Royal jelly peptides inhibit lipid peroxidation in vitro and in vivo.

Royal jelly peptides (RJPx) isolated from hydrolysates of water-soluble royal jelly proteins prepared with protease P exhibited significantly stronger hydroxyl radical-scavenging activity (p<0.001), and antioxidant activity against lipid peroxidation (LPO, p<0.001), than did water-soluble royal jelly protein (WSRJP) in vitro. We also investigated the in vivo antioxidant activity of RJPx against ferric nitrilotriacetate (Fe-NTA)-induced LPO. Male Wistar rats were divided into a control group (Group C), an Fe-NTA group (Group Fe), and an Fe-NTA with RJPx group (Group Fe+R). Rats in Group Fe+R were fed RJPx (2 g/kg body weight) daily for 5 wk. Fe-NTA (8 mg Fe/kg body weight) was then intraperitoneally injected, and serum lipid levels were examined 2 h later. Serum total cholesterol (TC) levels were lower (p<0.05) while low-density lipoprotein (LDL) and LPO were significantly higher (p<0.01) in Group Fe than in Group C. TC (p<0.05) and LPO levels (p<0.01) were lower in Group Fe+R than in Group Fe. Our data suggest that RJPx may inhibit LPO both in vitro and in vivo.