Synthesis, purification, and chemical characterization of 20-dihydro-6-methylprednisone, an isomeric metabolite of methylprednisolone in the horse, for use as an analytical standard.

This research study deals with the synthesis, purification, and chemical characterization of 20-dihydro-6-methylprednisone, which is a metabolic by-product of methylprednisolone in horses. This study was conducted to improve testing standards for methylprednisolone in horse samples to ensure no confusion occurs between the parent substance and its metabolites.

Objective and Background of the Research

• The research aims to create, purify, and chemically examine 20-dihydro-6-methylprednisone, an isomer metabolite of methylprednisolone present in horses.
• Methylprednisolone acetate is a widely used therapeutic medication in equine medicine, recognized by various equine associations, and is commonly given to horses in training.
• Administration of this medication is controlled through the testing of plasma and/or urine in horses, typically via the application of a regulatory threshold in plasma.
• However, there have been issues in distinguishing between the parent methylprednisolone and its isobaric equine metabolites in regular testing procedures. One of these metabolites is 20-dihydro-6-methylprednisone.

Need for the Research

• Given its close structural similarity to methylprednisolone, 20-dihydro-6-methylprednisolone can potentially interfere with the identification and quantification of methylprednisolone in horse racing samples.
• It is therefore necessary to create a research quality reference standard for 20-dihydro-6-methylprednisone to precisely determine its identity and quantity in equine samples after administering methylprednisolone.

Research Methodology and Results

• The researchers synthesized 20-dihydro-6-methylprednisone through a two-step process. First, they acquired 6α‑methylprednisolone as a starting material and reacted it with sodium borohydride at room temperature to produce a reduced compound.
• This reduced compound was then dissolved, added with p-toluenesulfonic acid and molecular sieves, and cooled to complete the reaction. The completed reaction’s progress was monitored by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC).
• The results were promising, leading to the creation of a research quality reference standard for 20-dihydro-6-methylprednisone, opening the way for more accurate testing procedures for methylprednisolone in horses.