Cat’s Claw Oxindole Alkaloid Isomerization Induced by Common Extraction Methods

Cat’s claw oxindole alkaloids are prone to isomerization in aqueous solution. However, studies on their behavior in extraction processes are scarce. This paper addressed the issue by considering five commonly used extraction processes. Unlike dynamic maceration (DM) and ultrasound-assisted extraction, substantial isomerization was induced by static maceration, turbo-extraction and reflux extraction. After heating under reflux in DM, the kinetic order of isomerization was established and equations were fitted successfully using a four-parameter Weibull model (R > 0.999). Different isomerization rates and equilibrium constants were verified, revealing a possible matrix effect on alkaloid isomerization.