Antimicrobial Activity and Thermal Degradation Kinetics of Total Alkaloids from Berberis poireti
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Abstract:
Total alkaloids from Berberis poireti were extracted by the semi-bionic method. The stability of total alkaloids, antimicrobial activity and the thermal degradation kinetics were investigated through examining the effects of natural light, ultraviolet light, temperature, and pH, and tracking the changes in the content of total alkaloids in Berberis poireti and difference between the inside and outside inhibitory zone (Dd). The results showed that the total alkaloids extracted from Berberis poiretii exhibited inhibitory effects on Gram-positive and Gram-negative bacteria. The stability and antimicrobial activity were significantly influenced by temperature and pH, whilst natural lighting for 30 days and ultraviolet lighting for 3 hours did not exhibit such effects. The rate of thermal degradation for total alkaloids increased with increasing temperature. The antimicrobial activity decreased with an increase of temperature, and was completely lost at 90 ℃ for 20 hours or 100 ℃ for 4 hours. The antimicrobial activity of the total alkaloids was largely enhanced after the acidic-alkaline treatment, and, was retained after the treatment at 80 ℃ for 48 h. The research showed that the stability of total alkaloids, antimicrobial activity were greatly affected by temperature and pH, with acidification increasing the (D-d) by 13~18 mm, alkalization increasing by 3~5 mm after the acidification and, respectively. The acidification and alkalization could also enhance the thermal stability and led to D-d as 20~22 mm and 5~9 mm. The thermal degradation of total alkaloids conformed to the first order dynamic process with the activation energy (Ea) is 58.8 KJ/mol. The half-life (t1/2) was shortened with an increase of temperature. This study preliminarily revealed the antibacterial activity and thermal degradation kinetics of total alkaloids under different conditions, and provided a theoretical basis and reference for the extraction and processing of alkaloids such as berberine.
