Ellagitannins Renewed the Concept of Tannins - Chemistry and Biology of Ellagitannins - page 42

inhibition of lipid peroxidation induced by ADP and NADPH in rat liver
microsomes. All tannins, except some small polyphenols and methylated
polyphenols among twenty-five compounds, showed significant
inhibitory effects in these two systems at a concentration of 1 μg/ml,
ellagitannins being generally much more potent than condensed tannins.
The peroxidation was almost completely inhibited by pedunculagin and
isoterchebin at a dose of 5 μg/ml (Okuda et al ., 1983b).
Fig. 1.12 Evidence of the radical scavenging effects of geraniin on the ESR spectrum of
DPPH. The ESR spectra were recorded in the absence [(a)] and in the presence [(b) 5.0 ×
10 -7 M , (c) 1.0 × 10 -6 M , (d) 2.5 × 10 -6 M , (e) 5.0 × 10 -6 M ] of geraniin.
In a study of the effects of tannins on arachidonic acid metabolism,
geraniin and corilagin inhibited the formation of the lipoxygenase
product 5-HETE ( i.e. , 5-hydroxyeicosatetraenoic acid) in rat peritoneal
polymorphonuclear leukocytes, dose dependently at concentrations
ranging from 10 -3 to 10 -6 M, whereas the formation of the
cyclooxygenase products HHT, thromboxane B 2 and 6-keto-PGF 1α was
not inhibited at these concentrations (Kimura et al ., 1986).