VARIABILITY IN BLOOD-PLATELET INHIBITORY ACTIVITY OF ALLIUM (ALLIACEAE) SPECIES ACCESSIONS

In the past 20 yr, the presence of blood platelet inhibitory activity in plant species from the genus Allium has been confirmed by a range of clinical and in vitro investigations. Although a number of Allium species have been identified as possessing antiplatelet properties, little is known of the variability for this trait among accessions in these species. Experiments were conducted to assess variability in antiplatelet activity of 58 Allium (Alliaceae) accessions. Extracts were prepared from a diverse collection of 16 Allium species accessions, 33 cultivated accessions of Allium cepa including standard cultivars, inbred lines, and open-pollinated populations, and nine Allium cepa plant introductions of diverse origin. Platelet inhibitory activity was determined via a platelet aggregation assay with human platelet-rich plasma. Relative in vitro inhibition of platelet aggregation was measured for each accession and control samples, and inhibition constants (IC50) were calculated. Dose-dependent inhibition was observed and measured for each Allium accession. Significant (P < 0.01) IC50 variability was detected among accessions, with the lowest accession IC50 values exhibiting nearly 50-fold greater inhibition of aggregation than the highest accession IC50 values. IC50 variability among Allium cepa accessions was approximate to 12 times less than among Allium species accessions. Results from this investigation demonstrate substantial variability for efficacy of the antiplatelet factor among Allium accessions.