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Review

Microbial Fermentation and Therapeutic Potential of p-Cymene: Insights into Biosynthesis and Antimicrobial Bioactivity

Department of Beauty Cosmetics, College of Biomedical and Health Science, Konkuk University, Chungju 27478, Republic of Korea
*
Author to whom correspondence should be addressed.
Fermentation 2024, 10(9), 488; https://doi.org/10.3390/fermentation10090488
Submission received: 4 September 2024 / Revised: 12 September 2024 / Accepted: 13 September 2024 / Published: 19 September 2024

Abstract

:
p-Cymene (p-C) [1-methyl-4-(1-methylethyl)-benzene] is a monoterpene found in a variety of plants and has several biological activities, including antioxidant, anti-inflammatory, antimicrobial, and anticancer properties. This paper explores the microbial fermentation pathways involved in the biosynthesis of p-C, with an emphasis on its potential as a therapeutic agent. Through microbial and biochemical processes, p-C can be produced using renewable precursors such as limonene and 1,8-cineole. Recent advances in fermentation technology have enhanced the efficiency of p-C production, highlighting its role in various industries. Additionally, this paper reviews the antimicrobial bioactivity of p-C, focusing on its ability to inhibit pathogens and modulate immune responses. The integration of microbial biosynthesis and fermentation methods offers a sustainable approach to producing p-C for applications in the perfume, cosmetics, food, and pharmaceutical sectors. Understanding these biosynthetic pathways is crucial for advancing the use of p-C as a bio-based chemical with therapeutic potential. In particular, p-C inhibits the expression of cytokine signal 3 in intestinal inflammation and modulates antioxidant and immunomodulatory systems to protect barrier cells and maintain the mucus layer.

Graphical Abstract

1. Introduction

p-Cymene (p-C) [1-methyl-4-(1-methylethyl)-benzene] is a monoterpene that can be obtained from a variety of plants and has biologically active effects of antioxidant, anti-infective, anti-anxiety, anti-inflammatory, antimicrobial, and anticancer. Due to its beneficial effects, it is used in biomedical applications and is considered a novel agent in the treatment of infectious diseases [1]. In particular, p-C has been shown to be one of the best anti-neurodegenerative potential monoterpenes for Alzheimer’s disease (AD). It may also play a positive role in improving memory and learning, reducing anxiety, and regulating sleep [2]. p-C exerts neuroprotective effects by reducing H2O2-induced caspase-3 expression in neurons. This leads to its role as a neuroprotective agent against oxidative stress, which helps prevent AD [3]. Among monoterpenes, p-C has shown protective effects on the pathogenesis of atherosclerosis through anti-inflammatory, antioxidant, and lipid metabolism modulation, and has been discussed as a new anti-atherosclerotic drug [4]. Essential oils, which are extracted from plants, are natural aromatic volatile compounds and are attributed to the treatment of various kinds of diseases due to their antimicrobial and antioxidant activities, and are beneficially used as applied ingredients in the cosmetics and perfumery industries [5,6]. The component responsible for the antioxidant activity of eucalyptus has also been identified as p-C [7]. It includes the genera Origanum and Thymus and is also present in food-based plants in carrots, orange juice, grapefruit, raspberries, tangerines, and many spices [8].
In addition, p-C has been shown to inhibit and interfere with the expression of the suppressor of cytokine signaling 3 (SOCS3) in the inflamed colon [9]. Also, rosmarinic acid has intestinal anti-inflammatory activity associated with modulating antioxidant and immunomodulatory systems to protect barrier cells, maintain the mucus layer, and preserve communication junctions [10]. It is an important compound found in the essential oil of thyme, with antimicrobial activity against Staphylococcus aureus, Salmonella typhimurium, and Streptococcus pyogenes in particular [11,12]. These p-Cs are naturally occurring compounds, and there are m-Cymene (meta-substituted alkyl groups) and o-Cymene (ortho-substituted alkyl groups) that do not occur in nature [13]. The odor of p-C is described as woody and slightly pungent [14,15].
The production of p-C has traditionally been achieved via the catalytic alkylation of petroleum feedstocks [16]. However, the use of hazardous acids, such as aluminum chloride (AICI3) and hydrogen fluoride (HF), can lead to safety, waste, corrosion, and environmental pollution, so an alternative approach to produce p-C from the dehydrogenation of terpenes has emerged [17,18,19]. It is a dehydrogenation reaction of the p-C of terpenes in a liquid or gas phase [20]. Also, high yields are obtained when zeolites and alkali metals are used as catalysts for liquid phase dehydrogenation and metal oxides are used as catalysts for gas phase dehydrogenation [21]. The formation of p-C can be expected from a wide range of volatile organic compounds (VOCs), including aromatic hydrocarbons obtained from the combustion and evaporation of fossil fuels, especially from the oxidation of α-pinene [22,23]. The potential importance of switchable mechanisms of p-C has been discussed, making extensive research on p-C very important [24]. In this context, increasing yields through an efficient approach by anticipating synergistic strategies of biological and chemical catalysis refers to the conversion of renewable biomass into chemicals and fuels, and thus the production of p-C [25,26]. Also, the development of the microbial platform enables the conversion of limonene, 1,8-cineole, to p-C through fed-batch fermentation, which is a promising research topic at the convergence of biology and chemistry [27].
As a pharmacological effect of p-C, p-C presents antimicrobial activity against bacteria and fungi, with activity against food poisoning and pathogens and a mechanism of bacterial growth inhibition against cell membrane disruption [28]. It also has antioxidant properties that scavenge free radicals and reduce oxidative stress, which can prevent cell damage and aging and reduce diseases such as Alzheimer’s disease (AD) [29]. p-C is an effective inhibitor of the inflammatory response [30,31]. It has been attributed to the modulation of the inflammatory response by reducing the production of inflammatory mediators and helps to reduce nociception, thereby enhancing analgesia and the pharmacologic effects of drugs [32].
The aim of this study is to provide a review of the microbial biosynthesis and antimicrobial bioactive effects of p-C and its potential as a therapeutic agent. Due to its special bioactive effects, p-C is widely used in the perfume, cosmetics, food, and pharmaceutical industries. In addition, this study analyzes and summarizes the data on the potential use of p-C in biologically active therapeutic and prophylactic applications.

