Studies on the Constituents of Digitalis purpurea L. VIII. The Isolation of Neogitostin, a New Cardiotonic Glycoside.

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Of the 17 kinds of unknown cardiotonic glycoside-like substances contained in the seeds of Digitalis purpurea, described in Part II of this series, a glycoside corresponding to substance A-IX was isolated. This substance was not obtained in crystalline form, but by the usual deacetylation of its acetate, monoacetate came as needle crytals of m.p. 249∼252° (Kofler, uncorr.) ; [α]²⁴_D-14.2°±3° ; C₄₄H₆₈O₂₀·H₂O ; negative to Keller-Kiliani reaction, giving carmine red sulfuric acid layer, and positive to Legal and Raymond reactions ; U.V. λ^EtOH_max218mμ (log ε 4.18). These results indicated the substance to be a cardiotonic glycoside. Its hydrolysis with 3.5% hydrochloric acid afforded dianhydrogitoxigenin and the sugar portion was found to be digitalose and glucose by paper partition chromatography. Determination of glucose showed the presence of two moles. Therefore this substance was found to be a new glycoside, an isomer of gitostin which was reported in Part III, and was named neogitostin. Gitostin monoacetate was prepared and compared with neogitostin monoacetate. By paper chromatography for strong polar glycoside portion, a new spot was confirmed between the spots of gitostin and neogitostin, and numbered A-VIII'.