Abstract
Vanillin and sulfuric acid used in a colorimetric assay of ginsenosides (saponins in the root of Panax ginseng C. A. Meyer) were directly applied to several sapo-genins (Tables II and III), and their glycosides, and related compounds (Table I) without any modifications of the reaction conditions. Steroidal sapogenins with or without double bond at C–5, triterpenoid sapogenins, sterols and bile acids which have an OH group at their C–3 position, gave chromogens with the reagents. Cholanic acid (no OH group) and corticosteroids (?
4
–3–keto and 20,21–ketol) did not give the typical red-purple color after the treatment with the reagents. When a C–3–OH group of a sapogenin was free, bound with sugar, or estenfied with acetic acid, its sapogenin moiety showed almost identical absorption properties after the color reaction. Every spirostane sapogenin tested gave two visible absorption maxima, one of them located around the 455 to 460 nm region. Spirostane–2, 3–diol and spirostane–1,2,3–triol showed atypical absorption spectra. Triterpenoid sapogenins with the C–23–OH group had an additional peak located around the 460 to 485 nm region. An OH group and a carbon-carbon double bond in rings B, C and D also seemed to affect the absorption properties due to C–3–OH in some cases.
