A study of the reaction of pentacyclic triterpenoids with concentrated sulfuric acid
SummaryThe conditions for the reaction of triterpenoids with concentrated sulfuric acid have been studied by the method of mathematical planning, and the optimum conditions for performing this reaction have been found.
Zur spektralphotometrischen Bestimmung von steroiden und triterpenoiden Verbindungen
Sterole, Steroide, Steroidsaponine, Triterpensaponine und deren Aglykone weisen bei der spektralphotometrischen Messung in konzentrierter Schwefelsäure im UV‐Bereich eine Absorptionsbande auf, die zur quantitativen Bestimmung der genannten Verbindungen verwendet werden kann. Die Messung kann mit den freien oder an ein DC‐Sorptionsmittel adsorbierten Verbindungen durchgeführt werden. Die Schwefelsäureumsetzungsprodukte wurden isoliert und analysiert, jedoch konnte der Reaktionsmechanismus noch nicht endgültig aufgeklärt werden.
Ultraviolet spectrophotometric determination of hexoses, pentoses, and uronic acids after their reactions with concentrated sulfuric acid.
Abstract The procedure described is a rapid, nonspecific micromethod for determining free sugars or glycosides in simple solutions. At sugar concentrations of 50 μg/ml, 0.25 ml may be analyzed with an accuracy of about ±2.5% in a single determination. This method is based upon the formation of UV-absorbing furan aldehydes in strong H 2 SO 4 . Although the strong absorption by furan aldehydes reduces interference from nonsugars, any substance absorbing near 300 mμ in H 2 SO 4 will cause some blank. The concentration of H 2 SO 4 is a most important variable because it determines not only the course of the sugar reactions but also the intensity and wavelength of light absorption by the products. A convenient concentration for many sugar analyses is 89% H 2 SO 4 produced by reacting 0.25 ml of sugar solution with 2.00 ml of 95.0% H 2 SO 4 . The molar absorptivity of the 5-hydroxymethyl-2-furaldehyde formed from hexoses increases appreciably with increasing H 2 SO 4 strength from 70 to 93%, thereby increasing the sensitivity of hexose measurements in the higher acid concentrations. Uronic acids react with 89% H 2 SO 4 to give 5-formyl-2-furoic acid as a major product. Ribose and 2-deoxyribose can be determined in 79% H 2 SO 4 , with some advantage in sensitivity to ribose as compared to current procedures which use 95% H 2 SO 4 .