Isolation and Characterization of Terpenoids with Promising Biopesticide Activity from Dittrichia viscosa (L.) Roots

The natural product composition of the hexane and methyl tert-butyl ether extracts of Dittrichia viscosa roots was examined. Eight terpenoids were identified by nuclear magnetic resonance (NMR) and high resolution mass spectroscometry (HRMS) techniques, four of which (1, 5, 6 and 8) are reported here for the first time as natural products. Of these eight compounds, four are thymol derivatives (1-4), two are guaianolides (5 and 7) and two are himachalanes (6 and 8). Additionally, the occurrence of himachalanes in this species is reported for the first time. Furthermore, a study of the potential plant protection effects of some of these natural products and the chemical derivative 6a was carried out. Promising preliminary results were obtained for compounds 1-3 and 6a as antifeedant agents against Spodoptera littoralis; 1-3 and 5 against Myzus persicae; 1-3 against Rhopalosiphum padi; and 4 as nematicide against Meloidogyne javanica. Finally, the phytotoxic activity of compounds 4, 5 and 6a against the monocotyledonous species Lolium perenne was also proven.