Nitric Oxide/cGMP Mediates the Spasmolytic Action of 3,4^′-Dihydroxy-5,5 ^′-dimethoxybibenzyl from Scaphyglottis livida [*]

Abstract:

Five aromatic compounds, 3,4^′-dihydroxy-5,5^′ -dimethoxybibenzyl (1), batatasin III (2), coelonin (3), 3,7-dihydroxy-2,4-dimethoxyphenanthrene (4), and 3,7-dihydroxy-2,4,8-trimethoxyphenanthrene (5) were isolated from the orchid Scaphyglottis livida (Lindley) Schltr. Compounds 1 -5 induced a concentration-dependent inhibition of the spontaneous contractions of the rat ileum with potencies comparable or higher to that of papaverine. The relaxation evoked by compounds 1-4 was blocked by _L-NAME, an inhibitor of nitric oxide synthase. It was also demonstrated that 1 increased cyclic GMP content in rat ileum rings. Compound 1-induced elevation of cGMP was inhibited by _L-NAME and ODQ, inhibitors of nitric oxide synthase and soluble guanylyl cyclase, respectively. These results indicate that nitric oxide/cGMP formation constitute the signaling pathway in the spasmolytic action of compound 1.

Key words:

Scaphyglottis livida - Orchidaceae - phenanthrenes - dihydrostilbenes - smooth muscle relaxation - nitric oxide - _L-NAME - ODQ - soluble guanylyl cyclase

1 Chemical Studies on Mexican Plants Used in Traditional Medicine XXXIX. Taken in part from the PhD thesis of S. Estrada.

1 Chemical Studies on Mexican Plants Used in Traditional Medicine XXXIX. Taken in part from the PhD thesis of S. Estrada.