Utilization of folin-ciocalteu phenol reagent for the detection

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J. Agric. Food Chem. 2003, 51, 1811−1815

1811

Utilization of Folin−Ciocalteu Phenol Reagent for the Detection
of Certain Nitrogen Compounds
MIYOSHI IKAWA,* TIMOTHY D. SCHAPER, CATHERINE A. DOLLARD,
JOHN J. SASNER

AND

Department of Zoology and Center for Freshwater Biology, University of New Hampshire,
Durham, New Hampshire 03824

To determine in more detail the reaction ofFolin-Ciocalteu phenol reagent with nitrogen compounds,
a number of hydroxylamine-related compounds and a large number of guanidine-containing
compounds were tested. In general, guanidine compounds did not react strongly unless they were
hydroxyamino or hydrazino derivatives. The non-hydroxyamino paralytic shellfish poison saxitoxin,
however, reacted to a significant extent. This may be due to thepresence of a five-membered ring
structure and its analogy to 2-aminopurines, which react strongly. A number of simpler amines were
also tested. Tertiary aliphatic amines, but not primary, secondary, or quaternary amines, reacted
strongly with the reagent. Primary, secondary, and tertiary aromatic amines all reacted strongly with
the reagent. Reactivity was extended to pyrroles and indolederivatives but not to imidazole and
benzimidazole derivatives. Defining the reactivity of Folin-Ciocalteau phenol reagent with nitrogen
compounds extends the usefulness of the reagent for the detection and determination of certain
nitrogen compounds in basic extracts by colorimetric means and by thin-layer chromatography.
KEYWORDS: Folin-Ciocalteu reagent; guanidines; paralytic shellfish poisons;hydroxylamine derivatives;
amines

INTRODUCTION

Folin-Ciocalteu phenol reagent consists of a mixture of the
heteropoly acids, phosphomolybdic and phoshotungstic acids,
in which the molybdenum and tungsten are in the 6+ state. On
reduction with certain reducing agents, the so-called molybdenum blue and tungsten blue are formed, in which the mean
oxidation state of the metals is between 5and 6 (1). Its reaction
with the amino acids tyrosine and tryptophan is the basis for
the widely used Lowry method for the colorimetric determination of protein (2). It is known that Folin-Ciocalteu reagent
reacts not only with phenols but also with a variety of other
types of compounds (3, 4). The extensive review by Peterson
(3) describes to what extent a large number of substances reactwith Folin-Ciocalteau reagent. The strongly reacting substances,
other than phenols, include tertiary aliphatic amines, tertiary
amine-containing biological buffers, tryptophan, hydroxylamine,
hydrazine, certain purines, and other miscellaneous organic and
inorganic reducing agents.
We have previously shown that Folin-Ciocalteu reagent can
be used for the detection of paralytic shellfishpoisons (PSPs)
(5-7). The ability to utilize the reagent for this purpose appears
to be somewhat remarkable when one considers the variety of
compounds that may react with the reagent and the fact that
PSPs occur at very low concentrations. Because of the similarity
* Author to whom correspondence should be addressed [telephone
(603) 862-2114; fax (603) 862-3784; e-mail mi@cisunix.unh.edu].of the PSP ring system to the purine ring system, we have
previously also studied the structural requirements for purines
to react with Folin-Ciocalteu reagent (8) and shown the
importance of an amino or hydroxyl group at the 2-position.
Our interest has been to better define the specificity of the
reaction of Folin-Ciocalteu phenol reagent with nitrogen
compounds in order to explore itspossible usefulness for the
detection and determination of certain nitrogen compounds in
natural extracts by colorimetric means and by thin-layer
chromatography (TLC). We tested a number of hydroxylamino
and hydrazino compounds and also focused our attention on
the guanidine-containing compounds, because these compounds
occur so widely in nature and in very diverse structures
(9-13). These...
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