The in vitro effects of verbascoside on human platelet aggregation

Preliminary in vitro and animal studies have shown that verbascoside, a phenolic compound, may have several favourable biological activities, including an influence on endothelial function and on platelet aggregation. We sought to evaluate the effects of verbascoside, biotechnologically produced from plant cell cultures, on human platelet aggregation (PA). The blood from 40 aspirin-na < ve volunteers with at least one cardiovascular risk factor was preincubated in vitro with verbascoside (1 and 2 mg/dL) and aspirin (100 mu M). The blood from 20 patients with a prior diagnosis of coronary heart disease who were chronically assuming aspirin was preincubated in vitro with verbascoside (1 and 2 mg/dL). PA is measured with a light transmission aggregometry and multiplate analyzer. As compared to reference, preincubation with verbascoside resulted in a significant inhibition of adenosine diphosphate (ADP) and arachidonic acid (AA)-induced PA (p < 0.01 for both). Verbascoside 2 mg/dL did not show a stronger effect as compared to verbascoside 1 mg/dL (p = 0.4). As expected, the in vitro addition of aspirin reduced AA induced PA (p < 0.01), but not that induced by ADP (p = 0.5). The addition of verbascoside to the blood of aspirin-treated patients did not improve the values of PA after AA stimulus (p = 0.8), whereas it ensured a stronger inhibition after ADP stimulus (p < 0.01). Verbascoside in vitro affects PA by mildly inhibiting aggregation, triggered both by ADP and AA. These preliminary data, while intriguing, require confirmation in subjects receiving verbascoside orally in order to determine whether these findings are clinically relevant.