A Carvacrol-Rich Essential Oil Extracted From Oregano (Origanum vulgare "Hot & Spicy") Exerts Potent Antibacterial Effects Against Staphylococcus aureus

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.

Study of the Resistance of Staphylococcus aureus Biofilm, Biofilm-Detached Cells, and Planktonic Cells to Microencapsulated Carvacrol Used Alone or Combined with Low-pH Treatment

Microbial biofilms pose severe problems in the medical field and food industry, as they are the cause of many serious infections and food-borne diseases. The extreme biofilms' resistance to conventional anti-microbial treatments presents a major challenge to their elimination. In this study, the difference in resistance between Staphylococcus aureus DSMZ 12463 biofilms, biofilm-detached cells, and planktonic cells against microcapsules containing carvacrol was assessed. The antimicrobial/antibiofilm activity of low pH disinfection medium containing the microencapsulated carvacrol was also studied. In addition, the effect of low pH on the in vitro carvacrol release from microcapsules was investigated. The minimum inhibitory concentration of microencapsulated carvacrol was 0.625 mg mL-1. The results showed that biofilms exhibited greater resistance to microencapsulated carvacrol than the biofilm-detached cells and planktonic cells. Low pH treatment alone, by hydrochloric acid addition, showed no bactericidal effect on any of the three states of S. aureus strain. However, microencapsulated carvacrol was able to significantly reduce the planktonic cells and biofilm-detached cells below the detection limit (no bacterial counts), and the biofilm by approximatively 3 log CFU mL-1. In addition, results showed that microencapsulated carvacrol combined with low pH treatment reduced biofilm by more than 5 log CFU mL-1. Thus, the use of microencapsulated carvacrol in acidic environment could be a promising approach to combat biofilms from abiotic surfaces.

Assessment of carvacrol-antibiotic combinations' antimicrobial activity against methicillin-resistant Staphylococcus aureus

Introduction

This study aimed to assess the antimicrobial activity of carvacrol in combination with approved antibiotics against methicillin-resistant Staphylococcus aureus (MRSA). Carvacrol, a phenolic monoterpenoid component of essential oils, has demonstrated antimicrobial properties against gram positive and gram negative bacteria. The study evaluated the antimicrobial effects of carvacrol combined with sulfamethoxazole, linezolid, minocycline, and trimethoprim.

Methods

The MRSA strain (ATCC-33591) was used, and various assays, including MIC determination, checkerboard assay, and microdilution assay were conducted.

Results

The results showed that the combination of carvacrol with antibiotics yielded better outcomes compared to monotherapy, leading to reduced bacterial colonization. Carvacrol, sulfamethoxazole, and trimethoprim exhibited weak anti-staphylococcal effects, while linezolid and minocycline demonstrated stronger effects. This suggests that conventional antibiotic therapy may not be sufficient to effectively treat MRSA infections, potentially causing delays in healing or an exacerbation of the condition. Carvacrol combinations with two antibiotics displayed superior results compared to other pairs, indicating synergistic or additive effects of carvacrol with linezolid, minocycline, and sulfamethoxazole.

Conclusion

These findings propose a new approach for developing drug molecules for MRSA treatment which combine volatile oils with available regimens. Further studies are recommended to evaluate the efficacy and biosafety of these combinations using in vivo or ex vivo models, aiming to minimize side effects and facilitate human trials. This study provides valuable insights into the potential use of carvacrol-antibiotic combinations as a novel therapeutic approach against MRSA.

