Anti-complementary activity of Crataegus sinaica.

The 80% and 70% acetone extracts from fruits and leaves of Crataegus sinaica Boiss (Rosaceae) and the ethyl acetate-, butanol-, and water-fractions obtained from these initial extracts as well as the isolated compounds, quercetin (1) (1), hyperoside (quercetin 3-O-galactoside) (2) (2), rutin (quercetin 3-O-rutinoside) (3) (2), vitexin (4) (1), rhamnosylvitexin (5) (3), monoacetylrhamnosylvitexin (6) (3), epicatechin (7) (4), procyanidin B-5 (8) (4), proanthocyanidin A-2 (9) (5), procyanidin B-2 (10) (4), and procyanidin C-1 (11) (4), were tested for their influence on the classical (CP) and alternative (AP) pathways of complement-mediated hemolysis. All extracts and fractions showed a strong anti-complementary effect in a dose-dependent way which was more pronounced on the CP than on the AP. The results indicated that the pure proanthocyanidins were active on the CP. Procyanidin C-1 and proanthocyanidin A-2 were the most active on the CP and also showed activity on AP, whereas the flavonoids isolated were generally less active. However, rutin, showed a strong activity, quercetin and rhamnosylvitexin a moderate activity on the CP. This is the first report on the chemical constituents and complement-modulating activity of C. sinaica and on the occurrence of proanthocyanidin A-2 (9) in hawthorn.