Effects of garlic preparations on superoxide production by phorbol ester activated granulocytes

Sulfur containing constituents of garlic are considered responsible for conveying the antioxidative properties of garlic preparations. The radical scavenging properties of garlic preparations against oxygen radicals, specifically their ability to inhibit the formation of superoxide anions, were investigated using human granulocytes activated with 10 nM phorbol myristyl acetate (PMA). A garlic powder preparation inhibited the production of superoxide with a calculated IC₅₀ of 390 μg/ml. An 8-10% alliin enriched garlic extract (alliinase inactivated) did not inhibit superoxide production even at concentrations as high as 1000 μg/ml. When the extract was mixed with garlic powder (90% garlic powder, 10% garlic extract), there was a clear inhibition of superoxide production with an IC₅₀ value of 295 μg/ml. An even stronger inhibitory effect could be achieved when garlic powder was added to garlic extract (10% garlic powder, 90% extract, IC₅₀ = 160 μg/ml). These experimental results suggest that the alliin metabolite allicin may be responsible for the oxygen radical scavenging properties of garlic.