INTRODUCTION:

Herbal Sunscreen (also known as Herbal sunblock, Herbal suntan lotion) is a lotion, spray or other topical product that helps protect the skin from the sun's ultraviolet (UV) radiation, and which reduces sunburn and other skin damage, with the goal of lowering the risk of skin cancer with the help of herbes. However, in the United States, the term suntan lotion usually means the opposite of sunscreen, and instead refers to lotion designed to moisturize and maximize UV exposure and tanning rather than block it. These are commonly called indoor tanning lotions when designed for use with tanning beds or just suntan lotion if designed for outdoor use and may or may not have SPF protection in them.^[1]

Advantages of Herbal Sunscreens:

(1) Easily available.

(2) No side effect.

(3) No special equipment needed for preparation.

(4) Renewable resources.

(5) Botanical ingredients are easily available.

(6) They are inexpensive^{. [2].}

Photo stability and Toxicity

Photo stability refers to the ability of a molecule to remain intact with irradiation. Photo stability is potentially a problem with all UV filters because they are deliberately selected as UVR-absorbing molecules.

This issue has been raised specifically with avobenzone, with photolysis demonstrated, especially in vitro systems that simultaneously irradiate and measure transmittance in situ. This effect may degrade other sunscreens in a formulation. This change has also been observed with octyl methoxycinnamate and octyl dimethyl PABA, while oxybenzone was shown to be relatively stable. Higher SPF sunscreen products have led to the use of multiple individual sunscreen agents used in combinations at maximum concentrations that may interact. The photo stability of the molecules also depends on the solvent or the vehicle used. Certain ingredients may have a stabilizing effect on others; octocrylene has been shown to photo stabilize avobenzone. The relevance of these observations to the in vivo situation remains unclear. Much work remains to be completed in this area. ^[3]

Possible adverse effects

Some individuals can have mild to moderate allergic reactions to certain ingredients in sunscreen, particularly the chemical benzophenone, which is also known as phenyl ketone, biphenyl ketone, or benzoylbenzene. It is not clear how much of benzophenone is absorbed into the bloodstream, but trace amounts can be found in urinalysis after use. Sunscreens are effective in reducing sunburn, but not necessarily the risk of cancer.

Photo protection

Sunscreens alone may provide insufficient protection from UVR. Sunscreens function best to prevent sunburn from UV-B radiation. They provide more limited protection from UV-A radiation. Sole dependence on sunscreens can have the unwanted effect of increasing outdoor exposure times, particularly in those individuals who burn easily and then poorly. Sun avoidance remains the most desirable form of sun protection.

Sun protection

It is vital to protect skin and eyes from the damaging effect of the sun because exposure to ultraviolet radiation contributes to ageing skin and is the main cause of skin cancer. Some people may need to take particular care because of photosensitivity. You should also be careful to protect your skin if you are at high altitude in any season, particularly when in the snow because it reflects extra ultraviolet radiation onto your skin^{. [4]}

Chemical vs. Physical Sunscreens

Chemical Sunscreens are synthetic chemical substances with the following properties:

They are powerful absorbers of UV radiation when they absorb radiation they remain relatively these sun filters are formulated with other compounds in order to obtain highly effective products with protection factors varying from 4 to 30. Importantly, they often have to be reapplied quite frequently.

Physical sunscreens

Contain inert mineral particles that reflect UV rays like a mirror. The most common type used is ultra fine titanium dioxide (TiO²), made up of minute particles only 20-30 mm³ in size. These products have advantages over chemical sunscreens in that they are inert substances that do not break down over time. They are far less liable to cause skin irritation, since they are in the form of insoluble particles that are not absorbed through the skin. Because of the small size of the particles, modern physical sunscreens reflect radiation in the UVB and short UVA regions better than earlier products.

