Effect of simulated foregut digestion on the antioxidant capacity of plants naturally consumed by horses

Abstract

Herbal medicine has impacted veterinary medicine including equine practice. Many of the postulated health-promoting effects of medicinal plants are discussed in the context of their antioxidative properties, but different factors such as digestion can have an effect on the activities of compounds. The effect of simulated foregut digestion conditions on the antioxidant capacity of seven different plants commonly consumed by horses and/or present in their complementary diet was investigated. Plants included willow tree (Salix cinerea), purple willow (Salix purpurea), willow regrowth (new sprouts growing at the foot of willows (Salix cinerea), oak tree (Quercus spp.), meadowsweet (Filipendula ulmaria spp.), hawthorn (Crataegus), and blackthorn (Prunus spinosa). Aqueous extracts obtained from the bark and from the leaves were compared. Two methods, Oxygen Radical Absorbance Capacity (ORAC) and Trolox equivalent antioxidant capacity (TEAC) using 2,2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assays, were used to measure the total antioxidant capacity (TAC) of the extracts before and after the digestion process. The results showed that the TAC of all studied plant extracts decreased (P < 0.05) following the digestion process indicating that the active compounds present in the extracts were degraded. In fact, a decrease in TAC values of up to 80 % and 83 % was observed using TEAC and ORAC assays respectively. Such a drop in the TAC must be taken into account when considering the antioxidative efficiency of plants consumed by animals.