Biodegradable polymers as carriers for tuning the release and improve the herbicidal effectiveness of Dittrichia viscosa plant organic extracts

BACKGROUNDThe organic extracts (OE) of Dittrichia viscosa, a ruderal plant common in the Mediterranean regions, proved to have herbicidal properties. In order to improve OE effectiveness and to develop novel eco-friendly bioherbicidal products, different amounts of OE were included in poly(butylene succinate)- and polycaprolactone-based films (PBS and PCL, respectively). Particular attention was given to the study of interactions between the polymers and OE, with a deep spotlight concerning the influence of OE on structural, morphological and thermal properties of both polymers, in order to assess the OE releasing kinetics from the matrices and its tuned herbicidal action against seeds.RESULTSThe bioassays carried out on Lepidium sativum and Phelipanche ramosa seeds evidenced a more controlled and effective OE release by PBS than PCL, and a longer lasting efficacy by the polymers with a higher OE content. The chemical-physical analyses were performed on films before and after biological assays. The thermogravimetric analysis confirmed that OE was a thermal stabilizer of the polymer; the presence of OE and polymer separated degradative kinetics suggested that only a partial and functional miscibility between polymers and OE occurred. The morphological analysis confirmed the good OE dispersion between PBS and PCL molecular chains. Infrared spectroscopy highlighted the enhanced hydrolyzed structure of the doped polymers after the bioassays. These outcomes well matched the quantitative information outlined by release kinetics.DISCUSSIONThe use of biodegradable polymers allows improving the effectiveness and tuning the release of the formulated bioactive compounds. The easy-to-obtain and -to-formulate OE could become a suitable and environmentally friendly instrument in weed management programs.