Lithuanian Royal jelly: quality assessment, biological activity and quantitative determination of trans-10-hydroxy-2-decenoic acid in various solvents

Abstract

Royal jelly is a bee product with a high commercial interest due to its exceptional biological properties and unique composition. In this study, we evaluated the quality of Lithuanian Royal jelly, including the water content, antioxidant activity, amount of polyphenolic compounds and pH. The results indicated that Lithuanian Royal jelly had the values of pH, water content as well as polyphenols that were comparable to the data already published. In the study, we also evaluated the impact of various solvents on the amount of 10-hydroxy-2-decenoic acid (10-HDA), the main fatty acid, naturally occurring only in Royal jelly and which is the quality marker, in solutions obtaining the amount using the HPLC method. According to solubility tests performed, 10-HDA from Royal jelly is best soluble in ethanol of various concentrations, yet in order to be used for exceptional Royal jelly antibacterial and many other biological properties it was important to increase the solubility in aqueous solutions. Addition of β-cyclodextrin has increased the amount of 10-HDA in solution up to the level of ethanol solutions. The antioxidant and antibacterial tests have demonstrated that Lithuanian Royal jelly exhibits positive effects against free radicals, as well as mostly occurring bacterial strains, such as Esherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus. As the conclusion of this study, we can assume that the quality assessment methods chosen for this study, are significant for standardizing the procedures for further studies.