Comparative Analysis of the Chemical Composition and Antimicrobial Activity of Four Moroccan North Middle Atlas Medicinal Plants’ Essential Oils: Rosmarinus officinalis L., Mentha pulegium L., Salvia officinalis L., and Thymus zygis subsp. gracilis (Boiss.) R. Morales

Abstract

Medicinal plants represent an inexhaustible source of traditional and effective remedies thanks to the various active ingredients they contain. Secondary metabolites present in plant extracts, such as essential oils (EO), have remarkable pharmacological properties, including antimicrobial effects. Here, the chemical composition and antimicrobial effects of four Moroccan medicinal plants, Rosmarinus officinalis L. (R. officinalis), Mentha pulegium L. (M. pulegium), Salvia officinalis L. (S. officinalis), and Thymus zygis subsp. gracilis (Boiss.) R. Morales (T. zygis), traditionally used in Morocco to treat microbial infections, were addressed. EO were extracted using the hydrodistillation method, and analyzed by gas chromatography coupled with mass spectrometry (GC/MS). EO yields were of 3.64 ± 0.12, 3.53 ± 0.06, 2.48 ± 0.06, and 2.34 ± 0.08%, respectively, for M. pulegium, R. officinalis, S. officinalis, and T. zygis. The main bioactive components present in these EO were piperitenone (32.9%) and pulegone (32.8%) for M. pulegium, 1,8-cineol (43.8%) and camphor (18.7%) for R. officinalis, 1,8-cineole (16.8%) and trans-thujone (15.9%) for S. officinalis, and thymol (36.4%), carvacrol (24.1%) and cymene (23.5%) for T. zygis. These EO showed, according to the results of their antimicrobial activities, good effectiveness against bacteria and fungi. Moreover, the T. zygis EO showed the most potent activity against all bacteria studied, while that of R. officinalis, M. pulegium, and S. officinalis showed moderate activity against the Enterobacter cloacae of Streptococcus agalactiae and Escherichia coli. The antifungal activity tests revealed a strong antifungal activity for the T. zygis EO and a moderate activity for the S. officinalis EO. On the other hand, the EO of R. officinalis, and M. pulegium were found to be inactive at the doses used against the selected strains. In conclusion, our results show that the medicinal plants studied contain biologically active molecules with antimicrobial effects. They can replace synthesized molecules, especially in the formulation of additives, and for therapeutic, cosmetic, and food-processing purposes.

In vitro antimicrobial activity of extracts and essential oils ofCinnamomum,Salvia, andMenthaspp. against foodborne pathogens: A meta‐analysis study

“…The results showed that the efficacy of plant extracts varied among different species of plants, which is consistent with prior research (Didehdar et al., 2022; Gourich et al., 2022; Huang et al., 2014; Hussein et al., 2018; Park et al., 2016; Pľuchtová et al., 2018). Notably, the meta‐analysis revealed significant differences in the MIC produced by extracts or EOs of various Mentha spp., but only for E. coli , while no significant differences were observed in MIC produced by different Salvia spp.…”

“…In this regard, prior research can provide valuable insight into the antimicrobial potential of various plant extracts, allowing researchers and clinicians to make informed decisions regarding the selection of appropriate extracts for treatment and/or application as food preservatives. The results showed that the efficacy of plant extracts varied among different species of plants, which is consistent with prior research (Didehdar et al, 2022;Gourich et al, 2022;Huang et al, 2014;Hussein et al, 2018;Park et al, 2016;Pľuchtová et al, 2018). Notably, the meta-analysis revealed significant differences in the MIC produced by TA B L E 4 Pooled minimum inhibitory concentrations (MICs) (mean and 95% confidence intervals [CIs]) produced by extracts (mg/mL) or essential oils (μL/mL) of cinnamon (Cinnamomum spp.…”

“…These findings are consistent with previous studies reporting the antimicrobial activity of Mentha spp. against these foodborne pathogens (Baali et al., 2019; Gourich et al., 2022; Pľuchtová et al., 2018; Shahbazi, 2015).…”

“…A number of possible sources of variability have been identified in the literature. For instance, the source, stage of development, and seasonality of the plants used to obtain the extracts have been shown to impact their antimicrobial properties (Chouhan et al., 2017; Costa et al., 2022; Gourich et al., 2022). Furthermore, the composition of these extracts, specifically the presence of phenolic compounds and their derivatives, fatty acids, terpenes, and other secondary metabolites, can also play a role in their antimicrobial activity (Altun & Yapici, 2022; Alves et al., 2022).…”

“…These findings are consistent with previous studies reporting the antimicrobial activity of Mentha spp. against these foodborne pathogens (Baali et al, 2019;Gourich et al, 2022;Pľuchtová et al, 2018;Shahbazi, 2015). The impact of different types of antimicrobials applied (extract or EO) derived from Cinnamomum, Salvia, and Mentha species was also examined.…”