species (T. erecta, T. filifolia, T. lucida, T. minuta, T. patula and T. tenuifolia) grown in northern Italy were evaluated for their morphophenological parameters and thiophene pattern in different plant parts (roots, shoots and flowers). RESULTS: Roots had the highest diversity and contents of thiophenes (from 64 to 100% of the total thiophene amount), with 5-(3-buten-1-ynyl)-2,2'-bithienyl (BBT) as the main component followed by 5-(4-acetoxy-1-butynyl)-2,2'-bithienyl (BBTOAc), 2,2':5',2 ''-terthienyl (alpha-T) and 5-(4-hydroxy-1-butynyl)-2,2'-bithienyl (BBTOH). Tagetes lucida and T. tenuifolia possessed the highest amounts of total thiophenes (6717.3 and 6452.5 mg kg(-1) dry weight respectively), while T. minuta had the highest total thiophene yield (518.8 mg m(-2)), with BBT accounting for 98% of the total. CONCLUSION: Considering both thiophene concentrations and biomass yields, T. minuta and T. lucida appeared to be the most promising Tagetes species, with high potential for use as biocidal crops for the implementation of pest control practices that are less harmful to human health and natural resources. (C) 2010 Society of Chemical Industry