| Summary: | 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.
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