Research on the Decarboxylation Conversion System of Cannabidiol Acid in Industrial Cannabis
Industrial hemp (Cannabis sativa L.), also known as Chinese hemp or fire hemp, is mostly dioecious and has a long history of cultivation and use in China. It is an annual herbaceous plant of the Cannabis genus in the Cannabis family and is a traditional economic crop in China. So far, plant cannabinoids and other plant-based active substances, including terpenes, phenols, lipids, alkaloids, etc., have been found in industrial hemp. Among these ingredients, the medicinal non psychoactive substance cannabidiol (CBD) in plant cannabinoids (see Figure 1) has been studied the most prominently, with good effects in the treatment of epilepsy, autism spectrum disorders, anxiety, depression, and anti-tumor therapy.
There are two main methods for producing CBD from industrial hemp: solvent extraction and supercritical CO2 fluid extraction. At present, the conversion process of CBD in industrial hemp plants through cannabidiol acid (CBDA) has been successfully revealed, but there are few reports on the corresponding conversion theory. It is impossible to rely on theoretical means to guide the efficient conversion of CBDA in industrial hemp to CBD, which inevitably leads to resource waste of plant components in the CBD production process.
This study used the group contribution method and Watson formula to calculate the basic thermodynamic parameters of each component in the thermal decarboxylation conversion of CBDA to CBD in industrial hemp. Based on the classical thermodynamic formula, the Gibbs free energy of the conversion of CBDA to CBD at atmospheric pressure and temperature of 40-140 ℃ in industrial hemp was determined, and the reaction equilibrium constant and equilibrium conversion rate were obtained. The possibility of spontaneous decarboxylation conversion of CBDA in industrial hemp under conventional conditions was judged. Research on the effects of factors such as temperature and moisture content of flowers and leaves on the conversion of CBDA to CBD content in industrial hemp, determining the kinetic function model of CBDA decarboxylation in industrial hemp, and calculating the conversion activation energy, providing theoretical and experimental support for the selection of conditions for obtaining high CBD content in industrial hemp industrialization processing.

This study calculated the basic thermodynamic parameters of each component in the CBDA decarboxylation conversion system in industrial hemp using the group contribution method and Watson formula. According to the classical thermodynamic formula, at temperatures between 40-140 ℃, as the temperature increases, the reaction image values become more negative. The conversion reaction can spontaneously occur within the temperature range of 40-140 ℃, and the trend of decarboxylation conversion increases with the increase of decarboxylation temperature. Based on the image values at different temperatures, the CBDA conversion image and α were calculated, theoretically indicating that the reaction can undergo sufficient conversion.
To prevent the conversion product CBD from losing weight due to high-temperature degradation, the highest temperature for decarboxylation reaction should not exceed 156.24 ℃ as determined by thermogravimetric analysis. Through investigating the influence of water content of industrial hemp and environmental temperature on the conversion and decarboxylation of CBDA to CBD, it was found that with the increase of environmental temperature and water content in industrial Fried Dough Twists leaves, the conversion rate of CB-DA decarboxylation to CBD in industrial hemp increased, indicating that on the premise of ensuring that CBD will not be degraded and lose weight, properly increasing the water content and temperature in industrial Fried Dough Twists leaves can improve the process of CBD decarboxylation in industrial hemp. According to the experimental results and comparison with eight common decomposition kinetic function models, the most probable model of CBD thermal decarboxylation in industrial Fried Dough Twists leaves was determined to be F1 model, and the activation energy E of industrial Fried Dough Twists leaves decarboxylation conversion was calculated to be 83.77kJ/mol respectively through Arrhrnius equation. The theory revealed the minimum energy required for 1mol of CBDA normal molecules to be converted into reactive active molecules.