358
F. No6elli et al. / Il Farmaco 54 (1999) 354–358
Two successive experiments were carried out, each
Finally, it is worth noting that in the binding test the
time employing concentrations of test compounds ex-
pressed as mg/ml (30, 10, 3, 1 mg/ml) or as mM (30, 10,
3, 1 mM); for the sake of homogeneity in Table 2
concentrations are always indicated as mM.
lead compound 1 failed to displace the specific ligand
[
125I]CGP-42112A from angiotensin AT2 receptors at
concentrations up to 10−5 M. Therefore any direct
interaction of 1 and similar compounds with this re-
ceptor should be excluded in the observed inhibition
of angiotensin II-induced contraction of guinea pig
ileum.
4.2. Angiotensin AT2 binding [13]
Membranes prepared from male rabbit adrenal glands
were incubated for 45 min at 25°C with 25 pM [125I]CGP-
42112A. Non-specific binding is estimated in the presence
of 1 mM angiotensin II. Membranes are filtered, washed
and counted to determine the bound [125I]CGP-42112A.
Compound 1 was screened at 10 mM concentration.
Saralasin was used as reference compound, exhibiting
IC50=1 nM and Ki=0.99 nM.
References
[1] F. Novelli, F. Sparatore, Thiolupinine and some derivatives of
pharmacological interest, Farmaco 48 (1993) 1021–1049.
[2] W.J. Kinnier, J.F. Kachur, V.H. Audia, C. Kaiser, Irritable
bowel syndrome: present and prospective pharmacological inter-
vention, Med. Res. Rev. 9 (1989) 325–342.
[3] C.J. Blankley, J.C. Hodges, S.R. Klutchko, R.J. Himmelsbach,
A. Chucholowski, C.J. Connolly, S.J. Neergaard, M.S. Van
Nieuwenhze, A. Sebastian, J. Quin, A.D. Essenburg, D.M. Co-
hen, Synthesis and structure–activity relationships of a novel
series of non-peptide angiotensin II receptor binding inhibitors
specific for the AT2 subtype, J. Med. Chem. 34 (1991) 3248–
3260.
[4] N.M. Barnes, B. Costall, M.E. Kelly, D.A. Murphy, R.J. Naylor,
Cognitive enhancing actions of PD123177 detected in a mouse
habituation paradigm, Neurol. Rep. 2 (1991) 351–353.
[5] A. Sparatore, A.M. Caviglia, M. Marchi, M. Raiteri, Pharmaco-
logical characterization of the presynaptic muscarinic autorecep-
tors regulating acetylcholine release from rat cortical
synaptosomes, Symp. Neurosci. (Liviana Press, Padua) 3 (1986)
447–452.
[6] A. Sparatore, M. Marchi, G. Maura, G. Bonanno, M. Ulivi, M.
Raiteri, Studies on some new indirect dopaminergic receptor
agonist, Symp. Neurosci. (Liviana Press, Padua) 5 (1988) 192–
196.
[7] A. Sparatore, M. Marchi, G. Maura, M. Raiteri, Effect of some
quinolizidine derivatives on the release of serotonin, nora-
drenaline, dopamine and acetylcholine from rat brain synapto-
somes, Farmaco 44 (1989) 1205–1216.
5. Results and discussion
The results of the pharmacological assays are collected
in Table 2, where the results concerning the previously
described compound 1 are also included for comparison.
Among the activities exhibited by the lead compound
1, only the inhibition of angiotensin II-induced guinea
pig contractions was found in all tested compounds,
while the remaining ones were seen only occasionally in
a few compounds. Thus, compound 7 inhibited the
arachidonic acid-induced platelet aggregation at a lower
concentration (6.6 mM) than that of 1 (25 mM), but the
remaining compounds were inactive, at least in the
concentration range explored. Compound 7 was clearly
more active than aspirin (MIC=16.6 mM).
As regards tracheal relaxation, compounds 2, 5 and 7
exhibited only moderate activity at the highest concentra-
tion employed (30 mg/ml=65–77 mM), while the lead
compound 1 was more than twice as active as
theophylline on a molar basis.
Compounds 3, 4, 6 and 8 inhibited significantly
(56–86%) the guinea pig ileum contractile response to
angiotensin II at 3 mM concentration, similar to the lead
compound 1 (2.5 mM), while the remaining compounds
2, 5 and 7 were active at higher concentrations (6.7–10
mM).
[8] I. Vazzana, F. Novelli, F. Sparatore, A. Sparatore, G. Fadda, G.
Manca, Quinolizidine derivatives with antitubercular activity,
Farmaco 49 (1994) 105–110.
[9] E. Sawicki, V.T. Oliverio, Reaction of thiaxanthydrol with com-
pounds containing active hydrogen, J. Org. Chem. 21 (1956)
183–189.
[10] J.A. Bristol, E.H. Gold, I. Gross, R.G. Lovey, J.F. Long, Gastric
antisecretory agents. 2. Antisecretory activity of 9-[(amino-
alkyl)thio]-9H-xanthenes
and
5-[(aminoalkyl)thio]-5H-
[1]benzopyrano-[2,3-b]-pyridines, J. Med. Chem. 24 (1981)
1010–1013.
Thus, xanthene, thioxanthene and diphenylmethane
backbones appear equally suitable for this kind of
activity; the chloro substitution on the benzene ring of
xanthene and thioxanthene does not produce significant
change of activity, while among the diphenylmethane
derivatives the halogen-substituted compounds 6 and 8
are more active than both the unsubstituted (5) and the
methoxy-substituted derivatives.
[11] M.A. Christie, R.L. Webb, A.M. Tickner, Synthesis of cyclo-
hexylidene–xanthenes via the Wittig–Horner reaction, J. Org.
Chem. 47 (1982) 2802–2804.
[12] L.F. Fieser, M. Fieser, Reagents for Organic Synthesis, vol. 1,
Wiley, New York, 1967, p. 1276.
[13] S.E. Whitebread, V. Taylor, S.P. Bottari, B. Kamfer, M. de
Gasparo, Radioiodinated CGP-42112A: a novel high affinity and
highly selective ligand for the characterization of angiotensin AT2
receptors, Biochem. Biophys. Res. Comm. 181 (1991) 1365–1371.
.