Herbal Cosmeceuticals for Photoprotection from Ultraviolet B Radiation : A Review

Ultraviolet B (UVB) rays vary with time and season and are the major cause of sunburns. Sunburned skin is a leading risk factor for melanoma and non-melanoma skin cancers. Protection against exposure to UVB rays may be achieved by a combination of various approaches such as use of broad spectrum sunscreen formulations. UV radiations (UVR) absorbed by the skin surface can produce harmful compounds called free radicals or reactive oxygen species (ROS), which can cause skin cancer and premature aging. To reduce ROS generation and damage, researchers recommend using sunscreen to protect the skin from harmful UVR. The realm of possibilities in photoprotection may include the development of sunscreens which remain at the surface of the skin for a longer time and may incorporate antioxidants that can neutralize ROS. By quenching free radicals, antioxidants may aid photoprotection effect. This review focuses on photoprotection from UVB radiation and discusses potential herbal candidates with antioxidant properties that can serve as a strong barrier in cosmeceuticals to protect skin against harmful UVB rays.


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) [1].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 [2].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 [3].Its high energy radiation, which is dependent on its wavelength, causes not only sunburn but also skin ageing, skin cancer, etc [4].

Fig 1: A schematic illustration of UV-induced inflammation, collagen loss and tissue damage
There is no Occupational Safety and Health Administration (OSHA, United States) standard for exposure to ultraviolet light, but the National Institute for Occupational Safety and Health (NIOSH, United States) recommends that the time of exposure to an intensity of 100 microwatts per square centimeter at a wavelength of 254 nm should not exceed 1 min.When averaged over an eight-hour work day, this value is 0.2 microwatts per square centimeter.Factors affecting protection from harmful UVR include behavior, environment, legislation and personal protection.Personal measures are obviously needed to avoid the harmful effects of repeated exposure to ultraviolet radiation.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 [5].As skin becomes less elastic, it gradually becomes drier and looks wrinkled.This paper will highlight and place in perspective studies and works related to herb-based cosmetics for photoprotection and associated body changes such as ageing and facial wrinkles.

The human body's photoprotection capacity
Paradoxically, when the skin is stimulated by ultraviolet radiation, the skin's self-protection mechanism is 2-fold.First, the swelling of the epidermis by UVB radiation increases protection by 3 to 4 times.Second, increase in the synthesis of melanin (tanning) induced by UVB and UVA radiation, gives the skin 2 to 3 times more protection.

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 sunscreenprotected 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 [7] 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/cm 2 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].

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 sideeffects, are easier to use, are generally less expensive and are more readily available [9].Herbal cosmetics must have one or more active sunscreening agent with antioxidant properties in order to achieve good photoprotection effect.
The concept of complementary or alternative medicine is increasingly becoming more widely accepted and there is a corresponding rising interest in herbal remedies.Recently, the role of herbal drugs, herbal products and certain phytochemicals in the control of ageing has been shown [10] .

Some Important Photoprotective Agents
The important photoprotecting agents (fig 2) include a number of constituents often incorporated in a cream base at different concentrations and used as herbal sunscreen cosmetics.
Plants with photprotective properties include the following: 1. Luffa cylindrica L. cylindrica (Linn) M. Roem. is a climber with a slender, slightly hairy stem with little furrowing.The seeds of L. cylindrica contain oil in which the fatty acids are stearic and linoleic acids -are unsaturated fatty acids [11].It has been reported that naturally occurring unsaturated fatty acids and phenolic compounds have free radical scavenging properties [12] In a study by Yoganandam et al [13], it was concluded that the fixed oil isolated from the seed kernels of the plant not only scavenges off the free radicals but also inhibits generation of free radicals.

Portulaca oleracea
Portulaca oleracea (Common Purslane; also known as Verdolaga, Pigweed, Little Hogweed or Pusley) is an annual succulent in the family Portulacaceae, which can reach 40 cm in height.It is found throughout India and the Middle East, but is naturalized elsewhere, and in some regions, is considered an invasive weed.The whole plant is considered antiphlogistic (takes the heat out), a bactericide, antidiabetic, anaphrodisiac (opposite to aphrodisiac), emollient, calmative, diuretic, and refreshing agent [14,15].Sanja et al has proved the antioxidant activity of the methanol extract using methods such as DPPH free radical scavenging, reducing power estimation by FeCl 3 , nitric oxide free radical scavenging, super oxide scavenging activity [16].The extract has a tendency to scavenge the free radicals involved in the ageing process and skin wrinkling and thus may provide some photoprotective action.

Terminalia chebula
Terminalia chebula, also called Harde, belongs to the family Combretaceae.It is used commonly in many Ayurvedic preparations as laxative, diuretic and cardiotonic, as well as in some health supplements [17].Its chemical constituents include ascorbic acid, gallic acid and ellagic acid, which are well known to exert free radical scavenging properties [18].

Piper longum
Piper longum L. belonging to the family Piperaceae, is commonly found in Indonesia, India and the Phillipines.It consists of a spike of fruits forming a structure about 4 cm long and 6 mm in diameter.The fruit (pepper) contains 1 -2.5 % volatile oil, 5 -95 % of crystalline alkaloid piperine and piperettine, and a resin [19].Piperine extracted from this plant has been used as an ingredient in Ayurvedic formulations because of its antioxidant potency both in vitro and in vivo in mice.[20].Piperine, due to this antioxidant property, is used topically in a cream base to treat sunburn diseases [21].