Proteomic Analysis of Staphylococcus aureus Treated with ShangKeHuangShui

Staphylococcus aureus (SAU) stands as the prevailing pathogen in post-traumatic infections, with the emergence of antibiotic resistance presenting formidable treatment hurdles. The pressing need is to explore novel antibiotics to address this challenge. ShangKeHuangShui (SKHS), a patented traditional Chinese herbal formula, has gained widespread use in averting post-traumatic infections, but its biological effects remain incomplete understanding. This study's primary objective was to delve into the antibacterial properties, potential antibacterial compounds within SKHS, and their associated molecular targets. In vitro SKHS antibacterial assays demonstrated that the minimum inhibitory concentration (MIC) was 8.625 mg/mL and the minimum bactericide concentration (MBC) was 17.25 mg/mL. Proteomic analysis based on tandem mass tag (TMT) showed significant changes in the expression level of 246 proteins in SKHS treated group compared to control group, with 79 proteins upregulated and 167 proteins downregulated (>1.5-fold, p < 0.05). Subsequently, thirteen target proteins related to various biological processes and multiple metabolic pathways were selected to conduct parallel reaction monitoring (PRM) and molecular docking screen. In protein tyrosine phosphatase PtpA (ptpA) docking screening, phellodendrine and obacunone can bind to ptpA with the binding energy of - 8.4 and - 8.3 kcal/mol, respectively. This suggests their potential impact on antibacterial activity by modulating the two-component system of SAU. The discovery lays a groundwork for future research endeavors for exploring new antibacterial candidates and elucidating specific active chemical components within SKHS that match target proteins. Further investigations are imperative to unveil the biological effects of these monomers and their potential synergistic actions.

Mediterranean Plants with Antimicrobial Activity against Staphylococcus aureus, a Meta-Analysis for Green Veterinary Pharmacology Applications

Antimicrobial resistance (AMR) has emerged as a global health crisis, necessitating the search for innovative strategies to combat infectious diseases. The unique biodiversity of Italian flora offers a treasure trove of plant species and their associated phytochemicals, which hold immense potential as a solution to address AMR. By investigating the antimicrobial properties of Italian flora and their phytochemical constituents, this study aims to shed light on the potential of phyto-complexes as a valuable resource for developing novel or supportive antimicrobial agents useful for animal production.

Microbiological Studies on the Influence of Essential Oils from Several Origanum Species on Respiratory Pathogens

Essential oils (EOs) with established and well-known activities against human pathogens might become new therapeutics in multidrug-resistant bacterial infections, including respiratory tract infections. The aim of this study was to evaluate the antimicrobial activity of EOs obtained from several samples of Origanum vulgare, O. syriacum, and O. majorana cultivated in Poland. EOs were analyzed by GC-MS and tested against four bacterial strains: Staphylococcus aureus (MRSA), Haemophilus influenzae, Haemophilus parainfluenzae, and Pseudomonas aeruginosa. Chemical analyses showed that the Eos were characterized by a high diversity in composition. Based on the chemical data, four chemotypes of Origanum EOs were confirmed. These were carvacrol, terpineol/sabinene hydrate, caryophyllene oxide, and thymol chemotypes. Thin-layer chromatography-bioautography confirmed the presence of biologically active antibacterial components in all tested EOs. The highest number of active spots were found among EOs with cis-sabinene hydrate as the major compound. On the other hand, the largest spots of inhibition were characteristic to EOs of the carvacrol chemotype. Minimal inhibitory concentrations (MICs) were evaluated for the most active EOs: O. vulgare ‘Hirtum’, O. vulgare ‘Margarita’, O. vulgare ‘Hot & Spicy’, O. majorana, and O. syriacum (I) and (II); it was shown that both Haemophilus strains were the most sensitive with an MIC value of 0.15 mg/mL for all EOs. O. majorana EO was also the most active in the MIC assay and had the highest inhibitory rate in the anti-biofilm assay against all strains. The most characteristic components present in this EO were the trans-sabinene hydrate and terpinen-4-ol. The strain with the least sensitivity was the MRSA with an MIC of 0.6 mg/mL for all EOs except for O. majorana, where the MIC value reached 0.3 mg/mL. Scanning electron microscopy performed on the Haemophilus influenzae and Haemophilus parainfluenzae biofilms showed a visible decrease in the appearance of bacterial clusters under the influence of O. majorana EO.

