Excess sulfate supply and onion-induced human antiplatelet activity

Awareness is growing of health-promoting functional foods and the use of va rious plants as nutraceuticals. Due to a suite of organosulfur compounds, o nion, and other vegetable Alliums possess a unique antiplatelet effect that may promote cardiovascular health because aggregating platelets can lead t o heart attack and stroke. Investigation of the consequences of S nutrition in onion has primarily focused on levels of S ranging from deficiency to j ust above sufficiency; however, little work has been conducted to examine t he effects of supraoptimal S nutrition on organosulfur-based traits. Four o nion selections were grown in hydroponic solutions with 2, 7, and 12 MM SO4 2- -S in greenhouse experiments during 1995-1996 and 1996-1997. Onion plant s were separated into root, leaf, and bulb portions and analyzed for minera l content. Onion bulb extracts were assayed for in vitro human antiplatelet activity. Bulb and leaf S were not affected by increasing solution culture S, but root S was increased by 98 % when solution culture S was increased from 2 mM to 12 mM. Similar increases in root Ca and Al were detected, sugg esting CaSO4 and AlSO4+ were accumulated in and on the root. No directional change in antiplatelet activity was detected as S was increased from 2 to 12 mM. This lack of significant change in antiplatelet activity with increa sing S levels suggests that modification of this trait by simply increasing S levels may not be feasible in a solution culture environment.