Fig: 1 UV-B sunlight spectrum (on a summer day in the Netherlands), along with the CIE Erythemal action spectrum. The effective spectrum is the product of the former two

The SPF can be measured by applying sunscreen to the skin of a volunteer and measuring how long it takes before sunburn occurs when exposed to an artificial sunlight source. In the US, such an in vivo test is required by the FDA. It can also be measured in vitro with the help of a specially designed spectrometer. In this case, the actual transmittance of the sunscreen is measured, along with the degradation of the product due to being exposed to sunlight. In this case, the transmittance of the sunscreen must be measured over all wavelengths in the UV-B range (290–350 nm), along with a table of how effective various wavelengths are in causing sunburn (the erythemal action spectrum) and the actual intensity spectrum of sunlight (see the figure). Such in vitro measurements agree very well with in vivo measurement^{. [5]}

Mathematically, the SPF is calculated from measured data as

Where, is the solar irradiance spectrum, the erythemal action spectrum, and the monochromatic protection factor, all functions of the wavelength .

The above means that the SPF is not simply the inverse of the transmittance in the UV-B region. If that were true, then applying two layers of SPF 5 sunscreen would be equivalent to SPF 25 (5 times). The actual combined SPF is always lower than the square of the single-layer SPF.

In practice, the protection from a particular sunscreen depends on factors such as:

· The skin type of the user.

· The amount applied and frequency of re-application.

· Activities in which one engages (for example, swimming leads to a loss of sunscreen from the skin).

What is SPF?

SPF stands for Sun Protection Factor and is the system used worldwide to determine how much protection a sunscreen provides, applied to the skin at a thickness of 2 mg/cm². The test works out how much UV radiation (mostly UVB) it takes to cause barely detectable sunburn on a given person with and without sunscreen applied. For example, if it takes 10 minutes to burn without a sunscreen and 100 minutes to burn with a sunscreen, then the SPF of that sunscreen is 10 (100/10).

A sunscreen with a SPF of 15 provides >93% protection against UVB. Protection against UVB is increased to 97% with SPF of 30+. The difference between a SPF 15 and a SPF 30 sunscreen may not have a noticeable difference in actual use as the effectiveness of a sunscreen has more to do with how much of it is applied, how often it is applied, whether the person is sweating heavily or being exposed to water. Hence a sunscreen with SPF 15+ should provide adequate protection as long as it is being used correctly.

Sensitive skin

If you have fair skin that burns easily you should choose a broad spectrum sunscreen with a high SPF e.g. 30+ If you have skin that tans readily you could choose a broad spectrum sunscreen with intermediate SPF e.g. 8-15+ If you have darkly pigmented skin and do not suffer from a sun / photosensitivity problem, you do not need sunscreen.

Dry / Oily skin

If your skin is dry you would benefit from a sunscreen with a moisturizing base e.g. sunscreen creams or ointments. If you have oily skin or readily develop acne, choose a sunscreen in a lighter base, e.g. lotion or gel. Lighter sunscreens are also better in hairy skin areas.

HERBAL SUNSCREEN PREPARATION

The regular, daily use of modern cosmetic products can potentially be very important for the long-term health of the skin. Among the most useful ingredients are sunscreens, which block ultraviolet radiation absorption by the skin, either wholly or in part. (Clothing, hats and sunglasses can all act as effective sunscreens.) The many formulations that are on sale include lotions, creams, pastes and gels, and rely on either chemical or physical agents for their protective action.

These are the most important group of preparation herbal sunscreen should either scatter the incident light effectively or they adsorb the erythemal portion of the suns radiant energy various other then the duration of exposure are also to be taken into account .opaque powder material either used in dry state or in a vehicle.^[6]

AN IDEAL HERBAL SUNSCREEN AGENT SHOULD HAVE FOLLOWING CHARACTERISTICS-

1) Absorb light preferentially over the range of 280mm – 320mm

2) Be stable to heat;’ light and perspiration

3) Be non-toxic and non-irritant

4) Not be rapidly absorbed

5) Be rapid soluble in suitable vehicle

6) Be neutral

Topical sunscreen agents

Based on their mechanism of action, topical sunscreens can be broadly classified into two groups, chemical absorbers and physical blockers. Chemical absorbers work by absorbing ultraviolet (UV) radiation and can be further differentiated by the type of radiation they absorb, UVA or UVB, or both UVA and UVB. Physical blockers work by reflecting or scattering the UV radiation.

