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Y.-F. Zhao et al. / Chinese Chemical Letters 24 (2013) 386–388
Approximately 4 ꢂ 103 cells, suspended in MEM medium, were
plated onto each well of a 96-well plate and incubated in 5% CO2
at 37 8C for 24 h. The subject compounds at indicated final
concentrations were added to the culture medium and the cell
cultures were continued for 72 h. Fresh MTT was added to each
well at a terminal concentration of 5 mg/mL and incubated with
cells at 37 8C for 4 h. The formazan crystals were dissolved in
100 mL DMSO each well, and the absorbency at 492 nm (for
absorbance of MTT formazan) and 630 nm (for the reference
wavelength) was measured with the ELISA reader. All of the
compounds were tested three times in each of the cell lines. The
results expressed as IC50 (inhibitory concentration 50%) were
the averages of three determinations and calculated by using the
Bacus Laboratories Incorporated Slide Scanner (Bliss) software.
The results were illustrated in Table 1 with Sorafenib as the
positive control.
2d also indicated that fluoro at the para-position kept, or improved,
the antitumor activity.
The effects of fluoro and trifluoromethyl substituents on
cytotoxic activities in the ortho-position of benzene ring were
also evaluated. Generally, compounds with fluoro or trifluoro-
methyl group in the ortho-position had weaker cytotoxicity than
those with chloro or methyl groups in the ortho-position. It is
worth noting that compounds 2a (2-fluoro) and 2i (2,6-difluoro)
exhibited weak cytotoxicity, whereas 2r (2-chloro-5-trifluoro-
methyl) and 2n (2,5-dimethyl) exhibited potent cytotoxicity. The
structure-activity relationship (SAR) information indicated that
the fluoro group at ortho-postion resulted in less activity.
4. Conclusion
In summary, a series of novel diaryl urea derivatives were
synthesized and evaluated for their antitumor activities on MDA-
MB-231, HT-29, MCF-7, SMMC-7721 and NCI-H446 cell lines, with
Sorafenib as the reference control. Compounds 2d, 2g, 2l, 2o, 2p
and 2q exhibited more potent activity against MDA-MB-231 and
HT-29 cell lines as compared with Sorafenib. From preliminary
SARs, we may conclude compounds with the chloro substitution in
the meta-position are required for optimal potency. Most
noteworthy was the steric effect of meta substituents, such as
chloro, bromo and methyl, which led to a significant improvement
in activity. Moreover, the substitution of the fluoro group at the
para-position of the benzene ring further increased cytotoxic
activity. This study may provide valuable information for future
design and development of antitumor agents with more potent
activities.
3. Results and discussion
As shown in Table 1, apparent growth inhibition against MDA-
MB-231, MCF-7 and SMMC-7721 cell lines was observed for most
of the compounds. Among them, compounds 2d, 2g and 2p
exhibited more potent anti-tumor activities against MDA-MB-231,
HT-29 and MCF-7 cell lines than Sorafenib. Especially, compound
2p, the most promising compound, displayed excellent anti-tumor
activity against MDA-MB-231, MCF-7, HT-29 cell lines with IC50
values of 0.016, 0.001, 0.63
mmol/L, respectively.
Contrasted to Sorafenib, the tested compounds displayed a
broader spectrum of anticancer activity. Some of them showed
moderate to strong cytotoxicity against MCF-7 and H446 cell lines.
However, Sorafenib exhibited only weak inhibitory activity on
these three cell lines.
Acknowledgment
From Table 1, the steric effect of group R appears to have some
relationship with the cytotoxicity of the series of compounds. Most
of the derivatives with meta-substitution, especially chloro (2d,
2p), bromo (2e), methyl (2n, 2o) group showed significantly higher
cytotoxicities than those with fluoro (2b) and trifluoromethyl (2f,
2m) groups or with no substituent. Of them, the chloro group in the
meta position appeared to increase the antitumor potency. There
was no obvious difference between the effects of electron-
donating and electron-withdrawing groups on the benzene ring.
Compounds 2g and 2h with the trifluoromethyl group and the
trifluoromethoxy group at the para-position of the terminal
benzene ring, respectively, exhibited much higher cytotoxicity
than those with such groups at other positions. This result showed
that trifluoromethyl and trifluoromethoxy groups were less
effective in the para-position. Moreover, the 3-Cl-4-F analog 2p
This work was supported by a grant from the National Natural
Science Foundation of China (No. 21002065).
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exhibited comparable cytotoxic activity (IC50 = 0.016
the 3-Cl analog 2c (IC50 = 0.015 mol/L) against MDA-MB-231 cell
line. Remarkably, compound 2p showed stronger inhibitory
activity against MCF-7 cell line than 2c (0.001 mol/L vs
4.88 mol/L). The differences resulting from 2q vs 2f and 2p vs
mmol/L) to
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Zhao, Yan-Fang
