Citral, carvacrol, eugenol and thymol: antimicrobial activity and its application in food

Design, spectroscopic characterization, in silico and in vitro cytotoxic activity assessment of newly synthesized thymol Schiff base derivatives

Cancer is a global public health problem affecting millions of people every year. New anticancer drug candidates are needed to overcome the resistance to drugs used in the treatment of various types of cancer. In this study, two new series of benzenesulfonate-based thymol derivatives (14-19 and 20-25) were synthesized for the first time as promising chemotherapeutic agents and characterized using FT-IR, 1D NMR (1H- and 13C-NMR, APT, DEPT 135), 2D NMR (HETCOR and HMBC), and elemental analysis (CHNS). Antiproliferative activity of the molecules was determined against cancer cell lines, namely, the human lung adenocarcinoma cell line (A549) and the colorectal adenocarcinoma cell line (DLD-1), using MTT method for both 48 and 72 h. Compounds (14-25) showed cytotoxic activities against A549 with IC50 values ranging from 9.98 to 81.83 μM, respectively, compared to cisplatin (6.65 μM). These compounds exhibited antiproliferative activities against DLD-1 cancer cells at concentrations ranging from 4.29 to 53.62 μM, respectively, compared to cisplatin (9.91 μM). Especially, compound 16 displayed significant cytotoxicity on A549 and DLD-1 cancer cells with IC50 values of 9.98 and 10.75 μM, respectively. Finally, molecular docking studies were performed with Bcl-2, VEGFR-2, EGFR, and HER2 targets using the Schrödinger 2021-2 Maestro Glide program. The binding energy values and binding interactions of compounds 16 and 22 were determined to be the result of their interactions with these targets. Schrödinger 2021-2 Qikprop wizard drug similarity ratios and ADME prediction of all compounds 14-25 were also calculated.

Unveiling the Broad-Spectrum Efficacy of Volatile Terpenes to Fight Against SARS-COV-2-Associated Mucormycosis

Mucormycosis, a life-threatening fungal infection caused by Mucorales, affects immunocompromised patients, especially SARS-CoV-2 ones. Existing antifungal therapies, like amphotericin B, have serious health risks. The current study reviews the literature regarding an overview of SARS-CoV-2-associated mucormycosis, along with different terpenes from diverse edible sources, such as basil, ginger, and clove, which are detected till June 2024. The antifungal potential of collected terpenes, their classifications, mechanisms of action, minimum inhibitory concentration (MIC) values, and future perspectives are discussed here. The search identified 89 fungicidal volatile terpenes, belonging to about 26 families, from which 45 were selected for further in silico analysis. The results highlighted oryzalexin B (60), oryzalexin D (62), carvacrol (4), mansorin B (66), muzigadial (86), and lubimin (80) as potential antifungal agents against lanosterol 14α-demethylase, CotH3, and mucoricin as potential targets in Mucorales. CotH3 is crucial for activating GRP-78, a host co-receptor for ACE2, which is essential for SARS-CoV-2 pathogenesis. Additionally, carvacrol was in vitro investigated against Mucor racemosus via the agar diffusion method, giving an MIC value of 1 mg/mL, compared to 0.1 mg/mL of ketoconazole. This study suggests promising potential for volatile terpenes in combating SARS-CoV-2-associated mucormycosis, with the need for further refined in vitro and in vivo studies to establish clinical efficacy.

Antibacterial Activity of Selected Essential Oil Components and Their Derivatives: A Review

Essential oils (EOs) are gaining ground and have been intensively studied due to their widespread use in the pharmaceutical, food, and cosmetics industries. The essential components of EOs have been recognized for diverse therapeutic activities and have gained significant attention for their potential antibacterial activities. Despite the popularity of EOs and potent biological properties, their bioactive components and their derivatives are still not comprehensively characterized. This review explores the antibacterial efficacy of selected EO components and their derivatives, focusing on monoterpenes chosen (i.e., carvacrol, menthol, and thymol) and phenylpropanoids (i.e., cinnamaldehyde and eugenol). Furthermore, this review highlights recent advancements in developing derivatives of these EO components, which have shown improved antibacterial activity with reduced toxicity. By summarizing recent studies, this review reveals the potential of these natural compounds and their derivatives as promising candidates for pharmaceuticals, food preservation, and as alternatives to synthetic antibiotics in combating bacterial resistance.

