GC–MS Characterization and Evaluation of Antifungal and Phytotoxic Activities of Essential Oils for Sustainable Crop Protection

Abstract

Essential oils (EOs) are extensively investigated for their bioactive compounds, which may provide natural alternatives to synthetic fungicides and plant growth regulators. This study aimed to characterize the chemical composition of essential oils (EOs) from Ocimum gratissimum and Lippia multiflora, evaluate their antifungal activity against Aspergillus flavus and Aspergillus parasiticus, and assess their phytotoxic effects on the germination of Zea mays, Arachis hypogaea, and Vigna unguiculata. Essential oils were obtained by hydrodistillation and analyzed by GC–MS. Antifungal activity was assessed using a broth microdilution assay to determine minimum inhibitory concentrations (MIC) and minimum fungicidal concentrations (MFC). Phytotoxicity was evaluated through seed germination and seedling development assays at concentrations of 1.5, 3, and 5 µL/mL. Data were analyzed statistically using ANOVA. The EO of L. multiflora contained 16 compounds, predominantly β‑caryophyllene and p‑cymene, whereas O. gratissimum oil comprised 10 compounds mainly γ‑terpinene and thymol. Both oils exhibited antifungal activity, with O. gratissimum showing greater efficacy (MIC 1.25 µL/mL). Thymol is recognized as the most active antimicrobial compound and would explain the antifungal effectiveness of the essential oil of O. gratissimum. In contrast, β‑caryophyllene and p‑cymene, identified in the essential oil of L. multiflora, are characterized by weaker antifungal activity. In phytotoxicity assays, L. multiflora strongly inhibited germination (10–25%) and seedling growth (15–28%) of Zea mays. In Vigna unguiculata, inhibition ranged from 11–25% for germination and 28–43% for seedling growth. Arachis hypogaea was the least affected by the essential oils. Essential oils have demonstrated promising antifungal properties and could be integrated into sustainable crop protection strategies; however, their phytotoxic effects require precise dosage to fully exploit antifungal activity without causing undesirable side effects.