Polyphenols from Silybum marianum inhibit in vitro the oxidant response of equine neutrophils and myeloperoxidase activity.

This study investigated the inhibitory effects of compounds found in the S. marianum plant extract, silymarin, on the production of harmful reactive oxygen species and an enzyme called myeloperoxidase in horse neutrophils. The results suggested potential applications for these compounds in managing diseases like equine laminitis.

Study Aim and Methodology

• The goal of this study was to examine the effects of certain compounds – quercetin, silybin, taxifolin, and dehydrosilybin – found in an extract called silymarin from the S. marianum plant on the production of reactive oxygen species (ROS) and the release of myeloperoxidase (MPO) enzyme in equine neutrophils (PMNs).
• The researchers tested these compounds in concentrations varying from 100 nm to 100 μm.
• The focus was specifically on PMNs, crucial immune cells that are known to cause harmful oxidative responses in diseases like equine laminitis, an inflammation of the horse’s foot that can lead to lameness.

Research Findings

• All tested compounds showed a dose-dependent inhibitory effect on the production of superoxide anion, a type of ROS, in stimulated PMNs.
• At concentrations as low as 10 μm, dehydrosilybin and quercetin managed to inhibit both superoxide production and MPO release.
• Using two different MPO assay methods (Classical and SIEFED MPO assay), the researchers found that quercetin was the most effective inhibitor of MPO activity, followed by taxifolin, dehydrosilybin, and silybin. In the SIEFED MPO assay, quercetin and taxifolin managed to maintain over 90% inhibition at 10 μm.

Implications of the Research

• This study suggests that the compounds found in silymarin have potential to modulate the harmful oxidation response of PMNs, which contributes to equine laminitis pathogenesis.
• Quercetin and dehydrosilybin, in particular, showed great potential in inhibiting the activation of PMNs, while quercetin and taxifolin were excellent at MPO inhibition.
• However, while these in vitro results are promising, the researchers highlighted the need for further in vivo studies to fully explore the practical use of silymarin compounds in preventing or managing equine laminitis.