Abstract
This report describes a rapid and selective method of sample preparation for the determination of brassinosteroids in samples of biological origin, based on solid-phase extraction. The steroids, brassinolide and castasterone, which possess a C-22, 23-diol group, were retained as their cyclic boronates formed on immobilized phenylboronic acid gel in a mixed solvent of pyridine and acetonitrile. After removal of impurities in the sample, parent brassinosteroids could easily be released from their boronates by a mixed solution of hydrogen peroxide and acetonitrile. The phenylboronic acid phase was shown to have a high affinity for brassinosteroids containing a C-22, 23-diol. The present method is a first example for the selective extraction of brassinosteroids in a biological sample using immobilized phenylboronic acid gel.
