G. E. Lee et al. / Bioorg. Med. Chem. Lett. 19 (2009) 954–958
957
dium accumulation assay (IC50, 0.25 vs 0.34
l
M), this compound
15a, 15d, 17b, and 15e with aliphatic groups (ethyl, allyl, n-propyl,
and 1-iodobutyl, respectively) at the R1 position had similar activ-
ities, whereas the compound with a 3,5-dimethoxybenzyl group
(15f) showed increased antagonistic potency with an IC50 value
showed much lower inhibitory activity than KN62 on IL-1b release.
Compound 19h, which showed a slightly more potent inhibitory
effect than KN62 on IL-1b release induced by 1 mM BzATP, was fur-
ther evaluated using full concentration–response curves to com-
pare IC50 values (data not shown). We found that the IC50 value
of 19h (175 51 nM) was twofold higher than that of KN62
(81 12 nM).
of 0.26 l
M. However, cyclohexylmethyl substitution at the R1 po-
sition (17c) resulted in a significant decrease of the antagonistic
activity.
Next, mono-, di-, and tri-substituted benzyl groups were
introduced at the R2 position. In general, electron-withdrawing
groups at the 2-position of the benzyl moiety were preferable
to electron-donating groups (e.g., CF3- in 19b vs CH3- in 19a;
NO2- in 19f vs CH3- in 19g) for the antagonistic activity. Further-
more, as in the case of compound 19d, introduction of a fluorine
group at the 4 position of the benzyl moiety of compound 19b
containing a 2-CF3 moiety increased the antagonistic activity
more than threefold (19d vs 19b). Among the di-substituted
derivatives at the benzyl moiety of R2 position, 2,4-and 2,5-
disubsitutions resulted in more potent antagonists than 2,3-di-
substitutions (e.g., 19c vs 19d, 19e, 19f, and 19g). The tri-substi-
tuted analog, 19h, containing 2-NO2- and 4,5-dimethoxy groups
at the benzyl moiety of R2 position, turned out to be the most po-
tent antagonist among all 5,6-dihydrodibenzo[a,g]quinolizinium
derivatives tested in this study, showing twofold more potency
In conclusion, a novel series of protoberberine-based P2X7
antagonists with modifications at the R1 and R2 positions was syn-
thesized and evaluated in ethidium accumulation and IL-1b release
assays. Compounds with alkyl groups at the R1 position (15a and
15d) showed high potency in both assay systems as P2X7 antago-
nists. In particular, compound 19h, which contains an ethyl group
at the R1 position and a 2-NO2-4,5-dimethoxy-benzyl group at the
R2 position, was discovered as the most potent antagonist of all
QPAs tested, and the antagonistic potency was comparable to the
positive control, KN-62.
Acknowledgments
This study was supported by a grant of the National R&D Pro-
gram for Cancer Control, Ministry of Health & Welfare, Republic
of Korea (0720430) and by a research grant from the Korea Science
and Engineering Foundation (R01-2006-000-10880-0).
than KN62 with an IC50 value of 0.17 lM. Neither halide (-Br
and -Cl) nor bulky group substitutions at the 3- or 4-position
at the benzyl moiety of R2 position (19i–n) exhibited appreciable
potency of single-digit micromolar IC50 values.
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Table 2
Antagonistic effects of protoberberine derivatives against BzATP-stimulated IL-1b
release by LPS/IFN
c
-differentiated human THP-1 cells39
Compound
% Inhibitiona
Compound
% Inhibition
KN-62
8
79
NAb
34
4
19d
19e
19f
13 18
42 18
( )-13
15a
15d
15e
15f
15g
17c
19a
19b
4
40
8
83
7
6
3
73 14
71 0.30
54 10
39 25
19g
19h
19i
33 13
19j
5
NA
NA
7
16
50
8
19k
19l
19m
19n
17 12
NAb
7
6
27. Baxter, A.; Bent, J.; Bowers, K.; Braddock, M.; Brough, S.; Fagura, M.; Lawson,
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Kinchin, E. C.; Laurent, C.; Lawson, M.; Luker, T. J.; Mortimore, M. M. P.; Pimm,
13 11
33
a
Mean SD percent inhibition of 1 lM compound against 1 mM Bz-ATP-induced
IL-1b release (n = 3).
b
No activity.