Antifungal Activity and Computational Study of Constituents from Piper divaricatum Essential Oil against Fusarium Infection in Black Pepper

Fusarium disease causes considerable losses in the cultivation of Piper nigrum, the black pepper used in the culinary world. Brazil was the largest producer of black pepper, but in recent years has lost this hegemony, with a significant reduction in its production, due to the ravages produced by the Fusarium solani f. sp. piperis, the fungus which causes this disease. Scientific research seeks new alternatives for the control and the existence of other Piper species in the Brazilian Amazon, resistant to disease, are being considered in this context. The main constituents of the oil of Piper divaricatum are methyleugenol (75.0%) and eugenol (10.0%). The oil and these two main constituents were tested individually at concentrations of 0.25 to 2.5 mg/mL against F. solani f. sp. piperis, exhibiting strong antifungal index, from 18.0% to 100.0%. The 3D structure of the beta-glucosidase from Fusarium solani f. sp. piperis, obtained by homology modeling, was used for molecular docking and molecular electrostatic potential calculations in order to determine the binding energy of the natural substrates glucose, methyleugenol and eugenol. The results showed that beta-glucosidase (Asp45, Arg113, Lys146, Tyr193, Asp225, Trp226 and Leu99) residues play an important role in the interactions that occur between the protein-substrate and the engenol and methyleugenol inhibitors, justifying the antifungal action of these two phenylpropenes against Fusarium solani f. sp. piperis.