Diarylheptanoid-rich extract of grey and black alder barks: an effective dietary antioxidant in mayonnaise

Diarylheptanoid-rich extracts (DAHEs) isolated from grey and black alder bark with pressurized ethyl acetate were tested in mayonnaise as a dietary antioxidant using the Oxipres method. DAHE contains > 700 mg g(-1) of oregonin possessing quite similar structure to the well-known dietary antioxidant curcumin, which is widely used as a bioactive constituent of food supplements. Strong radical scavenging capacity of oregonin was clearly demonstrated by the online HPLC-DPPHa (TM) scavenging assay. The antioxidative effect of DAHEs in mayonnaise was dose dependent; however, even the lowest concentration (0.5 mg g(-1)) of DAHE additive increased the induction period of oxidation more than two times. Consequently, DAHE may be considered as a promising natural antioxidant for commercial applications.