Identification of 24-Epibrassinolide in Bee Pollen of the Broad Bean, Vicia faba L.

24-Epibrassinolide (II), a C-24 epimer of naturally occurring brassinolide, was identified, together with brassinolide (I), brassinone (III) and castasterone (IV), from bee pollen of the broad bean, Vicia faba L. by means of the selected ion monitoring technique in gas chromatography-mass spectrometry and the rice-lamina inclination assay.