Chemical absorbers

The table below is a list of some of the common chemical absorbers available and the protection they provide against the UV range. Chemical absorbing sunscreens often contain a combination of ingredients to get coverage against both UVB and UVA radiation. Some are also combined with physical blockers. Some organic formulations may degrade when exposed to sunlight; they may therefore not perform as well as expected.

Table 1- Herbs Commonly Used In Herbal Sunscreen

COMMON NAME	LATIN NAME	PRINCIPAL CONSTITUENTS
Aloe Vera	Aloe barbidensis	Barbiloin , aloe emodin
Ginseng	Panax ginseng mayer	Gensenoside,panaxoside,glycoside
Arnica	Arnica Montana linn	Volatile oil .5% ,56%fatty in extract
Burdok	Aretium lappa linn	Glycoside (arctiin)
Bavchi	Psoralea corylifolia	Psoralea, corylifolin
Lily- of-the valley	Convallaria majalis linn	Glycoside
Turmeric	Curcuma longa linn	Curcumin , curcuminoid ,
Neem	Azandirachta indica	Azandirachtin ,nimbin nimbidin
Centaury	Erythraea centarium	Glycoside (erytannin pers
Gentian	Gentiana lutea linn	Glycoside ,gentiopicrin ,tannin
Lemmon	Citrus lamonis burm	Limonene ,citral ,geranyl acetate
Sandal wood	Santalum album linn	Alfa-santalol , beta-santalol
Papaya	Carica papaya	Papain ,chymopapain ,polypeptide
Withania	Withania somnifera linn	Withaferin ,somniferin ,anaferin
Terminalia	Terminalia arjuna rob	Arjunolic acid , ellegic acid
Camphor	Cinnamomumcamphora nees	Camphor ,safrol
Karanja	Pongemia glabra vent	Lignoceric acid , oleic acid
Caltsfoot	Tussilago farfara	Mucilage ,phytosterol ;tannin

Physical blockers

Physical blockers are effective at protecting against both UVA and UVB radiation. The two most common physical blockers are titanium dioxide and zinc oxide. These agents are the near ideal sunscreen as they are chemically inert, safe, and protect against the full UV spectrum. Their only drawback is their poor cosmetic appearance when applied to the skin. By decreasing the particle size, microsized or ultra fine grades have been developed, thereby reducing the whitening appearance. In some products, bright fluorescent colors have been added.^[7-9]

General procedure for herbal sunscreen manufacturing:-

This preparation can be aqueous or oily solution, cream or emulsion lotion and gel type, the general method will be different. Solution type aqueous or oily can be prepared sampling and mixing and dissolving the sunscreen and other ingredients in the vehicle i.e. water or oil .perfume should be added the entire last.

Cream preparation and emulsion type and are prepared by taking ingredients of oil phase and aqueous phase separately and heating to liquefy or dissolve all ingredients and then mixing them together with continuous stirring till the cream is produced .perfume should be added after cooling the cream to near room temperature and milling further.

Lotion can be solution and emulsion type and can be prepared accordingly gel are high viscous aqueous preparations. Thickening agent is dispersed in water separately. Other ingredient are mixed together and dissolved in water .then the dispersion of thickening agent is mixed with other with stirring to prepare gel.^[10-11]

Some useful formulae for herbal sunscreen preparation:^[12-14]

OILY TYPE

EXAMPLE 1: -W/O Emulsion of SPF 30

Oily Phase:

Poly isobutylene with an esterified succinic ending, diethyl ethanolamine salt (Lubrizol 5603)	3%
Cyclohexadimethylsiloxane	30%
Isohexadecane	25%
Ethylhexyl methoxycinnamate	7%
PDMS-coated titanium dioxide (UV Titan X170 from the company Kemira)	10% (A.M.)

