Search

Isolation of artemisinin from Artemisia annua L. and its quantification by the HPLC-MS method are considered. Different extraction methods were used for the isolation of artemisinin: maceration, ultrasonic and subcritical CO2-extraction. The component content of the CO2- and hexane extracts was studied by the GC-MS method.

1. The integral enthalpies of dissolution of 100% nitric acid in concentrated aqueous solutions of sulfuric acid\( - \Delta H_{HNO_3 } \) were measured calorimetrically at 298°K; when the concentration of H2SO4 was changed from 90.90 to 99.48% with\(C_{HNO_3 } \) = 0.1 mole/liter,\(\Delta H_{HNO_3 } \) changed from −4.4 to −8.4 kcal/mole. 2. The heat of dilution of the sulfuric acid makes the basic contribution to the value of the integral heat of dissolution of 100% nitric acid in concentrated aqueous solutions of sulfuric acid. 3. The value of the enthalpy of ionization of nitric acid in concentrated aqueous solutions of sulfuric acid (\(\Delta H_{HNO_2 } + _{ + HSO_4 } - \))was determined. The value of\(\Delta H_{HNO_2 } + _{ + HSO_4 } - \) with\(C_{HNO_3 } \) = 0.1 mole/liter decreased from 1.7 kcal/mole in 90.90% sulfuric acid to −0.3 to −0,5 kcal/mole in 99.48% sulfuric acid. 4. In the starting 99.48% and 98.44% sulfuric acid, the values of\(\Delta H_{HNO_2 } + _{ + HSO_4 } - \)were almost independent of the concentration of nitric acid with concentrations of the acid of 0.05 to 1 mole/liter.

1. A study was carried out on the effect of chloro and nitro derivatives of methane on the nature and quantitative indices of the nitration of cellulose by nitric acid. 2. The use of mixtures of HNO3 and an organic solvent gives rapid nitration of cellulose as a consequence both of the high rate of diffusion of these mixtures into the interior of the cellulose fiber and with structural transformations during nitration.

1. The esterification of cellulose is achieved with greatest efficiency relative to reaction time and nitrogen content in the products in a mixture containing 80% HNO3, 15% H3PO4, and 5% H2O. 2. The esterification of cellulose in this mixture proceeds under milder conditions and with a lower heat effect than upon using 100% HNO3 or HNO3-H2SO4, mixtures.