brassinolide [ 24-epibrassinolide,2alpha,3alpha,22alpha,23alpha-tetrahydroxy-24alpha-methyl-B-homo-7-oxa-5alpha-cholestan-6-one,brassinolide, (2alpha,3alpha,5alpha,22S,23S)-isomer,brassinolide, (2alpha,3alpha,5alpha.22R,23R)-isomer ] plant growth promoting steroidal lactone from rape pollen; RN given refers to (2alpha,3alpha,5alpha,22R,23R,24S)-isomer; structure in first source