Photoprotection

These sunscreen ingredients include octyl-dimethyl-PABA (UVB), 2-ethylhexyl-p-meth-oxycinnamate (UVB),octocrylene (UVA/UVB), octyl salicylate (UVB), benzophenones (UVB/ UVA), and methyl anthranilate (UVA). Avoben-zone or Parsol 1789 and mexoryl, a benzylidene camphor, block UVA. Mexoryl is the most efficient of the UVA organic sunscreens [10]. Many sunscreen formulations combine ingredients to maximize photoprotection. 

Physical agents include zinc oxide and titanium dioxide. These are the most effective sunscreens because they reflect UVA and UVB. When applied to the skin, they induce a white or ashen color, which many patients find cosmetically unacceptable. New micronized formulations of these agents are available which enhance cosmetic acceptability. Sunscreens 

Retinoids (i.e., tretinoin and tazarotene) mediate cellular responses primarily through activation of nuclear retinoid receptors [rr]. There are two types of nuclear retinoic acid receptors the retinoic acid receptors (RARs) and the retinoid X receptors. Each type of receptor contains three receptor subtypes alpha, beta, and gamma [rr, 11]. Among the commonly prescribed retinoids, tretinoin activates the RARs alpha, beta, and gamma directly, and the retinoid X receptors indirectly (through conversion of tretinoin to 9-cis-retinoic acid) [rr, 13]. Conversely, 

Ages 20S-30S Early photoaging Mild dyschromia No keratoses Minimal wrinkling Minimal, no makeup Minimal,or no scarring 

Late 30S-40S Early senile lentigines Dyschromia Early actinic keratoses Parallel smile lines Early wrinkling Some foundation worn Mild acne scarring 

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In addition, Montenegro et al., (2007) determined that the photosensitized RF-mediated degradation of vitamins A, D3, and RF itself in skimmed milk was strongly reduced by the addition of small amounts of lycopene-gum arabic-sucrose microcapsules, prepared by spray-drying. Under these conditions, the bulk properties of the skimmed milk were unmodified. The main photoprotection mechanism of the milk vitamins was the efficient quenching of the 3Rf by the protein moiety of GA. Small contributions (<5%) to the total photoprotection percentage was due to both inner filter effect and 1O2 quenching by the microencapsulated lycopene. 

Photoprotection of Vitamins in Skim Milk by Aqueous Soluble Lycopene - Gum Arabic Microencapsulated. Journal of Agricultural and Food Chemistry, Vol. 55, No. 2, (January 2007), pp. 323-329, ISSN 0021-8561. 

Wondrak, G. T. Jacobson, M. K. Jacobson, E. L. (2006). Endogenous UVA photosensitizers mediators of skin photodamage and novel targets for skin photoprotection. Photochemical Photohiological Sciences, Vol.5, (nd), (August 2005), pp. 215 - 237, ISSN 1474-905X. 

As has been shown above photorotective effects are most expressed in long-chain Ca-AR and C12-AR. However, some technological aspects are determined by low C12-AR solubilization in water, demanded its preliminary dissolution in ethanol that gave additional difficulties for AR addition into different media for electrophoresis. For this reason, in the current paragraph of the study Ce-AR was used, photoprotective effects of wich were compared with Ci-AR, C3-AR and C5-AR. 

A quantitative comparison of DNA band intensity at adding of different AR homologues into the buffer after 300 seconds of irradiation on the transilluminator has allowed to obtain a more detailed information about the structural integrity of DNA, depending on the AR concentration (Table 2). It was found that Cg-AR protected DNA greater than 1.5-fold in the range of lO- M and SxlO- M, with a maximum effect (163.5 + 15.2%) at concentrations of Id 3M. On this background, Ci-AR and C3-AR demonstrated poor photoprotective activity and Cs-AR showed a similar protective effect only at concentration of Id M. 

