Hot-water extracts from the inner bark of Norway spruce with immunomodulating activities

The inner bark of Norway spruce (Picea abies) was sequentially extracted with hot water at 100 °C, 140 °C and 160 °C. The hot-water extracts (IB 100 °C, IB 140 °C and IB 160 °C) contained pectic polysaccharides and showed immunostimulating activities. Structural analyses of their carbohydrate content, including glycosidic linkage analyses, revealed the presence of pectins with a large rhamnogalacturonan RG-I domain ramified with highly-branched arabinans. IB 100 °C also contained a large amount of terminal glucosyl residues, indicating the presence of highly substituted polymers. IB 160 °C was mainly composed of starch. The hot-water extracts were tested for two biological activities, namely complement fixation and macrophage stimulation. IB 100 °C exhibited the highest complement fixation activity, with a 1.7-times higher ICH50 than the control pectin, while IB 140 °C and IB 160 °C gave similar ICH50 values as the control. Macrophages were stimulated by IB 100 °C and IB 140 °C in a dose-dependent manner, but not by IB 160 °C. IB 100 °C presented the highest activity toward macrophages, comparable to the control pectin.