Effects of Anthraquinone Derivatives on Small Intestinal Motility of Rabbit

• Main Authors: Kuo, Daih-Huang, 郭代璜
• Other Authors: Juei-Tang Cheng
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/05794024517035573942

博士 === 中國醫藥學院 === 藥物化學研究所 === 84 === The effects of anthraquinone-2-carboxylate and anthraquinone-2-carboxamideson the motility of isolated rabbit small intestines was examined. It was found that some possessed concentration-dependent inhibitory activity. Comparisonof IC50 values revealed a requirement for a polar group, especially a hydroxygroup at B-1,2,5,8-tetrahydroxy and 3-methyl-1,6,8- trihydroxyl anthraquinoneinhibited the intestianl motility more potently than did the lead compound anthraquiaone-2-carboxylic acid. The potency of quinalizarin and emodin were increased about 50 times. Four structure-activity relationships were suggested from the results: (1) a polar group, especially hydroxy group at the B-position of anthraquinone derivatives is required for inhibition of motility; (2) thepresence of a polar group at the 2,7-position increased inhibition of motilitymore than substitution at the 2,6-position increased inhibition of motility more than substitution at the 2,6-position; (3) addition of an 1,8-dihydroxy group at the B-position; (4) substitution with a methyl or ethoxycarbonyl group destroyed bioactivity. But carboxylic acid group at the B-position would maked the intestine motilityto biphasic regulation obviously. It was said that the stimulating effect was atlower concentration and the inhibitory effect was appeared at higher dose. In fact, 2-hydroxyanthraquinone, anthraflavic acid, isoanthraflavic acid, quinalizarin,emodin and rhein had the smaller stimulating effect at lower dose. One the other hand, some derivatives stimulated the small intestine motility.For instance, sodium anthraquinone-2-sulfonate made the action from inhibition tostimulation (IC50 90 nmol/ml). Thus, we could conclude as the tranditional view that anthraquinone derivatives may be termed "stimulant" or "inhibitor" forintestinal motility mainly depending on the substitued group. The selection of solvent is very important for dissolving testing compounds.But propylene glycol (PLG), polyethylene glycol 400, glycerin and polyoxyethylene sorbitan monooleated (Tween 80) all have inhibited the spontaneous contraction ofrabbit isolsted small intestine. Tween 80 had the greatest inhibitory effect especially.In contrast, alcohol stimulated the contraction of small intestine. So it was very cautious for dissolving drug with organic solvent in screening test. In these solventsystem, it was found that five solvent systems which hardly had no effect on motilityof small intestine. They were alcohol: PLG: water (10%: 30%: 60%), alcohol: PEG 400:water (5%: 15%: 80%) and alcohol: PEG 400: water (10%: 20%: 70%). Spontaneous motility of small intestine was not affected by the alkaline solution and their pH value were adjusted from 7, 8, 9, 10, 11 to 12. But high concentrationoxygen (95%O2 -5%CO2) could prolong the vitro life of intestine tissue compaired with general air (20%O2-80%N2). In this study with treating compound 3, the IC50 was 80+-10nmol/ml inhigh concentration oxygen (95%O2-5%CO2), but 120+-10 nmol/ml in air. So theactivity of 3 was elevated by high concentration oxygen. In other cases, the activity of 22,30 and 31 were increased about 10 times by high concentration oxygen more than general air. So the composition of bubbling air is very impor-tant for biological activity of 22,30 and 31. Another study indicated that the activity of 22,30 and 31 dissolved inalkaline solution were 10 folds more than in organic solvent and they all wereimproved in high concentration oxygen. So it was said that both high concentra-tion O2 and alkaline solution were necessary for the most inhibitory activity on small intestine motility, the activity was decreased obviously when thecontrolled condition was lack of anyone above. It seems to be important to melanosis coli which was much related with colorectal cancer. In screen test of the bioactivities for anthraquinone derivatives, N,N-dimethylaminoethyl anthraquinone-2-carboxylate (3) was found to be the most effective compound in anthraquinone 2-carboxylic acid analogs to inhibit themotility of rabbit isolated small intestine. Addition of 3 into organ bathcontaining rabbit intestine produced a concentration-dependent reduction of spontaneous motility to have an approximately IC50 value of 80 nmol/ml. Par-ticipation of sympathetic activation was ruled out by the finding that prazo-sin and propanolol at the concentrations sufficient to block adrenergic recep-tors failed to modify the action of 3. In the presence of superoxide dismutase(SOD) and catalase, this inhibition was reversed significantly. Mediation of free radicals in the inhibition by 3 can thus be considered. Also, inhibitionby 3 was lowed by an increase of extracellular calcium ions. Radioactive cal-cium influx into the prepared single muscle cells was attenuated by 3 in a concen-tration-dependent manner at concentration that required to inhibit the motili- ties. Catalase reversed this inhibition by 3, both the motility and the influx of Ca+2, in a way more markedly than that of SOD. The results suggested that 3can block the influx of calcium ions to lower the intestinal motility through the mechanisim related to free radicals. How did quinalizarin(30) inhibit the contraction of small intestine?Bothprazosin(1 uM) and propanolol(0.1uM) would diminish the effect of 30. So we suggested that the inhibitory effect of 30 was mediated by sympathetic activa-tion. The partial structure of 30 is same as catechol group of norepinephrineand considered about inhibiting the spontaneous motility of small intestine. After incubation with 30, contraction by CaCL2 at several concentration was reduced obviously. In small intestine cells, radioactive calcium was used to evaluated spontaneous influx or specific influx into cell. Theses results indicated that the processes of Ca influx into cell was interfered with 30actually because both spontaneous influx and KCl-induced calcium influx werededucted. SOD could reversed this inhibitory effect of 30 on motility of smallintestine and radioactive calcium influx,but catalase did not. Emodin(31) was the most potent compound in this screening test for inhi-biting motility. And this inhibitory effect was not related to autonomic n現象:ous activation. The stimulating effects of CaCl2 at several concentrations were lowered by emodin. Also,radioactive calcium influxed into the prepared single cells was attenuated by emodin in a dose-dependent manner. In presence of SOD and catalase,the inhibition of 31 was reversed on both motility and calcium influx. But this action of SOD is lowered to reversed the effect of 31 at high dose. In conclusion,the present study suggested that anthraquinone derivativescould modify the spont臠 motility depending on substitutes on basic structu-re. For this action of biological products, emodin and N,N- dimethylaminoethylanthraquinone-2-carboxylate were related with free radicals generating to bolck calcium influx. In addition, quinalizarin inhibited intestinal motility through its catechol group which can activate noradrenergic function.