Effect of digestible versus non-digestible citral nanoemulsions on human gut microorganisms: an in vitro digestion study

Essential oil (EO) nanoemulsions have been recently studied due to their antimicrobial properties. Nevertheless, little is known about their possible negative effect against human gut microorganisms during their passage though the gastrointestinal tract. This work studied the effect of digestible (corn oil) or non-digestible (paraffin oil) citral nanoemulsions against specific microorganisms of human microflora under in vitro digestion conditions. The use of a citral lipid carrier (paraffin oil or corn oil) decreased the nanoemulsion particle size and increased its stability after gastric conditions with regards to the pure citral nanoemulsions. Digestible nanoemulsions formulated with corn oil and citral presented a lower bactericidal activity against Lactobacillus acidophilus and Escherichia coli after being subjected to in vitro digestion conditions in comparison to the initial nanoemulsion. However, a non-digestible nanoemulsion formulated with paraffin oil and citral presented a similar antimicrobial activity against L. acidophilus and E. coli to the one of the initial nanoemulsion. This evidences that non-digestible nanoemulsions may entrap the citral in the lipid core and thus retaining its antimicrobial potential during their passage though the gastrointestinal tract. Hence, this work evidences the impact of the lipid carrier digestibility when formulating antimicrobial nanoemulsions on certain intestinal probiotic bacteria.

This study was supported by the Ministerio de Economía y Competitividad throughout the project RTI2018-094268-B-C21 (Fondo Europeo de Desarrollo Regional (FEDER) and Ministerio de Economía y Competitividad). Authors would like to thank the “Conselho Nacional de Desenvolvimento Científico e Tecnológico” (CNPq, Grant 402745/2021-3) and “Coordenação de Aconselhamento de Pessoal de Nível Superior” (CAPES-Brazil; UFPB/CAPES/PrInt 88881.311776/2018-01 Sandwich Doctorate Grant 88887.370630/2019-00).