INTRODUCTION:

Ultraviolet (UV) radiation is defined as that portion of the electromagnetic spectrum between x rays and visible light, i.e., between 40 and 400 nm (30–3 eV). The UV spectrum is divided into Vacuum UV (40-190 nm), Far UV (190-220 nm), Ultraviolet C (UVC) (220-290 nm), Ultraviolet B(UVB) (290-320), and Ultraviolet A (UVA) (320-400 nm). UVA can be further divided into UVA I (340 - 400 nm) and UVA II (320 - 340 nm) . Solar UVR at the earth's surface comprises approximately 95 – 98 % UVA and 2 – 5 % UVB, all the UVC being absorbed by stratospheric ozone. Solar UVB radiation at any location, in cloudless sky conditions, depends on the solar zenith angle, column ozone content and column aerosol content as well the altitude of the observation site .The frequency of ultraviolet type B or UVB is largely responsible for erythema of sunburn and suntan of the skin. Once human skin is exposed to UVB, it is absorbed by DNA of keratinocyte. Its high energy radiation, which is dependent on its wavelength, causes not only sunburn but also skin ageing, skin cancer, etc. When UVR interacts with skin surface, biochemical changes in collagen, elastin and connective tissues, which are responsible for skin firmness and elasticity, start to occur. As skin becomes less elastic, it gradually becomes drier and looks wrinkled.

Exposure to ultraviolet (UV) radiation causes various forms of acute and chronic skin damage, including immunosuppression, inflammation, premature aging and photo damage. Furthermore, it induces thegeneration of reactive oxygen species, produces proinflammatory cytokines and melanocyte-stimulating hormone(MSH) and increases tyrosinase activity. Sunscreen products are very popular on markets last years. But, the reason for their production is different now.

In the beginning, people wanted to get beautiful sun tan easily and fast, without the risk to get burns. Nowadays, it is necessary for all people to use sunscreen products because of protection against ultraviolet (UV) radiation. This review covers all essential aspects of potential of herbs as photoprotective agents as well as radioprotective agents and it will highlight and place in perspective studies and works related to herb-based cosmetics.

HISTORY OF COSMETICS

The use of natural or synthetic cosmetics to treat the appearance of the face and condition of the skin is common among many cultures. The word “cosmetics” arises from a Greek word “kosmeticos” which means to adorn. Since that time, any material used for beautification or improvement of appearance is known as cosmetics. The urge to adorn one's own body and look beautiful has been an urge in the human race since the tribal days. The practice of adornment or improvement of appearance continued unabated across the centuries. Various kinds of natural materials were used for that purpose. In modern days, cosmetics are the rage and are considered to be essential commodities of life. This made the scientist carry out research in cosmetics and as a result, more and more products are being developed and marketed. Body and beauty care product are likely to surpass the consumption of drugs in future. A large segment of the world population is showing greater inclination toward natural cosmetics which seems to be the future hope.

Cosmetics or dermocosmetic preparations are used for skin care, cleaning, and protection. They have contact with external parts of human body (epidermis, hair, nails, lips, and external sexual organs), or with teeth and mouth mucosa. They clean, perfume, change look and/or make correction of body smells and/or keep them in appropriate condition. Cosmetics involve skin care products for UV protection.

Competition among manufacturers of cosmetics is intense. Because of that, companies formulate with added value ingredients to create products that can claim specific benefits—wrinkles decreasing, longwearing, moisturizing, transfer resistant, oil control. Today, another way of increasing the value of these products to consumers is delivering sun protection in foundations and lipsticks. This provides broad-spectrum protection against the harmful effects of UV light. There are a lot of government regulations for sunscreen actives. In the USA, the Food and Drug Administration regulate the sales of color cosmetics containing sunscreens under cosmetics and drug legislation. In Europe, sunscreen products are regulated like cosmetics. COLIPA, the trade association for the EEC, works with regulatory agencies in individual countries to establish legislation. France and Italy, unlike other EEC countries, require labeling of active ingredients and concentration present in finished products.

Sunscreen products

There are a lot of different types of sunscreen products (oils, sticks, gels, creams, lotions) which can be found on the world's market. All of them must have sunscreens that provide adequate protection from harmful UV rays (UVA and UVB).

There are two general types of sunscreens—chemical and physical. A chemical sunscreen absorbs the UV rays, while the physical sunscreen reflects the harmful rays away from the skin like a temporary coat of armor.

