Abstract

SERRA, Horacio Marcelo  and  CAFARO, Thamara Analía. Ascorbic acid: from chemistry to its crucial protective role in the eye. Acta bioquím. clín. latinoam. [online]. 2007, vol.41, n.4, pp.525-532. ISSN 0325-2957.

Vitamin C or L-ascorbic acid (AA) is an essential vitamin and a water soluble important antioxidant agent, chemically synthesized from glucose, by enzymatic reactions, being the L-gulono-g-lactone oxidase (GLO) the last enzyme involved. The inability to synthesize AA by some species, due to the absence of GLO seems to have happened hundreds of millions years ago. The degradation of the AA is carried out by oxidative processes which involve the hydrolysis of the lactona ring to produce 2,3-diketogulonic acid (DCG) that is later degraded by decarboxilation, generating colored products, found in some ocular pathologies. Among the different properties of the AA, it is worth mentioning its capacity to absorb ultraviolet radiation (RUV) and to avoid the photochemical damage of exposed tissues. In humans and in some animals (guinea pigs, primates, etc) the aqueous humor has bigger concentrations of AA than plasma. This responds to a mechanism of specialized active transport in the ciliary body that transfers AA from the blood towards the aqueous humor and from there to the corneal epithelium, transforming the cornea into the structure of the eye responsible for the biggest absorption of RUV.

Keywords : Ascorbic acid; Cornea; Ultraviolet radiation; Oxidative stress.

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