Effects of extract and ingredients isolated from Magnolia obovata Thunbergon catecholamine secretion from bovine adrenal chromaffin cells

The crude extract of magnolia bark, an herbal drug, inhibited the secretion of catecholamines from bovine adrenal chromaffin cells stimulated by acety lcholine (ACh) in a concentration-dependent manner (200-900 mu g/mL). The e xtract also diminished the secretion induced by high K+, which is a stimulu s directly depolarizing the plasma membranes, but its inhibition was weaker than that of ACh-evoked secretion. beta-Eudesmol, honokiol, magnolol, and bornyl acetate, but not alpha- and beta-pinenes, all of which are ingredien ts of magnolia bark, greatly reduced ACh-evoked secretion. beta-Eudesmol an d magnolol also inhibited high K+-induced secretion to an extent similar to that of ACh-evoked secretion. However, honokiol and bornyl acetate inhibit ed the secretion induced by high K+ much less than the secretion evoked by ACh. ACh-induced Na+ influx and ACh- or high K+-induced Ca2+ influx into th e cells were diminished by beta-eudesmol or honokiol. These results indicat e that magnolia bark contains some effective components inhibiting the secr etion of catecholamines from bovine adrenal chromaffin cells stimulated by ACh due to the antagonism of Na+ and Ca2+ influxes into the cells. However, inhibition by the extract of magnolia bark seems to be attributable to hon okiol and bornyl acetate. Furthermore, the results indicate that the inhibi tory effect of magnolia bark may be associated with its pharmacological eff ect on activities of the nervous system. BIOCHEM PHARMACOL 60;3: 433-440, 2 000. (C) 2000 Elsevier Science Inc.