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K. Musilek et al. / Bioorg. Med. Chem. Lett. 20 (2010) 1763–1766
residues of internal anionic and peripheral anionic site. Though the
pyridinium moiety was used within this series of compounds, the
other heteroaromatic moieties (e.g., quinolinium, iso-quinolinium)
might be probably used and will be object of further interest.
Secondly, the used linkage highly influenced the inhibitory abil-
ity of prepared compounds. The length of the connecting linkage
remained the most important factor within whole series of com-
pounds. The compounds with 8–12 methylene units (10–13) re-
sulted the as the best among tested inhibitors for hAChE. These
results apparently correlate with the distance of IAS and PAS in
hAChE and thus with interactions of pyridinium moiety. The situ-
ation changed for hBChE, where the PAS is not presented. Com-
pounds 10–13 were stacked between two Tyr residues and
consequently resulted as potent inhibitors. Compounds bearing
shorter (3–8) or longer methylene linkers (14) were found ineffi-
cient for both enzymes.
Differently, heteroatom (15–16), double bond (17–18), xylene
(19–21) and naphtylene linkage (22) were introduced to find pos-
sible interactions.33 Not surprisingly, most of these compounds
(15–21) displayed only minor inhibitory activity of both enzymes
(mM range). The length of the linkage in mentioned compounds
varied from 4 to 6 analogues of methylene units that were insuffi-
cient to interact similarly as the compounds 10–13. Due to the
poor in vitro results of 15–21, the plausible interactions with both
enzymes were not further studied. Most interestingly, compound
22 with naphtylene linkage exhibited the best inhibitory ability
for both used enzymes. Although its linker was shorter compared
to 10–13, it displayed the same binding between the AChE active
sites. Moreover, compound 22 showed one more T-stacking in
BChE directly released by naphtylene linker and consequently
resulted as the best inhibitor of hBChE.
was supported by the Grant Agency of the Czech Republic No.
203/09/P130 and by the Grant Agency of the Charles University
No. 117909/2009/B-CH/FaF.
Supplementary data
Supplementary data associated with this article can be found, in
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In summary, 20 symmetrical bispyridinium compounds were
prepared. Their ability to inhibit hAChE or hBChE was tested
in vitro and expressed as IC50. The inhibitory results were com-
pared to standard compounds for early MG treatment (pyridostig-
mine bromide, neostigmine bromide). Three newly prepared
compounds showed IC50 comparable to neostigmine bromide and
better than pyridostigmine bromide. Mentioned promising com-
pounds did not present selectivity between AChE and BChE. Conse-
quently, two prepared compounds with promising inhibitory
ability were determined via docking study with AChE and BChE.
The apparent molecular interactions of
p–p or p–cationic origin
were described, binding aside enzyme’s catalytic sites found out
and subsequently the in vitro data resolved. The kinetic studies
of two most promising compounds confirmed non-competitive
inhibition of AChE.
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Acknowledgements
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The authors express their appreciation to Mrs. M. Hrabinova
and Mr. Petr Stodulka for their technical assistance. This work