High recovery of stilbene glucosides by acetone extraction of fresh inner bark of Norway spruce

Stilbenes are plant polyphenols that have shown beneficial pharmacological activities in a variety of diseases. The considerable amount of stilbene glucosides in spruce inner bark encouraged us to develop a straightforward and simple method of extraction with high recovery and yield. Stilbene glucosides from fresh inner bark of Norway spruce were extracted in one simple step with acetone at 20 °C. After three weeks of soaking in acetone, the extracts were dried and the composition was determined by GC-FID using a short and a long column (HP-5) and GC-MS (HP-1). The amount of the extracted compounds was also compared with a similar extract from air dried inner bark samples. The extracts from the fresh sample contained 30-50% of stilbene glucosides and the average yield [0.185 g extract/g bark] was as good as or slightly better than in previously reported works. However, no drying, milling, or sequential extractions with different solvents in elevated temperatures were needed. Moreover, this study revealed that the drying process can decrease the amount of extractable stilbenes significantly. Therefore, this method can be considered as an alternative for preparative isolation of stilbene glucosides, especially isorhapontin and astringin from inner bark of Norway spruce.