Biochemical SocietyTransactions ( 1 992) 20 357s of 8-hvdroxvcruinolino and its derivatias on human Dlatalet auureaation.
8-Eydroxyquinoline and its derivatives: potential inhibitors of platelet aggregation
Tabla 1.
SBPIXE A. -ED*, RUKHSANA U. SIMJEE, ANWAR E. GILANI*, SALIMUZEAMAN SIDDIQUI, R W I N A SALEEM, SEAREEN FAIZI, BINA SIDDIQUI and
*IC,, is the concentration (mM) producing 50% inhibition of platelet aggregation. Each value represents the mean fS.E.M of four determinations;NA,not active.
SAHfNA FARNAZ.
*Department of Pharmacology, The Aga Khan University, Karachi-74800 and H.E.J Research Institute of Chemistry, University of Karachi, Karachi-75240, Pakistan. In recent years various efforts have focused on the search for inhibitors of platelet aggregation [1,2] which is a crucial factor in the pathogenesis of various ischaemic diseases [ 3,4] We have evaluated several plant derived materials as inhibitors of human blood platelet aggregation [5,61. These studies led us to synthesize and evaluate E-hydroxyquinoline and its derivatives as potential inhibitors of aggregation. Discussions are also extended to the structural activity relationships among the various 8-hydroxyquinoline derivatives against platelet aggregation.
.
The effect of various compounds on platelet aggregation was studied as follows. Blood was obtained from healthy volunteers who had not taken any drug for atleast 7 days. It was collected in siliconized glass tubes containing 3.8% (w/v) trisodium citrate (one-tenth of blood volume). Platelet-rich plasma was obtained by centrifugation at 260g for 15 min. The platelet count was determined by phase contrast microscopy and all aggregation studies were carried out at 37°C with platelet-rich plasma having platelet counts between 2.5 and 3.0 x 108/ml of plasma. Aggregation was monitored with a four channel Hema Tracer aggregometer (Model NKK PAT 4M Bioscience, Japan) using 225111 aliquots of platelet-rich plasma. The final volume was made upto 0.3ml with sodium chloride (0.9% w/v) or test compound and incubated for 1 min before challenge with the aggregating agent. Aggregation was induced with adenosine 5'diphosphate (ADP;2.2pl), arachidonic acid (AA;0.8mM) or platelet-activating factor (PAF;0.8pM) The resulting aggregation was expressed as percent inhibition compared with control at 4 min after challenge. All drugs were tested at three to four different concentrations in duplicate. Statistical differences between control and compound-treated platelet aggregation were determined by Students'ttest.
.
Table 1 and 2 summarize the effects of various 8-hydroxyquinoline and derivatives on platelet aggregation induced by ADP,AA and PAF. Out of 18 analogues;N-buty1,8-butyl;N-pentyl.8pentyl;N-propy1,8-propyloxyquinolinium bromides;8-benzyloxyquinoline, 8-propyloxy quinoline;4-benzyl, 8-benzyloxyquinolinium chloride and 8-hydroxy quinoline in decreasing order of potency specifically inhibited PAFinduced platelet aggregation with IC,, values of 0.22,0.23,0.27,0.37,0.53, 0.57 and 0.68 mM respectively. The relative order of potency of 8-hydroxyquinoline derivatives was different for arachidonic acid-induced platelet aggregation (Table 2). None of the hydroxy-quinoline derivatives, except N-pentyl, b-pentyloxyquinolinium bromide inhibited ADP-induced platelet aggregation.
Effect
8-nyd I-But
n n
0.22 i . O 1 0.22 t . O 1
bral I-9bral I-9rc bral
8-mu 8-9rc
&mu
ahlor 8
4
8
4
ahlor -
Table 2.
0.6 i .03
0.23 i . 0 0 2
p1
0.27 i.014
n n n n n
0.37 t.005 0.53 i . 0 1 8 0.57 t.004
n
n
Effect of 8-hvdroxvuuinoline and its derivatives on arachidonic acid-induced platelet mareaation.