2. p-C Terpenoid Biosynthetic Pathway

The fermentative production pathway of p-C can be approached from a non-traditional perspective. Marine bacteria that live in extreme environments have unique biosynthetic pathways, unlike typical fermentative organisms. The production of biosurfactants increases the bioavailability of substrates, which requires lipophilic substances such as p-C [33]. The p-C contained in citrus waste also provides an environmentally friendly alternative to prevent environmental pollution problems. Although citrus waste can cause environmental pollution, it can be utilized as a building block for new chemicals by producing p-C compounds. It can be utilized in food processing and pharmaceutical industries and is considered safer than conventional synthetic compounds [34].
Traditionally, however, the biosynthesis of p-C begins with limonene. The limonene used in the derivatization step of the dehydrogenated product, p-C, is produced by microbial systems, which motivates the development of renewable biomass through the biosynthetic pathway of terpenoids. Limonene, a natural product, is synthesized by limonene synthase as a cyclization of geranyl pyrophosphate (GPP) in either the methylerythritol 4-phosphate (MEP) pathway or the mevalonate (MVA) pathway [35,36,37,38]. In the terpenoid pathway of limonene, the biosynthetic pathway to 1,8-cineole has been shown in Escherichia coli in particular, using 1,8-cineole as a synthase in place of limonene synthase. Palladium (Pd) has been utilized for the conversion of 1,8-cineole to p-C [39,40]. A two-step mechanism using atmospheric oxygen as a green oxidant is also an efficient method for obtaining p-C, with the catalytic conversion of natural mordenite from limonene to p-C initiated by a non-catalytic process starting from limonene isomerization over natural mordenite [41,42]. The acidity is further enhanced by the use of acetic acid (CH3COOH), hydrochloric acid (HCI), sulfuric acid (HESO4), and nitric acid (HNO3) [43].
The biosynthesis of p-C from plants implies the integration of biological and chemical catalysis for the efficient production of p-C and produces the precursors limonene and 1,8-cineole via the mevalonate pathway. Using hydrogenating/dehydrogenating metals to convert p-C showed that 1,8-cineole the optimal biological precursor with low toxicity [44]. A favorable alternative route of p-C via biosynthesis, from biological intermediates to chemical synthesis, is the application of limonene dehydrogenation. This is where Pd-based catalysts are used to convert limonene to p-C, and palladium/silicon dioxide (Pd/SiO2) catalysts (where palladium is immersed in silicon dioxide) can be used to perform limonene dehydrogenation to improve the yield of the product. It has also been added to palladium catalysts immersed in ZSM-5 (a specific form of zeolite) to show the biosynthesis of p-C with the catalytic activation of p-C [45,46,47,48]. A favorable alternative route for p-C via biosynthesis, from biological intermediates to chemical synthesis, is the application of limonene dehydrogenation. This is the most commonly used palladium-bearing metal and metal oxide catalyst and performs limonene dehydrogenation over Pd/SiO2 catalysts [49]. The transition between these cycles is shown in Figure 1.

