Chemical volatile composition and phytotoxic potential of Daphne gnidium L. leaves

Daphne gnidium L. (Thymelaeaceae) is an evergreen shrub from the Mediterranean area traditionally used for its medicinal and non-medicinal properties. Several studies showed its adverse impact on different targets including malignant cells, microbes, radicals, insects. The negative interactions between D. gnidium and other plant species have been rather neglected so far, as well as its chemical volatile composition. Therefore, this work aimed to assess the phytotoxic activity of D. gnidium on filter paper and soil in pre-emergence conditions by testing both the aqueous extract (10–100%) and the powder (0.25–1 g) obtained from the leaves as bioagrochemicals. The results showed that D. gnidium was able to significantly decrease seed germination and growth parameters of the receiver plants with different effectiveness (p-values < 0.05). Overall, Sinapis alba L. (Brassicaceae) was the most susceptible species followed by Lolium multiflorum Lam. (Poaceae) and Trifolium incarnatum L. (Fabaceae) while aqueous extract was more active than the powder. Solid-Phase Microextraction (SPME) sampling technique and Gas Chromatograph/Mass spectrometer (GC/MS) analyses were used to characterize the volatile fraction highlighting considerable differences in the composition of the analyzed samples. Hexahydrofarnesyl acetone (29.7%) followed by 3,7,11,15-tetramethyl-2-hexadecen-1-ol (28.3%) and β-damascenone (32.0%) followed by eudesma-1,4(15), 11-triene (27.1%) were detected as main volatile compounds of the powder and the aqueous extract, respectively.