Aqueous Phase:

Preserving agent	qs
Mexoryl SX (water-soluble screening agent)	3%
Water	100%

Procedure: Each of the two phases is homogenized and they are then mixed together with stirring, dispersing the aqueous phase in the oily phase. A very soft fluid milk is obtained, which does not whiten on application. It has a fine, uniform appearance under a microscope and good dispersion of the pigments is observed. This emulsion remains stable after storage for two months at 45° C. It can be used as a protective daily care and as an antisun cream for the face and the body.

EXAMPLE 2

W/O Emulsion of SPF 40

Oily Phase:

Polyisobutylene with an esterified succinic ending,	3%
diethyl ethanolamine salt (Lubrizol 5603)
Cyclohexadimethylsiloxane10%
Isohexadecane	25%
Ethylhexyl methoxycinnamate	7%

Aqueous Phase:

Preserving agent	q.s.
Mexoryl SX (water-soluble screening agent)	3%
Nanotitanium oxide at 30% in water (Mirasun) TIW 60 from the company (Rhodia)	10%
Water	100%

Procedure: The two phases are homogenized and the emulsion is then prepared with stirring, dispersing the aqueous phase in the oily phase. A very soft fluid milk is obtained, which does not whiten the skin on application. It has a fine, uniform appearance under a microscope and good dispersion of the pigments is observed. This emulsion remains stable after storage for two months at 45° C. It can be used as a protective daily care and as an anti sun cream for the face and the body.

SUNSCREEN LOTION

EXAMPLE:

FORMULA	PERCENTAGES
Quinine bisulfate	3.5
Glycerin	5.0
Gum tragacanth powder	1.5
Alcohol	16.5
Citric acid	0.75
Water	72.25
Perfume	0.5

SUNSCREEN CREAM

EXAMPLE:

FORMULA	PERCENTAGES
Methyl salicylate	14.0
Borax	1.8
Beeswax	20.0
Mineral oil	20.0
Water	28.7
Petrolatum	15.0
Perfume	0.5

SUNSCREEN POWDER

FORMULA	PERCENTAGES
Quinine bisulfate	3.0
Zinc stearate	10.0
Titanium dioxide	7.0
Talc	58.0
Colloidal clay	13.0
Precipated chalk	5.0
Suntan color base	4.0

EVALUATION SCHEME FOR HERBAL SUNSCREEN: - ^[15]

As in any other preparation identification quantitative determination of various ingredients are essential for evaluation and quality control point of view. A part from these routine tests some special tests are necessary for this type of product –

Evaluation of Sunscreen Protection by Measurement of Epidermal DNA Synthesis:-

Different sunscreens were tested to determine their protection of epidermis from ultraviolet light effects. Ultraviolet light-induced changes in hairless mouse epidermal DNA synthesis were used for measurement of sunscreen protection. Visual assessment of erythema and edema was also performed. This initial study has evaluated sunscreens containing para-aminobenzoic acid (PABA) as the principal sunscreen chemical. These experiments were conducted using fluorescent sunlamp tubes and hydroxylapatite extraction of epidermal DNA. The ultraviolet light exposure was measured using a recording radiometer. The results showed that the sunscreens tested were able to partially prevent ultraviolet light induced changes in epidermal DNA.^[16]

An evaluation of sunscreens in patients with broad action-spectrum photosensitivity

The photo protection afforded by three sunscreens available by prescription in the U.K. has been studied in patients with severe broad action-spectrum photosensitivity. All products investigated exhibited high protection against UV-B radiation in accordance with the protection factors quoted by the respective manufacturers. On the other hand, the protection against UV-A ranged only from fair to poor. The need for a sunscreen which has good protection against UV-A is shown to be important for the satisfactory management of patients with severe broad action spectrum photosensitivity

Sunscreen testing using the mouse ear model:

