Viola calcarata L. and Viola dubyana Burnat ex Gremli hydrolates: DI-SPME-GC-MS analysis and biological activity evaluation

The hydrolates obtained from the aerial parts of two indigenous Viola L. species (V. calcarata L. and V. dubyana Burnat ex Gremli) growing in the Italian Alps were studied for the first time. The direct immersion solid-phase microextraction (DI-SMPE) sampling and the GC–MS analysis revealed the presence of methyl salicylate as the main compound in both samples along with a different set of terpenes for each hydrolate and some other minor compounds. The most interesting results were achieved by evaluating their phytotoxic potential against two target species (Sinapis alba L. and Lolium multiflorum Lam.) through treatments without direct contact with the seeds. In general, the hydrolates showed species and dose-dependent effects. They were more active on growth (maximum reduction = -86.8% due to V. dubyana hydrolate on S. alba) than on germination (maximum inhibition = -45.9% due to V. calcarata hydrolate on S. alba). No sign