Synergistic properties of Eucalyptus caesia and Dracocephalum multicaule Montbr & Auch essential oils: Antimicrobial activity against food borne pathogens and antioxidant activity in pear slices

Abstract

The objective of this study was to evaluate the possible synergistic interactions on antibacterial and antioxidant efficacy of two plant essential oils (EOs) Eucalyptus caesia Benth and Dracocephalum multicaule Montbr & Auch in vitro and in pear slices. Antibacterial combination effect was evaluated against seven important pathogenic bacteria (Bacillus cereus, Listeria monocytogenes, Staphylococcus aureus, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, and Escherichia coli) using microbroth dilution, agar, and vapor diffusion methods. Fractional inhibitory concentration (FIC) and fractional bactericidal concentration (FBC) were performed to quantify the efficacy of target EOs in combination. An in vivo antibacterial assay was performed on treated pear slices during storage at 4 and 25°C. The in vitro and in vivo antioxidant effect of EOs both alone and in combination was assessed by DPPH free radical‐scavenging method. The results indicated that the examined EOs are more active against Gram‐positive than Gram‐negative bacteria and E. caesia EO exhibited more antibacterial activity compared to D. multicaule. The combination of E. caesia with D. multicaule EOs induced a synergistic effect against B. cereus, S. aureus, and L. monocytogenes, whereas caused an additive effect against E. coli, S. typhi, S. flexneri, and P. aeruginosa. Among all combination concentration treatment, 2:1 (vol/vol) (E. caesia + D. multicaule, respectively) was determined as the most effective concentration against target bacterial which was exhibited a good antimicrobial efficacy even in agar and vapor diffusion methods. The in vivo test also represented considerable antibacterial inhibitory effects of EOs combination treatments. The synergistic effect of the EO combination was also evident in the total soluble phenolic and antioxidant activity in pear slices. The results provide evidence that E. caesia/D. multicaule EO combination can be used as a potential source of effective natural antibacterial and antioxidant agents. Practical applications Deterioration of fruits during storage can be reduced by avoiding damage to the fruit through harvesting and subsequent handlings and storage in cold or under changed atmosphere environment. The main issue of fresh fruit is susceptible to spoilage through storage. Therefore, preservatives are essential for increase of shelf‐life of food products. However, society needs more safe and natural preservatives with increased shelf‐life. Among natural antimicrobial agents, essential oils can be used as antibacterial, antifungal, and antioxidant in food industry.

Boswellic Acids as Effective Antibacterial Antibiofilm Agents

“…The use of a complex extract may be more advantageous due to the synergistic interaction of the individual components of the extract, which increase the resulting efficiency of such complex mixtures. Hashemi and Jafarpour [61] tested the effectiveness of Eucalyptus caesia Benth and Dracocephalum multicaule complex essential oils on E. coli. They found that essential oils were more effective against Gram-positive than against Gram-negative bacteria.…”

Antimicrobial activity of Carum copticum and Satureja khuzestanica essential oils and acetic acid in vapor phase at different relative humidities and temperatures in peanuts

“…The main components of CEO were thymol, γ‐ terpinene, and p‐cymene and for SEO were carvacrol and myrcene. It has been shown that chemical compounds such as aldehydes, phenolics, carvacrol, thymol, and eugenol play an important role in the antimicrobial properties of EOs (Clemente et al., 2016; Hashemi & Jafarpour, 2020a). It seems that the inactivation of the studied pathogens is related to the impact of volatile compounds of CEO and SEO in the vapor phase.…”

“…The interior of the container consists of three sections: one where samples are treated with the vapors, one where the vapors are created, and one including saturated salt solution (NaNO 2 : RH: 63 ± 1%; NaCl: RH: 75 ± 0%; KNO 3 : RH: 84 ± 1% at 25, 37, and 50°C) for altering RH of the interior atmosphere. Fumigation was performed for 2 hr at the interval time of 0, 1, and 2 hr (Hashemi & Jafarpour, 2020a).…”

“…Plant‐derived compounds are promising alternative preservatives since different types of metabolites derived from plants often show good antimicrobial properties. In this regard, plant essential oils (EOs) have received much attention because they have shown a wide range of antifungal, antiviral, antibacterial, antioxidant, and insecticidal activities (Dhifi et al., 2016; Hashemi & Jafarpour, 2020a; Sayadi et al., 2021). EOs are specific secondary metabolites produced by medicinal herbs and aromatic plants.…”

The synergistic effects of aloe vera gel and modified atmosphere packaging on the quality of strawberry fruit

“…Although cold temperatures and a modified atmosphere can extend the storage time of strawberries, supplemental methods to maintain the fruit quality are being developed (Ghorbani et al., 2021). For example, edible coatings have recently been shown to improve product quality and increase shelf life periods of various fruits such as papaya and strawberries (Hashemi & Jafarpour, 2020; Tapia et al., 2008; Tarafdar et al., 2021). Coatings can provide moisture and gas permeability barriers and thus help with microbial growth control and protection of color and texture (Bourtoom, 2008; Hosseini et al., 2017; Mousavian et al., 2021).…”