Liquid chromatography-tandem mass spectrometry profile and antioxidant, antimicrobial, antiproliferative, and enzyme activities of Thymus pectinatus and Thymus convolutus: in vitro and in silico approach

BACKGROUND

The objective of this study is to investigate the antiproliferative, antioxidant, antimicrobial, and enzyme activity capacities and phytochemical compositions of Thymus pectinatus (TP), Thymus convolutus (TC), which are endemic to Türkiye. Quantitative analysis of phenolic compounds in the extracts was conducted using liquid chromatography-tandem mass spectrometry, targeting 53 phenolic compounds.

RESULTS

Rosmarinic acid, quinic acid, and cynaroside were identified as the major compounds, exhibiting quantitative variation in both extracts. The extracts had a high total phenolic content, with 113.57 ± 0.58 mg gallic acid equivalents (GAE)/g extract for TP and 130.52 ± 1.05 mg GAE/g extract for TC. Furthermore, although both extracts exhibited high total flavonoid content; the TP extract (75.12 ± 1.65 mg quercitin equivalents (QE)/g extract) displayed a higher flavonoid content than the TC extract (30.24 ± 0.74 mg QE/g extract) did. The extracts had a promising antiproliferative effect on C6, HeLa, and HT29 cancer cell lines with a less cytotoxic effect (10.5-14.2%) against normal cells. Both extracts exhibited very potent inhibitory activity against the xanthine oxidase enzyme, with half-maximal inhibitory concentration values of respectively 2.07 ± 0.03 μg mL-1 and 2.76 ± 0.06 μg mL-1 and moderate activity against tyrosinase and α-glucosidase. Docking simulations proved that rosmarinic acid and cynaroside, the major components of the extracts, were the most potent inhibitors of xanthine oxidase. According to antimicrobial activity results, the TC extract exhibited moderate activity against Staphylococcus aureus, and the TP extract had strong activity against both Enterococcus faecium and S. aureus.

CONCLUSION

These findings emphasize the beneficial effects of the two endemic Thymus species on human health and suggest their potential use as plant-derived bioactive agents. © 2024 Society of Chemical Industry.

Thymus mastichina (L.) L. and Cistus ladanifer L. for skin application: chemical characterization and in vitro bioactivity assessment

ETHNOPHARMACOLOGICAL RELEVANCE

Thymus mastichina (L.) L. (TM) and Cistus ladanifer L. (CL) are two Portuguese autochthonous species with traditional skin application in folk medicine. TM is majorly known for its antiseptic and wound healing properties, as an external anti-inflammatory agent and for its application in folk cosmetics and hygiene products. Its use in acne vulgaris has also been reported. CL is traditionally used in remedies for wounds, ulcers and other skin ailments such as psoriasis and eczema. Its application has been found useful due to its anti-inflammatory, astringent, wound healing and antiseptic properties.

AIM OF THE STUDY

With this work, we aimed to investigate relevant bioactivities related with the traditional application of TM and CL essential oils (EOs) and hydrolates (by-products of EO production) in skin ailments. Specifically their in vitro antioxidant, anti-inflammatory, cytotoxic, wound healing and antimicrobial properties were evaluated. The chemical composition of both EOs and respective hydrolates was also characterized.

MATERIALS AND METHODS

Chemical characterization of EOs and hydrolates was performed by GC-FID and GC-MS. Cellular biocompatibility was evaluated using the MTT assay in macrophages (RAW 264.7) and fibroblasts (L929) cell lines. Anti-inflammatory activity was investigated by studying nitric oxide (NO) production by macrophages with Griess reagent. Wound healing potential was evaluated with the scratch-wound assay. The antioxidant potential was studied by the DPPH scavenging method. Antimicrobial activity was evaluated by broth microdilution assay against relevant microbial strains and skin pathogens, namely Staphylococcus aureus, Staphylococcus epidermidis, Cutibacterium acnes, Pseudomonas aeruginosa, Escherichia coli, Candida albicans and Aspergillus brasiliensis.