During the developmental stages of sunscreen formulation it is desirable to have a simple, accurate and inexpensive biological model to test product effectiveness. Another desirable attribute is a quantitative, unbiased response endpoint for evaluation. We have developed such a test system based upon the ear swelling response of hairless albino mice. With this system, irradiation times are greatly reduced; furthermore, the response parameter is metric and can be determined noninvasively with an inexpensive micrometer. Protection factors determined with the mouse ear model show high correlation with the sun protection factors as determined on human subjects (r = 0.92) and were linearly related over a wide range of values. This new method affords a simple, accurate and inexpensive system for evaluation of efficacy and safety of new products.^[17]

CONCLUSION:

Days with sunscreen correlated not with days without risk behavior, but with days "sunbathing with the intention to tan," indicating that sunscreens were used as tanning aids to avoid sunburn.

REFERENCES:

1) Boyd AS, Naylor M, Cameron GS, et al. The effects of chronic sunscreen use on the histologic changes of dermatoheliosis. J Am Acad Dermatol. Dec 1995; 33(6):941-6

2) DeBuys HV, Levy SB, Murray JC, et al. Modern approaches to photo protection. Dermatol Clin. Oct 2000; 18(4):577-90.

3) Diffey BL and Grice J. The influence of sunscreen type on photo protection. Br J Dermatol. Jul 1997; 137(1):103-5.

4) Dromgoole SH and Maibach HI. Sunscreening agent intolerance: contact and photo contact sensitization and contact urticaria. J Am Acad Dermatol. Jun 1990; 22(6):1068-78.

5) Fotiades J, Soter NA and Lim HW. Results of evaluation of 203 patients for photosensitivity in a 7.3- year period. J Am Acad Dermatol. Oct 1995; 33(4):597-602.

6) Mithal BM and Saha RNA. Hand book of cosmetics, first edition, reprint-2007, Vallabh Prakashan, Delhi 122-124.

7) Gasparro FP, Mitchnick M and Nash JF. A review of sunscreen safety and efficacy. Photochem Photobiol. Sep 1998; 68(3):243-56.

8) Kaidbey KH. The photo protective potential of the new super potent sunscreens. J Am Acad Dermatol. Mar 1990; 22(3):449-52.

9) Kullavanijaya P and Lim HW. Photo protection. J Am Acad Dermatol. Jun 2005; 52(6):937-58; quiz 959-62.

10) Levy SB. How high the SPF? Arch Dermatol. Dec 1995; 131(12):1463-4.

11) Moloney FJ, Collins S and Murphy GM. Sunscreens: safety, efficacy and appropriate use. Am J Clin Dermatol. 2002; 3(3):185-91.

12) Naylor MF and Farmer KC. The case for sunscreens. A review of their use in preventing actinic damage and neoplasia. Arch Dermatol. Sep 1997; 133(9):1146-54.

13) Roberts LK and Beasley DG. Commercial sunscreen lotions prevent ultraviolet-radiation-induced immune suppression of contact hypersensitivity. J Invest Dermatol. Sep 1995; 105(3):339-44.

14) Schauder S and Ippen H. Contact and photo contact sensitivity to sunscreens. Review of a 15-year experience and of the literature. Contact Dermatitis. Nov 1997; 37(5):221-32.

15) Shaath NA. Sunscreens: Regulation and Commercial Development. Third ed. White Plains, NY: Marcel Dekker; 2005.202-206.

16) Berneburg M, Plettenberg H, Medve-König K, et al. Induction of the photo aging-associated mitochondrial common deletion in vivo in normal human skin. J Invest Dermatol , 2004, 122 (5): 1277-83. PMID 15140232.

17) Holick M “Environmental factors that influence the cutaneous production of vitamin D". Am J Clin Nutr 1995, 61 (3 Suppl): 638S-645S. PMID 7879731. 20.

Received on 01.06.2011 Accepted on 18.06.2011

Res. J. Topical and Cosmetic Sci. 2(2): July – Dec. 2011 page 35-39