Biotransformation of ent-kaur-16-ene and ent-trachylobane 7β-acetoxy derivatives by the fungus Gibberella fujikuroi (Fusarium fujikuroi).
Candol A (7β-hydroxy-ent-kaur-16-ene) (6) is efficiently transformed by Gibberella fujikuroi into the gibberellin plant hormones. In this work, the biotransformation of its acetate by this fungus has led to the formation of 7β-acetoxy-ent-kaur-16-en-19-oic acid (3), whose corresponding alcohol is a short-lived intermediate in the biosynthesis of gibberellins and seco-ring ent-kaurenoids in this fungus. Further biotransformation of this compound led to the hydroxylation of the 3β-positions to give 7β-acetoxy-3β-hydroxy-ent-kaur-16-en-19-oic acid (14), followed by a 2β- or 18-hydroxylation of this metabolite. The incubation of epicandicandiol 7β-monoacetate (7β-acetoxy-18-hydroxy-ent-kaur-16-ene) (10) produces also the 19-hydroxylation to form the 18,19 diol (20), which is oxidized to give the corresponding C-18 or C-19 acids. These results indicated that the presence of a 7β-acetoxy group does not inhibit the fungal oxidation of C-19 in 7β-acetoxy-ent-kaur-16-ene, but avoids the ring B contraction that leads to the gibberellins and the 6β-hydroxylation necessary for the formation of seco-ring B ent-kaurenoids. The biotransformation of 7β-acetoxy-ent-trachylobane (trachinol acetate) (27) only led to the formation of 7β-acetoxy-18-hydroxy-ent-trachylobane (33).
Instituto de Productos Naturales y Agrobiología, CSIC, La Laguna, Tenerife, Canary Islands, Spain. bmfraga@ipna.csic.es
Braulio M
BM
Fraga
Carlo
C
Bressa
Victoria
V
González-Vallejo
Pedro
P
González
Ricardo
R
Guillermo
D000085:Acetates / Q000378:metabolism*; D001711:Biotransformation; D005591:Chemical Fractionation / Q000379:methods; D002851:Chromatography, High Pressure Liquid; D003470:Culture Media / Q000378:metabolism / Q000592:standards; D004224:Diterpenes / Q000378:metabolism*; D005670:Fusarium / Q000378:metabolism*; D005875:Gibberellins / Q000096:biosynthesis* / Q000302:isolation & purification; D006900:Hydroxylation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D031365:Sideritis / Q000737:chemistry; D013379:Substrate Specificity
C576725:7beta-acetoxy-18-hydroxy-ent-kaur-16-ene; C576723:7beta-acetoxy-ent-kaur-16-ene; C576726:7beta-acetoxy-ent-trachylobane; D000085:Acetates; D003470:Culture Media; D004224:Diterpenes; D005875:Gibberellins