Biology Reference
In-Depth Information
antimicrobial agents (see Chapter 2).
Helicobacter pylori
, a Gram-
negative spirillum that may cause chronic gastritis, gastric ulcer,
duodenal ulcer and also stomach cancer, was potently inhibited by
tellimagrandin I and corilagin at a minimum inhibitory concentration
(MIC) of 6.25 μg/ml.
The effect of β-lactam against MRSA (methicillin-resistant
Staphylo-
coccus aureus
) aquiring multi-drug resistance was restored by corilagin
and tellimagrandin I, as well as by several other polyphenols (see
Chapter 2 for further details). Potent effects against leishmanises, a group
of diseases with extensive morbidity and mortality in developing
countries, were observed using several dehydroellagitannins, the
ellagitannin hippophaenin A and also several gallotannins, while the
effect of proanthocyanidins was generally less pronounced. Differences
were found between
Leishmania
promastigotes and
L
. amastigotes in the
anti-leishmanial activity of each polyphenol. These intriguing differences
may be indicative of an activation of leishmanicidal macrophage
function, which led researchers to rely on several functional bioassays,
including a biochemical assay for nitric oxide (NO), a fibroblast-lysis
assay for release of tumor necrosis factor (TNF-α
),
and a cytopathic
effect inhibition assay for interferon (IFN)-like properties, for carrying
out in-depth investigations of the activity of tannins on leishmanises (see
Chapter 2).
1.7.2 Antitumor activities
A large amount of hard data has been gathered during the last two
decades on the inhibitory activities of polyphenols, including
ellagitannins and analogs, on tumor incidence and propagation. This is in
sharp contrast to what was commonly thought earlier on, when precise
chemical evidence of tannins was not available. Indeed, induction of
cancers by some plant species was believed to be due to their high
content in “tannins”. Today, the cytotoxic activity of several tannins of
defined structure has been reported. Recent evidences of the antitumor
activities of ellagitannins are reviewed thereafter.
