Design, synthesis and pharmacological evaluation of 6-hydroxy-4-methylquinolin-2(1H)-one derivatives as inotropic agents

Figures & data

Figure 1.  Chemical structure of some PDE inhibitors.

Figure 2.  Multiple alignment of PDE3A (blue) and PDE3B (green). The residues in the active site of PDE3B (within 15å) are highlighted in yellow (generated by Clustal X (1.81)).

Figure 3.  The structure of amide moiety of compounds 4a-m.

Scheme 1.  General procedure for the synthesis of compounds 4a-m.

Table 3.  Docking analysis data of consensus conformers.

Compound	Ki	AGb	Ea	RMSD (å)
4a	1.56e^−7	−9.29	−10.30	56.559
4b	2.69e^−7	−8.96	−10.57	47.462
4c	1.91e^−7	−9.17	−10.96	53.605
4d	1.22e^−7	−9.43	−11.02	53.956
4h	2.52e^−7	−9.00	−11.49	44.320
4i	3.25e^−7	−8.85	−10.78	53.762
4j	3.73e^−8	−10.13	−11.71	53.384
4k	2.21e^−7	−9.08	−10.38	49.086
4l	2.20e^−6	−7.72	−9.02	53.499
4m	7.04e^−7	−8.39	−10.07	45.776
cilostamide	1.88e^−7	−9.18	−10.27	50.001

(ΔG_b: Estimated Free Energy of Bonding, E_d: Final Docking Energy, K_i: Estimated Inhibition Constant and RMSD: root mean square deviation from reference structure).

Table 1.  Effects of the test compounds upon force of contractility of whole atria from reserpine-pretreated rats: comparison with IBMX, amrinone and cilostamide.

Compound	base	1×10^−6	1×10^−5	1×10^−4
IBMX	100 ± 5	134 ± 5	159 ± 7	147 ± 6
Cilostamide	100 ± 1	105 ± 3	112 ± 3	122 ± 3
Amrinone	100 ± 5	107 ± 5	130 ± 6	144 ± 4
4a	100 ± 5	112 ± 6	116 ± 7	127 ± 5
4b	100 ± 6	119 ± 9	125 ± 5	132 ± 2
4c	100 ± 3	107 ± 2	111 ± 3	139 ± 4
4d	100 ± 2	99 ± 6	103 ± 3	149 ± 4
4e	100 ± 4	102 ± 4	96 ± 5	103 ± 3
4l	100 ± 5	97 ± 6	101 ± 7	105 ± 6
4g	100 ± 5	104 ± 7	106 ± 8	103 ± 4
4h	100 ± 4	109 ± 4	123 ± 3	136 ± 5
4i	100 ± 4	109 ± 4	113 ± 5	129 ± 5
4j	100 ± 6	110 ± 5	126 ± 4	165 ± 4
4k	100 ± 7	108 ± 5	115 ± 5	133 ± 3
4l	100 ± 6	105 ± 7	108 ± 4	109 ± 4
4m	100 ± 1	104 ± 3	108 ± 5	113 ± 3

The effect of each concentration was defined by the difference between the contraction, before and after its addition to the bathing fluid, and was expressed as a percent variation in developed tension in respect to the controls. The value of basal force of contraction was 7.07 ± 0.65 mN. Results are as means ± SEM from six atria.

Table 2.  Effects of the test compounds upon frequency rate of whole atria from reserpine-treated rats: comparison with IBMX amrinone and cilostamide.

Compound	base	1×10^−6	1×10^−5	1×10^−4
IBMX	100 ± 3	123 ± 11	166 ± 10	164 ± 11
cilostamide	100 ± 7	122 ± 7	143 ± 5	168 ± 4
amrinone	100 ± 5	104 ± 2	116 ± 6	120 ± 4
4a	100 ± 3	106 ± 10	108 ± 9	98 ± 10
4b	100 ± 4	109 ± 5	112 ± 2	109 ± 2
4c	100 ± 9	110 ± 6	116 ± 6	119 ± 10
4d	100 ± 6	105 ± 6	111 ± 6	122 ± 8
4e	100 ± 6	117 ± 4	121 ± 11	116 ± 6
4l	100 ± 3	100 ± 6	114 ± 7	110 ± 7
4g	100 ± 9	110 ± 4	108 ± 10	112 ± 5
4h	100 ± 7	102 ± 4	110 ± 4	116 ± 9
4i	100 ± 8	104 ± 4	111 ± 7	109 ± 6
4j	100 ± 4	100 ± 8	104 ± 9	115 ± 7
4k	100 ± 6	104 ± 8	108 ± 7	113 ± 8
4l	100 ± 6	105 ± 9	104 ± 6	108 ± 7
4m	100 ± 9	112 ± 5	106 ± 6	110 ± 5

The effect of each concentration of a compound was defined by the difference between the frequency before and after its addition to the bathing fluid, and was expressed as a percent variation in frequency in respect to the controls. The value of basal heart rate was 116  ±  6 bpm. Results are means  ±  SEM from six atria.

Figure 4.  Superimposition of the consensus bonding conformations of cilostamide (black), 4c-d and 4h-m in green stick in the PDE3B active site. (Protein Data Bank: 11 SO)

Figure 5.  Stick (above) and two view of solvent surface (below) of the interacted amino acids with 4j (colored stick with transparent surface). The three proposed regions A, B and C are distinguished by yellow, green and blue respectively.

Figure 6.  Clustal X (1.81) multiple alignment of human PDEs. The amino acids in the regions A, B and C are highlighted by yellow, green and blue respectively.

Figure 7.  Solvent surface (green) of pocket C conserved amino acids having polar and non-polar interactions with consensus structure of compounds 4l (red stick), 4m (green stick), 4j (yellow stick) and 4k (bleu stick). The amide groups of inhibitors have been drawn in contrasted colors.

Figure 8.  Diagram of increase in force of contractility versus estimated inhibition constant (K_i) for compounds 4c-l.

Figure 9.  Concentration-effect curves for inhibition of the activity of PDE3 partially purified from rat ventricle by cilostamide and 4j-m. Results are means ± SEM from four experiments. Data are expressed as percent inhibition of the basal enzyme activity (0.35 ± 0.004 pmol hydrolyzed cAMP/μL of protein/min).

Figure 10.  Diagram of -log IC₅₀ versus -log K_i for compounds 4j-m and cilostamide (cil.).