Efficiency of Calamintha officinalis essential oil as preservative in two topical product types

Essential oils used in dermocosmetics: Review about its biological activities

INTRODUCTION

Currently, the demand for the use of constituents of natural origin in cosmetic formulations in detriment of synthetic compounds is noticeable. Several studies assess the potential of essential oils when incorporated into various cosmetic formulations and study their biological activities. This work intends to prepare a literature review on essential oils tested in dermocosmetic formulations and whose biological activities were evaluated through in vitro and/or in vivo tests. The main objectives for this study were as follows: to identify the essential oils that have been used in cosmetic formulations; and compile information on the main biological activities tested in cosmetic formulations.

METHODS

A search was carried out until 2021 in the scientific databases PubMed and Web of Science, using different search terms, and several scientific articles from in vitro and in vivo studies in animals and clinical trials were selected and analyzed of involving development dermocosmetic formulations containing essential oils and the analysis of their biological activities.

RESULTS

These studies demonstrate that the antimicrobial activity (antibacterial and antifungal) is the one most studied, mainly through in vitro tests. In vivo studies were also carried out either in animals or in clinical studies showing different effects, such as repellent action, inhibition of hair growth, and action against migraine. Regarding formulations, it was evident that creams are the most used.

CONCLUSIONS

There is enormous potential for the use of essential oils in future formulations in the cosmetic and pharmaceutical industry, in particular as preservatives, exploring their other biological activities.

Review of the safety of application of cosmetic products containing parabens

Cosmetics are a source of lifetime exposure to various substances including parabens, being the most popular synthetic preservatives. Because the use of cosmetics shows an increasing trend and some adverse health outcomes of parabens present in these products have been reported, the present review focused on the safety of dermal application of these compounds. Special attention has been paid to the absorption of parabens and their retention in the human body in the intact form, as well as to their toxicological characteristics. Particular emphasis has been placed on the estrogenic potential of parabens. Based on the available published data of the concentrations of parabens in various kinds of cosmetics, the average ranges of systemic exposure dose (SED) for methylparaben, ethylparaben, propylparaben, and butylparaben have been calculated. Safety evaluations [margin of safety (MoS)] for these compounds, based on their aggregate exposure, have also been performed. Moreover, evidence for the negative impact of methylparaben on skin cells has been provided, and the main factors that may intensify dermal absorption of parabens and their impact on the skin have been described. Summarizing, the use of single cosmetics containing parabens should not pose a hazard for human health; however, using excessive quantities of cosmetic preparations containing these compounds may lead to the development of unfavorable health outcomes. Due to the real risk of estrogenic effects, as a result of exposure to parabens in cosmetics, simultaneous use of many cosmetic products containing these preservatives should be avoided.

Plant Complexity and Cosmetic Innovation

Plants have been used in cosmetic products since ancient times and are the subject of scientific investigation even nowadays. During the years, a deeper understanding of both the behavior of skin and of plants have become available drawing increasingly complex pictures. Plants are complex organisms that produce different metabolites responding to the environment they live in. Applied to the skin, phytomolecules interact with skin cells and affect the skin well-being and appearance. Ethnobotanical studies on the one hand and physico-chemical analyses on the other have pictured a rich inventory of plants with potential to enrich modern cosmetic products.

Antifungal Activity of Essential Oils Against Candida Species Isolated from Clinical Samples

We evaluated the in vitro antifungal activity of essential oils obtained from the aromatic plants Laurus nobilis, Thymus vulgaris, Mentha piperita, Cymbopogon citratus and Lippia junelliana against the following Candida species isolated from clinical samples: C. krusei (n = 10); C. albicans (n = 50); C. glabrata (n = 70) and C. parapsilosis (n = 80). The minimal inhibitory concentration (MIC) was determined according to EDef 7.3.1 document from EUCAST. Amphotericin B and fluconazole were the antifungal drugs used as inhibition control. The concentration ranges evaluated were 0.4-800 and 0.03-128 mg l^-1 for essential oils and antifungal drugs, respectively. MIC₅₀ and MIC₉₀, mode and ranges were calculated. All the Candida spp. evaluated were susceptible to amphotericin B (MIC ≤ 1 mg l^-1), while fluconazole was inactive for C. krusei (MIC ≥ 32 mg l^-1) and intermediate for C. glabrata (MIC≤ 32 mg l^-1). The essential oils showed antifungal activity on Candida spp. tested with MIC₉₀ values ranging from 0.8 to 800 mg l^-1. In general, the most active essential oils were L. nobilis and T. vulgaris (MIC₉₀ 0.8-0.16 mg l^-1), and the least active was C. officinalis (MIC₉₀ 400-800 mg l^-1). C. krusei was inhibited by 5/6 of the essential oils evaluated, and C. glabrata was the least susceptible one. This in vitro study confirms the antifungal activity of these six essential oils assayed which could be a potential source of new molecules useful to control fungal infections caused by some Candida species, including those resistant to antifungal drugs.

