The effect of simulated gastro-intestinal conditions on the antioxidant activity of herbal preparations made from native Irish hawthorn

The ability of plant phenolics to act as free radical scavengers has led to increased interest in their ability to act as antioxidants in vivo. Polyphenolic compounds, commonly present in hawthorn (Crataegus spp.), as well as herbal preparations of hawthorn were examined using the TEAC and DPPH assays to determine their antioxidant activity. Initial results have shown the standards to be efficient free radical scavengers. Quercetin dihydrate was found to be the most effective with ability to inhibit up to 87.9% of the DPPH radical and over 90% of the ABTS radical. The herbal preparations tested showed infusions of hawthorn leaf and flower to be almost as effective with 82.9% of DPPH radicals and 87.9% of ABTS radicals being inhibited. Most hawthorn preparations are consumed orally, however, and the effect of gastro-intestinal conditions on the ability of phenolic compounds to scavenge free radicals is not taken into account. Both, the standards and crude herbal preparations were exposed to simulated gastro-intestinal conditions to determine their effect, if any, on antioxidant activity. This study indicates that the scavenging activity of hawthorn phenolics may be reduced by the digestive process. The scavenging activity of Luteolin against ABTS radicals was found to have decreased by 67.8%. The effect of the process on the herbal preparations varied with the ability of the berry decoction to scavenge DPPH decreasing by 43% while the scavenging of the leaf and flower infusion decreased by only 1.94%.