3. Antimicrobial Activities of p-C

p-C can increase the adenosine triphosphate (ATP) permeability of the cytoplasmic membrane and is a monoterpene with a benzene ring structure that is a precursor of carvacrol [50,51]. It has antimicrobial activity when used alone and can also increase the antimicrobial activity of other compounds. This is because p-C has a high affinity for microbial membranes and can perturb, extend, and affect the membrane potential of the cell [52,53,54,55]. The therapeutic properties of monoterpenes have been attributed to several plant-derived essential oils. In particular, p-C has attracted attention for its antiviral and antibacterial properties, and its anti-inflammatory effects are being investigated for their anticancer effects by modulating cytokine production [56].

3.1. Biosynthesis and Antibacterial Effects from Plants

p-C is the main compound in the genera Thymus and Origanum, and is a precursor to essential oils and carvacrol, which has antimicrobial properties. Although p-C is weakly antimicrobial on its own, it plays an important role in the overall antimicrobial composition and facilitates the synergistic effects of carvacrol and thymol [57,58,59]. p-C increases antimicrobial activity through intracellular penetration, integrates bacteria, and aids in the transport of carvacrol across lipid layers and cytoplasmic membranes. p-C is also hydrophobic, which allows for the easy swelling of the cytoplasmic membrane and has a high solubility in water [60,61,62,63]. The antimicrobial properties of p-C have also been demonstrated in experiments on Thymus species. The different biological activities of Thymus bulgaris (TVEO) and Thymus serpyllum (TSEO) are attributed to their main component, p-C. TSEO showed a 2,2-diphenyl-1-picrylhydrazyl (DPPH) value of 4.88 μL/mL and a ferric-reducing antioxidant power (FRAP) of 701.25 μmol FRAP/g, and in addition to its bacterial activity, it caused apoptosis via caspase-3. TVEO showed a DPPH value of 4.49 μL/mL and FRAP of 1130.27 μmol FRAP/g and was found to induce the apoptosis of cervical adenocarcinoma Henrietta Lacks (HeLa) cells through the activation of caspase-3 and caspase-8. In particular, HeLa cells decrease the expression levels of matrix metalloproteinase-2 (MMP2) and increase the levels of microRNA (miR)-16 and miR-34a, which may have potential tumor suppressive effects in the future [64].
The antimicrobial effect of p-C was demonstrated in a mixture of the natural compounds carvacrol, thymol, and p-C as a potential food preservative. It inhibited yeast growth at a concentration of 1 mmol/L for at least 21 days. p-C in particular showed effective antimicrobial activity with an extension to 45 days [65]. The antimicrobial role of p-C is also applied in food by its bactericidal effect. This is because p-C (33.14%), mainly contained in Satureja horvatii, improved the color and flavor of meat after 4 days of storage and inhibited the development of Listeria monocytogenes. This in turn shows that it can be used as a useful source of food spoilage microbial inhibitors and natural antioxidants [66]. Apple juice contaminated with Escherichia coli O157:H7 can lead to food poisoning outbreaks, serious illness, and death. In response, the addition of p-C’s natural antimicrobial properties is being discussed as a processing method to prevent vitamin loss and preserve flavor. As a phenolic substance, p-C, together with carvacrol, is a component derived from essential oils of herbs and spices and may provide a new route for potential shelf-life extension [67].
It was also found that p-C, as a precursor to carbacrol, has similar antimicrobial activity to carbacrol against foodborne pathogens, but carbacrol alone is more effective against non-vibrio cholera [68,69,70]. Although p-C alone does not show a good inhibition of Vibrio cholerae, synergistic antimicrobial activity with carbacrol has been demonstrated. This demonstrates the potential of combining p-C and carbacrol [71]. Essential oils obtained from cumin (Cuminum cyminum) and ajowan (Trachyspermum ammi) also showed antimicrobial and antioxidant activities of the main component p-C. Compared to standard antibiotics, it was found that cumin had a stronger antibacterial effect than chloramphenicol, cumin had weak antioxidant activity (12.36%), and azowan had strong antioxidant activity (71.68%) in scavenging DPPH radicals. Furthermore, azowan had a stronger antioxidant effect than ascorbic acid (20.24%), indicating that it has significant potential for food pathogen control [72].
In a study evaluating the antimicrobial and antioxidant activities of thyme (Thymus vulgaris) essential oil, naturally derived p-C was found to have potent antimicrobial effects and higher antioxidant activity than oreganum (Origanum vulgare), ginger (Zinger officinale), and fennel (Foeniculum vulgare) [73]. In oreganum (Origanum vulare L.), p-C is the main component that imparts the typical oregano odor and has been found to present antimicrobial activity against E. coli, S. aureus, Bacillus cereus, and S. typhimurium [74]. Essential oils are highly concentrated natural extracts obtained from plants and are reported to be very rich in bioactive components with antimicrobial properties [75]. Mint (Mentha spp.) and thyme (Thymus spp.) are also aromatic herbal plants that contain the antimicrobial effects of p-C. They are members of the tribe Mentheae, part of the mint family (Lamiaceae), and have been used as potential antimicrobial drug preparations [76]. The p-C obtained from essential oils is also used as an insecticide due to its antimicrobial properties [77,78]. p-C has significant toxic activity against pests and demonstrates great potential as a safe, plant-derived insecticide in insecticidal activity tests against red flour beetle (Tribolium castaneum), tobacco beetle (Lacioderma sericorneum), and buzzards (Liposcelis bostricophila) [79]. The antimicrobial activity of thyme, thymol, and carvacrol, the main components of which are p-C, has been shown by essential oils, especially by Shigella sp., and has also been implicated in organoleptic properties, such as browning and strong odor [80].
Experimental studies have also shown that p-C has antioxidant potential for the brain and may act as a neuroprotective agent. This demonstrates the potential of p-C as a therapeutic development agent for important pathophysiological diseases through p-C-induced oxidative stress [81,82]. The antimicrobial activity of p-C from the essential oils of these plants was also significant in the antimicrobial activity test of thyme, which showed greater antimicrobial activity than marjoram, which contains limonene, linalool, terpinene-4-ol, α-terpineol, and linalyl acetate [83]. The evaluation of antioxidant activity from plant extracts includes a variety of organic chemicals, including the main volatile compound p-C, and the high antioxidant capacity of thyme and savory can be attributed to thymol and carvacrol. This indicates that the antioxidant power of oregano, sage, and hyssop may be influenced by non-phenolic components, such as terpin, o-cymene, terpinolene, and terpin-4-ol [84]. These are shown in Table 1.

