Investigation of antibacterial activity of new classes of essential oils derivatives

The recent discovery of a promising pharmacological scaffold derived from carvacrol: A review

Carvacrol, called CA, is a dynamic phytoconstituent characterized by a phenol ring abundantly sourced from various natural reservoirs. This versatile scaffold serves as a pivotal template for the design and synthesis of novel drug molecules, harboring promising biological activities. The active sites positioned at C-4, C-6, and the hydroxyl group (-OH) of CA offer fertile ground for creating potent drug candidates from a pharmacological standpoint. In this comprehensive review, we delve into diverse synthesis pathways and explore the biological activity of CA derivatives. We aim to illuminate the potential of these derivatives in discovering and developing efficacious treatments against a myriad of life-threatening diseases. By scrutinizing the structural modifications and pharmacophore placements that enhance the activity of CA derivatives, we aspire to inspire the innovation of novel therapeutics with heightened potency and effectiveness.

Exploring the potential of 1,8-cineole from cardamom oil against food-borne pathogens: Antibacterial mechanisms and its application in meat preservation

Food-borne pathogenic bacteria are a major public health concern globally. Traditional control methods using antibiotics have limitations, leading to the exploration of alternative strategies. Essential oils such as cardamom possess antimicrobial properties and have shown efficacy against food-borne pathogenic bacteria. The utilization of essential oils and their bioactive constituents in food preservation is a viable strategy to prolong the shelf-life of food products while ensuring their quality and safety. To the best of our knowledge, there are no studies that have utilized 1,8-cineole (the main active constituent of cardamom essential oil) as a preservative in meat, so this study might be the first to utilize 1,8-cineole as an antibacterial agent in meat preservation. The application of 1,8-cineole had a significant suppressive impact on the growth rate of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Salmonella Typhimurium in meat samples stored for 7 days at 4 °C. Additionally, the surface color of the meat samples was not negatively impacted by the application of 1,8-cineole. The minimum inhibitory concentration was 12.5-25 mg/ml, and the minimum bactericidal concentration was 25-50.0 mg/ml. The bacterial cell membrane may be the target of cardamom, causing leakage of intracellular proteins, ATP, and DNA. The obtained data in this study may pave a new avenue for using 1,8-cineole as a new perspective for dealing with this problem of food-borne pathogens and food preservation, such as meat.

Carbon dots, cellulose nanofiber, and essential oil from Torreya grandis aril added to fish scale gelatin film for tomato preservation

In this study, carbon dots (CDs), cellulose nanofibers (CNF) and essential oil nanoemulsion (EON) were extracted from the aril waste of Torreya grandis following nuts production. These three nanomaterials were formulated for the preparation of a composite film to be employed for postharvest tomato storage. Visual, microscopical and physicochemical properties of the prepared nanocomposite films were analyzed at different levels of CDs and CNF for optimization purposes. The UV absorption and antioxidant capacity of gelatin film with 10 % CDs (G/10CD) were enhanced compared with gelatin (G) film, concurrent with a reduction in water barrier capacity, water contact angle (WCA) and tensile strength (TS). Compared with G/10CD film, the WCA of gelatin film after incorporation of 10 % CDs and 3 % CNF (G/10CD/3CNF) was significantly increased by 14.5°at 55 s. In contrast, TS increased by 1.26 MPa, as well as the significant enhancement in water barrier capacity. The above composite film mixed with NEO (G/10CD/3CNF/EON) exerted further antimicrobial effects against Escherichia coli. G/10CD/3CNF/EON coating effectively extended tomato shift life compared with the control group. Therefore, this new eco-friendly film presents several advantages of biodegradability, sustainability as well as multifunctional properties posing it as potential packaging material for food applications.

