Synergistic inhibition of the seed germination by crude glycerin and defatted oilseed meals

•Inhibitory effect on seed germination of crude glycerin from biodiesel production.•Inhibitory effect on seed germination of Brassica defatted oilseed meals in relation to their glucosinolate content.•Crude glycerin and Brassica defatted meals act in synergy on germination inhibition.•Plant germination and growth of both small and large size seeds can be inhibited.•A 100% bio-based product for weed control could be developed from biodiesel byproducts.

The main co-products of biodiesel and biolubricant chains are defatted oilseed meals and crude glycerin, generally considered as by-products and mainly used in animal feeding, bioenergy production and other minor uses. However, these co-products could have other interesting features, and high value added outlets could be developed in order to significantly improve the overall economic and environmental impact of the entire biodiesel chain. When defatted seed meals derive from some specific oilseed crops belonging to Brassicaceae they are characterized by high levels of glucosidic molecules potentially able to release biologically active compounds by means of an enzymatic hydrolysis reaction. The second biodiesel chain by-product, crude glycerin, contains glycerol and some impurities (including water) up to 20%. This manuscript reports in vitro and in vivo bioassay results on the application of crude glycerin and defatted seed meals of some Brassicaceae species (Brassica carinata, Brassica nigra, Barbarea verna, Crambe abyssinica) in seed germination inhibition. These features open new perspectives for obtaining bio-based products for weed control, starting from both main co-products of the biodiesel chain. Indeed, the results confirmed the inhibitory effect of crude glycerin and seed meals used alone and, moreover, showed a synergistic activity when combined. As expected, the inhibitory activity was correlated to glycerol concentrations and to the quali–quantitative release of isothiocyanates from defatted seed meals.