RESULTS

The major compounds present in TM and CL EOs were 1,8-cineole and α-pinene, respectively. 1,8-cineole and E-pinocarveol were the major compounds in the correspondent hydrolates. CL EO presented the highest anti-inflammatory potential [EC₅₀ = 0.002% (v/v)], still with significant cytotoxicity [IC₅₀ = 0.012% (v/v)]. TM preparations presented anti-inflammatory potential, also presenting higher biocompatibility. The same profile was present on fibroblasts regarding biocompatibility of the tested preparations. CL EO and hydrolate increased fibroblasts' migration by 155.7% and 148.4%, respectively. TM hydrolate presented a milder activity than CL hydrolate, but wound healing potential was still present, increasing cell migration by 125.1%. All preparations presented poor antioxidant capacity. CL EO presented higher antimicrobial activity, with MICs ranging from 0.06% (v/v) to 2% (v/v), against different microorganisms.

CONCLUSIONS

Anti-inflammatory and skin repairing potential were present for CL preparations. TM hydrolate presented an interesting biocompatible profile on both cell lines, also presenting anti-inflammatory potential. Furthermore, EOs from both species presented antimicrobial activity against a panel of different microorganisms. These in vitro bioactivities support some of their traditional skin applications, specifically regarding their antiseptic, wound healing and anti-inflammatory uses.

Variations in the Chemical Composition of Essential Oils in Native Populations of Korean Thyme, Thymus quinquecostatus Celak

The genus Thymus (Lamiaceae) contains numerous medicinally important species. Among them, Thymus quinquecostatus Celak. has been extensively utilized as a traditional medicine and a food flavoring agent in the Korean peninsula, owing to its unique aroma. In particular, T. quinquecostatus has been used for the treatment of gastroenteritis, inflammation, stomach problems, liver disease, arthritis, arteriosclerosis, and menstrual problems. This study aimed to investigate the chemical diversity of essential oils among 103 Korean native populations of T. quinquecostatus. For this purpose, seedlings of T. quinquecostatus populations were purchased from different regions in the Korean Peninsula, and seedlings were grown in the experimental field under the same environmental conditions. The chemical compositions of steam-distilled essential oils were determined using GC-MS. In total, 212 components were identified from 103 populations of T. quinquecostatus. Furthermore, principal component analysis (PCA) was performed in order to understand variations in the essential oil compositions among 103 Korean native populations of T. quinquecostatus. According to the essential oil compositions, 30 components were selected for PCA. Based on the most abundant essential oil components, four chemotypes were identified in T. quinquecostatus populations. PCA and cluster analyses revealed that 103 individuals of T. quinquecostatus could be classified into four clusters, such as thymol, geraniol, geranyl acetate, and linalool. Furthermore, dendrogram construction demonstrated that geraniol and geranyl acetate, as well as linalool and thymol groups, were closely related. This study suggested the significant chemical polymorphism of essential oils in local populations of T. quinquecostatus in Korea. It could be concluded that the intraspecific variations in the essential oil compositions may be associated with genetic diversity among the individuals.

The Chemical Composition and Biological Activities of Essential Oil from Korean Native Thyme Bak-Ri-Hyang (Thymus quinquecostatus Celak.)

Thymus quinquecostatus Celak. (Korean name: bak-ri-hyang) is an important medicinal and aromatic herb in Korea, which is named for the spread of its fragrance over a distance of approximately 40 km. In traditional Korean systems of medicine, T. quinquecostatus has been used to treat cancer, constipation, hepatic disease, arteriosclerosis, poor circulation in women, constipation, and menstrual irregularities. At present, T. quinquecostatus is used only for ornamental and ground cover purposes. A literature search was conducted to retrieve information regarding the essential oil composition and biological properties of T. quinquecostatus from PubMed, Science Direct, Wiley, Springer, Taylor and Francis, Wiley, and other literature databases. T. quinquecostatus can be divided into different chemotypes, such as γ-terpinene, thymol, phenol, carvacrol, and geraniol, according to the presence of major components in its essential oil. Further, the essential oil from T. quinquecostatus has been reported to possess various therapeutic properties such as antioxidant, antimicrobial, anticancer, anti-inflammatory, analgesic, sleep prolonging, soothing, skin protection and whitening, anti-aging, anti-obesity, and anti-acne properties. In conclusion, this review will be helpful for utilizing the T. quinquecostatus plant in different industries including food, pharmaceuticals, pesticides, perfumery, and cosmetics.

