Preponderance of Oxygenated Sesquiterpenes and Diterpenes in the Volatile Oil Constituents of Lactuca serriola L. Revealed Antioxidant and Allelopathic Activity.

Using synthetic chemicals in industry and agriculture has led to several environmental problems. Thus, plant products derived from volatile oils (VOs) could be a potential green source for bioherbicides. Little is known about the VOs of Lactuca serriola. Hence, the present study aimed to characterize the VOs chemical composition from the aerial parts of L. serriola, assessment of antioxidant activity, and evaluate allelopathic potential against the noxious weed Bidens pilosa. The VOs were extracted by hydrodistillation and analyzed by GC/MS. The VOs from the Egyptian ecospecies of L. serriola were found to comprise 34 compounds mainly oxygenated sesquiterpenes and diterpenes. The major compounds were isoshyobunone (64.22 %), isocembrol (17.35 %), and alloaromadendrene oxide-1 (7.32 %). So, L. serriola can be considered as a good source for isoshyobunone, considering that it has a much higher concentration than any other plants. Also, this plant has a high content of the oxygenated diterpene compound, isocembrol, which is rarely found in the VOs of most plants. The VOs expressed strong antioxidant activity. Also, for the first time, our results showed a strong allelopathic activity of VOs from L. serriola on germination and seedling growth of the noxious weed, B. pilosa. We suppose that the activity of the VOs from L. serriola could be attributed to these previously mentioned major compounds, as they represent about 89 % of the total identified oil constituents. Nevertheless, to evaluate these compounds as new allelochemicals, further study is needed to test the allelopathic activity of authenticated standard of these compounds either singular or in combination on several weeds as well as evaluate the safety, and improve the efficacy and stability at the field scale.