Biocontrol Mechanisms of Three Plant Essential Oils Against Phytophthora infestans Causing Potato Late Blight

Late blight, caused by the notorious pathogen Phytophthora infestans, poses a significant threat to potato (Solanum tuberosum) crops worldwide, impacting their quality as well as yield. Here, we aimed to investigate the potential use of cinnamaldehyde, carvacrol, and eugenol as control agents against P. infestans and to elucidate their underlying mechanisms of action. To determine the pathogen-inhibiting concentrations of these three plant essential oils (PEOs), a comprehensive evaluation of their effects using gradient dilution, mycelial growth rate, and spore germination methods was carried out. Cinnamaldehyde, carvacrol, and eugenol were capable of significantly inhibiting P. infestans by hindering its mycelial radial growth, zoospore release, and sporangium germination; the median effective inhibitory concentration of the three PEOs was 23.87, 8.66, and 89.65 μl/liter, respectively. Scanning electron microscopy revealed that PEOs caused the irreversible deformation of P. infestans, resulting in hyphal shrinkage, distortion, and breakage. Moreover, propidium iodide staining and extracellular conductivity measurements demonstrated that all three PEOs significantly impaired the integrity and permeability of the pathogen's cell membrane in a time- and dose-dependent manner. In vivo experiments confirmed the dose-dependent efficacy of PEOs in reducing the lesion diameter of potato late blight. Altogether, these findings provide valuable insight into the antifungal mechanisms of PEOs vis-à-vis late blight-causing P. infestans. By utilizing the inherent capabilities of these natural compounds, we could effectively limit the harmful impacts of late blight on potato crops, thereby enhancing agricultural practices and ensuring the resilience of global potato food production.

Carvacrol nanocapsules as a new antifungal strategy: Characterization and evaluation against fungi important for grape quality and to control the synthesis of ochratoxins

Fungi are a problem for viticulture as they can lead to deterioration of grapes and mycotoxins production. Despite the widespread use of synthetic fungicides to control fungi, their impact on the agricultural ecosystem and human health demand safer and eco-friendly alternatives. This study aimed to produce, characterize and assess the antifungal activity of carvacrol loaded in nanocapsules of Eudragit® and chia mucilage as strategy for controlling Botrytis cinerea, Aspergillus flavus, Aspergillus carbonarius, and Aspergillus niger. Eudragit® and chia mucilage were suitable wall materials, as both favored the encapsulation of carvacrol into nanometric diameter particles. Fourier Transform Infrared Spectroscopy (FTIR) analysis suggested a successful incorporation of carvacrol into both nanocapsules, which was confirmed by presenting a good encapsulation efficiency and loading capacity. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) analyses revealed adequate thermal resistance. All fungi were sensible to carvacrol treatments and B. cinerea was the most sensitive compared to the Aspergillus species. Lower concentrations of encapsulated carvacrol than the unencapsulated form were required to inhibit fungi in the in vitro and grape assays. Additionally, lower levels of carvacrol (unencapsulated or encapsulated) were used to inhibit fungal growth and ochratoxin synthesis on undamaged grapes in comparison to those superficially damaged, highlighting the importance of management practices designed to preserve berry integrity during cultivation, storage or commercialization. When sublethal doses of carvacrol were used, the growth of A. niger and A. carbonarius was suppressed by at least 45 %, and ochratoxins were not found. The nanoencapsulation of carvacrol using Eudragit® and chia mucilage has proven to be an alternative to mitigate the problems with fungi and mycotoxins faced by the grape and wine sector.

Antimicrobial activity of eugenol and carvacrol against Salmonella enterica and E. coli O157:H7 in falafel paste at different storage temperatures

The objectives of the current study were: i) to investigate the antimicrobial activity of 0.125, 0.250 and 0.50 % (7.54, 15.08 and 30.17 mmol/Kg of eugenol) and (8.15, 16.31, and 33.61 mmol/Kg of carvacrol) against S. enterica and E. coli O157:H7 in falafel paste (FP) stored at 4, 10 or 25 °C for 10 d; and ii) to study the sensory properties of fried falafel treated with eugenol and carvacrol. S. enterica grew well in untreated falafel (control) samples at 10 and 25 °C, while E. coli O157:H7 grew only at 25 °C. However, numbers of S. enterica and E. coli O157:H7 in FP stored at 4 °C were reduced by 1.4-1.6 log CFU/g after 10 d. The antimicrobial agents were more effective at 25 °C against S. enterica, but were better at 4 and 10 °C against E. coli O157:H7. Addition of 0.125-0.5 % eugenol or carvacrol reduced the S. enterica numbers to undetectable level by direct plating (2 log CFU/g) by 2-10 d at 25 °C. FP samples treated with 0.5 % eugenol or 0.25-0.5 % carvacrol were negative for S. enterica cells by enrichment (1 CFU/5 g) by 10 d at 25 °C. In contrast, viable E. coli O157:H7 were not detected by direct plating when FP was treated with 0.25-0.5 % carvacrol or 0.5 % eugenol and stored at 4 °C by 2 d. Addition of eugenol or carvacrol did not affect the color, texture, and appearance of fried falafel but decreased the flavor and overall acceptability scores compared to untreated falafel. Using eugenol and carvacrol as natural antimicrobials have the potential to enhance the safety of FP by reducing the threat from foodborne pathogens.

