The roots of Rehmannia glutinosa (RG) have been widely used for medicinal purposes in Asia. The traditional processing of RG involves repetitive steaming and drying, and 9-time-steamed RG (NSRG) is the most commonly consumed form. For a development of a convenient processing method, RG was puffed at various pressures resulting in significantly increased solid extraction yield by up to 14%. The amount of the Maillard reaction product 5-hydroxymethylfurfural and the antioxidant capacities determined by the ABTS and DPPH radical scavenging assays were enhanced at increasing puffing pressure. Treatment of lipopolysaccharide-stimulated RAW 264.7 macrophages with RG extracts revealed that puffing of RG enhanced its suppression of the pro-inflammatory cytokine IL-6 by up to 37%. The 5-hydroxymethylfurfural contents, ABTS/DPPH radical scavenging capacities, and IL-6 regulatory effects of puffed RG samples were greater than those of the NSRG control, indicating that puffing is a desirable processing technique for development of nutraceuticals using RG.
Keywords: Antioxidant; Cytokine; Extraction yield; Puffing; Rehmannia glutinosa.