Influence of Lyophilisation and Oven-Drying on Extraction Yield of Oregonin from European Black Alder (Alnus glutinosa (L.) Gaertn.) Bark

Oregonin ((5S)-1,7-bis(3,4-dihydroxyphenyl)-5-(β-D-xylopyranosyloxy)-heptan-3-one) is the first discovered and reported naturally occurring diarylheptanoid glycoside. It exhibits high biological activity, but it is also the compound of interest because of its ability to form reddish-orange and reddish-brown colours. In this research, European black alder (Alnus glutinosa (L.) Gaertn.) bark was separately subjected to lyophilisation and oven-drying before oregonin extraction with two different solvents. According to the results, methanol has proven to be more suitable as solvent compared to deionised water for oregonin extraction by maceration from black alder bark matrix regardless of the dehydration method. Accordingly, in the case of methanol, much higher yields of oregonin were obtained after lyophilisation, than after oven-drying. Furthermore, extraction by deionised water produced slightly higher yield of oregonin after oven-drying than after lyophilisation, as opposed to methanol. However, in much lower oregonin concentrations. Among other things, oregonin propensity to degradation at elevated temperature could probably be applied for improving and facilitating alder wood hydrothermal processing by minimizing uneven discolouration.