Photolysis of the folic acid.

ANDRÉS H. THOMAS; FERNANDO S. GARCÍA EINSCHLAG; MARIO R. FÉLIZ; ALBERTO L. CAPPARELLI

Foz de Iguazú, Brasil

Congreso; Eighth Inter-American PhotoChemical Society Conference; 1996

Folic acid (pteroylglutamic acid) which plays a very important role in several biological proceses (1) has strong tendency to chelates metal ions (2). Biological studies showed that folic acid is inactivated by action of light and this process is faster under UV irradiation(3). However, there are no photochemistry studies this substance though it is well known that folic acid presents fluorescence and phosphorence. This properties are employed for analytical purposes (4)-(5). Only few studies about its complexation capacity are reported compounds with metal ions are reported in the literature(6).             In the present communication a conventional flash and steady state photolysis on this substance is reported.             Experiments were carried out at pH higher than 6. Temperature was 25°C and folic acid concentration 2x10-5 M. Spectral changes were observed between 250 and 600 nm.             The folic acid absorbance in the UV-visible is usually analized as a composite of the absorbances of the pterydine and paraammine benzoic moieties (8). The spectrum changes with the pH of the solutions. At pH 6 two bands are observed at 280 and 350 nm. After the photolysis, the band at 280 nm decreases but no significant changes are observed in the other one. At pH 11,a new band appears at lmax= 255 nm and the other peaks red shift to 285 and 365 nm respectively. During the first minutes of photolysis, the 365 nm band increases and later decreases. The other two band always diminish. When a photolysed solution at pH 6 is alkalinized the band at 255 nm appears, suggesting that the pterydin moiety does not suffers photolysis in acid medium.             Flash photolysis experiments showed two processes, the faster one in the millisecond range and the slower one in the minutes´ domain. When a 320 nm cut-off filter (acetone) is employed no absorbance changes are observed. This behaviour indicate that transitions at longer wavelenghts than 320 nm are not photochemically active.             The effects of oxygen.and kinetics results are reported References: (1) O. Isler, G. Brubacher, S. Ghisla und B. Kräutler, Vitamine, vol II, G. Thieme Verlag, Stuttgart, (1988) and the literature therein. (2) E. Mironov and S. Nabokov, Khim. Farm. Zh., 10, 136 (1976) (3) C. Cailley, S. Flavian & P. Douzou, C.R. Hebd. Seances Acad. Sci. Ser C. 263, 272 (1966). (4) A. de Leenheer, W. Lambert & M. Ruyter, Modern chromatographic analysis of the vitamins, Marcel Dekker Inc., New York, pg. 303 (1985) and the literature therein. (5) R. Freedlander, R. Parker, B. Dunlop, Spectrochim. Acta, A, 50A, 551 (1994),  R. Van Wandruska & R. Huturbise, Anal. Chem., 49, 2146 (1977) (6) A. Thomas, M.R. Féliz & A.L. Capparelli, Trans. Metal Chem. (in revision)