Non-conventional therapeutical approaches to acne vulgaris related to its association with metabolic disorders

The ever-increasing frequency of metabolic syndrome (MetS) is still a major challenge of the public health care system, worldwide. In recent years, researchers have been drawn to the uncommon (at first look) link between skin illnesses and MetS. Because of the pro-inflammatory mechanisms and insulin resistance (IR) that are upregulated in metabolic syndrome, many skin disorders are correlated to metabolic dysfunctions, including acne vulgaris. A comprehensive understanding of the link between MetS and acne vulgaris may contribute to the development of new treatment strategies. The current review focuses on dietary and therapeutic interventions and assesses the effect of various approaches such as improving diet by avoiding certain food products (i.e., milk and chocolate) or increasing the intake of others (i.e., food products rich in omega-3 fatty acids), metformin administration, therapy with plant extracts, plant essential oils, and probiotic supplementation on the improvement of certain acne vulgaris severity parameters. These therapeutic approaches, when combined with allopathic treatment, can improve the patients' quality of life.

Growth Inhibitory Activity of Callicarpa americana Leaf Extracts Against Cutibacterium acnes

Acne vulgaris is a common skin disease affecting adolescents and young adults of all ethnic groups, negatively impacting self-esteem, self-confidence, and social life. The Gram-positive bacteria Cutibacterium acnes colonizes the sebum-rich follicle and contributes to inflammation of the pilosebaceous gland. Long-term antibiotic therapies targeting C. acnes lead to the development of antimicrobial resistance, and novel acne vulgaris therapies are needed. This study investigated the C. acnes inhibitory activity of Callicarpa americana leaves, a native Southeastern United States shrub historically used by Native Americans to treat fever, stomachache, and pruritis. Flash chromatography fractions of the ethyl acetate-soluble C. americana ethanol leaf extract (649C-F9 and 649C-F13) exhibited MICs ranging from 16 to 32 µg ml-1 and IC50 range of 4-32 μg ml-1 against a panel of 10 distinct C. acnes isolates. Cytotoxicity against an immortalized human keratinocyte cell line (HaCaTs) skin was detected at more than eight times the dose required for growth inhibitory activity (IC50 of 256 μg ml-1 for 649C-F9 and IC50 of >512 μg ml-1 for 649C-F13). This work highlights the potential of C. americana leaf extracts as a cosmeceutical ingredient for the management of acne vulgaris. Further research is necessary to assess its mechanism of action and in vivo efficacy.

Traditional Uses, Chemical Constituents and Biological Activities of Plants from the Genus Thymus

The genus Thymus (Lamiaceae) comprises about 214 species throughout the world, mainly found in North Africa, Europe, and temperate Asia zone. They are traditionally used as food additives and folk medicines. This review comprehensively summarizes information about traditional uses, chemical constituents, and biological activities of this genus and provides recommendations for future investigations. All information was gathered from scientific databases including Google Scholar, Sci-Finder, Web of Science, ScienceDirect, and CNKI. Volatile oils are the most concerned constituents of this genus. Flavonoids, phenylpropanoids, tannins, organic acids, terpenoids, and phytosterols were also summarized. This genus plants possessed a variety of activities including antimicrobial, antioxidant, anti-inflammatory, cytotoxic, analgesic, and antidiabetic. In brief, this review will be helpful to provide valuable data for explorations and create more interests towards Thymus genus in the future.

In Vitro Antimicrobial Activity of Essential Oils from Sardinian Flora against Cutibacterium (Formerly Propionibacterium) acnes and Its Enhancement by Chitosan

The in vitro antibacterial activity of some essential oils from Sardinian flora, both alone and in combination with chitosan, was investigated against a strain of Cutibacterium acnes, a bacterium involved in pathogenesis of acne. The composition of the essential oils was determined by gas chromatography and gas chromatography/mass spectrometry. The results of this investigation demonstrated that some of the oils examined, characterised by different chemical profiles, possessed some activity against C. acnes. Interestingly, this antibacterial effect was enhanced by sub-inhibitory concentrations of chitosan. These observations suggest the potential application of this synergy in the development of innovative topical formulations useful in the management of acne.

