Abstract
In Japan, the three most common cause of death are cancer (30%), cardiovascular disorder (16%), and cerebral vascular disorder (10%). Since hypertension often leads to cardiovascular disorder and cerebral vascular disorder, the discovery of new compounds with vasodilating or hypotensive effects may contribute in controlling these disorders. Our continuous search for bioactive natural products from medicinal plants targeting vasorelaxant activity leads to the methanol extract from the bark of Tabernaemontana dichotoma which showed vasorelaxant activity on rat aorta. Further investigation on extract of T dichotoma resulted in the isolation of a new indole alkaloid, 10-methoxyalstonerine, together with seven known alkaloids, 10-methoxyaffinisine, lochnerine, cathafoline, 19,20-dehydro-10-methoxytalcarpine, alstonerine, alstonisine, and alstonal. Their structures were elucidated based on spectroscopic data analysis. 10-methoxyaffinisine, cathafoline, and alstonisine showed vasorelaxant effect on rat aorta in concentration-dependent manners and were also investigated for the mechanism of vasorelaxation. Furthermore, 10-methoxyaffinisine showed hypotensive effect on normotensive rats.
