Structures of Geraniin Metabolites
J. Agric. Food Chem., Vol. 56, No. 2, 2008 399
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scopic and spectrometric data. These compounds, except for
M1, were characterized as ellagitannin metabolites for the
first time. Furthermore, M1-M4 were predominantly ex-
creted in rat urine after the ingestion of 1; among which,
M2 showed an antioxidant activity comparable to 1. Although
the metabolites are present in the circulatory system as
conjugated forms, several data have been reported about
biological activity of conjugates. Quercetin conjugates retain
antioxidant activity in plasma (35–37). Luteolin glucuronide
is deconjugated into aglycone by ꢀ-glucuronidase released
from neutrophils after induction of inflammation (38). Thus,
these findings support the idea that these metabolites were
absorbed into the circulatory system and transported in urine
after ellagitannin intake, which may contribute to the health
benefits of ellagitannins. Further study of the bioavailability
of ellagitannins is under investigation to clarify the active
principles of antioxidant and cancer chemopreventive effects.
ABBREVIATIONS USED
ESIMS, electrospray ionization mass spectrometry; COSY,
1H-1H correlated spectroscopy; NOESY, nuclear Overhauser
enhancement spectroscopy; HSQC, heteronuclear single quan-
tum coherence; HMBC, heteronuclear multiple-bond correlation;
SOD, superoxide-dismutase; PMS, phenazine methoxysulfate;
NBT, nitroblue tetrazolium; DPPH, 1,1-diphenyl-2-picrylhy-
drazyl.
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ACKNOWLEDGMENT
The authors are grateful to the SC-NMR Laboratory of
Okayama University for NMR measurements.
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