Decreasing Effect of Honey on Hydroxy Acids in Royal Jelly Products

Royal jelly has been used as a material for “health food” and crude drugs. In order to estimate the royal jelly content in various royal jelly products, 10-hydroxy-2-decenoic acid (10-HDA), one of the specific fatty acids of royal jelly, has been analyzed by gas chromatography. A survey on commercial royal jelly products containing honey revealed 10-HDA concentrations in the range from 1.03-1.60%, though 10-HDA in fresh royal jelly samples was in the range from 1.84 to 2.50%. 10-Hydroxy decanoic acid contents were 0.60 to 0.78%.The 10-HDA concentration in honey-containing royal jelly products was less than in fresh royal jelly samples. Therefore, experiments were conducted to investigate the relationship between the decrease of 10-HDA concentration and time in samples of 0.20% 10-HDA with 10.0% honey in neutral aqueous solution and 10.0% fresh royal jelly with 10.0% honey in neutral aqueous solution. The concentration of 10-HDA in the former sample decreased to 0.04% (initially 0.20%) after 90 days, while that in the latter sample decreased to 0.14% (initially 0.20%).