3.2. Antifungal Effects of p-C Based on Fermentation Characteristics

p-C has been shown to be effective against Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus, and p-C is a bioactive compound like eugenol and thyme essential oil [85]. It was also found to have no effect on total volatile fatty acid (VFA) production or ratio but could alter fermentation by reducing the production of methane by 30%. The use of p-C has complex effects on animals due to the fermentation process involved, and it is important to find the right concentration, method, and conditions of use [86]. Antibacterial effect is the effect of inhibiting bacteria, and antifungal effect is the effect of acting on fungi. In particular, eucalyptus extract with p-C as the main component has excellent antifungal and antibacterial effects and can inhibit the growth of fungi, even at low concentrations [87].
In kombucha, p-C is one of the organic compounds (VOCs) that play an important role in the fermentation process. Synthesized mainly in the early stages of fermentation, p-C is a terpene-like compound that is associated with yeast activity. In addition, p-C contributes to flavor changes that occur early in the fermentation process. As the fermentation process progresses, the flavor of kombucha changes from initially citrusy, floral, and sweet due to p-C, to citrus, herbal, lavender, and bergamot, and finally to sweet, floral, and honey [88]. The role of p-C in wine, the quintessential fermented beverage, is also manifested through fermentation. Linalool is the main monoterpene produced in grapes, and p-C is an oxidized derivative of grape and wine volatiles and its precursor, linalool [89,90]. The fermentation and aging of wine is driven by volatile compounds, including p-C, and flavors are linked to evolution [91]. In addition, p-C is responsible for odor and p-C imparts odor characteristics through the aging of the compound [92,93]. It has a pencil-like odor of thyme and oregano with phenolic, earthy, and weak modifications by p-C, which leads to a distinctive cedar-like odor. Thymoquinone, which exhibits a distinctive pencil-like aroma, is reported to determine the structural motif of the aroma by synthesizing and characterizing its p-C derivatives and showing the highest odor threshold of the compound in thymohydroquinone [94].

