Puffing of Rehmannia glutinosa enhances anti-oxidant capacity and down-regulates IL-6 production in RAW 264.7 cells

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.