Study of the action of AR on . coli precA luxCDABE-Anvp has confirmed it photoprotective effects and has shown features of such activity in live systems. Surprising was the interrelation between preservation of viability of AR-processed bacterial cells in the conditions of a long and intensive UV-irradiation and depression of activity their reparing SOS-systems. It has assumed AR action and the SOS-answer as alternative "passive" and "active" mechanisms for protection of bacterial cells DNA at various intensivity of UV-irradiation. 

Kaidbey KH, Agin PP, Sayre RM, Kligman A (1979) Photoprotection by melanin - a comparison of black and Caucasian skin. J Am Acad Dermatol 1 249-260... 

Bissett DL, Chatterjee R, Hannon DP (1990) Photoprotective effect of superoxide-scavenging antioxidants against ultraviolet radiation-induced chronic skin damage in the hairless mouse. Photodermatol Photoimmunol Photomed 7 56-62... 

Perricone NV (1993) The photoprotective and antiinflammatory effects of topical ascorbyl palmitate. J Ger Dermatol 1 5-10... 

ELMETS C A, SINGH D, TUBESING K, MATSUI M, KATIYAR S and MUKHTAR H (2001) CutaneOUS photoprotection from ultraviolet injury by green tea polyphenols , JA mAcad Dermatol, 44, 425-32. 

BARTLEY G E and SCOLNIK P A (1995) Plant carotenoids pigments for photoprotection, visual attraction, and hmnan health . Plant Cell, 7, 1027-38. 

The photoprotective role of carotenoids is demonstrated in plant mutants that cannot synthesize essential leaf carotenoids. These mutants are lethal in nature since without carotenoids, chlorophylls degrade, their leaves are white in color, and photosynthesis cannot occur. Generally, the carotenoids are effective for visible light but have no effects in ultraviolet, gamma, or x-radiation. The reactions are listed as follows ... 

Krol, E.S. and Liebler, D.C., Photoprotective action of natural and synthetic melanins, Chem. Res. Toxicol, 11, 1434, 1998. 

Seagle, B.L. et al., Melanin photoprotection in the human retinal pigment epithelium and its correlation with light-induced cell apoptosis, Proc. Natl. Acad. Sci. USA, 102, 8978, 2005. 

The comparison of the light effect on carotenoids in foods is very difficult to carry out because different foods with different isomer compositions are employed at the beginnings of experiments. The presence of large molecules offers some photoprotection to carotenoids in food systems, either by complexation with proteins as found in carrots or acting as a filter to reduce the light incidence. Different storage conditions are often found because different light intensities are used or sometimes they are not even reported and experiments are carried out under air, N2, or in a vacuum. 

Natural pigment production for food coloration includes the entire spectrum of biotechnologies. For example, biological production of carotenoid pigments has medical implications because carotenoids are nutritive (pro-vitamin A), antioxidant, and photoprotective. Carotenoids are produced alternately in agricultural systems (plants), industrial bioreactors (bacterial and fungi), and marine systems (cyanobacteria and algae). 

Physiologically, violaxanthin is an important component of the xanthophyU cycle a high light stress-induced de-epoxidation of the violaxanthin pool to the more photoprotective zeaxanthin is mediated by violaxanthin de-epoxidase (VDE). Violaxanthin and neoxanthin, an enzymatically (NXS)-produced structural isomer, are the precursors for the abscisic acid (ABA) biosynthetic pathway (Figure 5.3.1, Pathway 4 and Figure 5.3.2). In non-photosynthetic tissues, namely ripe bell peppers, antheraxanthin and violaxanthin are precursors to the red pigments, capsanthin and capsorubin, respectively (Figure 5.3.3B). 

Niyogi, K.K., Safety valves for photosynthesis, Curr. Opin. Plant Biol. 3, 455, 2000. Pogson, B.J. and Rissler, H.M., Genetic manipulation of carotenoid biosynthesis and photoprotection, Philos. Trans. R. Soc. Lond B 355, 1395, 2000. 

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