Critical factors of vanillin assay for catechins and proanthocyanidins

Several parameters mostly affecting the precision and accuracy of vanillin assay were reexamined and optimized. The reexamination was performed both by vanillin reaction with catechins and by vanillin reaction with purified proanthocyanidins. In addition to the acid nature and concentration, the reaction time, the temperature, and the vanillin concentration, other factors such as the water content, the presence of interfering substances, and the standard utilized, for both vanillin reaction with catechins and vanillin reaction with proanthocyanidins, were also important. However, the kinetics of the two types of reactions were markedly different. For estimating accurately catechins or proanthocyanidins that exist simultaneously in plant tissues, it is necessary to preliminarily separate them from each other.