Abstract
The alkaline ethanol precipitation process is investigated as an example of a technique for the removal of tannins extracted from Salviae miltiorrhizae Radix et Rhizoma for the manufacture of Danshen injection. More than 90% of the tannins can be removed. However, the recoveries of danshensu, rosmarinic acid, and salvianolic acid B were less than 60%. Total tannin removal increased as the refrigeration temperature decreased or the amount of NaOH solution added increased. Phenolic compound recoveries increased as refrigeration temperature increased or the amount of NaOH solution added decreased. When operated at a low refrigeration temperature, a relative high separation selectivity can be realized. Phenolic compound losses and tannin removal were mainly caused by precipitation. The formation of phenol salts, whose solubility is small in the mixture of ethanol and water used, is probably the reason for the precipitation. A model considering dissociation equilibrium and dissolution equilibrium was established. Satisfactory correlation results were obtained for phenolic compound recoveries and total tannin removal. Two important parameters in the model, which are the water content and pH value of alkaline supernatant, are suggested to be monitored and controlled to obtain high batch-to-batch consistency.
Highlights
Tannins, polyphenolic compounds with relative large molecular weight, widely exist in medicinal plants and are considered to have antioxidant properties
Concentrated supernatant is the material of the alkaline ethanol precipitation process, as seen in value of the concentrated supernatant was 10.4
The alkaline ethanol precipitation process used in the manufacture of Danshen injection was investigated as an example of tannin removal
Summary
Polyphenolic compounds with relative large molecular weight, widely exist in medicinal plants and are considered to have antioxidant properties. Alkaline ethanol precipitation is a traditional method used in the manufacture of botanical injections, such as Danshen injection and Guanxinning injection. According to the pharmacology studies, phenolic compounds such as danshensu (DSS), protocatechuic aldehyde (PA), rosmarinic acid (RA), and salvianolic acid B (SaB) are considered the active constituents of Danshen injection [22,23,24,25,26]. A mathematical model based on dissociation equilibrium and dissolution equilibrium was established to correlate the experimental data
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