Thymol — Is Thyme Oil Stronger Than Pharmacy Remedies?

Aim of the study: Thymol is a naturally occurring phenol monoterpene derivative of cymene and isomer of carvacrol. Thymol (10–64%) is one of the major constituent of essential oils of thyme (Thymus vulgaris L., Lamiaceae), a medicinal plant with several therapeutic properties.

Results: Moreover, this compound also exhibits antimicrobial, antioxidant, anticarcinogenesis, anti-inflammatory, and antispasmodic activities, as well as a potential as a growth enhancer and immunomodulator. In the present review, these bioactivities have been covered because some of them can contribute to explain the ethnopharmacology of thymol and its main source, T. vulgaris. Other important aspects about thymol are discussed: its toxicity and bioavailability, metabolism, and distribution in animals and humans.

Aim of the study: Thymol (2-isopropyl-5-methylphenol) belongs to the phenolic monoterpenes and mostly occurs in thyme species. It is one of the main compounds of thyme essential oil.

Results: The current search for new directions of biological or therapeutic activities of natural plant substances with known structures includes thyme essential oil and thymol. Novel studies have demonstrated their antibiofilm, antifungal, antileishmanial, antiviral, and anticancer properties. Also, their new therapeutic formulations, such as nanocapsules containing these constituents, can be beneficial in medicinal practice and create opportunities for their extensive use. Extensive application of thymol and thyme essential oil in the healthcare sector is very promising but requires further research and analysis.

Aim of the study: Thyme is a herb with broncholytic und secretomotoric effects. Its activity on beta (2) receptors as a possible mechanism of action was demonstrated.

Results: Thyme extracts with very low thymol contents (practically free of volatile oil) were equally effective with respect to endothelin effects. When an extract with very low thymol contents is spiked with increasing concentrations of thymol, a concentration-dependent increase concerning the antispasmodic effect (Ba (++)-induced trachea contraction) is observed. In conclusion, the data show that in various models of antispasmodic effect (ileum and trachea) and by measuring ciliary activity, thymol (and carvacrol) is (are) active, although other not identified components of thyme extract appear to be very important as well, since extracts with very low thymol contents are active. On the basis of these results the standardization on thymol alone appears not to be justified.

Aim of the study: Urinary tract infections are caused primarily by uropathogenic Escherichia coli (UPEC), and indwelling catheters are usually colonized by UPEC biofilms tolerant to common antibiotics. Hence, UPEC biofilms pose a substantial challenge, and there is an urgent need for effective control strategies.

Results: In this study, 79 essential oils were screened for antibiofilm ability against UPEC. Components of active oils were identified, and their antibiofilm activities were also investigated using 96-well plates with crystal violet assay, scanning electron microscopy, and confocal laser scanning microscopy. Oregano oil and thyme red oil and their major common constituents, carvacrol and thymol, significantly inhibited UPEC biofilm formation at subinhibitory concentrations (<0·01%). These findings were supported by observations that carvacrol and thymol reduced fimbriae production and the swarming motility of UPEC. Furthermore, carvacrol and thymol markedly decreased the hemagglutinating ability of UPEC, and UPEC was more easily killed by human whole blood in the presence of carvacrol and thymol. Carvacrol-rich oregano oil and thymol-rich thyme red oil have high antibiofilm and antivirulence activities against UPEC.

Aim of the study: Multidrug-resistant pathogens present a major global challenge in antimicrobial therapy and frequently complicate otitis externa in dogs. In vitro efficacy of oregano oil, thyme oil and their main phenolic constituents against bacterial and fungal isolates associated with canine otitis externa were investigated. It was hypothesized that the main phenolic components would have greater antimicrobial activity compared to the relative essential oil.

Results: Oregano oil, thyme oil, carvacrol and thymol exhibited antibacterial activity against all bacterial and fungal isolates tested. MIC90 values ranged from 0.015 to 0.03% (146–292 μg/mL) for the Gram-positive bacteria and P. mirabilis. For P. aeruginosa and M. pachydermatis, MIC90 values ranged from 0.09 to 0.25% (800–2,292 μg/mL). Oregano oil, thyme oil, carvacrol and thymol showed good in vitro bactericidal and fungicidal activity against 100 isolates from dogs with otitis externa, including some highly drug-resistant isolates. These essential oils and their main phenolic constituents have the potential to be further investigated in vivo for the treatment of canine otitis externa.

Aim of the study: Trichomonas vaginalis is a sexually transmitted protozoan parasite that usually causes infections in women. Metronidazole is used as the first choice in the treatment of this parasitic disease, but there is a need for new drugs since 1980's with increasing numbers of reported resistance.

Results: According to in vitro activity tests, cinnamaldehyde was determined to be most effective essential oil component. Clinical isolates were susceptible to metronidazole. In combination study, metronidazole showed synergy with cinnamaldehyde and carvacrol, and partial synergy with thymol. It was determined that cinnamaldehyde, carvacrol and thymol, which are known to have high antimicrobial activity, also have strong activity against T. vaginalis isolates and show a synergistic interaction with metronidazole. The use of metronidazole at lower doses in the synergistic interaction may contribute to the literature in terms of reducing drug side effects, creating a versatile antimicrobial target, and reducing the rate of resistance development.

Aim of the study: Doxorubicin (DOX) is an effective anticancer agent with a wide spectrum of activities. However, it has many adverse effects on various organs especially on the liver.

Results: Thyme oil and thymol also reduced the high levels of TNF-α and the decreased levels of both albumin and IL-4. These agents ameliorated doxorubicin-induced elevation in hepatic lipid peroxidation and associated reduction in GSH content and GST and GPx activities. Further, the supplementation with thyme oil and thymol significantly augmented mRNA expression of the level of antiapoptotic protein Bcl-2 and significantly downregulated nuclear and cytoplasmic levels of the hepatic apoptotic mediator p53. Thus, thyme oil and thymol successfully counteracted doxorubicin-induced experimental hepatotoxicity via their anti-inflammatory, antioxidant, and antiapoptotic properties.

Aim of the study: The development of biodegradable active packaging systems incorporating natural antimicrobial and antioxidant compounds represents a promising strategy for improving the quality and shelf life of fresh meat.

Results: All CH-based systems reduced microbial growth compared with uncoated controls, which exceeded 6-7 log CFU g-1 for several microbial groups after 5 days. CH-based packaging also reduced protein oxidation and maintained low lipid oxidation. However, 3% TEO caused significant colour deterioration by day 5. These results demonstrate the potential of CH-based active films enriched with TEO as a natural and biodegradable packaging alternative to enhance the shelf life and safety of refrigerated chicken meat.

Aim of the study: The growing global burden of antimicrobial resistance (AMR) highlights the urgency of identifying new therapeutic options or adjuvant agents capable of limiting microbial growth. This study aimed to evaluate the potential applicability of selected essential oils (EOs) as alternative antimicrobial agents by assessing their biocidal activity against clinically relevant microorganisms and determining their cytotoxicity toward human cell lines.

Results: For thymol, yeast strains exhibited eight-fold lower susceptibility compared to bacterial strains. Cytotoxicity of the tested EOs towards the studied cell lines was significant. EOs proved to be effective against microorganisms but at the same time showed substantial cytotoxicity, thus potentially limiting their application. Further research on formulation strategies, selective delivery, and dose optimization is required to enhance their safety profile and clinical feasibility.