Studies on biochemical transformation of plant steroids. Part I. Biochemical interconversion of the Δ25(27)- and the saturated 25D-or 25L-sapogenins

Abstract

Some Δ²⁵⁽²⁷⁾-sapogenins were isolated from Hosta kiyosumiensis F. Maek. together with the corresponding saturated sapogenins: i.e., Δ²⁵⁽²⁷⁾-tigogenin, Δ²⁵⁽²⁷⁾-gitogenin, Δ²⁵⁽²⁷⁾-manogenin, and Δ²⁵⁽²⁷⁾-9(11)-dehydromanogenin. [27-¹⁴C]-Δ²⁵⁽²⁷⁾-Gitogenin, [27-¹⁴C]-gitogenin ([27-¹⁴C]-neogitogenin), and [27-¹⁴C]-25-hydroxygitogenin were synthesised from Δ²⁵⁽²⁷⁾-gitogenin. Each labelled sapogenin thus obtained was incubated with the homogenate from the epigeous part of Hosta kiyosumiensis at 37° for 6–7 hr. The results from these experiments indicate the following interconversion between the unsaturated and the saturated sapogenins occurring by the action of the plant enzyme: Δ²⁵⁽²⁷⁾-gitogenin ⇄ gitogenin and/or neogitogenin. It was thus shown that the Δ²⁵⁽²⁷⁾-sapogenin is not an artifact but a naturally occurring product. We suggest three classifications of the naturally occurring spirostans: 25D- or R-sapogenin (iso); 25L- or S-sapogenin (neo); 25,27-unsaturated sapogenin.