Physical sunblocks

There are two types of physical sunblocks that are mostly used: Zinc oxide and titanium dioxide. Both provide broad-spectrum UVA and UVB protection. They are gentle enough for everyday use, especially for individuals with sensitive skin and for children, because they rarely cause skin irritation. But, because of scattering effect, they often causes so called “whitening” phenomenon when they are applied on the skin, which seriously affects the aesthetics and the efficacy of sunscreen products.

Chemical sunblocks

Most chemicals only block narrow region of the UV spectrum. Therefore, most chemical sunblocks are composed of several chemicals with each one blocking a different region of UV light. Mostly, chemicals used in sunblocks are active in UVB region. Only a few chemicals block the UVA region. The best sunblock is the sunblock that combine both chemical and physical active ingredients. Dermatologists routinely recommend sunblocks that contain either a physical blocking agent or avobenzone (Parsol^®1789) in combination with other chemicals. However, in the USA, combinations of avobenzone and physical sunscreens are not permitted. Avobenzone has been reported to be unstable when contained in formulations with physical sunscreens. Surface coating of pigment has sometimes been shown to increase its stability.

Whitening is unacceptable in beach and skin care products with sun protection factor (SPF). It is difficult to create elegant formulations useful to protect against harmful UVA/B rays. Now, broad-spectrum protection in foundations is achievable using titanium dioxide with greater scattering power and iron oxides. Many of the organic chemicals commonly used in sunscreen products have not been established safe for long-term human use. For example, titanium dioxide- and zinc oxide-based sunscreens are being promoted on the basis that they may be less harmful than organic sunscreen absorbers. But, the use of microfine titanium dioxide as a sunscreen product also has no long-term safety data. Today, manufacturers use a lot of different natural components for skin protection from UV radiation. These products contain a high level of natural UV absorbers such as squalane, peptides, and nucleotides that have been protecting mammalian skin for over 100 million years.

Sunscreen Cosmetics for Photoprotection

The use of sunscreen as photoprotecting agents for UV protection is becoming very popular. Sunscreens are used to aid the body's natural defense mechanisms to protect against harmful UV radiation from the sun. Its function is based on its ability to absorb, reflect or scatter the sun's rays. The Sun protection factor (SPF) of a sunscreen is calculated by comparing the amount of time needed to produce sunburn on sunscreen protected skin to the amount of time needed to cause sunburn on unprotected skin. Higher SPF sunscreens offer greater protection from sunburn. Thus, prevention of premature ageing of skin and defense against possible skin cancer may be acquired by employing sunscreen cosmetics. In the United States, the Food and Drug Administration (FDA) states that any cosmetics with sun protection property must comprised of one or more active ingredients chosen from a regulatory list[6]. These ingredients include protective chemicals and ultraviolet (UV) filters which must be listed on sunscreen labels. Before sale to consumers, the finished product must prove its protective ability in a test conducted on human volunteers. Similar rules govern sunscreens around the world. If a product label implies in any way that the product protects from the sun, then it is a sunscreen. Applying a sunscreen to skin changes the way the body reacts to the sun’s rays. In a way, sunscreens are like products which are to be applied on skin to enable it remain healthy and protective. If the sunscreen product contains a herbal antioxidant, it should be applied just before exposure to the sunlight and after every two hours depending on the activity of the person Swimming, excessive perspiration and drying off with a towel are some of the actions which may minimize the effectiveness of a sunscreen product. Experimental measurements of SPF are determined by applying the product in significant quantities(2 mg/cm2 of skin). In practice, it has been found that consumers actually apply lower quantities than this. This means that the effective SPF will be less than the figure indicated on the product label and protection from UVB radiation and sunburn is likely to be reduced. Thus, using formulations with SPF higher than 15 is probably advisable for those who need better photoprotection [8].

Natural sources of antioxidants

The main destroying factors for skin are oxygenated molecules which are often call “free radicals.” To stimulate the skin to repair and build itself naturally, we need an arsenal of potent ingredients. The “antioxidant power” of a food is an expression of its capability both to defend the human organism from the action of the free radicals and to prevent degenerative disorders deriving from persistent oxidative stress. Plants like olive trees have their own built-in protection against the oxidative damage of the sun, and these built-in protectors function as cell protectors in our own body. The very pigments that make blueberries blue and raspberries red protect those berries from oxidative damage.