Current State of Knowledge Regarding WHO High Priority Pathogens-Resistance Mechanisms and Proposed Solutions through Candidates Such as Essential Oils: A Systematic Review

Combating antimicrobial resistance (AMR) is among the 10 global health issues identified by the World Health Organization (WHO) in 2021. While AMR is a naturally occurring process, the inappropriate use of antibiotics in different settings and legislative gaps has led to its rapid progression. As a result, AMR has grown into a serious global menace that impacts not only humans but also animals and, ultimately, the entire environment. Thus, effective prophylactic measures, as well as more potent and non-toxic antimicrobial agents, are pressingly needed. The antimicrobial activity of essential oils (EOs) is supported by consistent research in the field. Although EOs have been used for centuries, they are newcomers when it comes to managing infections in clinical settings; it is mainly because methodological settings are largely non-overlapping and there are insufficient data regarding EOs' in vivo activity and toxicity. This review considers the concept of AMR and its main determinants, the modality by which the issue has been globally addressed and the potential of EOs as alternative or auxiliary therapy. The focus is shifted towards the pathogenesis, mechanism of resistance and activity of several EOs against the six high priority pathogens listed by WHO in 2017, for which new therapeutic solutions are pressingly required.

Glucosylation of Isoeugenol and Monoterpenes in Corynebacterium glutamicum by YdhE from Bacillus lichenformis

Corynebacterium glutamicum has been regarded as a food-grade microorganism. In recent years, the research to improve the activities of beneficial therapeutics and pharmaceutical substances has resulted in the engineering of the therapeutically favorable cell factory system of C. glutamicum. In this study, we successfully glucosylated isoeugenol and other monoterpene derivatives in C. glutamicum using a promiscuous YdhE, which is a glycosyltransferase from Bacillus lichenformis. For efficient glucosylation, cultivation conditions such as the production time, substrate concentration, carbon source, and culture medium were optimized. Our system successfully converted about 93% of the isoeugenol to glucosylated compounds in the culture. The glucoside compounds were then purified, analyzed, and identified as isoeugenol-1-O-β-d-glucoside and isoeugenol-1-O-β-d-(2″-acetyl)-glucoside.

Tailored Functionalization of Natural Phenols to Improve Biological Activity

Phenols are widespread in nature, being the major components of several plants and essential oils. Natural phenols' anti-microbial, anti-bacterial, anti-oxidant, pharmacological and nutritional properties are, nowadays, well established. Hence, given their peculiar biological role, numerous studies are currently ongoing to overcome their limitations, as well as to enhance their activity. In this review, the functionalization of selected natural phenols is critically examined, mainly highlighting their improved bioactivity after the proper chemical transformations. In particular, functionalization of the most abundant naturally occurring monophenols, diphenols, lipidic phenols, phenolic acids, polyphenols and curcumin derivatives is explored.

Phytochemical properties, biological activities and medicinal use of Centaurium erythraea Rafn

ETHNOPHARMACOLOGICAL RELEVANCE

Centaurium erythraea is an important medicinal plant in many countries, e.g. Morocco, Algeria, Italy, Spain, Portugal, and countries of Balkan Peninsula. It is used in folk medicine to treat various illnesses. It is also used as an antiapoplectic, anticoagulant, anticholagogue, antipneumonic, hematocathartic, and as a hypotensive agent.

AIM OF THE REVIEW

In this review, previous reports on the taxonomy, botanical description, geographic distribution, ethnomedicinal applications, phytochemistry, pharmacological properties, and toxicity of Centaurium erythraea were critically summarized.

MATERIALS AND METHODS

Scientific search engines including PubMed, ScienceDirect, SpringerLink, Web of Science, Scopus, Wiley Online, SciFinder, and Google Scholar were consulted to collect data on C. erythraea. The data presented in this work summarized the main reports on C. erythraea phytochemical compounds, ethnomedicinal uses, and pharmacological activities.

