Biological activity of essential oil from Piper mikanianum leaves and its major compound against storage pests and fungi

The use of synthetic insecticides and fungicides is the main method for controlling of coleopteran pests and fungal contamination during storage. However, intensive use of these products has caused several negative impacts. Thus, as an effective and safer alternative, essential oils (EOs) are a promising and efficient solution for integrated management in storage systems. The present study aimed to investigate the biological activity of Piper mikanianum EO against storage pests and fungi. The EO was extracted by hydro-distillation for 4 h, and the chemical composition was determined by gas chromatography coupled to mass spectrometry. A total of 29 compounds were identified in P. mikanianum EO, with safrole as the major compound, corresponding to 30.46%. This compound was later isolated by crystallization. The insecticidal effect of P. mikanianum EO and safrole was evaluated by fumigation, causing 100% mortality of Sitophilus zeamais, Sitophilus oryzae, Cryptolestes ferrugineus, and Rhyzopertha dominica at 138.38 μL L⁻¹ of air. The fungicidal activity was assessed by volatilization and direct contact against Fusarium graminearum. Piper mikanianum EO and safrole inhibited fungal growth by volatilization at 92% and 78.3%, respectively, at a 100% concentration; by contact, both treatments caused inhibition above 90% at a 1.5% concentration. Safrole showed a lower value (0.5%) of minimum inhibitory concentration compared to EO (1.5%) by contact. These results confirmed the potential of P. mikanianum EO and its main compound, safrole, as biopesticides in the combined management of storage pests and diseases, proving to be a promising alternative to synthetic pesticides.