Volatile Constituents of Calamintha origanifolia Boiss. Growing Wild in Lebanon

The essential oil of aerial parts of Calamintha origanifolia Boiss. (Lamiaceae), growing wild in Lebanon, was obtained by hydrodistillation and was analysed by GC and GC-MS. 49 compounds, representing 92.2% of the oil, were identified. The major components, belonging to the class of oxygenated monoterpenes, were pulegone (22.5%), isomenthone (12.2%) and piperitenone (9.6%). The oil showed a slight antimicrobial activity against three bacterial strains.

Screening of acute and sub-chronic dermal toxicity of Calendula officinalis L essential oil

The objective of the study is to access the safety of Calendula essential oil by studying acute and sub-chronic dermal toxicity. The dermal toxicities of Calendula essential oil were evaluated in accordance with OECD guidelines number 402 and 411 respectively. The animals were exposed to Calendula officinalis (CO) essential oil dose of 20 mL/kg body weight for acute dermal toxicity, whereas for dermal sub-chronic toxicity study, rats were exposed to CO oil 2.5, 5 and 10 mL/kg body weight, respectively, for 7 times in a week for 90 days. The parameters studies included CNS stimulation, depression, hematological parameters (RBC, WBC, Hb, Lymphocyte % etc), biochemical parameters (total protein, albumin, total bilirubin, ALP, AST, etc), relative organ weight, necropsy and histopathology. In toxicity studies, all animals exhibited normal behavior without any change in hematology, blood biochemistry, necroscopical and histopathology. The no observed effect level (NOEL) and no observed adverse effect level (NOAEL) of CO oil were 2.5 and 10 mg/kg/day, respectively. CO oil is under the herbal medicinal product according to the European Medicines Agency with the claim of an LD₅₀ value of 20 mL/kg body weight. The result indicates that CO essential oil did not produce any significant toxic effects.

Cosmetics Preservation: A Review on Present Strategies

Cosmetics, like any product containing water and organic/inorganic compounds, require preservation against microbial contamination to guarantee consumer’s safety and to increase their shelf-life. The microbiological safety has as main goal of consumer protection against potentially pathogenic microorganisms, together with the product’s preservation resulting from biological and physicochemical deterioration. This is ensured by chemical, physical, or physicochemical strategies. The most common strategy is based on the application of antimicrobial agents, either by using synthetic or natural compounds, or even multifunctional ingredients. Current validation of a preservation system follow the application of good manufacturing practices (GMPs), the control of the raw material, and the verification of the preservative effect by suitable methodologies, including the challenge test. Among the preservatives described in the positive lists of regulations, there are parabens, isothiasolinone, organic acids, formaldehyde releasers, triclosan, and chlorhexidine. These chemical agents have different mechanisms of antimicrobial action, depending on their chemical structure and functional group’s reactivity. Preservatives act on several cell targets; however, they might present toxic effects to the consumer. Indeed, their use at high concentrations is more effective from the preservation viewpoint being, however, toxic for the consumer, whereas at low concentrations microbial resistance can develop.

Preservative efficacy of selected antimicrobials of natural origin in a cosmetic emulsion

OBJECTIVE

To investigate the efficacy of 13 antimicrobial substances (11 substances of natural origin and two conventional preservatives as controls) at two concentrations in an o/w cosmetic emulsion.

METHODS

Cosmetic formulations were analysed for total aerobic bacterial count and total combined yeast count according to the European Pharmacopoeia 8.0. Challenge tests were performed according to the ISO 11930 standard.

RESULTS

The total aerobic bacterial count, the total combined yeast count and the total aerobic mesophilic microorganisms were below the acceptable limit for all cosmetic formulations. Challenge test criterion A was fulfilled by all antimicrobials of natural origin, except levulinic acid in the challenge test with Candida albicans, Lactobacillus ferment in the challenge test with C. albicans and Pseudomonas aeruginosa, and grapefruit seed extract in the challenge test with C. albicans. Phenoxyethanol and the combination of methylparaben and propylparaben were inefficient at the minimum studied concentrations.