4. Therapeutic Potential and Applications of p-C

The antimicrobial properties of p-C lead to tissue regenerative activity, managing resistant antifungal infections, such as wound dressings [95,96,97]. This speeds up healing and restores wounds, and studies on the development of gellan/polyvinl alcohol nanofibers loaded with p-C have demonstrated the strong antibiotic activity of p-C, especially that the nanofibers do not form scars and can heal skin lesions quickly [98]. The gastroprotective effect of p-C against gastric mucosal hemorrhagic lesions was demonstrated in two experimental groups of Sprague Dawley rats. It was shown that p-C decreased pH, reduced edema and leukocyte infiltration, increased antioxidant enzymes (SOD, CAT) and prostaglandin E2 (PGE2), and decreased malondialdehyde (MDA) levels, and finally decreased the proinflammatory cytokines TNF-α and IL-6 and increased IL-10 [99].
p-C has been shown to reduce inflammation and oxidative damage and may be used as an anticancer agent or ruthenium-bound anticancer chemical. p-C reduced the levels of IL-6, COX-2, and IL-1, which are associated with inflammation, and adiponectin, which is secreted by adipose tissue [100]. It also reduces levels of superoxide dismutase and malondialdehyde, markers associated with oxidative stress. This indicates that p-cymene contributed to the reduction in oxidative damage through its antioxidant activity [101]. p-C as an anticancer agent can be used alone or as a ligand for the metal ruthenium. Combined with ruthenium, p-cymene forms several organometallic compounds, which may have promising anticancer properties [102]. Furthermore, p-C decreased leptin and IL-1 levels and increased IL-6 levels, suggesting the anticancer, antioxidant, and anti-inflammatory effects of p-C on colorectal cancer [103,104]. In addition to its anticancer and anti-tumor properties, p-C also has anti-infective properties. Oncologic pain is a difficult symptom to treat in cancer patients, and in addition to its pharmacologic properties, p-C has been shown to have preventive properties and antihyperalgesic effects in pain models. This was shown in a preclinical blinded and randomized study on Swiss male rats, which decreased the expression of the fos proto-oncogene in the spinal cord and increased the expression in the periaqueductal gray nucleus raphe magnus in mechanical hypersensitivity tests [105].
The value of p-C as a potential therapeutic agent can also be seen in the prevention of dermatitis inflammation by p-C in cinnamon extract, which was found to reduce sulfurylated leukotriene release and CD63 expression in macrophages [106]. In addition, p-C is involved in inflammatory processes that play an important role in disease. This has been demonstrated by the effects of cinnamon extract and its active compounds on inflammatory signaling pathways, particularly toll-like receptor 2 (TLR2) and TLR4 [107]. p-C can also reduce ulcerations, lesion scores, and diarrhea in colonic inflammation, and has been shown to enhance immunostaining by affecting the expression of the suppressor of cytokine signaling 3. Specifically, it has been shown to reduce IL-1β and TNF-α and maintain IL-10 [108]. Furthermore, in experiments using HCT116 and HepG2 cells, O. onites essential oil, carvacrol, and p-C were used at a concentration of 400 µg/mL. The results of cell experiments using the MTT assay and DCFH-DA method confirmed that p-C from O. onites essential oil can be considered as a drug candidate for cancer treatment [109]. As such, the potential therapeutic value of p-C is shown in Table 2.

5. Conclusions and Future Direction

p-C is found in the essential oils of natural plants, such as oregano, thyme, and various herbs, and is particularly useful in flavoring and perfumery, as well as in the food and pharmaceutical industries. Depending on the natural fermentation and synthesis processes, it can be used as an efficient and sustainable energy source and as a natural fuel for environmentally friendly production systems. As discussed in this review paper, natural synthesis and derivative realization are methods to obtain p-C, which has been analyzed for its excellent antioxidant, anti-infective, anti-pain, anti-bacterial, anticancer, and anti-anxiety biological activities. It is also being used in biomedical applications and has a potential role in the treatment of diseases. While synthetic therapeutics may come with side effects, the use of naturally derived therapeutics will allow them to have a significant impact on the human body. This review showed that the use of essential oils derived from plants, p-Cs, in therapeutic products can contribute to anti-inflammatory, antioxidant, and anti-pain properties, improving the quality of cosmetics, food products, and even medicines and therapeutic uses. It also shows that the use of p-C is particularly valuable as a sustainable fuel and can help in safe treatment and prevention. However, specific research is needed on the dose and duration of p-C use to express its properties. In particular, it is important to further study p-C as a viable p-C-based therapeutic agent that can be applied to humans through clinical studies. Also, the feasibility of utilizing various plant-based ingredients as naturally derived sustainable therapeutics needs to be established.

Author Contributions

Conceptualization, Y.P.; methodology, Y.P.; software, Y.P.; validation, Y.P.; formal analysis, Y.P.; investigation, Y.P.; resources, Y.P.; data curation, Y.P.; writing—original draft preparation, Y.P.; writing—review, Y.P.; editing, Y.P.; visualization, Y.P.; supervision, Y.P. and Y.J.J. All authors have read and agreed to the published version of the manuscript.

Funding

Following the results of a study on the “Revitalization of Regional universities Project, supported by the Ministry of Education and Konkuk University”.

