Microbial contamination of cosmetic products is a matter of great importance to the industry and it can become a major cause of both product and economic losses. Moreover, the contamination of cosmetics can result in their being converted into products hazardous for consumers.
The water and nutrients present in cosmetics make them susceptible to microbial growth. More often, microorganisms are the cause of organoleptic alterations, such as offensive odours, and changes in viscosity and colour. The need to check and control microbial activity is a task of utmost importance to a formulator of cosmetic products. It requires a product to retard the growth of microbes, or destroy them, and preserve the product for a longer shelf life. Synthetic compounds are, up until now, well-accepted as effective in controlling the growth of the bacteria. However, these compounds are closely watched by environmentalists for safety and environmental concerns.
Cosmetics preservatives and microbial resistance
Microbiologists working in the field of cosmetics are frequently required to design preservative systems that provide good protection of cosmetic products against microbial contamination. Microbiologists must therefore work within a narrow range of preservative concentrations in order to achieve effectiveness against microorganisms while avoiding toxicity for end users. For this reason, regulations in the EU and in other countries have specified preservatives allowed, their maximum concentrations, and other directions specifically related to the kind of cosmetic product. In the search for an effective preservative system, it is necessary to consider not only its efficacy against microorganisms, but also the compatibility of the preservatives with other cosmetic raw materials, their synergism with other ingredients, and the product manufacturing process. Cosmetic preservatives are molecules that are potentially toxic for the consumer as well as potential sources of allergies and skin disorders. In order to evaluate the biocide effectiveness of a cosmetic product, various test are carried out to illustrate that the product will not be contaminated during its shelf-life. The assay advised by different pharmacopoeias and by cosmetic organisations, such as the Cosmetic, Toiletries and Fragrance Association (CTFA), is the challenge test, in which the product is artificially and heavily contaminated by representative microorganisms. After defined periods of time, a specifically defined reduction in the microbial populations must take place. Furthermore, it is advisable to perform challenge tests using adapted strains isolated from contaminated products or from the production plant (house organisms) in addition to those obtained from culture collections, as required in pharmacopoeias. Preservative systems usually consist of two or more molecules with different modes of action against microorganisms. The challenge is to extend preservative action to all kinds of microorganisms in cosmetics microbiology. Antibacterial substances added to diverse cosmetic products, when used correctly, inhibit bacterial growth. The growth of microbial biofilms resistant to several preservatives and disinfectants is favoured by the dilution of cosmetic products in different areas of the production plant. Biofilms result in contamination by bacteria resistant to preservatives commonly used in cosmetics. The addition of higher concentrations of preservatives to products (always according to regulations) in order to avoid this kind of contamination could solve the problem in some instances, but this approach is not practical since it could generate toxicity for the consumer.
Current trends
Cosmetics microbiologists face new challenges, such as the need to develop formulations that are less aggressive to consumers but also well-protected against microbial contamination. Current trends in the field include research on natural plant sources with biocide power and good toxicological profile, analysis of the synergisms of preservative blends, and the search for fast, reliable methods to detect microbial contamination and to test preservative efficiency in each formulation. There is a need for specialists in cosmetics development, preservation, plant hygiene and sanitation, good manufacturing practices, toxicology, etc., to solve problems involving cosmetics contamination. Some of the essential oils and plant based extracts are presented below which can be used in various combinations synergistically to protect the product and also give some additional benefits such as antioxidant performance and good aroma. The extraction in most cases is carried out by super critical CO2 extraction which further enhances the properties and retains critical ingredients in the essential oils The blend of Curry Leaf Oil, Cinnamon Oil (Salinatural CCL) when tested for the Eye Irritation Test (HET CAM TEST) shows slight to moderate irritation potential in a shampoo. The same blend when tested for skin irritation test (HRIPT TEST) did not indicate a potential for dermal irritation or allergic contact sensitisation.
