Antiplatelet activity of BRX-018, (6aS,cis)-malonic acid 3-acetoxy-6a9-bis-(2-methoxycarbonyl-acetoxy)-6,6a,7,11b-tetrahydro-indeno[2,1-c]chromen-10-yl ester methylester.
Brazilin (7,11b-dihydrobenz[b]indeno[1,2-d]pyran-3,6a,9,10 (6H)-tetrol), the major component of Caesalpinia sappan L., was reported to show antiplatelet activity through the inhibition of phospholipase A2 (PLA2) activity and the increase in intracellular free Ca2+ concentration ([Ca2+]i). To search more potential antiplatelet agent, brazilin derivatives were synthesized and examined for their effects on the platelet aggregation. Among those compounds, BRX-018, (6aS,cis)-Malonic acid 3-acetoxy-6a9-bis-(2-methoxycarbonyl-acetoxy)-6,6a,7,11b-tetrahydro-indeno[2,1-c]chromen-10-yl ester methylester, was confirmed as one of the potential antiplatelet agents. In the present study, we investigated the antiplatelet mechanism of BRX-018. BRX-018 inhibited the thrombin-, collagen-, and ADP-induced rat platelet aggregation in a concentration-dependent manner, with IC50 values of 35, 15, and 25 microM, respectively. BRX-018 also inhibited thrombin-induced dense granule secretion, thromboxane A2 (TXA2) synthesis, and [Ca2+]i elevation in platelets. BRX-018 was also found to inhibit A23187-induced [Ca2+]i and aggregation in the presence of apyrase (ADP scavenger) but not in the presence of both apyrase and indomethacin (a specific inhibitor of cyclooxygenase, COX). Although BRX-018 significantly inhibited arachidonic acid (AA)-induced aggregation and TXA2 synthesis, it had no significant inhibitory effect on cyclooxygenase activity in vitro. In contrast, BRX-018 inhibited the activity of purified PLA2. Dixon plot showed that this inhibition was mixed type with an inhibition constant of Ki=23 microM. Taken together, the present study suggests that BRX-018 may be a promising antiplatelet agent and that its antiplatelet activity may be based on the inhibitory mechanisms on TXA2 synthesis in stimulated platelets.
Lee
Gwi-Yeop
GY
College of Pharmacy, Seoul National University, Seoul 151-742, Republic of Korea.
Chang
Tong-Shin
TS
Lee
Ki-Seon
KS
Khil
Lee-Yong
LY
Kim
Deukjoon
D
Chung
Jin-Ho
JH
Kim
Young-Chul
YC
Lee
Byung-Hoon
BH
Moon
Chang-Hyun
CH
Moon
Chang-Kiu
CK
D000244:Adenosine Diphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000494:pharmacology; D001578:Benzopyrans / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects / Q000502:physiology; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000097:blood; D002417:Cattle; D015550:Cell Degranulation / Q000187:drug effects; D003094:Collagen / Q000494:pharmacology; D066298:In Vitro Techniques; D007476:Ionophores / Q000494:pharmacology; D008297:Male; D008314:Malonates / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D010741:Phospholipases A / Q000037:antagonists & inhibitors; D054467:Phospholipases A2; D010975:Platelet Aggregation Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D011451:Prostaglandin-Endoperoxide Synthases / Q000097:blood; D051381:Rats; D017207:Rats, Sprague-Dawley; D013552:Swine; D013917:Thrombin / Q000494:pharmacology; D013929:Thromboxane B2 / Q000097:blood
D001578:Benzopyrans; D007476:Ionophores; D008314:Malonates; D010975:Platelet Aggregation Inhibitors; C502733:malonic acid 3-acetoxy-6a,9-bis(2-methoxycarbonylacetoxy)-6,6a,7,11b-tetrahydroindeno(2,1-c)chromen-10-yl ester methyl ester; D016718:Arachidonic Acid; D000001:Calcimycin; D013929:Thromboxane B2; D000244:Adenosine Diphosphate; D003094:Collagen; D011451:Prostaglandin-Endoperoxide Synthases; D010741:Phospholipases A; D054467:Phospholipases A2; D013917:Thrombin; C044362:brazilin; D002118:Calcium