Data Availability Statement

No new data were created or analyzed in this study. Data sharing is not applicable to this article.

Conflicts of Interest

The author declares no conflicts of interest.

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Figure 1. Limonene to p-Cymene cycle conversion.
Figure 1. Limonene to p-Cymene cycle conversion.
Fermentation 10 00488 g001
Table 1. Antibacterial effects of p-C from natural plants.
Table 1. Antibacterial effects of p-C from natural plants.
Plant SpeciesAntimicrobial ComponentExperimental DesignResultsReferences
TVEOp-C (29.52%), thymol (22.8%), linalool (4.73%)Evaluation of biological activities of any TVEO, TSEO in Montenegro: antioxidant, antimicrobial, cytotoxicity, apoptosis, oxidative stress reduction, tumor suppressor gene expressionEssential oil shows high antibacterial activity against E. coli
TVEO induces cervical adenocarcinoma HeLa cell apoptosis via caspase-3 and caspase-8
TSEO induces apoptosis via caspase-3
Shows antioxidant activity in the MRC-5 cell line
May have potential as a cancer prevention and cancer treatment agent
[64]
TSEOp-C (19.04%), geraniol (11.09%), linalool (9.16%), geranyl acetate (6.49%), borneol (5.24%)
Candida lusitaniaenisin, thymol, carvacrol, p-CAdding different concentrations of antimicrobial ingredients at 25 °C
Observation of yeast growth
p-C completely inhibits yeast growth for at least 21 days at concentrations above 1 mm[65]
Satureja horvatiip-C (33.14%), thymol (26.11%), thymol methyl ether (15.08%)Uses hydroxyl radicals generated in the Fenton reaction
Bacteria: 0.07 to 1.15 mg/mL
Yeast: 1.11 to 5.57 mg/mL
Successfully inhibiting the development of Listeria monocytogenes in pork[66]
Indian spicescumin and ajowancumin: cuminaldehyde (36.67%), caren-10-al (21.34%)
azowan: p-cymene (15.54%), thymol (15.48%)
Antimicrobial activity evaluation: Disk diffusion method, broth microdilution method
Evaluation of DPPH radical scavenging capacity
Spice essential oils have significant potential for controlling human and food pathogens[72]
Thyme (Thymus vulgaris)Thymol, p-CFolin Ciocalteu, DPPH, CUPRAC, and ABTSThyme and oregano oils show the highest antioxidant activity
Thyme’s antibacterial and antioxidant activities are due to thymol and p-C
[73]
Adenosma buchneroides Bonati (A. buchneroides)Thymol, p-CEvaluate p-C for insecticidal activity against red flower beetle (Tribolium castaneum), tobacco beetle (Lasioderma serricorne), and bookworm (Liposcelis bostrychophila)p-C shows potent toxic activity against insect pests
Shows potential to be developed into a plant-derived biopesticide that is safe for humans and the environment
[79]
Basil, thymeThymol, carvacrol, p-C, estragon, linalool, linaloolAntimicrobial testing, evaluating cleaning effectivenessAntimicrobial effects of thyme essential oil, thymol, and carvacrol against Shigella sp.
The use of thyme essential oil, thymol, and carvacrol is limited by the organoleptic properties of lettuce (browning, strong odor)
[80]
Essential oils from a variety of plantsp-CSubjects: Swiss mice
Treatment: p-C 50, 100, 150 mg/kg, ascorbic acid 250 mg/kg, control (0.05% Tween 80 and 0.9% saline)
Measured: lipid peroxides (TBARS), nitrite concentration, CAT and SOD activities
Lipid peroxide nitrate concentrations decreased in p-C treated groups compared to controls
All p-C treatments increased SOD and CAT activity at all doses
[81]
Thyme, marjoramThyme oil: p-Cymene (25.2%), thymol (31.4%), carvacrol (3.8%)
Marjoram oil: limonene (17.3%), linalool (15.5%), terpinen-4-ol (7.3%), α-Terpineol (13.0%), linalyl acetate (14.1%)
Gradient GC and combined GC/MS
Evaluate antimicrobial activity against 10 bacteria and 8 yeast species
Thyme oil showed excellent antimicrobial activity against the tested microorganisms, while marjoram oil showed relatively low antimicrobial activity
The antimicrobial activity of the oils was higher against yeast than bacteria
[83]
Thyme, savory, oregano, sage, hyssop, lavender and mintMajor volatile compounds, including p-CEvaluate antioxidant activityThyme and savory show the highest antioxidant activity, driven by thymol and carvacrol, surpassing oregano, sage, and hyssop. Oregano’s, sage’s, and hyssop’s activities are influenced by terpin, o-cymene, terpinolene, and terpin-4-ol. Activity against ABTS radicals is higher than against DPPH radicals[84]
