Carotene photoprotection

Photoprotection is an inhibition of heme photosensitization via the quenching of photoreactive intermediates ( 02) by orally administrated P-carotene. Photoprotection concerns some kinds of porphyrias (the hereditary or chemically induced production of excessive amount of porphyrins in human and animals). Similarly as in photodynamic therapy, a raised concentration of porphyrins (Mb, Hg, cytochromes) causes the destruction of cells in the presence... 

Carotenoid pigments, in particular P-carotene, photoprotect systems in... 

Offord, EA, JC Gautier, O Avanti et al. 2002. Photoprotective potential of lycopene, beta-carotene, vitamin E, vitamin C and camosic acid in UVA-irradiated human skin fibroblasts. Free Radio Biol Med 32(12) 1293-1303. 

A study on the photoprotective effect of the topical application of 2% vitamin E and 5% vitamin C in humans showed no effect with the application of each substance alone, but an enhanced photo-protective effect after applying vitamins E and C combined, which was attributed to the regeneration of vitamin E by vitamin C.20 This enhanced effect has also been shown with the topical application of a combination of 15% ascorbic acid and 1% a-tocopherol to porcine skin.21 The combined systemic supplementation of vitamins C and E was similarly able to reduce sunburn reactions22 and to increase the minimal erythema dose (MED), a measure for individual photosensitivity, more than supplementation with either vitamin E or vitamin C alone.23,24 An oral supplementation with an anti-oxidative combination of carotenoids (P-carotene and lycopene), vitamin C, vitamin E, selenium, and proanthocyanidins (Seresis , Pharmaton SA, Lugano, Switzerland) also reduced the development and grade of UVB-induced erythema 25... 

Anstey, A.V., Systemic photoprotection with alpha-tocopherol (vitamin E) and beta-carotene, Clin. Exp. Dermatol., 27, 170, 2002. 

These results demonstrate forcefully that a photoprotective strategy predicated upon extremely rapid chlorophyll or porphyrin to carotene triplet energy transfer can succeed. We note here that the yield of the energy transfer process in the absence of oxygen is not the figure of merit for photoprotective function. It is 100% for both 24 and 26. 

The first demonstration that /3-carotene could inhibit photosensitized oxidation and was, therefore, an efficient quencher of O was reported by Foote and Denny (1968). Wilkinson and Ho (1978) showed that quenching by electron exchange energy transfer to produce the carotenoid triplet state ( CAR) is the principal mechanism of carotenoid photoprotection against O ... 

Taken together, 8-carotene displays three functions in LHC I. This carotenoid is associated with the long-wavelength chi forms (6) which act as an energy sink in LHC I upon closure of the reaction centres (7). Recently we have shown that at least some of the 8-carotene molecules in the isolated LHC I are involved in photoprotection (4). Consequently we conclude that these 8-carotene molecules shield the energy valve system of the native PS 1-200 complex from excessive excitation energy. 

Alternatively, there are certain circumstances in which photoinhibition exerts an effect that is useful. Under certain environmentally stressful conditions, secondary metabolite production may be increased to deal with that particular stress. It has been demonstrated in some species, including Dunaliella salina, that when insolation levels are high, beta carotene can accumulate as a photoprotective pigment, acting to protect the chloroplasts and cellular DNA under high light intensity. ... 

Carotenoids are a family of pigments that are divided into two main groups carotenes and xanthophyUs. They are introduced to the human body through dietary means alone, and although not considered to be essential micronutrients, they have important antioxidant and photoprotective properties. These functions have prompted interest in their potential role in prevention of disease. 

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