Aplicação de óleos essenciais como controle alternativo de fitopatógenos de citros (Colletotrichum abscissum e Colletotrichum gloeosporioides): avaliação antifúngica, sinergismo e identificação de compostos bioativos por análises quimiométricas

Abstract

The rapid post-harvest deterioration of fruits is a major challenge for the food industry. Essential oils (EOs) have been applied as food preservation additives due to their antimicrobial properties, presenting a potential alternative to extending fruit shelf life. Thus, this study aimed to evaluate the Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) of different EOs against the fungi Colletotrichum abscissum and Colletotrichum gloeosporioides, which cause diseases such as Postblom fruit drop (PFD) and Anthracnose, respectively. Furthermore, the study sought to identify the main bioactive compounds through correlation between the chemical profiles obtained by Gas Chromatography-Mass Spectrometry (GC-MS) and MIC results, using the Partial Least Squares (PLS) chemometric regression method. The MIC and MFC of eleven EOs (pine, ginger, fennel, bitter orange, rosemary, sweet orange, basil, tea tree, thyme, cinnamon, and clove) were tested. Among them, the five EOs with the best results were selected to prepare ten binary combinations (50:50). The calculation of the Fractional Inhibitory Concentration Index (FICi) revealed synergistic effects for the combinations of cinnamon and tea tree EOs against C. abscissum, and cinnamon and clove EOs against C. gloeosporioides, with an MIC of 0,016% for both combinations. The chemical profile by GC-MS was obtained for all pure EOs. To further identify the bioactive compounds, the EOs that exhibited synergistic effects had their MICs and chemical profiles evaluated at different proportions (20:80 and 80:20). The chemical profile and MICs were correlated using PLS, and the active compounds were identified based on VIP scores and regression coefficient models. The mixture containing tea tree EO (20%) and cinnamon EO (80%) was the most promising, with an MIC of 0,0078% against C. abscissum, suggesting that cinnamaldehyde and 3-allylguaiacol were the possible active agents. For C. gloeosporioides, the binary mixture of clove and cinnamon EOs was the most effective, with a MIC of 0,016%, with eugenol, β-caryophyllene, and cinnamyl acetate identified as the probable antifungal agents. Antioxidant analyses were also performed to assess the ability of the studied EOs to combat oxidation, highlighting clove EO, which demonstrated antioxidant potential in the Folin-Ciocalteu assay, with a value of 2811,81 mg AGE/mg at a concentration of 3 mg/mL. These results indicate the potential of EOs as antifungal agents, suggesting that their incorporation into formulations for citrus fruit treatment could be a promising strategy for disease control. Future analyses may evaluate their direct application on fruits to confirm efficacy in controlling the spread of the studied pathogens, extending post-harvest shelf life, and reducing deterioration-related losses.