Assessment of metabolome diversity in black and white pepper in response to autoclaving using MS- and NMR-based metabolomics and in relation to its remote and direct antimicrobial effects against food-borne pathogens

Piper nigrum L. (black and white peppercorn) is one of the most common culinary spices used worldwide. The current study aims to dissect pepper metabolome using 1H-NMR targeting of its major primary and secondary metabolites. Eighteen metabolites were identified with piperine detected in black and white pepper at 20.2 and 23.9 μg mg-1, respectively. Aroma profiling using HS-SPME coupled to GC-MS analysis and in the context of autoclave treatment led to the detection of a total of 52 volatiles with an abundance of β-caryophyllene at 82% and 59% in black and white pepper, respectively. Autoclaving of black and white pepper revealed improvement of pepper aroma as manifested by an increase in oxygenated compounds' level. In vitro remote antimicrobial activity against food-borne Gram-positive and Gram-negative bacteria revealed the highest activity against P. aeruginosa (VP-MIC 16.4 and 12.9 mg mL-1) and a direct effect against Enterobacter cloacae at ca. 11.6 mg mL-1 for both white and black pepper.

Essential oils on the control of fungi causing postharvest diseases in mango

The use of fungicides in the postharvest treatment of mangoes has been widespread due to the incidence of pathogens, but awareness of the health risks arising from their use has increased, driving the search for more sustainable treatments. This study aimed to evaluate the activity of antifungal treatment of seven essential oils (EO) against four fungi that cause postharvest diseases in mangoes and define the minimum inhibitory concentration (MIC) and chemical composition, analyzed by gas chromatography (GC-MS). The results showed that the EOs of oregano, rosemary pepper, cinnamon bark, and clove inhibited 100% of the mycelial growth of the studied pathogens, with MIC ranging from 250 to 2000 μL.L-1. The main compound found in oregano was carvacrol (69.1%); in rosemary and pepper oil, it was thymol (77.2%); cinnamaldehyde (85.1%) was the main constituent of cinnamon bark, and the eugenol (84.84%) in cloves. When evaluating the antifungal activity of these compounds, thymol and carvacrol showed greater inhibitory activity against fungi. Therefore, this study showed the great potential of oregano, clove, rosemary pepper, and cinnamon bark essential oil as alternative treatments to synthetic fungicides in controlling postharvest diseases in mangoes.

Chitosan-based emulgel and xerogel film containing Thymus pubescens essential oil as a potential wound dressing

Controlling the wound exudates accompanied by microbial wound infections has still remained as one the most challenging clinical issues. Herein, a chitosan/gelatin/polyvinyl alcohol xerogel film containing Thymus pubescens essential oil is fabricated for antimicrobial wound dressing application. The chemical and physical characteristics of the devised formulation is characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, atomic force microscope, and tensile tests. Moreover, swelling capability, water vapour transmission rate, water contact angle, solubility, moisture content, and release properties are also studied. The antimicrobial and antibiofilm tests are performed using the broth microdilution and XTT assay, respectively. The produced formulation shows excellent antimicrobial efficacy against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida species. It is also demonstrated that the obtained film can reduce (∼80 %) Candida albicans biofilm formation, and its biocompatibility is confirmed with MTT (∼100 %) and hemolysis tests. The antimicrobial activity can be correlated to the microbial membrane attraction for Candida albicans cells, illustrated by flow cytometry. This proposed film with appropriate mechanical strength, high swelling capacity in different pH values (∼200-700 %), controlled release property, and antimicrobial and antioxidant activities as well as biocompatibility can be used as a promising candidate for antimicrobial wound dressing applications.