CONCLUSION

The results offer important comparative data on the level of preservative efficacy within the group of antimicrobials of natural origin and in reference to some typical, widely used conventional preservatives. Further research must be encouraged regarding cosmetic over-preservation. This article is protected by copyright. All rights reserved.

Antimicrobial Ingredients as Preservative Booster and Components of Self-Preserving Cosmetic Products

This review reports cosmetic ingredients with antimicrobial activity including synthetic and natural (plant and microbial) origin as alternative for preservatives used in cosmetics as well described mechanism of their action.

Calamintha nepeta (L.) Savi and its Main Essential Oil Constituent Pulegone: Biological Activities and Chemistry

Medicinal plants play an important role in the treatment of a wide range of diseases, even if their chemical constituents are not always completely recognized. Observations on their use and efficacy significantly contribute to the disclosure of their therapeutic properties. Calamintha nepeta (L.) Savi is an aromatic herb with a mint-oregano flavor, used in the Mediterranean areas as a traditional medicine. It has an extensive range of biological activities, including antimicrobial, antioxidant and anti-inflammatory, as well as anti-ulcer and insecticidal properties. This study aims to review the scientific findings and research reported to date on Calamintha nepeta (L.) Savi that prove many of the remarkable various biological actions, effects and some uses of this species as a source of bioactive natural compounds. On the other hand, pulegone, the major chemical constituent of Calamintha nepeta (L.) Savi essential oil, has been reported to exhibit numerous bioactivities in cells and animals. Thus, this integrated overview also surveys and interprets the present knowledge of chemistry and analysis of this oxygenated monoterpene, as well as its beneficial bioactivities. Areas for future research are suggested.

Effect of tea tree (Melaleuca alternifolia) oil as a natural antimicrobial agent in lipophilic formulations

There has been increased interest surrounding the use of tea tree oil (TTO) as a natural antimicrobial. In this study, the antimicrobial activity of TTO and its components were investigated in vitro and in a predominantly lipid-based personal care formulation. In vitro, TTO showed minimal inhibitory concentrations of 0.2% (for Saccharomyces cerevisiae and Pythium sulcatum), 0.4% (for Escherichia coli, Bacillus subtilis, and Rhizopus stolonifer), and 0.8% (for Botrytis cinerea). TTO at 0.08%-0.8% was often as efficient as parabens. Comparison of the antimicrobial activities of TTO components showed that terpinen-4-ol and γ-terpinene were generally most effective in inhibiting microbial growth. TTO activity in a personal care product was evaluated through air and water exposure, artificial inoculation, and shelf life studies. While TTO did not increase shelf life of unopened products, it decreased microbial load in products exposed to water and air. Results from this study support that antimicrobial activity of TTO can be attributed to varying levels of its components and that low levels of TTO were effective in reducing microbial growth during the use of the product. This study showed that TTO can act as a suitable preservative system within an oil-based formulation.

Preliminary safety assessment of C-8 xylitol monoester and xylitol phosphate esters

OBJECTIVES

Most of the cosmetic compounds with preservative properties available in the market pose some risks concerning safety, such as the possibility of causing sensitization. Due to the fact that there are few options, the proper development of new molecules with this purpose is needed. Xylitol is a natural sugar, and the antimicrobial properties of xylitol-derived compounds have already been described in the literature. C-8 xylitol monoester and xylitol phosphate esters may be useful for the development of skincare products. As an initial screen for safety of chemicals, the combination of in silico methods and in vitro testing can aid in prioritizing resources in toxicological investigations while reducing the ethical and monetary costs that are related to animal and human testing. This study was designed to evaluate the safety of C-8 xylitol monoester and xylitol phosphate esters regarding carcinogenicity, mutagenicity, skin and eye irritation/corrosion and sensitization through alternative methods.

METHODS

For the initial safety assessment, quantitative structure-activity relationship methodology was used. The prediction of the parameters carcinogenicity/mutagenicity, skin and eye irritation/corrosion and sensitization was generated from the chemical structure. The analysis also comprised physical-chemical properties, Cramer rules, threshold of toxicological concern and Michael reaction. In silico results of candidate molecules were compared to 19 compounds with preservative properties that are available in the market. Additionally, in vitro tests (Ames test for mutagenicity, cytotoxicity and phototoxicity tests and hen's egg test--chorioallantoic membrane for irritation) were performed to complement the evaluation.

