Antibacterial and antioxidant activity of Thymus essential oil (Thymus vulgaris) and aqueous extract of cinnamon (Cinnamomum verum) and their nanoemulsions

Abstract

As natural antioxidants and antimicrobials, essential oils (EOs) have been increasingly used to control foodborne pathogens. However, the application of EO in the food industry is limited due to low water solubility, intensive flavor, and high volatility. Therefore, to enhance water dispersion and prevent EO from degradation, nanoemulsions may be an alternative. In this study, two types of thyme essential oil (TEO) nanoemulsions, with distilled water (NEO) and with cinnamon aqueous extract (NEOC), were prepared. The physical, antimicrobial and antioxidant properties of TEO extracts and nanoemulsions were determined. The results showed that the mean particle size and PDI index of NEOC and NEO were 728.2 and 162.4 nm and 0.19 and 0.30, respectively. Polyphenolic compounds of aqueous extract of cinnamon, TEO, NEO and NEOC were in the range of 33.4 to 10.9 mg gallic acid equivalent/g. The antioxidant activity (DPPH) was in the range of 16.3 to 66.4%. Phenolic compounds and DPPH, TEO and NEOC were the highest. Also, the antimicrobial effects of NEO and NEOC against Staphylococcus aureus and Salmonella Typhimurium were significantly higher than TEO and cinnamon aqueous extract. The lowest values of MIC and MBC were first related to NEOC and then to NEO, which indicates the greater sensitivity of the studied microorganisms to nanoemulsions. According to the results, the highest antimicrobial and antioxidant activity was related to NEOC nanoemulsion. Therefore, it can be used in food products to prevent food poisoning and to treat diseases caused by S. aureus and S. Typhimurium.

Keywords

• cinnamon aqueous extract
• thyme essential oil
• nanoemulsion