8-eyazoryrpcpolbU O-loqquhol+nr hydraahhridm 8-Crotonoyloqquholln. hydroohhrid 8 - C r o t o n o y l O ~ O l . 0-9-y-m 8-.thoryrlubolhU I-mtyl, 8 - b u t y L a q q U h 0 l h ~ brori& 8 ~ c y l ~ ~ o ~ E 9 a t y l . 8-p.ntyloxyqubolhium braidm
0.25 0.25 0.25 0.37 0.42 0.43 0.56
i0.02 tO 0 1 fO.O1
.
tO.03 i0.02 iO.01
i0.004
0 . 8 3 t0.005 0.85 10.02
The above data demonstrates differential inhibition of platelet aggregation induced by endogenous aggregating agents by a variety of 8-hydroxyquinoline derivatives. Substitution of 8-hydroxyquinoline with groups; N-methyl, 8methoxy: N-ethyl, 8-ethoxyquinolinium iodide: 8-benzenesulphonyloxy-quinoline, 8-cinnamoyl oxyquinoline,E-croto-noyloxyquinoline, 8-allyloxyquinoline and 8-methoxyquinoline led to complete loss of inhibitory activity against PAF-induced aggregation. Whereas 8-cinnamoyloxyquinoline, 8-crotonoyloxyquinoline and 8ethoxyquino-line selectively inhibited arachidonic acid-induced platelet aggregation. Although extensive conclusions could not be made with only the present results, the observations are considered important for the designing of follow up research in the investigation of selective anti-PAF compounds and inhibitors of arachidonic acid induced platelet aggregation. 1. 2. 3. 4. 5.
6.
Thomas, E . W . , Nishizawa, E.E., Zimmermann, D.C.6 William, D.J. (1985) J. Med. Chem. 28, 442-446. Gachalyi, B., Tihanyi, K., Vas,A., Nadas, B.& Kaldor, A. (1986) Thromb. Res. 42, 113-114. Verstraete, M.D. (1976) Am. J. Med. 61, 897-914. Weiss, H.J. (1978) N. Engl. J. Med. 298, 1403-1406. Saeed, S.A., Simjee, R.U., Bhatti, M.K. & Atta-ur-Rahman. (1990) in Frontiers in Natural Products Chemistry (Atta-ur-Rahman ed), pp. 755-761, Shamim press, Karachi. Rahman, N.N., Simjee, R.U., Faizi, S., Atta-ur-Rahman, Ali.S.S., Mahmood. F. & Saeed, S.A. (1991) Pak. J. Pharmaceut. Sci. 4, 35-42.
8-Eydroxyquinoline and its derivatives: potential inhibitors of platelet aggregation
Tabla 1.
SBPIXE A. -ED*, RUKHSANA U. SIMJEE, ANWAR E. GILANI*, SALIMUZEAMAN SIDDIQUI, R W I N A SALEEM, SEAREEN FAIZI, BINA SIDDIQUI and
*IC,, is the concentration (mM) producing 50% inhibition of platelet aggregation. Each value represents the mean fS.E.M of four determinations;NA,not active.
SAHfNA FARNAZ.
*Department of Pharmacology, The Aga Khan University, Karachi-74800 and H.E.J Research Institute of Chemistry, University of Karachi, Karachi-75240, Pakistan. In recent years various efforts have focused on the search for inhibitors of platelet aggregation [1,2] which is a crucial factor in the pathogenesis of various ischaemic diseases [ 3,4] We have evaluated several plant derived materials as inhibitors of human blood platelet aggregation [5,61. These studies led us to synthesize and evaluate E-hydroxyquinoline and its derivatives as potential inhibitors of aggregation. Discussions are also extended to the structural activity relationships among the various 8-hydroxyquinoline derivatives against platelet aggregation.
.
The effect of various compounds on platelet aggregation was studied as follows. Blood was obtained from healthy volunteers who had not taken any drug for atleast 7 days. It was collected in siliconized glass tubes containing 3.8% (w/v) trisodium citrate (one-tenth of blood volume). Platelet-rich plasma was obtained by centrifugation at 260g for 15 min. The platelet count was determined by phase contrast microscopy and all aggregation studies were carried out at 37°C with platelet-rich plasma having platelet counts between 2.5 and 3.0 x 108/ml of plasma. Aggregation was monitored with a four channel Hema Tracer aggregometer (Model NKK PAT 4M Bioscience, Japan) using 225111 aliquots of platelet-rich plasma. The final volume was made upto 0.3ml with sodium chloride (0.9% w/v) or test compound and incubated for 1 min before challenge with the aggregating agent. Aggregation was induced with adenosine 5'diphosphate (ADP;2.2pl), arachidonic acid (AA;0.8mM) or platelet-activating factor (PAF;0.8pM) The resulting aggregation was expressed as percent inhibition compared with control at 4 min after challenge. All drugs were tested at three to four different concentrations in duplicate. Statistical differences between control and compound-treated platelet aggregation were determined by Students'ttest.