The in vitro antimicrobial evaluation of commercially essential oils and their combinations against acne

OBJECTIVE

The study investigated the efficacy of commercial essential oil combinations against the two pathogens responsible for acne with the aim to identify synergy and favourable oils to possibly use in a blend.

MATERIALS AND METHODS

Antimicrobial activity was assessed using the minimum inhibitory concentration (MIC) assay against Staphylococcus epidermidis (ATCC 2223) and Propionibacterium acnes (ATCC 11827), and the fractional inhibitory concentration index (ΣFIC) was calculated. Combinations displaying synergistic interactions were further investigated at varied ratios and the results plotted on isobolograms.

RESULTS

From the 408 combinations investigated, 167 combinations were identified as displaying noteworthy antimicrobial activity (MIC value ≤1.00 mg mL-1 ). Thirteen synergistic interactions were observed against S. epidermidis, and three synergistic combinations were observed against P. acnes. It was found that not one of the synergistic interactions identified were based on the combinations recommended in the layman's aroma-therapeutic literature. Synergy was evident rather from leads based on antimicrobial activity from previous studies, thus emphasizing the importance of scientific validation. Leptospermum scoparium J.R.Forst. and G.Forst (manuka) was the essential oil mostly involved in synergistic interactions (four) against S. epidermidis. Cananga odorata (Lam.) Hook.f. and Thomson (ylang ylang) essential oil was also frequently involved in synergy where synergistic interactions could be observed against both pathogens. The combination with the lowest MIC value against both acne pathogens was Vetiveria zizanioides Stapf (vetiver) with Cinnamomum verum J.Presl (cinnamon bark) (MIC values 0.19-0.25 mg mL-1 ). Pogostemon patchouli Benth. (patchouli), V. zizanioides, C. verum and Santalum spp. (sandalwood) could be identified as the oils that contributed the most noteworthy antimicrobial activity towards the combinations. The different chemotypes of the essential oils used in the combinations predominantly resulted in similar antimicrobial activity.

CONCLUSIONS

The investigated essential oil combinations resulted in at least 50% of the combinations displaying noteworthy antimicrobial activity. Most of the synergistic interactions do not necessarily correspond to the recommended layman's aroma-therapeutic literature, which highlights a need for scientific validation of essential oil antimicrobial activity. No antagonism was observed.

Aromatherapy, botanicals, and essential oils in acne

Complementary and alternative medicine approaches are popular among some patient segments due to the perception that they are "natural" and thus are believed to be less likely to be dangerous, to be less toxic, or to cause fewer side effects. In dermatology, these can include aromatherapy, botanicals, and essential oils (plant extracts). Preliminary evidence, biological activity studies, and small pilot clinical trials conducted outside of North America, mostly in young adults, suggest that some may have value in acne treatment. When additional research and larger clinical trials are conducted, both clinicians and patients will be able to understand the risks and benefits compared with allopathic remedies.

Commercial Essential Oils as Potential Antimicrobials to Treat Skin Diseases

Essential oils are one of the most notorious natural products used for medical purposes. Combined with their popular use in dermatology, their availability, and the development of antimicrobial resistance, commercial essential oils are often an option for therapy. At least 90 essential oils can be identified as being recommended for dermatological use, with at least 1500 combinations. This review explores the fundamental knowledge available on the antimicrobial properties against pathogens responsible for dermatological infections and compares the scientific evidence to what is recommended for use in common layman's literature. Also included is a review of combinations with other essential oils and antimicrobials. The minimum inhibitory concentration dilution method is the preferred means of determining antimicrobial activity. While dermatological skin pathogens such as Staphylococcus aureus have been well studied, other pathogens such as Streptococcus pyogenes, Propionibacterium acnes, Haemophilus influenzae, and Brevibacterium species have been sorely neglected. Combination studies incorporating oil blends, as well as interactions with conventional antimicrobials, have shown that mostly synergy is reported. Very few viral studies of relevance to the skin have been made. Encouragement is made for further research into essential oil combinations with other essential oils, antimicrobials, and carrier oils.

