Ellagitannins Renewed the Concept of Tannins - Chemistry and Biology of Ellagitannins - page 43

In an investigation of the protective effects of tannins against
oxidative damage induced in mouse ocular lenses by incubating them
with xanthin-xanthine oxidase, ADP and Fe 3+ ( i.e. , X-XOD system), lipid
peroxide concentration in the lens was markedly lowered by geraniin, but
the effect was low when using polyphenolic small molecules (Iwata
et al ., 1987).
The effects of twenty-five tannins, including ellagitannins and small
polyphenols, on the concentration of superoxide anion radical generated
in the hypoxanthine-xanthine oxidase system, were evaluated by ESR
measurements of the adduct of 5,5-dimethyl-1-pyrroline- N -oxide
(DMPO) and the radical. Increasing the ellagitannin concentration in the
solution of superoxide generating mixture inhibited the appearance of
signals of the DMPO adduct in a dose-dependent manner. The
scavenging effect of ellagitannins on the superoxide anion radical
increased generally with increase of the number of phenolic hydroxyl
groups in the molecule. The radical scavenging mechanism of
ellagitannins and related polyphenols on the superoxide anion radical
was thus substantiated (Hatano et al ., 1989c).
1.7. Biological and Pharmacological Activities
1.7.1 Antiviral, antimicrobial and immunomodulatory activities
Monomeric and dimeric ellagitannins, as well as some gallotannins,
potently inhibited Herpes simplex infection, as reported by Fukuchi and
co-workers (Fukuchi et al ., 1989). Dimeric ellagitannins efficaciously
inhibited reverse transcriptase from RNA tumor virus (Kakiuchi et al .,
1985). Several ellagitannins, including gemin D (a monomer), gemin A,
camelliin B and nobotanins A, B and F (dimers), and trapanin B and
nobotanin K (tetramers), among 87 tannins and related polyphenols,
were shown to inhibit HIV-induced cytopathic effects and HIV-specific
antigen expression, but condensed tannins expressed no similar activity
(Nakashima et al ., 1992).
Ellagitannins and other tannins exhibited interesting antimicrobial
activities on some drug-resistant bacteria in the presence of some other