Chiang Mai Journal of Science

Padina minor Yamada, a brown alga which is found to be abundant on both sides of the coastal area of the gulf of Thailand and the Andaman Sea was examined for gastroprotective activity.  The aqueous extract of  P. minor (Aq. P) given orally to rats at the doses of 100, 200 and 500 mg/kg significantly inhibited gastric ulcer formation induced by (1) restraint water immersion stress (2) acid ethanol (HCl /EtOH), (3) indomethacin (4) histamine. In the pylorus-ligated rat experiment, the Aq. P caused a decrease of the total acidity and an increase in gastric pH.   Additionally, the Aq. P could not preserve the mucus content in the gastric wall of rats with gastric ulceration induced by HCl /EtOH. Results were obtained from the isolated guinea-pig right atrium experiment of which the inhibitory effects of cimetidine (Histamine H₂-antagonist) and the Aq. P on histamine-induced chronotropic responses were determined and these results suggest that they share a similar mechanism.  The findings therefore indicate that P. minor possesses a gastroprotective activity, which involves an anti-secretory mechanism mediated via histamine H₂-antagonism. The polysaccharide present in the P. minor is likely to contribute to the gastroprotective activity.