Precise and accurate assay of pregnenolone and five other neurosteroids in monkey brain tissue by LC–MS/MS

• There is a need for accurate quantitation of neurosteroids from various matrices.
• A highly sensitive and specific LC–MS/MS assay of six neurosteroids is proposed.
• The method proposed allows accurate measurements from Cynomolgus monkey brain tissue.
• The method is based on a Girard T ketone derivatization.

A series of steroids present in the brain have been named “neurosteroids” following the possibility of their role in the central nervous system impairments such as anxiety disorders, depression, premenstrual dysphoric disorder (PMDD), addiction, or even neurodegenerative disorders such as Alzheimer’s and Parkinson’s diseases. Study of their potential role requires a sensitive and accurate assay of their concentration in the monkey brain, the closest model to the human. We have thus developed a robust, precise and accurate liquid chromatography–tandem mass spectrometry method for the assay of pregnenolone, pregnanolone, epipregnanolone, allopregnanolone, epiallopregnanolone, and androsterone in the cynomolgus monkey brain. The extraction method includes a thorough sample cleanup using protein precipitation and phospholipid removal, followed by hexane liquid-liquid extraction and a Girard T ketone-specific derivatization. This method opens the possibility of investigating the potential implication of these six steroids in the most suitable animal model for neurosteroid-related research.