Chemical Composition, Antibacterial and Antioxidant Activities of Essential Oil from Centipeda minima

This study elucidated the chemical composition of essential oil from Centipeda minima (EOCM) and its antibacterial and antioxidant activities with two chemical monomers thymol and carvacrol. The main chemical composition of EOCM, analyzed by GC-MS, were trans-chrysanthenyl acetate, thymol, aromadendrene and β-caryophyllene. In the screening of antibacterial activity against S. aureus, two monomers with antibacterial activity were obtained: thymol and carvacrol. The MIC of EOCM, thymol and carvacrol were 0.625 mg/mL, 0.156 mg/mL and 0.156 mg/mL, respectively. The experimental results were shown that three drugs could inhibit the growth of S. aureus and inhibit the formation of biofilm by changing the permeability of cell membrane and interfering with the metabolic activities in bacteria. The scavenging effects of the three drugs on DPPH radical and hydroxyl radical showed that the antioxidant effect of the three drugs was EOCM > carvacrol > thymol.

Combined effect of thyme and clove phenolic compounds on Xanthomonas campestris pv. campestris and biocontrol of black rot disease on cabbage seeds

The seed-borne bacterium Xanthomonas campestris pv. campestris (Xcc) as a causal organism of black rot disease remains the most serious bacterial problem of agricultural production of cruciferous plants worldwide. The eradication of a primary inoculum originating in seeds is available, but no treatment is totally effective. With the threat of developing chemical resistance and increasing pressure for sustainable disease management, biocontrol methods represent one of the main strategies currently applied in agriculture. Natural antimicrobials, including essential oils, are promising tools in disease management with low risks of environmental pollution and impact on human health. Thyme and clove essential oils were demonstrated to be highly effective in Xanthomonas studies in vitro; therefore, their application in black rot control was evaluated in this study. From five phenolic substances originating from thyme and clove essential oils (carvacrol, eugenol, linalool, p-cymene and thymol), the most promising in vitro results were observed with carvacrol, for which 0.0195% led to the death of all Xcc cells in 30 min. Moreover, a synergistic antibacterial effect of carvacrol and thymol solutions decreased the minimal inhibition concentration to 0.0049% and 0.0195% for carvacrol and thymol, respectively. Using the quadruple bactericidal values, the complete elimination of Xcc from the surface of infested cabbage seeds was obtained for both carvacrol and thymol solutions and their combined mixture at 2 MIC value. The elimination of bacterial infection from germinated cabbage plants was observed for both plate counting and quantitative real-time PCR methods. We also evaluated the effect of the application of phenolic treatment on the seed germination and germinated plants. Our results suggest a high potential of the application of carvacrol and thymol in vegetable seed production, specifically for cabbage, thus representing a suitable alternative to cupric derivatives.

Comparison of Origanum Essential Oil Chemical Compounds and Their Antibacterial Activity against Cronobacter sakazakii

Origanum vulgare L. (oregano) is an aromatic plant with wide applications in the food and pharmaceutical industries. Cronobacter sakazakii, which has a high detection rate in powdered infant formula, adversely impacts susceptible individuals. Oregano essential oil (OEO) is a natural antibacterial agent that can be used to fight bacterial contamination. Here, OEO chemical compounds from eight oregano varieties were analyzed by gas chromatography–mass spectrometry and their antibacterial properties were assessed. The eight OEOs were clustered into two groups and were more diverse in group 2 than in group 1. Six compounds, including p-cymene, 3-thujene, γ-terpinene, thymol, carvacrol, and caryophyllene, were shared by eight OEOs. Among the eight oregano varieties, OEOs from O. vulgare sc2 had the strongest antibacterial activity against C. sakazaki, with the inhibition zone of 18.22mm. OEOs from O. vulgare jx, O. ‘Nvying’, O. vulgare ‘Ehuang’, and O. vulgare ssp. virens were also potent. Moreover, the antibacterial activity of OEOs was positively correlated with the relative content of thymol. As the main OEO antibacterial compound, thymol affected the normal growth and metabolism of C. sakazakii cells by destroying the bacterial membrane and decreasing the intracellular ATP concentration. Thus, in light of the antibacterial activity detected in the OEOs from the eight oregano varieties, this study provides a theoretical foundation for oregano cultivar management and development.