.
Table 1 and 2 summarize the effects of various 8-hydroxyquinoline and derivatives on platelet aggregation induced by ADP,AA and PAF. Out of 18 analogues;N-buty1,8-butyl;N-pentyl.8pentyl;N-propy1,8-propyloxyquinolinium bromides;8-benzyloxyquinoline, 8-propyloxy quinoline;4-benzyl, 8-benzyloxyquinolinium chloride and 8-hydroxy quinoline in decreasing order of potency specifically inhibited PAFinduced platelet aggregation with IC,, values of 0.22,0.23,0.27,0.37,0.53, 0.57 and 0.68 mM respectively. The relative order of potency of 8-hydroxyquinoline derivatives was different for arachidonic acid-induced platelet aggregation (Table 2). None of the hydroxy-quinoline derivatives, except N-pentyl, b-pentyloxyquinolinium bromide inhibited ADP-induced platelet aggregation.
Effect
8-nyd I-But
n n
0.22 i . O 1 0.22 t . O 1
bral I-9bral I-9rc bral
8-mu 8-9rc
&mu
ahlor 8
4
8
4
ahlor -
Table 2.
0.6 i .03
0.23 i . 0 0 2
p1
0.27 i.014
n n n n n
0.37 t.005 0.53 i . 0 1 8 0.57 t.004
n
n
Effect of 8-hvdroxvuuinoline and its derivatives on arachidonic acid-induced platelet mareaation.
8-eyazoryrpcpolbU O-loqquhol+nr hydraahhridm 8-Crotonoyloqquholln. hydroohhrid 8 - C r o t o n o y l O ~ O l . 0-9-y-m 8-.thoryrlubolhU I-mtyl, 8 - b u t y L a q q U h 0 l h ~ brori& 8 ~ c y l ~ ~ o ~ E 9 a t y l . 8-p.ntyloxyqubolhium braidm
0.25 0.25 0.25 0.37 0.42 0.43 0.56
i0.02 tO 0 1 fO.O1
.
tO.03 i0.02 iO.01
i0.004
0 . 8 3 t0.005 0.85 10.02
The above data demonstrates differential inhibition of platelet aggregation induced by endogenous aggregating agents by a variety of 8-hydroxyquinoline derivatives. Substitution of 8-hydroxyquinoline with groups; N-methyl, 8methoxy: N-ethyl, 8-ethoxyquinolinium iodide: 8-benzenesulphonyloxy-quinoline, 8-cinnamoyl oxyquinoline,E-croto-noyloxyquinoline, 8-allyloxyquinoline and 8-methoxyquinoline led to complete loss of inhibitory activity against PAF-induced aggregation. Whereas 8-cinnamoyloxyquinoline, 8-crotonoyloxyquinoline and 8ethoxyquino-line selectively inhibited arachidonic acid-induced platelet aggregation. Although extensive conclusions could not be made with only the present results, the observations are considered important for the designing of follow up research in the investigation of selective anti-PAF compounds and inhibitors of arachidonic acid induced platelet aggregation. 1. 2. 3. 4. 5.
6.
Thomas, E . W . , Nishizawa, E.E., Zimmermann, D.C.6 William, D.J. (1985) J. Med. Chem. 28, 442-446. Gachalyi, B., Tihanyi, K., Vas,A., Nadas, B.& Kaldor, A. (1986) Thromb. Res. 42, 113-114. Verstraete, M.D. (1976) Am. J. Med. 61, 897-914. Weiss, H.J. (1978) N. Engl. J. Med. 298, 1403-1406. Saeed, S.A., Simjee, R.U., Bhatti, M.K. & Atta-ur-Rahman. (1990) in Frontiers in Natural Products Chemistry (Atta-ur-Rahman ed), pp. 755-761, Shamim press, Karachi. Rahman, N.N., Simjee, R.U., Faizi, S., Atta-ur-Rahman, Ali.S.S., Mahmood. F. & Saeed, S.A. (1991) Pak. J. Pharmaceut. Sci. 4, 35-42.
