Synthesis and bioactivity of 6α- and 6β-hydroxy analogues of castasterone

• Published in: Phytochemistry (Oxford) Vol. 55; no. 2; pp. 121 - 126
• Main Authors: Sung, Gabriel C.Y., Janzen, Loeke, Pharis, Richard P., Back, Thomas G.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 01.09.2000; Elsevier
• Subjects: 6-Hydroxycastasterone; Agronomy. Soil science and plant productions; Biochemistry & Molecular Biology; Biological and medical sciences; Brassinosteroids; Castasterone; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Growth and development; Growth regulators; Indole-3-acetic acid; Life Sciences & Biomedicine; Metabolism; Plant physiology and development; Plant Sciences; Rice leaf lamina inclination assay; Science & Technology; Brassinosteroids; Rice leaf lamina inclination assay; Indole-3-acetic acid; Castasterone; 6-Hydroxycastasterone; BRASSINOSTEROIDS; CONCISE; Rice leaf lamina inclination assay brassinosteroids; BRASSINOLIDE; castasterone; SIDE-CHAIN; 6-hydroxycastasterone; PLANT-GROWTH; indole-3-acetic acid; Steroid; Monocotyledones; Bioassay; Cereal crop; Biological activity; Oryza sativa; Brassinosteroid; Gramineae; Indoleacetic acid; Phytosterol; Angiospermae; Plant growth substance; Spermatophyta; Chemical synthesis
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/S0031-9422(00)00259-4

The reduction of castasterone with sodium in ethanol produced chiefly the known 6α-hydroxy stereoisomer, whereas reduction with sodium borohydride in methanol afforded mainly the novel 6β-epimer. Both compounds showed variable bioactivity through four separate assays via the rice leaf lamina inclination bioassay. However, when treated with an appropriate statistical program to remove outliers, the averaged results clearly indicated that the two 6-hydroxy epimers possess comparable and significant bioactivity, which is, however, lower than that of castasterone or brassinolide. When applied together with 1000 ng of the auxin, indole-3-acetic acid (IAA), the activity of both the 6α and 6β hydroxy epimers was enhanced by ca. one order of magnitude across a wide range of doses.