Desenvolvimento de nanocápsulas de poli(ácido lático) contendo óleo essencial de capim-limão e avaliação contra fungos fitopatogênico

Abstract

Brazilian agricultural production reached 226.5 million tons in 2018, being Mato Grosso, Paraná and Rio Grande do Sul the states responsible for the major amount of the country’s production. Among the challenges of agricultural production is the control of diseases caused by phytopathogens, such as, Colletotrichum gloeosporioides and Colletotrichum acutatum. These fungi are responsible for the diseases known as ripe rot on grapes and anthracnose, usually controlled with fungicides containing pyraclostrobin + metiram and tetraconazole. Nevertheless pesticides-free foods are a growing demand of population. That requires, especially from the scientific community, actions for an efficient and safe control of the phytopathologies. Essential oils, which are products from plants secondary metabolism, show antifungal properties and are seen as an alternative for commercial fungicides. However, essential oils are volatile and photodegradable, inhibiting their activity in long-term. Thus, this work aimed to develop PLA nanocapsules with a lemongrass essential oil core (LG-PLA-NCs), with the purpose of gradual essential oil liberation. The essential oil was characterized by gas chromatography with mass spectrometry (GC-MS) and refraction index before the development of nanocapsules by nanoprecipitation of preformed polymer. The effects of the amount of the surfactants (Tween 80 and Span 60) and essential oil were evaluated using a 23 factorial design and the mean diameter (MD), zeta potential (ZP) and encapsulation efficiency (EE) as responses. After determining the best synthesis condition, the nanocapsules were additionally characterized by scanning electron microscopy, thermogravimetric analysis and Fourier-transform infrared spectroscopy. The nanocapsules antifungal activity was evaluated based on a spore germination assay for C. gloeosporioides and C. acutatum. It was also performed an assay, in vivo, in apples for C. gloeosporioides. The optimized methodology led to 99.8% EE, with a MD of 96.4 nm and ZP of -25.2 mV. The minimum inhibitory concentration (MIC) for both evaluated species in presence of the encapsulated essential oil was 0.1% v/v. The postharvest assay with apples displayed that encapsulated essential oil presented lesion diameters up to three times smaller than apples treated with non-encapsulated essential oil.