TVEO, Thymus bulgaris; TSEO; Thymus serpyllum; p-C, p-Cymene; MRC-5, medical research council cell strain 5; CAT, catalase; SOD, superoxide dismutase.
Table 2. The use of p-C as a potential therapeutic agent, with a focus on clinical examples.
Table 2. The use of p-C as a potential therapeutic agent, with a focus on clinical examples.
SubjectsTreatment StrategiesSettingFindingsReferences
Candida albicans and Candida glabrata (antimicrobial test strains)
NIH3T3 cell line (cytotoxicity test)
Electrospinning of p-C loaded gellan/PVA nanofibers
Loading of p-C into nanofibers based on gellan and PVA for use as wound dressing material
In vitro: Characterize nanofibers’ morphologically and physicochemically evaluate antimicrobial and biocompatibility
In vivo: Conduct wound healing studies using full-thickness excisional wound models
p-C is an effective biomaterial for skin tissue regeneration, with antimicrobial, biocompatible, and rapid wound healing properties[98]
30 Sprague Dawley ratsNormal vs. ulcer control: Oral administration of 0.5% CMC
Baseline: 20 mg/kg omeprazole orally
Experimental group: 30 mg/kg and 60 mg/kg p-cymene orally
Absolute ethanol-induced acute gastric mucosal hemorrhagic lesion model
Rats were sacrificed after the experiment to perform gastric mucosal and inflammation-related analyses
p-C significantly reduced ethanol-induced gastric lesions, increased mucus secretion, increased pH, and decreased ulcer area and edema
SOD, CAT, and PGE2 activities increased and MDA levels decreased
Increased PAS staining intensity, increased HSP 70 expression, decreased Bax expression, decreased TNF-α and IL-6, and increased IL-10
No signs of toxicity at a 500 mg/kg dose and enhanced gastric mucosal protection
[99]
HeLa cells (cervical cancer cells)
MCF-7 cells (breast cancer cells) BGM cells (healthy monkey kidney skin cells)
Ruthenium(II) complexes [(η6-p-cymene)RuCl2L] (L = 4-cyanopyridine, 2-aminophenol, 4-aminophenol, pyridazine) and [(η6-p-cymene)RuClL2]PF6 (L = cyanopyridine, 2-aminophenol)In vitro: Cytotoxicity evaluation of each ruthenium complex against the above cell linesComplex II showed selectivity for healthy BGM cells, a promising property that could reduce side effects of current therapies in cancer treatment[100]
Ruthenium(II) complexes: RuII(cym)Cl (cym = η6-p-cymene)
Osmium, rhodium, and iridium complexes: Os(cym), Rh-, Ir(Cp*) (Cp* = pentamethylcyclopentadienyl)
Amino acids: Cys, His
Replacing the metal center of plecstatin 2, the most promising oral anticancer drug, with Ru, Os, Rh, and Ir
Spectroscopic techniques and X-ray diffraction analysis
Reaction with amino acids (Cys, His) in
in vitro experiments
Solvent: Ligand exchange reaction in aqueous solution
Analytical methods: 1H NMR spectra, amino acid reactions, and in vitro experiments to assess anticancer activity
RuII(cym)Cl complexes show strongest anticancer activity
Effective regardless of halogen leaving groups
Implying that the metal center has a significant impact on anticancer activity
[102]
40 Wistar ratsGroups G2 and G4 received subcutaneous injections of DMH and groups G3 and G4 received oral administrations of p-CExperiments: Tumor development, inflammatory factors, glucose and fat metabolism, and gut microbiome analysisSignificant decrease in IL-1, increase in IL-6, and decrease in LEP after p-C use
p-C works by preventing high-fat-diet-associated colon cancer development, modulating inflammatory factors, and promoting beneficial bacteria
[103]
HT-29 colon cancer cellsSFN processingIL-1β induction experimentsSFN reduces IL-6 expression induced by IL-1β
Reduces oxidative stress by inhibiting ROS production and inhibits HT-29 cell proliferation and invasiveness by regulating MAPK/AP-1 and STAT3 signaling pathways. SFN has potential in the treatment and prevention of CRC
[104]
Male Swiss rat (tumor induction in the right hind leg with S180 cells)p-C dosing: 12.5, 25, and 50 mg/kg, subcutaneous injection (s.c.)Preclinical studies, long-term, blinded, and randomized study designsAntinociceptive effects of p-C on oncologic pain
