ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P101. Complexation of Boric Acid with Vitamin C
D. A. Köse and B. Zümreoğlu-Karan
Hacettepe University Science Faculty Department of Chemistry Beytepe/Ankara/TURKEY 06800
The exact biological function of boron in animals and humans remains unknown. The current hypothesis is that
it stabilizes biological molecules by linking them through ester bridges. An exciting article suggests that borate
minerals could play a crucial role in the early world by stabilizing the cyclic ribose during RNA synthesis [1]. At
intracellular pH, nearly all boron exists as boric acid which behaves as a Lewis acid and forms molecular
addition compounds with amino- and hydroxy acids, carbohydrates, nucleotides and vitamins through electron
donor-acceptor interactions. The complexation with sugars is particularly important in understanding the role of
boron as carrier for nucleotides and carbohydrates and for the appropriate design of boron compounds in terms
of biomimetic aspects.
(a) (b)
Vitamin C (Ascorbic acid, H2A) is a sugar acid with a cis-enediol group on the sugar ring and adjacent alcoholic
hydroxy groups on the side chain, available for complex formation with boron. Little is known about the
interaction of ascorbic acid with boric acid. We present here the complexation of H2A and iso-propylidene-H2A
with boric acid, characterization of the isolated complexes by 13 C CP- & 11 B-MAS NMR and the relative
stabilities of 1:1 (a) and 1:2 (b) complexes in aqueous phase.
Acknowledgement: Support from Hacettepe University through project 06D021002 is acknowledged.
References:
[1] A. Ricardo, M.A. Carrigan, A.N. Olcott, S.A. Benner, Science, 303 (2004) 196.
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