The antifungal potency of the essential oils of Rhanterium adpressum was evaluated against four mycotoxigenic strains of the genus Fusarium. The essential oils were obtained, separately, by hydro-distillation of the aerial parts of R. adpressum (leaves and flowers). The parts were collected during the period of bloom (3 months) for 3 years. The GC-MS analysis revealed thirty-six compounds for the essential oils, divided into four classes of chemical compounds, with variable percentages according to the month of extraction. The monoterpene hydrocarbons form the main class in these oils. On the other hand, the highest percentages of the oxygenated compounds are observed in the samples collected during the month of May. The direct contact method was used to evaluate the antifungal activity of the essential oils. The activity can be attributed to their relatively high composition of oxygenated monoterpenes. Flowers extract showed strong inhibitory activity, with very interesting concentrations of IC50 and MIC for both tests on solid and liquid medium. The effect of these oils on the production of type B trichothecenes (TCTBs) was evaluated, showing a significant inhibitory effect on TCTBs production, for both extracts (leaves and flowers). The rates of inhibition were 66-97 and 76-100% of FX, 3-ADON and 15-ADON, respectively. The inhibition of fungal biomass and the production of TCTBs depended on the used concentration of the essential oils. These results suggest that the essential oils from R. adpressum are able to control the growth of the tested strains and their subsequent production of TCTB mycotoxins.

Summary The present study evaluates the antioxidant and antifungal effects of essential oils (EOs) from Thymus vulgaris, Thymus algeriensis, Mentha piperita, Mentha pulegium, Artemisia herba-alba and Artemisia campestris, on five strains of Fusarium. The chemical composition of EOs of T. vulgaris, T. algeriensis, A. herba-alba, M. piperita and M. pulegium is characterized by a dominance of the family of oxygenated monoterpenes with 73.85%, 59.41%, 70.01%, 60.01% and 87.2%, respectively. On the other hand, the EO of A. campestris showed a diverse composition by similar percentages between all families. The two strains BD17 and INRA 349 were found to be resistant to low concentrations of EOs from T. algeriensis, A. campestris and A. herba-alba, sensitive to EOs of M. pulegium and M. piperita and very sensitive to T. vulgaris EO (0.25 μl/ml). A high antioxidant effect was recorded by T. vulgaris EO in BCB assay with an effective concentration (0.5 mg/ml) 3 to 60 times higher compared to the other EOs tested. This antioxidant capacity of T. vulgaris EO was also recorded with DPPH assay at an EC50=1.41 mg/ml.

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This study aims to predict the impact of bioclimatic variables in current and future climatic scenarios on the distribution of Inuleae tribe species. Modeling the distribution of 30 species of the Inuleae tribe in Algeria was carried out with a maximum entropy model. Two models with 99 occurrence points were obtained with mean values of Area Under a Curve (AUC) of 0.987±0.01 and 0.971±0.02, reflecting excellent predictive power. Three bioclimatic variables contributed mainly to the first model and four - to the second one with cumulative contributions of 83.8% and 79%, respectively elucidating differences between species of the two major climatic zones in Algeria: the Tell and the Sahara. Two-dimensional niches of Algerian Inuleae species allowed to distinguish these two groups with the distribution of 18 Tell species, characterized by high rainfall (14-18°C, 400-1000 mm) and the other 12 species – distributed in hot and dry environments (17-24°C, 20-200 mm). Modeling the distribution under future conditions showed that habitats of the Saharan region would be much less suitable for these species with a variation in the annual mean temperature increase up to 20% and a decrease in annual precipitation, which could raise to 11 and 15%.

Essential oils (EO) from leaves and flowers of Rhanterium adpressum have shown to inhibit the mycelial growth and type B trichothecenes production. The four strains of Fusarium culmorum and Fusarium graminearum were inhibited with 0.25 μL.mL-1 of each oil. The inhibitory activity of 11 sesquiterpenes identified in these oils was here examined in silico against two key enzymes in the biosynthesis pathway  of trichotecenes namely: 15-O-trichothecene acetyltransferase and 3-O-trichothecene acetyltransferase. In sesquiterpene composition, T-Muurolol and α-Eudesmol have the highest percentages ranging from 1.4 to 2.75 %. Three-dimensional structures of these two enzymes were modeled using SWISS-MODEL with GMQE = 0.93 and QMEAN = -0.45 for 3-O-trichothecene acetyltransferase and GMQE = 0.93, QMEAN = -0.58 for 15-O-trichothecene acetyltransferase. By the results of docking, T-Muurolol and α-Eudesmol showed high affinity compared to 15-Decalonectrin and Deoxynivalenol. These molecules are all sesquiterpenes with no major conformational difference with an RMSD of 3.7 Å and 3.5 Å between 15-decalonectrin and α-Eudesmol, T-Muurolol respectively. The results of docking prove the inhibitory effect of R. adpressum EO sesquiterpenes on the enzymes of mycotoxins biosynthesis pathway of F. culmorum and F. graminearum.

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