Aqueous extracts of Ocimum basilicum L. (sweet basil) decrease platelet aggregation induced by ADP and thrombin in vitro and rats arterio - venous shunt thrombosis in vivo

Objective: To study the effects of aqueous extract of Ocimum basiticum L (OBL) on platelet aggregation and experimental thrombus. Methods: Platelet aggregation induced by ADP (5 mu M) and thrombin (4 Ul), and thrombus weight in an arteriovenous thrombosis (AVT) model were tested after 2 weeks treatment with 15, 75 and 375 mg/kg OBL orally in rats, compared to 8.8 mg/kg/day aspirin. AVT was also tested 2 h after 75 mg/kg OBL orally, after 3 and 7 days treatment, and one, three and seven days after the end of a two-week treatment. Analysis was done by ANOVA followed by protected t-tests (Tukey). Results: OBL (15, 75, 375 mg/Kg) dose-dependently inhibits platelet aggregation by ADP and thrombin, with 75 mg/kg/day having approximately the same effect as 8.8 mg/kg/day aspirin. ADP induced aggregation reached 45%, 28% and 18% for OBL, respectively, 15, 75, 375 mg/kg compared to 71% for control and 27% for aspirin (all p < 0.01 except aspirin vs. OBL 75 mg/kg/dayp=0.7). Thrombin-induced aggregation reached 33%, 22%, 21% for OBL, respectively, 15, 75, 375 mg/kg compared to 67% for control and 48% for aspirin (all p < 0.01 except OBL75 vs. OBL375 mg/kg/day, p = 1.0). Compared to a control thrombus weight of 48.1 mg (SD 4.9), thrombus weight was 29.4 (3.3), 19.0 (1.9) and 12.3 (1.7) after treatment for 2 weeks with 15, 75 and 375 mg/kg OBL, respectively, and 27.4 (5.3) after 8.8 mg/kg aspirin (all p < 0.001 except aspirin vs. OBL 75 mg/kg/day p = 1.0). Maximum effect of OBL was reached after one week's treatment. The effect subsided between 3 and 7 days. Conclusion: OBL possesses an inhibitory effect on platelet aggregation induced by ADP and thrombin, that is dose-dependent and results in an anti-thrombotic effect in vivo which develops progressively over 7 days and disappears over 3-7 days. The active ingredient now needs to be characterized. (c) 2006 Elsevier Ltd. AR rights reserved.