Relaxing activity of two linear diterpenes from Cystoseira brachycarpa var. balearica on the contractions of intestinal preparations
1995
Pieta, F.D. | Breschi, M.C. | Scatizzi, R. | Cinelli, F. (Universita degli Studi di Pisa (Italy). Dept. di Scienze dell'Ambiente e del Territorio)
Eleganolone and elegandiol, two linear diterpenes isolated from Cystoseira brachycarpa var. balearica, were tested on guinea-pig intestinal preparations. Both these compounds inhibited the contractile activities of acetylcholine (Ach) and histamine (Hist) on ileum musculature; the relative pIC50 values of eleganolone were found to be 4.60 (+- 0.03) and 4.84 (+- 0.20), respectively, while those of elegandiol were 4.71 (+- 0.18) and 5.18 (+- 0.01), respectively. Furthermore, 1 and 2 dose-dependently relaxed the same preparations precontracted with 300 microM BaCl2(pIC50 4.34 (+- 0.18) for Eleganoloneand pIC50 = 4.34 (+- 0.02) for elegandiol or with 60 mM KCI (pIC50 = 4.73 (+- 0.18) and 4.47 (+- 0.06), respectively). On colon smooth muscle, the diterpenes inhibited the spontaneous contractile tone and this effect was reversed by both methylene blue (0.000003 M) and haemoglobin (0.000003 M). Tetraethylammonium (TEA), furosemide, N omega-nitro L-arginine methyl ester (L-NAME), indomethacin, alpha-chymotrypsin, and metoprolol were unable to block the eleganolone and elegandiol relaxing action on colonic musculature, but rather potentiated this response. On the contrary, the beta2-blocker butoxamine partially inhibited the diterpenes activity. These results suggest that Cystoseira diterpenes act at a second messenger cyclase system rather than at a receptor level.
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