Extraction of (+)-catechin from oak ( Quercus spp.) bark: Optimization of pretreatment and extraction conditions.

Oaks ( Quercus L., Fagaceae ) are a widespread tree species worldwide, and in Hungary they account for nearly 30 % of the forests. Their wood is valuable, but their bark is considered as a by-product. Oak bark, available in large quantities but with no dedicated use, contains a significant amount of valuable extractives. Its (+)-catechin content is around 1 %. (+)-Catechin is mostly used for food industry, medicine and many other industrial purposes, representing a significant financial value. The aim of the present research was to compare the (+)-catechin concentrations in the bark of the most important oak species found in Hungary and to optimize sample pretreatment (conservation) and extraction methods in order to achieve fast and efficient extraction. From these species the highest concentrations were measured in Q. robur and Q. robur ssp. slavonica (8-12 mg (+)-catechin/g dry bark). The combination of microwave sample pretreatment and microwave assisted extraction proved to be the most time- and cost-effective method. The utilization of the extracted bark powder for energetic purposes requires further investigations.
Competing Interests: The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:T. Hofmann reports financial support was provided by National, Research, Development and Innovation Office. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(© 2023 The Authors.)