The fruit of Nandina domestica Thunberg (ND, Berberidaceae) has been used to improve cough and breathing difficulties in Japan for many years, but very little is known about the constituent of ND responsible for this effect. We have recently reported that the crude extract from ND (NDE) inhibits histamine- and serotonin-induced contraction of isolated guinea pig trachea, and the inhibitory activity was not explained by nantenine, a well-known alkaloid isolated from ND. To explore other constituent(s) of NDE with tracheal smooth muscle relaxant activity, we fractionated NDE and assessed the pharmacological effects of the fractions using isolated guinea pig tracheal ring preparations. NDE was introduced into a polyaromatic absorbent resin column and stepwise eluted to yield five fractions, among which only the 40 % methanol fraction was active in relaxing tracheal smooth muscle precontracted with histamine. Further separation of the 40 % methanol fraction with high-performance liquid chromatography yielded multiple subfractions, one of which was remarkably active in relaxing histamine-precontracted trachea. Chemical analysis with a time-of-flight mass spectrometer and nuclear magnetic resonance spectrometer identified the constituent of the most active subfraction as higenamine, a benzyltetrahydroisoquinoline alkaloid. The potency and efficacy of the active constituent from NDE in relaxing trachea were almost equivalent to synthetic higenamine. In addition, the effect of the active constituent from NDE was competitively inhibited by the selective beta (2)-adrenoceptor antagonist ICI 118,551. These results indicate that the major constituent responsible for the effect of NDE is higenamine, which probably causes the tracheal relaxation through stimulation of beta (2) adrenoceptors.
Using cultured normal human keratinocytes, we compared the activities of 1 alpha,24-dihydroxyvitamin D3 (1,25(OH)2D3), a biologically active form, in inducing cell differentiation. Treatment with 10(-6) M of 1,24R(OH)2D3 and 1,25(OH)2D3 increased the number of involucrin positive cells (differentiated from 6.4% to 24.1% and 25.1%, respectively. These results indicate that 1,24R(OH)2D3 has an ability comparable to that of 1,25(OH)2D3 to induce cell differentiation in human keratinocytes. The clinical effectiveness of 1,24R(OH)2D3 for the treatment of psoriasis may be, in part, related to its direct effect on hyperproliferative keratinocytes.
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