Potencial antimicrobiano e toxicológico do óleo essencial de Cymbopogon citratus, terpenóides naturais e suas nanoemulsões

Abstract

The food industry increasingly aims to promote the quality and safety of its products by adopting conservative techniques that employ the application of compounds with bioactive principles, especially those that act on the growth of undesirable microorganisms. The use of traditional synthetic preservatives is often associated with cytotoxic and antinutritional factors for consumers, which has driven the search for new alternative compounds. Terpenes, derived from the secondary metabolism of plant biosynthetic pathways, are recognized for their diverse bioactive activities such as antimicrobial and antioxidant effects, but their application is limited due to their hydrophobic properties. Techniques such as nanoemulsification emerge to increase solubility and improve the physicochemical properties of lipid matrices. In this context, the present study aimed to evaluate the antimicrobial and toxicological potential of the essential oil of Cymbopogon citratus, citral, eucalyptol, as well as their respective nanoemulsions (NEs) in three distinct formulations. Citral NE samples demonstrated stability in all formulations, while lemongrass oil only remained stable in formulation 02. They exhibited pseudoplastic flow, high encapsulation efficiency (≥ 99.6%), with rounded or approximate conformations ranging in size from 227 to 200 nm, -13 to 22 mV, and a polydispersity index > 0.09. Through physical characterization, it was possible to observe the levels of the active component citral present in the lipid samples tested through its isomers (neral and geranial) and the predominance of aldehydic functional groups. Both lipidic and nanoemulsified samples demonstrated significant antimicrobial action against the tested pathogens, especially the samples of C. citratus oil (CBM 1,855 mg/mL) and NF03CT (CBM 1,573 mg/mL) against S. aureus, with an increase in the active's action in the emulsions. The toxicological actions were relative to the concentrations of active components, with the lowest LC50 values observed for eucalyptol (153.85 mg/mL) and the NEs NF01CT (LC50 > 25.18 mg/mL) and NF02CS (26.70 mg/mL). In the in vitro application test, a decrease of up to 1 Log10 CFU/g was obtained in the mesophilic microorganism load naturally present in cheese, with reduced antimicrobial action possibly due to interference from macronutrients and the varied microbial load present in the cheese. The results obtained demonstrated the potential use of both citral lipidic samples and C. citratus oil and their NEs in food products, especially those containing citral, due to their superior bioactive action compared to other samples.