The choice of the extraction process, solvents and operational
conditions is always conditioned by the required extract
quality and by other particular specifications, like extraction yield and presence of undesired compounds. Conventional solid–liquid
extraction with water, alcohols and/or acidified alcohols is usually
employed for extraction of procyanidins. However, and because
natural products usually contain a wide variety of low and high
molecular weight phenolic compounds (and their complexes), natural
extracts from these materials will always contain a mixture
of different classes of these phenolic substances, depending on the
chosen extraction solvent and on the particular employed operational
conditions. Usually, additional steps are then required in
order to purify/concentrate the desired compounds and to remove
the undesired phenolic and other non-phenolic substances.