Twenty-three carbazole alkaloids, murrayafoline-A (1), 3-methyl-carbaz
ole (2), murrayanine (3), mukoeic acid (4), murrayazolidine (5), bicyc
lomahanimbine (6), murrayamine-A (10), -D (13), -E (14), -F (15), -I (
16), -J (17), -K (18), -M (7), -N (19), murrayazoline (8), girinimbine
(9), mahanimbine (11), (+)-mahanine (12), isomahanine (20), murrafoli
ne-A (21), -B (22) and bismurrayafoline-A (23) and a triterpenoid, fri
edelin together with p-sitosterol were isolated and characterized from
the leaves and root bark of M. euchrestifolia. Their structures were
elucidated by spectroscopic analyses and/or direct comparison with aut
hentic samples. The isolated carbazole alkaloids 1-12 were subjected t
o evaluation for antiplatelet aggregation activity and vasorelaxing ef
fect. Most of the isolated carbazole alkaloids showed potent inhibitor
y, activity on rabbit platelet aggregation induced by arachidonic acid
(100 mu M), collagen (10 mu g/mL) and PAF (2 ng/mL). Only murrayafoli
ne-A (1) showed inhibition of tonic contraction induced by K+ (80 mM)
+ Ca2+ (1.9 mM). Compounds 1, 7 and 12 showed the promotion of the pla
telet aggregation or lysis at high dose. In contrast, they also exhibi
ted antiplatelet aggregation activity at low concentration. This resul
t could continue the philosophy of use in Chinese medicine, in that th
e dose variation in a prescription produced different, promotive or in
hibitive, effects on therapy. (C) 1998 John Wiley & Sons, Ltd.