RESULTS

C. erythraea is used in traditional medicine to treat various diseases such as diabetes, fever, rhinitis, stomach ailments, urinary tract infections, dyspeptic complaints, loss of appetite, and hemorrhoids, and as diuretic. The essential oils and extracts of C. erythraea exhibited numerous biological properties such as antibacterial, antioxidant, antifungal, antileishmanial, anticancer, antidiabetic, anti-inflammatory, insecticidal, diuretic, gastroprotective, hepatoprotective, dermatoprotective, neuroprotective, and inhibitory agent for larval development. Phytochemical characterization of C. erythraea revealed the presence of several classes of secondary metabolites such as xanthonoids, terpenoids, flavonoids, phenolic acids, and fatty acids.

CONCLUSIONS

Ethnomedicinal studies demonstrated the use of C. erythraea for the treatment of various disorders. Pharmacological reports showed that C. erythraea especially its aerial parts and roots exhibited potent, and beneficial activities. These findings confirmed the link between the traditional medicinal use and the results of the scientific biological experiments. Considering these results, further investigation using diverse in vivo pharmacological assays are strongly recommended to validate the results of its traditional use. Toxicological tests and pharmacokinetic studies are also required to validate the safety and efficacy of C. erythraea and its bioactive contents.

Zn, Cu, and Fe Concentrations in Dehydrated Herbs (Thyme, Rosemary, Cloves, Oregano, and Basil) and the Correlation with the Microbial Counts of Listeria monocytogenes and Other Foodborne Pathogens

Zn, Cu, and Fe concentrations were measured in dehydrated herbs (thyme, rosemary, cloves, oregano, and basil) marketed in bulk or packaged in glass or polyethylene terephthalate (PET). Microbial counts of Listeria monocytogenes and other five foodborne pathogens were also checked when herbs were previously added to the growing media. The highest mean concentrations were found in basil for Zn and Cu, and in thyme and basil for Fe; the lowest ones for these minerals were in cloves (p < 0.05). Basil had significantly higher microbial counts in five of the six foodborne pathogens studied (p < 0.05). Cloves have the best hygienic quality as there is no microbial growth of L. monocytogenes, Clostridium perfringens, and Bacillus cereus; they therefore could be used as a natural preservative in food. Aromatic herbs marketed in bulk showed a significantly higher microbial count (p < 0.05). Zn, Cu, and Fe concentrations were positively correlated with microbial growth for L. monocytogenes, C. perfringens, B. cereus, and psychrophilic microorganisms (p < 0.05), so they could act as a growing factor for the foodborne pathogens.

Synergistic Effect of Eugenol and Probiotic Lactobacillus Plantarum Zs2058 Against Salmonella Infection in C57bl/6 Mice

Previously, we showed the preventive effects of Lactobacillus plantarum ZS2058 (ZS2058) on Salmonella infection in murine models. In this work, we found that eugenol has a selective antibacterial effect, which inhibited Salmonella more than probiotics ZS2058 in vitro. It suggested a synergistic effect of them beyond their individual anti-Salmonella activity. We verified the conjecture in murine models. The results showed that the combination of ZS2058 and eugenol (CLPZE) significantly increased (p = 0.026) the survival rate of Salmonella-infected mice from 60% to 80% and the effect of CLPZE on preventing Salmonella-infection was 2-fold that of ZS2058 alone and 6-fold that of eugenol alone. CLPZE had a synergistic effect on inhibiting ST growth (the coefficient drug interaction ((CDI) = 0.829), reducing its invasiveness (CDI = 0.373) and downregulating virulence genes’ expression in vitro. CLPZE helped the host form a healthier gut ecosystem. CLPZE also elicited a stronger and earlier immune response to systemic infection. In conclusion, these obtained results suggest that ZS2058 and eugenol have a synergistic effect on preventing Salmonella infection and open new perspectives in the strategies of controlling the prevalence of Salmonella by combination of probiotics and functional food components.