Aloe vera
The leaves of Aloe vera (A.barbadensis) (Fam.Liliaceace) are the source of aloe vera gel.The gel does not include the sap of Aloe vera, which contains anthraquinones.Aloe vera gel is widely used in cosmetics and toiletries for its moisturizing and revitalizing action [22,23].The whole leaf of Aloe vera is known to aid cellular repair as well as digestion, assimilation of foods, vitamins, minerals and other vital nutrients to rejuvenate the skin [24].The fresh gel, juice or formulated products have been used for medical and cosmetic purposes and to enhance general health [25].

Emblica officinalis
Emblica officinalis Gaertn., commonly known as amla, is a rich dietary source of vitamin C, minerals and amino acids [26].It also contains various phenolic compounds.Amla extract is known to exhibit potent antioxidant properties and to provide protection for human dermal fibroblasts against oxidative stress and therefore, it is assumed to be useful for natural dermal care [27].Recently, it was reported that amla extract has effect on human skin fibroblasts, especially production of procollagen and matrix metalloproteinases (MMPs) [28].The water extract from dried amla powder contains 2 % ascorbic acid and 29.4 % polyphenols including gallic acid and elaeocarpusin [29].Amla extract elevates the mitochondrial activity of human skin fibroblasts and promotes production of procollagen.Therefore, due to its potential mitigative, therapeutic and cosmetic applications, amla has been used for skin treatment since ancient times [30].

Crocus sativus
Saffron, the dried stigma of the plant Crocus sativus L, popularly used as a spice and food colorant, has been used in traditional medicine for the treatment of many diseases including tumors.The chemical constituents of saffron include the colored carotenoidscrocin and crocetin -and the monoterpene aldehydes -picrocrocin and saffranol [31].Salomi et al reported the anti-promoting and non-mutagenic activity of saffron extract [32].Lin et al showed that crocins can protect from the adverse effects of hepatocarcinogenic compounds and that crocetin, the deglycosylated crocin derivative, can inhibit intracellular nucleic acid synthesis [33].The anticarcinogenic effect of the aqueous infusion of saffron, administered orally, using a two-stage skin carcinogenesis model in mice, has been evaluated; the protective role of saffron against carcinogenic exposure was attributed to its action on the physiological detoxification processes and this proved that saffron can prevent chemically-induced skin carcinogenesis in Swiss albino mice [34].

Peumus boldus Molina
Peumus boldus belonging to the family Monimiaceae (a tree whose leaves have been traditionally employed in folk medicine) is now widely recognized as an herbal remedy by a number of Pharmacopoeias.Its leaves are rich in several aporphine-like alkaloids, among them, boldine, which is the most abundant one [37].Research conducted during the early 1990s claimed that boldine is one of the most potent natural antioxidants.Its pharmacological actions, which arise from its antioxidant properties, includes cytoprotective, anti-tumor promoting, antiinflammatory, anti-diabetic and antiatherogenic actions; it has also shown some actions which do not seem to be associated with these activities, e.g., vasorelaxing, anti-trypanocidal, immuno-and neuro-modulator, cholagogic and/or choleretic actions.Free radicals are known to participate in either the aetiology or the development of most UV-induced skin lesions [38].Through the experiments conducted on boldine, it has been proved that boldine has a UV light-filtering property relevant to a photoprotective action.In fact, Hidalgo et al showed boldine to be photo-unstable when irradiated at wavelengths up to 300 nm and to display a photo-protector effect against UV-B, both in vitro and in vivo in mice [39].Photo-protection was evidenced by the prevention of UV-induced increase in the skin temperature of rodents.Recently, Rancan et al investigated the photo-filtering properties of boldine in humans and found that application of boldine (25 mM) onto a 12 cm 2 area of the back of volunteers protected their skin against erythema formation to an extent slightly lower than that of a commercial sun cream [Nivea sun spray LSF -5] which has a UV-protection factor of 5 [40].
There are number of plants, with antioxidant potentials, which are generally used in common diets and may play a role in treating free radical generated conditions such as sunburn, wrinkles, and ageing.Some of these plants are listed in Table 1.

Some Commercially Available Herbal Antioxidant Cosmeceuticals
A number of cosmetics manufacturer have incorporated some of the natural antioxidants mentioned earlier in cosmetic formulations.Some examples of these are listed in Table 2.

CONCLUDING REMARKS
Herbal cosmeceuticals are natural products whose ingredients have properties to rejuvenate and protect the skin from environmental pollution, chemicals, atmospheric temperature fluctuation, Ultraviolet A and Ultraviolet B radiation, wrinkling, hyper pigmentation (excessive tanning) and inflammations.The present review focuses on scientific account on use of herbs in cosmetics.In future, more effective formulations containing herbal component may come in trend.The addition of herbal extracts for therapeutic use requires better understanding of herbal potential.The present trend towards herbal cosmetics with effective therapeutic property will continue and may be some newer herbs will also be placed in cosmetics world.In coming future, the regulatory authorities will need to frame some laws concerned with safety, efficacy and quality assessment of these newer herbal cosmeceuticals.

Fig 2 :
Fig 2: Effect of ROS on skin

Table 1 :
Plants with antioxidant potentials as well as anti-wrinkling and anti-aging properties and are commonly used in diet

Table 2 :
Some branded herbal cosmeceuticals for photoprotection of skin from harmful UVB radiations