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N. Ribeiro et al. / Bioorg. Med. Chem. Lett. 17 (2007) 5523–5524
Table 1. Inhibition of TNF-a secretion by THP-1 cells and human PBMCsa
Entry
Compounds (method, yield)
X
R
% Inhibition of TNF-a releasea
THP-1 PBMC
10 lM
50 lM
10 lM
50 lM
1
2
3
4
5
6
7
1 (a, 38%)
2 (a, 31%)
3 (b, 31%)
4 (c, 78%)
5 (d, 10%)
6 (c, 66%)
7 (c, 54%)
H
H
H
H
H
H
H
OMe
Et
7
3
10
80
93
83
97
59
21
24
32
67
50
SMe
NMe2
49
0
78
95
ND
36
NDb
ND
ND
67
NHMe
N(CH2CH2OMe)2
NMeCH2CH2OH
50
0
ND
ND
0
8
8 (c, 43%)
H
21
43
ND
ND
N
N CONMe2
9
10
9 (e, 61%)
10 (b, 59%)
H
NO2
NH2
SMe
ND
ND
ND
ND
29
86
79
94
a Cells were incubated for 24 h with 5 lg/ml LPS in the presence of the tested compound or DMSO alone as a control. Concentrations of TNF-a were
assessed by ELISA in culture supernatants (for a detailed assay description, see Ref. 9).
b ND, not determined.
11e. Displacement of the bromide by an amine followed
by an alkaline cyclisation afforded compounds 4, 6–8
(method c).7 Synthesis of the methylamino 5 required
a transient protection with a Boc (method d).
NHMe retained an activity similar to that of 3-O-meth-
ylveridicatin 1 (entries 5 and 9), indicating that this po-
sition is very sensitive to steric hindrance.
Introduction of a nitro group at the 6 position was well
tolerated (entry 10, IC50 = 3.5 lM), suggesting that
functionalization of this position should be considered
in further studies.
Interestingly, reaction of 11c and 11d with sodium meth-
anethiolate gave an intermediate that cyclised spontane-
ously to afford the thio-isosteres 3 and 10 (method b).8
Compound 10 was synthesized by alkylation of pyridine
by bromoamide 11c, followed by hydrazinolysis accord-
ing to established procedures (method e).9
In summary, we performed the first study on the struc-
ture–activity relationships of 3-O-methylviridicatin and
we identified its thio-isosteres 3 and 10 as lead com-
pounds to develop new anti-inflammatory drugs.
First, we assayed the anti-inflammatory activity of 3-O-
methylviridicatin 1 and its analogues 2–8 in an inhibi-
tion model of TNF-a secretion by human monocytic
THP-1 cells after human LPS activation (Table 1).
Then, we confirmed these data on human LPS-activated
peripheral blood mononuclear cells (PBMCs).10
PBMCs, unlike THP-1 cells, do not extrude drugs out-
side due to multidrug-resistant pumps, and represent
therefore a better model to study anti-inflammatory
drugs.
References and notes
1. Palladino, M. A.; Bahjat, F. R.; Theodorakis, E. A.;
Moldawer, L. L. Nat. Rev. Drug Disc. 2003, 2, 736.
2. Desai, S. B.; Furst, D. E. Best Pract. Res. Clin. Rheumatol.
2006, 20, 757.
3. Paul, A. T.; Gohil, V. M.; Bhutani, K. K. Drug Discovery
Today 2006, 11, 725.
4. Austin, D. J.; Myers, M. B. J. Chem. Soc. 1964, 1,
1197.
3-O-Methylviridicatin 1 weakly inhibits the production
of TNF-a in vitro by THP-1 and PBMCs (7% and
24% inhibition, respectively, at a 10 lM concentration)
(Table 1, entry 1). Replacement of the 3-methoxy by
an ethyl did not significantly modify the activity (entry
2), but replacement by a thiomethyl dramatically in-
creased the inhibition of TNF-a liberation (entry 3,
IC50 = 1 lM). This might be due to the enhanced ability
of vinyl-thioethers substituted by a carbonyl to trap rad-
icals by captodative effect.11 In a previous study, we
have shown that celastrol, which displays similar fea-
tures, exhibits also potent anti-inflammatory activity.10
All together these data suggest that at least a part of
the mechanism of action of these drugs may involve
trapping radicals.
5. Heguy, A.; Cai, P.; Meyn, P.; Houck, D.; Russo, S.;
Michitsch, R.; Pearce, C.; Katz, B.; Bringmann, G.;
Feineis, D.; Taylor, D. L.; Tyms, A. S. Antiviral Chem.
Chemother. 1998, 9, 149.
1
6. All tested compounds exhibited proper H and 13C NMR
spectra and satisfactory elemental analyses.
7. Rehwald, M.; Gewald, K.; Lankau, H.-J.; Unverferth, K.
Heterocycles 1997, 45, 483.
8. Prezent, M. A.; Dorokhov, V. A. Russ. Chem. Bull. 2003,
52, 2454.
9. Hewawasam, P.; Fan, W.; Knipe, J.; Moon, SL.; Boissard,
C. G.; Gribkoff, V. K.; Starrett, J. E., Jr. Bioorg. Med.
Chem. Lett. 2002, 12, 1779.
10. Pinna, G. F.; Fiorucci, M.; Reimund, J. M.; Taquet, N.;
Arondel, Y.; Muller, C. D. Biochem. Biophys. Res.
Commun. 2004, 322, 778.
´
11. Viehe, H. G.; Janousek, Z.; Merenyi, R.; Stella, L. Acc.
Chem. Res. 1985, 18, 148.
Substitution by a bulky amine led to a dramatic loss of
activity (entries 4, 6–8), but substitution by NH2 or