Carvacrol Prodrugs with Antimicrobial Activity Loaded on Clay Nanocomposites

Background: Carvacrol, an essential oil with antimicrobial activity against a wide range of pathogens, and its water soluble carvacrol prodrugs (WSCP1-3) were intercalated into montmorillonite (VHS) interlayers to improve their stability in physiological media and promote their absorption in the intestine. Methods: Intercalation of prodrugs by cation exchange with montmorillonite interlayer counterions was verified by X-ray powder diffraction and confirmed by Fourier transform infrared spectroscopy and thermal analysis. Results: In vitro release studies demonstrated that montmorillonite successfully controlled the release of the adsorbed prodrugs and promoted their bioactivation only in the intestinal tract where carvacrol could develop its maximum antimicrobial activity. The amount of WSCP1, WSCP2, and WSCP3 released from VHS were 38%, 54%, and 45% at acid pH in 120 min, and 65%, 78%, and 44% at pH 6.8 in 240 min, respectively. Conclusions: The resultant hybrids successfully controlled conversion of the prodrugs to carvacrol, avoiding premature degradation of the drug.

Isorhamnetin, Hispidulin, and Cirsimaritin Identified in Tamarix ramosissima Barks from Southern Xinjiang and Their Antioxidant and Antimicrobial Activities

As a natural potential resource, Tamarix ramosissima has been widely used as barbecue skewers for a good taste and unique flavor. The polyphenolics in the branch bark play a key role in the quality improvement. The purposes of the present work were to explore the polyphenolic composition of T. ramosissima bark extract and assess their potential antioxidant and antimicrobial activities. Hispidulin and cirsimaritin from T. ramosissima bark extract were first identified in the Tamarix genus reported with UPLC-MS analysis. Isorhamnetin (36.91 μg/mg extract), hispidulin (28.79 μg/mg extract) and cirsimaritin (13.35 μg/mg extract) are rich in the bark extract. The extract exhibited promising antioxidant activity with IC₅₀ values of 117.05 μg/mL for 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 151.57 μg/mL for hydroxyl radical scavenging activities, as well as excellent reducing power with an EC₅₀ of 93.77 μg/mL. The bark extract showed appreciable antibacterial properties against foodborne pathogens. Listeria monocytogenes was the most sensitive microorganism with the lowest minimum inhibitory concentration (MIC) value of 5 mg/mL and minimum bactericidal concentration (MBC) value of 10 mg/mL followed by S. castellani and S. aureus among the tested bacteria. The T. ramosissima bark extract showed significantly stronger inhibitory activity against Gram-positive than Gram-negative bacteria. Nevertheless, this extract failed to show any activity against tested fungi. Overall, these results suggested that T. ramosissima shows potential in improving food quality due to its highly efficacious antioxidant and antibacterial properties.

Effects of 1,8-cineole on Carbohydrate Metabolism Related Cell Structure Changes of Salmonella

Salmonella is gram-negative foodborne zoonotic bacteria which triggers disease in humans. Our previous studies showed 1,8-cineole possessed remarkable antimicrobial effects on foodborne zoonotic bacteria indicating it could serve as a new source of antibiotic for Salmonella. Present study elucidated the antibacterial mechanism of 1,8-cineole by analyzing serum protein expressed by Salmonella following treatment with 1,8-cineole (0.25 mg/mL, 3 h) using isobaric tags for relative and absolute quantification (iTRAQ) with two-dimensional liquid chromatography/tandem mass spectrometry (2D-LC-MS/MS). 1,8-cineole was found to significantly damage the structure of Salmonella cell walls and membranes. A total of 3011 proteins were extracted from the experimental group, of which 435 were differentially expressed (1.5-fold) with 123 upregulated and 312 downregulated. The expressed proteins were involved in 935 intracellular biological processes, 98 cellular components, 477 molecular functions and 86 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Among them, proteins associated with carbohydrate, nucleotide, amino acid, lipid, and energy metabolism were significantly changed following treatment with 1,8-cineole. Carbohydrate metabolism and membrane protein-related genes was down-regulated at the mRNA level when Salmonella was treated with 1,8-cineole. 1,8-cineole may be a potential antibiotic for Salmonella infections.

