2762
R. S. Nandurdikar et al. / Bioorg. Med. Chem. Lett. 19 (2009) 2760–2762
ative activity profiles (Fig. 2). The quaternary ammonium salt 17
with an IC50 value of 10.8 M againstHL-60 cells showeddiminished
l
levels of intracellular nitric oxide relative to JS-K in this assay.
Acknowledgments
This research was supported by the Intramural Research Pro-
gram of the NIH, National Cancer Institute, Center for Cancer Re-
search, as well as by National Cancer Institute contract NO1-
CO-2008-00001 to SAIC-Frederick.
Supplementary data
Figure 2. Intracellular NO release after treating HL-60 cells pre-loaded with DAF-
FM diacetate with various compounds (5 lM) for 40 min; p values <0.001 (***) and
p value = 0.03 (**).
Supplementary data (preparation procedures and analytical
data for all new compounds, and NMR spectra of 2b and 10) asso-
ciated with this article can be found, in the online version, at
First, glutathione-activated nitric oxide yields from these
compounds were determined using a chemiluminescence assay.
All compounds were found to release nearly quantitative amounts
of NO on reaction with GSH (Table 2).
References and notes
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Next, JS-K and its analogues were tested for their in vitro anti-
proliferative activities against human leukemia cell lines HL-60
and U937 (Table 2). Compounds 3–9 were found to display nearly
identical anti-proliferative activities (Table 2) but changing the
ethyl carbamate to a diethyl phosphamate group resulted in a
lowering of inhibitory activity (Table 2, compound 10). All the
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lower in potency than JS-K (Table 2).
Finally, in order to test the role of cell permeability and NO in
cytotoxicity of these compounds, we measured the levels of
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compounds and compared these with JS-K.13,14 The intracellular
NO was estimated using the nitric oxide-sensitive fluorophore, 4-
amino-5-methylamino-20,70-difluorofluorescein diacetate (DAF-FM
diacetate); briefly, human leukemia HL-60 cells were pre-loaded
with DAF-FM diacetate, followed by treatment with DMSO solu-
tions of various JS-K analogues; fluorescence measurements after
40 min provided estimates of levels of intracellular NO (Fig. 2).
Aplotof therelativefluorescencesuggeststhatcompoundsform-
ing NO at levels comparable with JS-K showed similar anti-prolifer-
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E.; Keefer, L. K. Leukemia Res., in press, doi:10.1016/j.leukres.2009.01.002.
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14. Andrei, D. A.; Maciag, A. E.; Chakrapani, H.; Citro, M. L.; Keefer, L. K.; Saavedra, J.
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