RESULTS

In silico evaluation of both molecules presented no structural alerts related to eye and skin irritation, corrosion and sensitization, but some alerts for micronucleus and carcinogenicity were detected. However, by comparison, C-8 xylitol monoester, xylitol phosphate esters showed similar or better results than the compounds available in the market. Concerning experimental data, phototoxicity and mutagenicity results were negative. As expected for compounds with preservative activity, xylitol-derived substances presented positive result in cytotoxicity test. In hen's egg test, both molecules were irritants.

CONCLUSION

Our results suggested that xylitol-derived compounds appear to be suitable candidates for preservative systems in cosmetics.

Essential oils and herbal extracts as antimicrobial agents in cosmetic emulsion

The cosmetic industry adapts to the needs of consumers seeking to limit the use of preservatives and develop of preservative-free or self-preserving cosmetics, where preservatives are replaced by raw materials of plant origin. The aim of study was a comparison of the antimicrobial activity of extracts (Matricaria chamomilla, Aloe vera, Calendula officinalis) and essential oils (Lavandulla officinallis, Melaleuca alternifolia, Cinnamomum zeylanicum) with methylparaben. Extracts (2.5 %), essential oils (2.5 %) and methylparaben (0.4 %) were tested against Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Candida albicans ATCC 14053. Essentials oils showed higher inhibitory activity against tested microorganism strain than extracts and methylparaben. Depending on tested microorganism strain, all tested extracts and essential oils show antimicrobial activity 0.8-1.7 and 1-3.5 times stronger than methylparaben, respectively. This shows that tested extracts and essential oils could replace use of methylparaben, at the same time giving a guarantee of microbiological purity of the cosmetic under its use and storage.

Rubus rosaefolius extract as a natural preservative candidate in topical formulations

Even though the synthetic preservatives may offer a high antimicrobial efficacy, they are commonly related to adverse reactions and regarded as having potentially harmful effects caused by chronic consumption. The development of natural preservatives provides a way of reducing the amount of synthetic preservatives normally used in pharmaceutical and cosmetic preparations. In addition, these agents have less toxic effects and represent a possible natural and safer alternative of the preservatives. The purpose of this research was to evaluate the Rubus rosaefolius Smith extract efficiency as a natural preservative in base formulations. Of the extract, 0.2% (w/w) was assayed for its effectiveness of antimicrobial protection in two different base formulations (emulsion and gel). The microbial challenge test was performed following the standard procedures proposed by The United States Pharmacopoeia 33nd, European Pharmacopoeia 6th, Japanese Pharmacopoeia 15th, and the Cosmetics, Toiletries, and Fragrance Association using standardized microorganisms. The results demonstrated that R. rosaefolius extract at the studied concentration reduced the bacterial inocula, satisfying the criterion in all formulations, even though it was not able to present an effective preservative behavior against fungi. Thus, the investigation of new natural substances with preservative properties that could be applied in pharmaceutical and cosmetic products is relevant due to the possibility of substituting or decreasing the concentration of synthetic preservatives, providing a way for the development of safer formulas for the use of consumers.

Lavender, tea tree and lemon oils as antimicrobials in washing liquids and soft body balms

The aim of this study was to evaluate the antimicrobial activity of commercial essential oils: lavender, tea tree and lemon, antimicrobials in washing liquid and O/W soft body balm. The inhibition efficacy of essential oils in washing liquid (1% alone or in mixtures), in soft body balm (0.5% alone), as well as combined with the synthetic preservative DMDM hydantoin and 3-iodo-2-propynyl butyl carbamate mixture (0.1 and 0.3%), was tested against S. aureus ATCC 6538, P. aeruginosa ATCC 9027, Candida sp. ŁOCK 0008 and A. niger ATCC 16404 in compliance with the European Pharmacopoeia standards. The components of the system preserving soft body balm were supplemented with a solubilizer. Washing liquids containing only essential oils met Criterion A E.P. only for S. aureus, Candida sp. and A. niger. In soft body balm formulations, oils at a concentration of 0.5% did not reveal any preserving activity. The introduction of a solubilizer to a system containing 0.5% tea tree oil led to a substantial increase in the bacteriostatic activity of the formulation, but did not significantly affect its fungistatic properties. A combination of 0.5% tea tree oil, 5% solubilizer and 0.3% synthetic preservative ensured the microbiological stability of soft body balm in accordance with Criterion A E.P.