Vitamin E

The antioxidant vitamin E (α-tocopherol) may protect both animal and plant cell membranes from light-induced damage. Topical application of these antioxidants to the skin has been shown to reduce acute and chronic photodamage. Topically applied, only the natural forms of vitamin E—alpha-tocopherol and tocotrienol—effectively reduce skin roughness, the length of facial lines, and the depth of wrinkles. Topically applied vitamin E increases hydratation of the Stratum corneum and increases its water-binding capacity. Alpha-tocopherol reduces the harmful collagen-destroying enzyme collagenase, which unfortunately increases in aging skin. Vitamin E is a free radical scavenger and an emollient too.

Triticumvulgare (wheat germ) oil is particularly rich in vitamin E and offers excellent antioxidant promise in topical antiaging formulations. Also, it nourishes and prevents loss of moisture from the skin. Extra virgin Corylusavellana (hazelnut) oil has good levels of tocopherols, as do Helianthus annuus (sunflower) and Sesamumindicum (sesame) oils.

Cucurbitapepo (pumpkin) seed oil deserves greater recognition. With a lipid profile containing high levels of linoleic acid (43 – 53%), it contains two classes of antioxidant compounds: Tocopherols and phenolics, which account for 59% of the antioxidant effects. It is especially valued in the healing folklore of Eastern and Central Europe and the Middle East for its nutritious benefits and is used both topically and orally for a range of medical conditions. Due to the strong, rich aroma, it is only used in small proportions in topical formulations.

Ascorbic acid (Vitamin C)

Vitamin C (L-ascorbic acid) is the body's most important intracellular and extracellular aqueous-phase antioxidant. Vitamin C provides many benefits to the skin—most significantly, increased synthesis of collagen and photoprotection. Photoprotection is enhanced by the anti-inflammatory properties of vitamin C. Photoprotection over many months allows the skin to correct previous photodamage, the synthesis of collagen and inhibition of MMP-1 was proven to decrease wrinkles, and the inhibition of tyrosinase and anti-inflammatory activity result in depigmenting solar lentigines.

Vitamin C is found in active form and substantial quantities in Rosehip seed extract or oil.

WHOLE HERBAL EXTRACTS IN USE

Whole herbal extracts consist of numerous compounds that together provide better effects on the skin. One herbal extract may show antioxidant, anti-inflammatory, emollient, melanin-inhibiting, antimutagenic, antiaging properties, etc.

Green and black tea

Most people have tea in their kitchen. Tea (Camellia sinensis) is commonly used as a home remedy for sunburn. The Chinese recommend applying cooled black tea to the skin to soothe sunburn. One says that the tannic acid and theobromine in tea help remove heat from sunburns. Other compounds in tea called catechins help prevent and repair skin damage and may even help prevent chemical- and radiation- induced skin cancers.

The complex polyphenolic compounds in tea provide the same protective effect for the skin as for internal organs. They have been shown to modulate biochemical pathways that are important in cell proliferation, inflammatory responses, and responses of tumor promoters. Green tea has been shown to have anti-inflammatory and antioxidant effects in both human and animal skin. Animal studies provide evidence that tea polyphenols, when applied orally or topically, ameliorate adverse skin reactions following UV exposure, including skin damage, erythema, and lipid peroxidation. Since inflammation and oxidative stress appear to play a significant role in the aging process, green tea may also have antiaging effects by decreasing inflammation and scavenging free radicals. Researchers have found that the main active ingredient in green tea, epigallocatechin-3-gallate (EGCG), works well as an anti-inflammatory, antioxidant, and sunscreen. Topical green tea applied to human skin provide a photoprotective effect, reduced the number of sunburns cells, protecting epidermal Langerhans cells from UV damage, and reduced the DNA damage that formed after UV radiation. Green tea was also found to decrease melanoma cell formation with topical and oral administration in mice. Most cosmeceuticals products containing tea extracts or phenols have not been tested in controlled clinical trials, but these substances have shown compelling evidence for antioxidant, anti-inflammatory, and anticarcinogenic activities.

Aloe vera

The reputable Aloe vera or Aloe barbadensis has been scientifically proven for all forms of burn, be it radiation, thermal, or solar. It has also been demonstrated that it has a prophylactic effect if used before, during, and after these skin damaging events. Clearly, the plant is mainly used for its soothing and cooling effect; however, the plant is useless if used at less than 50% and it is recommended that it is used at 100% to be sure of any beneficial effect. The polysaccharides, mannose-6-phosphate, and complex anthraquinones all contribute synergistically to the benefits of this material. The natural chemical constituents of Aloe vera can be categorized in the following main areas: Amino acids, anthraquinones, enzymes, lignin, minerals, mono- and polysaccharides, salicylic acid, saponins, sterols, and vitamins. Aloe vera not only improved fibroblast cell structure, but also accelerated the collagen production process. Aloe vera is a uniquely effective moisturizer and healing agent for the skin (both human and animal.

