Identification of a New Brassinosteroid, Cathasterone, in Cultured Cells ofCatharanthus roseusas a Biosynthetic Precursor of Teasterone

Biological Activities of Biosynthetically-related Congeners of Brassinolide

“…Cathasterone (5) was about 500 times active than 6-oxocampestanol (4), judging from the concentration giving about 50° bending angle. 3-Dehydroteasterone (7) had almost the same activity as teasterone (6) and typhasterol (8). Relative activity was estimated from the concentration at which the bending angle reached 80 0 , the midpoint of the maximum response.…”

“…This indicates that the introduction of a hydroxyl group into the side chain (C-22) should be a prerequisite to exerting the typical brassinosteroid bioactivity. Very recently, we have shown the occurrence of cathasterone (5), and the conversion of cathasterone (5) to teasterone (6) in cultured cells of Catharanthus roseus. 6 ) However conversion of 6-oxocampestanol (4) to cathasterone (5) has not been detected.…”

“…Very recently, we have shown the occurrence of cathasterone (5), and the conversion of cathasterone (5) to teasterone (6) in cultured cells of Catharanthus roseus. 6 ) However conversion of 6-oxocampestanol (4) to cathasterone (5) has not been detected. This is presumably due to the fact that the endogenous level of cathasterone (5) was 1/500 that of 6-oxocampestanol (4) in the cells.…”

“…To test this speculation, we investigated the biological activity of each steroid using two bioassay systems, the rice-lamina inclination testS) and wheat-leaf unrolling test. 9 ) Steroids (3,4,5,6,7,8,11, and 12) tested in this study were synthesized as already reported.S.6.7.10) Compound (13) was prepared by saponification of (22R,23R,24S)-3f3-acetoxy-22,23~epoxy-5tX-ergostan-6-one, 10) and the structure was confirmed by IH-NMR and MS.…”

Studies on Biosynthesis of Brassinosteroids

“…As the results, we identified 22cx-hydroxy-6-oxocampestanol in the cells of C. roseus and named it cathasterone (7).16) Moreover, conversion of 7 to teasterone (8) by the cells was demonstrated using the deuterio-Iabeled compound. 16) No endogeneous occurrence or conversion of the other intermediates to 8 were detected in the cells. Thus, 6-oxocampestanol (6) must be converted to teasterone (8) through cathasterone (7).…”