The chemical composition of essential oils isolated by hydrodistillation from the needles of Tunisian Pinus nigra L. subsp. laricio was analyzed by GC and GC/MS. 27 compounds were identified, representing 97.9% of total oil, which was found to be rich in oxygenated diterpenes (38.5%) particularly manool oxide (38%) and sesquiterpene hydrocarbons (41.4%) that included germacrene D (16.7%), δ-cadinene (9%) and (E)-caryophyllene (8.9%). Results of the herbicidal effects of the oil when tested on Phalaris canariensis L., Trifolium campestre Schreb. and Sinapis arvensis L., indicated that the oil completely inhibited germination and seedling growth at a high concentration (5 μL/mL−1), while at low doses the oil acted by decreasing germination and partially inhibiting seedling growth of all tested weeds

This study is designed to examine the chemical composition of the hydrodistillated essential oils obtained from Cymbopogon citratus ( DC) Stapf, Eucalyptus cladocalyx, Origanum vulgare L, and Artemisia absinthium L. GC and GC-MS analysis of the four oils has shown a determination of 18 different components representing 89.3 % of the total oil for Cymbopogon citratus ( DC) Stapf that are neral (29.2 %) and geranial (18.2 %), followed by α-pinene (4.8 %) and myrcene (3.9 %) which are determined as the major compounds of the oil; for Eucalyptus cladocalyx oil there are 29 different components representing 79.0 % of the total oil, the major components are spathulenol (21.6 %) and 1,8-cineole (20.5 %), followed by p-cymene (15.1 %); for Origanum vulgare L. oil there are 25 different components representing 87.6 % of the total oil, the major components are carvacrol (34.0 %) and γ-terpinene (21.6 %), followed by p-cymene (9.4 %) and for Artemisia absinthium L. oil there are 26 different components representing 72.3 % of the total oil, which are determined as the major compounds of the oil. On the other hand, the four oils were experimented for their herbicidal activity against Sinapis avensis weed at different concentration then compared with commercial herbicides (2.4 D and glyophosate). The four essential oils have presented an interesting activities, the activity of C. citratus (DC) Stapf and E. cladocalyx have been evaluated as important. In the light of these findings, we suggested that the four essential oils may be considered as an interesting sources of bioherbicide components used as potent agents in weeds control.

The chemical composition of the essential oils of Melaleuca armillaris Sm., Melaleuca styphelioides Sm. and Melaleuca acuminata F. Muell., collected in Tunisia, was studied by means of GC and GC-MS analysis. In all, 46 compounds were identified, 38 for M. armillaris, 20 for M. acuminata and eight for M. styphelioides, respectively. The presence of a sesquiterpenic fraction (52.2%) characterized the oil from M. armillaris; M. sthypheliodes oil was rich in methyl eugenol, a phenolic compound (91.1%), while M. acuminata oil is mainly constituted by oxygenated monoterpenoids (95.6%). The essential oils were evaluated for their in vitro potentially phytotoxic activity against germination and initial radicle growth of Raphanus sativus L., Lepidium sativum L., Sinapis arvensis L., Triticum durum L. and Phalaris canariensis L. seeds. The radicle elongation of five seeds was inhibited at the highest doses tested, while germination of all seeds was not affected. Moreover, the essential oils showed low antimicrobial activity against eight selected microorganisms.

Many plants are able to synthesize essential oils (EOs), which play key roles in defense against weeds, fungi and pests. This study aims to analyze the chemical composition and to highlight the antioxidant, antimicrobial and phytotoxic properties of the EOs from Eucalyptus falcata, E. sideroxylon and E. citriodora growing in Tunisia. EOs were analyzed by gas chromatography coupled to mass spectrometry (GC/MS) and their antioxidant properties were determined by total antioxidant capacity (TAC), DPPH and ABTS assays. The phytotoxic potential was assessed against weeds (Sinapis arvensis, Phalaris canariensis) and durum wheat crop (Triticum durum) and compared to chemical herbicide glyphosate. The antifungal activity was investigated in vitro against eight target fungal strains. All EOs displayed a specific richness in oxygenated monoterpenes (51.3–90%) and oxygenated sesquiterpenes (4.8–29.4%), and 1,8-cineole, citronellal, citronellol, trans-pinocarveol, globulol, spathulenol and citronellyl acetate were the main constituents. Eucalyptus EOs exhibited remarkable antioxidant activity and E. citriodora oil exhibited significant activity when compared with E. falcata and E. sideroxylon EOs. The phytotoxic potential of the tested oils had different efficacy on seed germination and the growth of seedlings and varied among tested herbs and their chemical composition variability. Their effectiveness was better than that of glyphosate. At the post-emergence stage, symptoms of chlorosis and necrosis were observed. Furthermore, a decrease in chlorophyll and relative water content, electrolyte leakage and high levels of MDA and proline were indicators of the oxidative effects of EOs and their effectiveness as bioherbicides. Moreover, all the EOs exhibited moderate fungitoxic properties against all the tested fungal strains. Therefore, according to the obtained results, Eucalyptus EOs could have potential application as natural pesticides.