Urease inhibitory potential and soil ecotoxicity of novel 'polyphenols - Deep Eutectic Solvents' formulations

New formulations based on red grape pomace polyphenols and deep eutectic solvents (DES) have been here evaluated as inhibitors of urease of agricultural interest (jack bean urease, JBU). DES based on choline chloride (CHO) and betaine (BET), combined with ethylene glycol (EG), citric acid (CA), and urea (U), were used both as extracting and carrying agents for polyphenols, becoming active components of the formulations here obtained. Among the various DES combinations, U- and CA-based ones gave the best polyphenol extraction performances, 1.2-1.4-times higher than those of the hydroalcoholic mixture. Among the various DES-polyphenols formulations, the one composed by CHO-EG showed the best antioxidant potential and urease inhibition: 60-90% inhibition of the total JBU activity was achieved with a CHO concentration of 5-20 mM. Good results were also achieved with the BET-EG polyphenol formulation, which was able to inhibit ca. 50% of urease activity at 20 mM concentration of BET. Low phytotoxicity of DES and their polyphenol formulations tested at a concentration of 34 mM of CHO or BET was here observed on cress seedlings and the early growth of oat, in particular, for EG-based DES. On the other hand, tests performed on earthworms showed that CHO-based DES could impair the reproduction, and U-based DES caused severe mortality.