New perspectives on antiacne plant drugs: contribution to modern therapeutics

Acne is a common but serious skin disease, which affects approximately 80% adolescents and young adults in 11-30 age group. 42.5% of men and 50.9% of women continue to suffer from this disease into their twenties. Bacterial resistance is now at the alarming stage due to the irrational use of antibiotics. Hence, search for new lead molecule/bioactive and rational delivery of the existing drug (for better therapeutic effect) to the site of action is the need of the hour. Plants and plant-derived products have been an integral part of health care system since time immemorial. Therefore, plants that are currently used for the treatment of acne and those with a high potential are summarized in the present review. Most active plant extracts, namely, P. granatum, M. alba, A. anomala, and M. aquifolium exhibit minimum inhibitory concentration (MIC) in the range of 4-50 µg/mL against P. acnes, while aromatic oils of C. obovoides, C. natsudaidai, C. japonica, and C. nardus possess MICs 0.005-0.6 μL/mL and phytomolecules such as rhodomyrtone, pulsaquinone, hydropulsaquinone, honokiol, magnolol, xanthohumol lupulones, chebulagic acid and rhinacanthin-C show MIC in the range of 0.5-12.5 μg/mL. Novel drug delivery strategies of important plant leads in the treatment of acne have also been discussed.

Neolitsea aciculata Essential Oil Inhibits Drug-Resistant Skin Pathogen Growth and Propionibacterium acnes-Induced Inflammatory Effects of Human Monocyte Leukemia

This study examined the chemical composition of Neolitsea aciculata essential oil (NAE) and its biological activities. NAE was obtained by hydrodistillation of N. aciculata leaves collected in Jeju Island and analyzed by gas chromatography equipped with a mass spectrometer detector. 1-Dodecen-3-yne (12.5%), calarene (11.5%) and elemol (9.5%) were identified as the major components of NAE. The antibacterial and anti-inflammatory activities of NAE against skin pathogens were examined to determine the protective properties against acne vulgaris. NAE exhibited moderate to strong antibacterial activity against drug-susceptible and -resistant Propionibacterium acnes and Staphylococcus epidermidis, which are known as acne-causing bacteria. In addition, NAE reduced the P. acnes-induced secretion of tumor necrosis factor-α (TNF-α) and interleukin-8 (IL-8) in THP-1 cells, highlighting its anti-inflammatory effects. The DPPH radical scavenging activities of NAE also revealed moderate antioxidant properties (IC50, 21.3 μL/mL). Overall, NAE is an attractive candidate as an ingredient in skin care products.

Inhibitory effects of Fortunella japonica var. margarita and Citrus sunki essential oils on nitric oxide production and skin pathogens

A number of essential oils from citrus peels are claimed to have biological activities. Citrus peel, called 'Jin-Pi', is used in traditional medicine for digestion, severe cold, and fever. However, the antibacterial activities against skin pathogens and anti-inflammatory effects of the essential oils of Citrus sunki (JinGyul) and Fortunella japonica var. margarita (GumGyul) have not yet been described. Therefore, in this study, the essential oils of the citrus species C. sunki (CSE) and F. japonica var. margarita (FJE), both native to the island of Jeju, Korea, were examined for their anti-inflammatory and antimicrobial activities against skin pathogens. Four human skin pathogenic microorganisms, Staphylococcus epidermidis CCARM 3709, Propionibacterium acnes CCARM 0081, Malassezia furfur KCCM 12679, and Candida albicans KCCM 11282, were studied. CSE and FJE exhibited strong antimicrobial activity against most of the pathogenic bacteria and yeast strains that were tested. Interestingly, CSE and FJE even showed antimicrobial activity against antibiotic-resistant S. epidermidis CCARM 3710, S. epidermidis CCARM 3711, P. acnes CCARM9009, and P. acnes CCARM9010 strains. In addition, CSE and FJE reduced the lipopolysaccharide (LPS)-induced secretion of nitric oxide (NO) in RAW 264.7 cells, indicating that they have anti-inflammatory effects. We also analysed the chemical composition of the oils by gas chromatography-mass spectrometry (GC-MS) and identified several major components, including dl-limonene (68.18%) and beta-myrcene (4.36%) for CSE, and dl-limonene (61.58%) and carvone (6.36%) for FJE. Taken together, these findings indicate that CSE and FJE have great potential to be used in human skin health applications.