Evaluation of antimicrobial effectiveness of C-8 xylitol monoester as an alternative preservative for cosmetic products

Xylitol is a natural sugar derived from plants, fruits and vegetables, whose antimicrobial properties are described in the literature. This study aimed to evaluate the antimicrobial effectiveness of C-8 xylitol monoester, for its use as a preservative in cosmetic formulations. The minimum inhibitory concentration (MIC) was determined by the broth macrodilution method, and the antimicrobial effectiveness of C-8 xylitol monoester was determined by using challenge test method. The results obtained in the determination of minimum inhibitory concentration are between 1.0% and 1.25% for Staphylococcus aureus, Escherichia coli and Candida albicans and between 1.0% and 1.5% for Pseudomonas aeruginosa and Aspergillus niger. The amount of 1% of C-8 xylitol monoester was added to the lotion used in the challenge test, observing a rapid decline in the number of CFU g(-1) in stages of evaluation after contamination of the product by all bacteria. The same occurs in relation to C. albicans, which shows a 90% reduction in the number of CFU g(-1). Regarding A. niger, similar reduction is observed when pH value of the lotion is adjusted from 5.5 to 7.0. The results indicate that under the tests conditions, C-8 xylitol monoester has antimicrobial activity and could be considered as an alternative preservative for cosmetic formulations.

Antimicrobial activity of lavender, tea tree and lemon oils in cosmetic preservative systems

AIMS

The aim of the study was to verify the antimicrobial activity of commercial essential oils: lavender, tea tree and lemon as the components of a preservative system in oil in water body milks.

METHODS AND RESULTS

The inhibition efficacy of essential oils alone (0.5%), in mixtures (1%) as well as combined with the synthetic preservative 1,3-dimethylol-5,5-dimethylhydantoin and a 3-iodo-2-propynyl butyl carbamate mixture (0.1% and 0.2%) was tested against Staphylococcus aureus ATCC 6538, Pseudomonas aeruginosa ATCC 9027, Candida sp. ŁOCK 0008 and Aspergillus niger ATCC 16404 in compliance with the standards of the European Pharmacopoeia Commission. The in vitro activity of oils determined by an impedimetric method was also compared with their activity in cosmetic preparations. Criterion A for bacteria (reduction in the inoculum by 3 logarithmic units within 7 days with no increase up to the 28th day) and fungi (reduction in the inoculum by 2 logarithmic units within 14 days with no increase up to the 28th day) was fulfilled for cosmetic formulations containing the tested essential oils with 0.2% of the synthetic preservative. The preservative concentration could be decreased to 0.1% (with preserving the same efficacy) in combination with lavender and tea tree oils at a concentration of 0.5% each.

CONCLUSIONS

In all combinations of essential oils with the synthetic preservative, a synergistic effect of the preservative system components was observed, which made it possible to reduce the usable level of the synthetic preservative up to 8.5 times.

SIGNIFICANCE AND IMPACT OF THE STUDY

To develop an effective preservative system in cosmetics in which a synthetic chemical preservative is replaced by natural essential oils.

Self-preserving cosmetics

Preservatives are added to products for two reasons: first, to prevent microbial spoilage and therefore to prolong the shelf life of the product; second, to protect the consumer from a potential infection. Although chemical preservatives prevent microbial growth, their safety is questioned by a growing segment of consumers. Therefore, there is a considerable interest in the development of preservative-free or self-preserving cosmetics. In these formulations traditional/chemical preservatives have been replaced by other cosmetic ingredients with antimicrobial properties that are not legislated as preservatives according to the Annex VI of the Commission Directive 76/768/EEC and the amending directives (2003/15/EC, 2007/17/EC and 2007/22/EC). 'Hurdle Technology', a technology that has been used for the control of product safety in the food industry since 1970s, has also been applied for the production of self-preserving cosmetics. 'Hurdle Technology' is a term used to describe the intelligent combination of different preservation factors or hurdles to deteriorate the growth of microorganisms. Adherence to current good manufacturing practice, appropriate packaging, careful choice of the form of the emulsion, low water activity and low or high pH values are significant variables for the control of microbial growth in cosmetic formulations. This paper describes the application of the basic principles of 'Hurdle Technology' in the production of self-preserving cosmetics. Multifunctional antimicrobial ingredients and plant-derived essential oils and extracts that are used as alternative or natural preservatives and are not listed in Annex VI of the Cosmetic Directive are also reported.