Curry leaf oil (Murraya koenigii)
The curry leaf is native to India and is found nearly everywhere in the Indian subcontinent. It is also found in Sri Lanka and many parts of South East Asia. The curry leaf plants are planted just before monsoon and the plants mature after 15 months, after which the leaves are harvested. A fully grown curry tree can yield nearly 100 kg of leaves. Curry leaf essential oil is extracted by super critical CO2 extraction/steam distillation. Following is the major chemical composition of curry leaf oil: beta phellandrene, alpha pinene, alpha phellandrene, beta caryophyllene, farnesol, limonene. Although there is no medical documentation available, it is used in diabetics, hair loss and helping skin in maintaining its pigmentation.
Cinnamon leaf oil (Cinnamomum zeylanicum)
Cinnamon is a member of the Lauraceous family and grown in India and Sri Lanka. Cinnamon is harvested from a particular variety of evergreen tree which grows in tropical forests. Oil is extracted from its leaves and was used in ancient Egypt and the Middle East for controlling bacterial and viral outbreaks. Cinnamon leaf oil also strengthens the immune system against the disease caused by fungi, viruses and bacteria. It is also quite popular as a mouthwash and breath freshener. Cinnamon leaf oil consist of major component eugenol. It is also antibacterial, anti infectious, carminative, antiseptic, antispasmodic, and it is commonly used in the fragrance industry.
Basil extract (Ocimum sanctum)
Extracted from the herb Ocimum sanctum of the Lamiaceae family, and much favoured in India, the constituents of basil extract are: eugenol, germacren, b-caryophyllene, epi-caryophyllene, ursolic acid, flavonoids, beta-sitosterol. Basil is used commonly in many of the Indian and Chinese medicines. Its medicinal qualities are said to include: analgesic, antidepressant, antispasmodic. It also has fungicidal and insecticidal properties.
Turmeric oil (Curcuma longa)
Constituents: curcuminoids, alphatumerone, beta-tumerone zingiberene, 1-8-cineole, p-cymene, beta–pienene, alpha-terpenene, r-terpinene terpinolene, limonene. Extracted from the herb Curcuma longa of the Zingiberaceae family, turmeric oil is extracted by super critical extraction of the dried rhizomes. Studies have shown that it is antibacterial and antifungal, antiinflammatory, antioxidant, anticarcinogenic. Turmeric also improves skin tone and has insect repelling qualities.
Orange oil (Citrus aurantium)
Orange oil is an essential oil produced by glands inside the rind of an orange fruit. Sweet orange oil is citrusy and brightly fragrant. Orange oil is useful to blend with other oils for adding a sweet citrus note. Orange oil is anti-inflammatory, antiseptic, antibacterial, fungicidal, carminative, and antidepressant. It is also used for skin problems, especially for skin sores.
Clove bud oil (Syzygium aromaticum)
Clove bud oil is extracted from Eugenia carophyllata of the Myrtaceae family. It is a native of Indonesia and the Malacca Islands. It is an evergreen tree that grows to about 30 feet and has bright green leaves and nail-shaped rose peach flower buds, which on drying become red brown. It is further dried and used for extraction. The latin word clavus, meaning nailshaped, refers to the buds. The clove bud oil is analgesic, antiseptic, antispasmodic, and antibacterial. It helps with toothache and mouth sores. The clove bud oil contains: eugenol, eugenol acetate, iso-eugenol and carophyllene.
Lemon grass oil (Cymbopogon citratus)
Lemon grass oil is extracted from Cymbopogon citrates of the Poacae family. Lemon grass is an aromatic herb that is native to India. It is a tall, perennial grass and its oil contains citral as major component along with myrcene, which is antibacterial, citronella, citronellol and geranilol. Lemon grass oil is extracted by steam distillation. It has medicinal properties and is extensively used in ayurvedic medicinal preparations. Lemon grass oil is analgesic, an anti depressant, antomicobial, antipyretics, antiseptic, astringent, and a deodorant. It also has some fungicidal properties.
Conclusion
This article is an overview of some of the natural plant based alternatives to synthetic preservatives which can be slowly replaced with the synergistic blends presented here, and will benefit cosmetics and personal care manufacturer when working with green or all natural products. Since all of these blends can further enhance certain properties of the formulations, more synthetic chemicals can be eliminated, taking the end customer closer to nature.
