Elevated Antiplatelet Activity Induced by Extracts from Onion Umbels

Epidemiological data suggest that onion (Allium cepa L.) consumption promotes cardiovascular health (Kendler, 1987). Among the salutary effects of Allium vegetables on the cardiovascular system is the inhibition of platelet activity (Ariga et al., 1981; Goldman et al., 1995; Kiesewetter et al., 1991; Makheja et al., 1980), thus reducing clotting time and promoting blood circulation. To my knowledge, bulbs are the only onion plant organ so far examined for antiplatelet activity. Observation of high levels of pungency in onion umbels during rouging of our onion breeding nursery led me to the hypothesis that high concentrations of organosulfur compounds may be present in onion umbels, therefore imparting greater antiplatelet activity. In the present report, I compared inducement of human antiplatelet activity by onion bulbs and umbels. Seed of the inbred line W420B was sown in the center two rows of bordered four-row plots 4.2 m long at four locations: two in Randolph, Wis., and one each in Lake Labish, Ore., and Brooks, Ore., in 1994. Plots were arranged in a randomized complete block design with four replications in Wisconsin and two replications in Oregon. At maturity, onion bulbs were harvested from the middle two rows of each plot, placed in mesh bags, and stored at 4C . An equal volume of tissue from five onion bulbs was excised with a longitudinal slice from each bulb, and homogenized via standard methods in a mechanical juicer. In this way, a transverse section (including top and bottom of bulb) was sampled from each bulb. Bulb tissue was juiced and centrifuged immediately following excision and the resulting supernatant was frozen at –80C. All bulb tissue samples were excised, juiced, and centrifuged for identical durations. Following vernalization, a sample of stored W420B bulbs was planted in six rows, each 4 m long at a spacing of 60 cm between rows in an onion nursery at the Asgrow Seed Co. in