Aim: 

Flavonoids comprise a large group of naturally occurring polyphenolic compounds, which constitute an integral part of the human diet, being ingested with vegetables and beverages. The purpose of the present study was to investigate the effects of flavonoids on the mouse gastric tone and to examine the possible underlying mechanisms.

Methods: 

Intraluminal pressure from the isolated stomach was recorded in vitro and the mechanical responses induced by flavonoids were analyzed after different pharmacological treatments.

Results: 

All flavonoids tested produced a concentration-dependent relaxation. The relative order of potency of the flavonoids was apigenin >= genistein > quercetin > naringenin >= rutin > catechin. Analysis of the chemical structure showed that the relaxant activity was progressively diminished by the presence of hydroxyl group at C-3, saturation of the C-2, C-3 double bound, saturation of the C-2, C-3 double bound coupled with lack of the C-4 carbonyl and glycosylation. The flavonoid-induced relaxations were not modified in the presence of tetrodotoxin, a voltage-dependent Na⁺ -channel blocker, N_w-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) synthase, indomethacin, an inhibitor of cycloxygenase or tetraethylammonium (TEA), a non-selective blocker of potassium channels. The responses to apigenin or quercetin were significantly reduced in the presence of nifedipine or calcium-free solution, but not by ryanodine.

Conclusions: 

This study provides the first experimental evidence for an inhibitory modulation of gastric motility by flavonoids. This action is influenced to a great extent by the structure of the molecules and it is not dependent on neural action potentials, NO/ prostaglandin production or activation of K⁺ channels. L-type voltage-dependent Ca²⁺ channels appear to be involved in the action of apigenin and quercetin.