Toxicity and growth inhibition potential of vetiver, cinnamon, and lavender essential oils and their blends against larvae of the sheep blowfly, Lucilia sericata

BACKGROUND

Myiasis induced by the sheep blowfly, Lucilia sericata, represents a public health problem widely distributed throughout the world. L. sericata larval stages feed on both humans and animals. L. sericata adults and larvae can play a role in spreading agents of mycobacterial infections.

OBJECTIVES

It is critical to establish new and safe alternative methods of controlling L. sericata.

METHODS

The insecticidal effectiveness and growth inhibition potential of three commercially available essential oils (EOs), vetiver (Chrysopogon zizanioides), cinnamon (Cinnamomum zeylanicum), and lavender (Lavandula angustifolia), as well as their blends, were tested against the second (L2) and third (L3) larval stages of L. sericata. Sunflower (Helianthus annuus) oil was used as a carrier and tested on L2 and L3 larvae. To the best of our knowledge, all applied essential oils, except lavender, and oil blends were tested against L. sericata for the first time.

RESULTS

All applied oils did not repel L2 from the treated liver but adversely affected their development. Contact treatments on L. sericata L3 indicated that vetiver and cinnamon oils significantly affected treated larvae. Total mortality rates were 93.33 and 95.56%, respectively. Furthermore, oil blends tested through contact assays killed larvae when used at higher concentrations; adult emergence was eliminated post-treatment with doses >30% for oil blend 1 and >10% for oil blend 2.

CONCLUSION

Overall, cinnamon and vetiver oils (5%) were selected as reliable and cheap biopesticides for controlling larvae of L. sericata. The tested oils are inexpensive and represent new promising botanical insecticides in the fight against blowflies causing myiasis.

Semisynthetic Phenol Derivatives Obtained from Natural Phenols: Antimicrobial Activity and Molecular Properties

Semisynthetic phenol derivatives were obtained from the natural phenols: thymol, carvacrol, eugenol, and guaiacol through catalytic oxychlorination, Williamson synthesis, and aromatic Claisen rearrangement. The compounds characterization was carried out by ¹H NMR, ¹³C NMR, and mass spectrometry. The natural phenols and their semisynthetic derivatives were tested for their antimicrobial activity against the bacteria: Staphylococcus aureus, Escherichia coli, Listeria innocua, Pseudomonas aeruginosa, Salmonella enterica Typhimurium, Salmonella enterica ssp. enterica, and Bacillus cereus. Minimum inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) values were determined using concentrations from 220 to 3.44 μg mL^-1. Most of the tested compounds presented MIC values ≤220 μg mL^-1 for all the bacteria used in the assays. The molecular properties of the compounds were computed with the PM6 method. Through principle components analysis, the natural phenols and their semisynthetic derivatives with higher antimicrobial potential were grouped.

Antibacterial activities of a cinnamon essential oil with cetylpyridinium chloride emulsion against Escherichia coli O157:H7 and Salmonella Typhimurium in basil leaves

This study examined the antibacterial activities of two different cinnamon essential oil emulsions against Escherichia coli O157:H7 and Salmonella Typhimurium on basil leaves. Cinnamon oil (0.25%) treatments containing CPC (0.05%) exhibited greater effects on the pathogenic bacteria than cinnamon oil treatment without this emulsifier (p < 0.05). Treatment with cinnamon bark and leaf oil emulsions (CBE and CLE, respectively) reduced the populations of E. coli O157:H7 by 4.10 and 5.10 log CFU/g, and S. Typhimurium by 2.71 and 2.82 log CFU/g, respectively. Scanning electron micrographs showed morphological changes in the two pathogenic bacteria following emulsion treatment. In addition, there was no difference in the color or ascorbic acid content of the basil leaves by the emulsion treatment. These results suggest that CBE or CLE treatment can be an effective way to ensure the microbial safety of minimally processed vegetables and a good alternative to chlorination treatment in the fresh produce industry.