Acts on both ascending and descending pain pathways, and exerts effects by modulating calcium channel currents
[105]
Monocyte-derived mature DCs and autologous CD4+ T cells from people with allergic reactions
BALB/c mice (mice sensitized with OVA)
CE, p-C, and trans-cinnamaldehyde
Controls: Ethanol and CE plus ethanol treatment
In vitro: Dendritic cells were injected with allergen, then co-cultured with CE, p-cymene, CA, or ethanol
In vivo: Oral administration of CE or ethanol to BALB/c mice immunized with OVA
In vitro: CE, p-cymene, and CA inhibited DC maturation and allergen-specific T-cell proliferation, Th1 and Th2 cytokine production, and reduced sulfide leukotriene release and CD63 expression in macrophages
In vivo: In OVA-sensitized mice, CE inhibits IgE to IgG2a conversion and OVA-specific proliferation, reduces airborne inflammation and anaphylaxis, and prevents atopic dermatitis-like inflammation
[106]
THP-1 monocytes, HEK-TLR2 and HEK-TLR4 reporter cellsAnti-inflammatory effects of cinnamon extract, trans-cinnamaldehyde, p-C, and their combinationHigh-performance liquid chromatography, mass spectrometry, and cell stimulation and measurementTrans-cinnamaldehyde and p-C reduced IL-8 secretion, mitigated phosphorylation of Akt and IκBα, and their combination enhanced anti-inflammatory effects[107]
Rats in a TNBS-induced colitis modelp-C and rosmarinic acid administered orally (25–200 mg/kg)TNBS-induced colitis modelp-C and RA reduce ulceration, lesion score, and diarrhea index in colonic inflammation
Reduces MDA and MPO, restores GSH, and increases SOD activity
Reduces IL-1β and TNF-α and maintains IL-10
Modulates T-cell populations and inflammation-related gene expression
Increases MUC-2 and ZO-1 expression
[108]
HCT116 and HepG2 cellsO. onites essential oil, carvacrol, and p-C at a concentration of 400 µg/mLCell experiments (using MTT assay and DCFH-DA method)p-C, carvacrol in O. onites essential oil may be considered as a pharmaceutical product candidate for cancer treatment[109]
* p-C, p-Cymene; PVA, polyvinyl alcohol; CMC, carboxymethylcellulose; SOD, superoxide dismutase; CAT, catalase; PGE2, prostaglandin E2; MDA, malondialdehyde; PAS, periodic acid–Schiff; HSP, heat shock protein; Bax, bcl-2 associated X protein; TNF-α, tumor necrosis factor-alpha; IL, interleukin; Cys, cysteine; His, histidine; DMH, dimethylhydrazine; LEP, leptin; SFN, sulforaphane; MAPK, mitogen-activated protein kinase; STAT3, signal transducer and activator of transcription 3; AP-1, activator protein 1; CRC, colorectal cancer; DC, dendritic cell; CD, cluster of differentiation; BALB/c, BALB/c mice; OVA, ovalbumin; CE, cinnamon extract; CA, trans-cinnamaldehyde; Th, T-helper; IgE, immunoglobulin E; IgG2a, immunoglobulin G2a; HEK-TLR, human embryonic kidney toll-like receptor (HEK) cells; Akt, protein kinase B (PKB); IκBα, inhibitor of nuclear factor kappa B alpha; TNBS, trinitrobenzenesulfonic acid; RA, rosmarinic acid; MDA, malondialdehyde; MPO, myeloperoxidase; GSH, glutathione; SOD, superoxide dismutase; MUC-2, Mucin 2; ZO-1, zonula occludens-1; HCT116, human colon tumor 116 cell; HepG2, human hepatocellular carcinoma 2 cell; DCFH-DA, 2′,7′-Dichlorofluorescin diacetate; MTT, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide.
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Pyo, Y.; Jung, Y.J. Microbial Fermentation and Therapeutic Potential of p-Cymene: Insights into Biosynthesis and Antimicrobial Bioactivity. Fermentation 2024, 10, 488. https://doi.org/10.3390/fermentation10090488

AMA Style

Pyo Y, Jung YJ. Microbial Fermentation and Therapeutic Potential of p-Cymene: Insights into Biosynthesis and Antimicrobial Bioactivity. Fermentation. 2024; 10(9):488. https://doi.org/10.3390/fermentation10090488

Chicago/Turabian Style

Pyo, Yeonhee, and Yeon Ja Jung. 2024. "Microbial Fermentation and Therapeutic Potential of p-Cymene: Insights into Biosynthesis and Antimicrobial Bioactivity" Fermentation 10, no. 9: 488. https://doi.org/10.3390/fermentation10090488

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