Formulation of lemongrass oil (Cymbopogon citratus)-loaded solid lipid nanoparticles: an in vitro assessment study

Cymbopogon citratus (DC) stapf. (Gramineae) is a herb known worldwide as lemongrass. The oil obtained, i.e., lemongrass oil has emerged as one among the most relevant natural oils in the pharmaceutical industry owing to its extensive pharmacological and therapeutic benefits including antioxidant, antimicrobial, antiviral and anticancer properties. However, its usage in novel formulations is constrained because of its instability and volatility. To address these concerns, the present study aims to formulate lemongrass-loaded SLN (LGSLN) using hot water titration technique. In the Smix, Tween 80 was selected as a surfactant component, while ethanol was taken as a co-surfactant. Different ratios of Smix (1:1, 1:2, 1:3, 2:1 and 3:1) were utilized to formulate LG-loaded SLN. The results indicated the fact that the LGSLN formulation (abbreviated as LGSLN1), containing lipid phase 10% w/w (i.e., LG 3.33% and SA 6.67%), Tween 80 (20% w/w), ethanol (20% w/w) and distilled water (50% w/w), revealed suitable nanometric size (142.3 ± 5.96 nm) with a high zeta potential value (- 29.12 ± 1.7 mV) and a high entrapment efficiency (77.02 ± 8.12%). A rapid drug release (71.65 ± 5.33%) was observed for LGSLN1 in a time span of 24 h. Additionally, the highest values for steady-state flux (Jss; 0.6133 ± 0.0361 mg/cm2/h), permeability coefficient (Kp; 0.4573 ± 0.0141 (cm/h) × 102) and enhancement ratio (Er; 13.50) was also conferred by LGSLN1. Based on in vitro study results, the developed SLN appeared as a potential carrier for enhanced topical administration of lemongrass oil. The observed results also indicated the fact that the phyto-cosmeceutical prospective of the nanolipidic carrier for topical administration of lemongrass oil utilizing pharmaceutically acceptable components can be explored further for widespread clinical applicability.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03726-5.

Production of nanocellulose from corn husk for the development of antimicrobial biodegradable packaging film

Packaging is a potential way of keeping food products safe from various environmental pollutants, and biological, chemical, & physical deterioration. Hence, the demand for an effective antimicrobial active packaging material is increasing tremendously to improve the shelf-life of food products. Thus, we extracted nanocellulose from corn husks and developed a eugenol-incorporated biodegradable antimicrobial active packaging film. The extracted nanocellulose showed a particle size of 149.67 ± 3.56 nm and an overall surface charge of -20.2 mV ± 0.76 V. The film casting method is one of the promising methods to fabricate biodegradable films using plant-based biopolymers. Therefore, different concentrations of eugenol (0.5-5 % v/v) were incorporated to formulate the functional film (FF0.5-FF5) by employing the casting process. FF exhibited comparable tensile strength as compared to the control film (CF), however, FF5 showed the least tensile strength (85 MPa). Based on the mechanical characterization, the FF3 film sample was further selected for characterization. The morphological evaluation revealed that the surface of the film was smooth and non-porous with reduced moisture content and density. The film exhibited high thermal stability as the degradation occurred above 400 °C, indicating the strong hydrogen bonding between the hydroxyl groups of the film. The Fourier transform infrared spectroscopy analysis revealed the existence of COOH vibration and COC stretching groups of cellulose and eugenol. The antimicrobial studies showed high efficacy against Staphylococcus aureus followed by Salmonella typhmurium, Pseudomonas aeruginosa, and Klebsiella pneumoniae bacteria. Overall, eugenol-incorporated nanocellulose-based biodegradable packaging film could be an excellent candidate as an alternative to active packaging material and provide an opportunity for the efficient utilization of corn husk.

Effect of Gaseous Citral on Table Grapes Contaminated by Rhizopus oryzae ITEM 18876

Rhizopus oryzae is responsible for rapidly producing a deliquescent appearance in grape berries, generally favoured by cold chain interruptions. To counteract fruit spoilage and to meet consumer acceptance, innovative strategies based on the application of natural compounds are ongoing. Due to their biological activities, including antimicrobial ones, natural flavour compounds extend the shelf life and improve the nutritional value as well as the organoleptic properties of foods. Thus, in this work, the application of the antimicrobial citral, a flavor component of monoterpenes identified in plant and fruit essential oils, was developed and validated against one spoiler of R. oryzae. Citral, as pure compound, was first investigated in vitro against R. oryzae ITEM 18876; then, concentrations equal to the minimal inhibitory concentration (MIC) and 4-fold MIC (4MIC) value were applied on the table grape cv Italia infected with this strain and stored. The MIC value was equal to 0.0125 μL/cm3; both citral concentrations (0.0125 and 0.05 µL/cm3) were effective in counteracting the microbial decay of infected table grapes over the storage period. The HS-SPME/GC-MS method showed citral persistence in the head space of plastic trays with the infected samples; as expected, a higher content of citral isomers was found in the sample treated with 4MIC value. In conclusion, citral revealed its efficacy to counteract the onset of soft rot by R. oryzae ITEM 18876 under storage conditions. Thus, it could be successfully exploited to develop an active packaging or natural preservatives to extend table grape shelf life without affecting its quality and sensory characteristics, whilst also satisfying the consumer demand for natural preservative agents.