Krameriatriandra

The antioxidant/photoprotective potential of a standardized Krameriatriandra root extract (15% neolignans) has been evaluated in different cell models, rat erythrocytes, and human keratinocytes cell lines, exposed to chemical and physical (UVB radiation) free radical inducers. In cultured human keratinocytes exposed to UVB radiation, Krameriatriandra root extract significantly and dose-dependently restrained the loss in cell viability and the intracellular oxidative damage. The cytoprotective effect of the extract was confirmed in a more severe model of cell damage: Exposure of keratinocytes to higher UVB doses, which induce a 50% cell death. In keratinocyte cultures supplemented with 10 μg/ml, cell viability was almost completely preserved and more efficiently than with (-)-EGCG and green tea. The results of this study indicate the potential use of Rhatany extracts, standardized in neolignans, as topical antioxidants/radical scavengers against skin photodamage.

Plant oils as sunscreens

Researchers have found that some plant oils contain natural sunscreens. For example, sesame oil resists 30% of UV rays, whereas coconut, peanut, olive, and cottonseed oils block out about 20%. Although mineral oil does not resist any UV rays, it helps to protect skin by dissolving the sebum secreted from oil glands, thus assisting evaporation from the skin.

Borage oil

Borage (Boragoofficinalis) oil stimulates skin cell activity and encourages skin regeneration. It contains high levels of gamma-linoleic acid (GLA), making it useful in treating all skin disorders, particularly allergies, dermatitis, inflammation, and irritation. Borage penetrates the skin easily and benefits all types of skin, particularly dry, dehydrated, mature, or prematurely aging skin.

Evening primrose oil

Evening primrose (Oenotherabiennis) oil has a high GLA content that promotes healthy skin and skin repair. It is usually yellow in color. It soothes skin problems and inflammation, making it a good choice for people with eczema, psoriasis, or any type of dermatitis. Evening primrose skin oil discourages dry skin and premature aging of the skin.

Avocado oil

High-quality, natural suntan and after-sun products are found in abundance at natural food stores. Avocado (Perseaamericana) oil is rich in vitamin E, β–carotene, vitamin D, protein, lecithin, and fatty acids and offers considerable benefits when added to preparations. From avocado oil to botanicals such as rosemary and comfrey, these ingredients soothe and protect the skin.

Tea tree oil

Tea tree (Melaleucaalternifolia) oil is an ancient aboriginal remedy. It is an effective antiseptic, fungicide, and germicide. It is a popular component of many sunscreen formulations that relieve sunburn by increasing blood flow in capillaries, bringing nutrients to damaging skin.

Porphyra

Porphyra (Bangiales, Rhodophyta), delicious red algae widely consumed in eastern Asia, contains high levels of free amino acids; when exposed to intense radiations, it synthesizes UV-absorbing secondary metabolites such as mycosporine-like amino acids. There are almost seven species of Porphyra identified in India. Among all of these, nowadays Porphyravietnamensis are gaining more attention. Marketed Aloe vera gel had low absorption power over broad UV wavelength (250-400 nm) as compared with isolated compound gel, suggesting that Porphyra-334 is more potent.

Benefits of Herbal Cosmetics for Photoprotection

A number of people with sensitive skin, such as those suffering from skin hypersensitivity don’t want to use chemical sunscreens due to concern about skin exposure to unknown chemicals. Although a variety of hypoallergenic cosmetic products have been introduced for customers with sensitive skin, there are still limited options in sunscreen agents. Now, however, researchers have claimed that cosmetics having herbal components are more suitable for hyperallergic skin because they are less irritant and more easily adjustable to skin. Topical cosmetic formulations are the most preferred treatments asked by patients and are also often most prescribed by family physicians and dermatologists for sun burn. Patients feel more comfortable using topical therapies because they have milder side effects, are easier to use, are generally less expensive and are more readily available. Herbal cosmetics must have one or more active sunscreening agent with antioxidant properties in order to achieve good photoprotection effect.

Photoprotective agents are capable of preventing the adverse effects of ultraviolet radiation on the skin, which are caused by excessive generation of reactive oxygen species(ROS).