Metabolic profiling unravels the effects of enhanced output and harvesting time on royal jelly quality.

Royal jelly (RJ), a natural secretion of nurse bees, is a functional food with health-promoting properties. To investigate RJ quality changes with enhanced output and harvesting time, we compared metabolic profiles of RJ harvested at 24 h, 48 h, and 72 h after larval grafting into queen cells from Italian bees (ITBs) and high RJ-producing bees (RJBs) selected from ITBs. A total of 77 high-abundance compounds were identified with reverse-phase liquid chromatography- and hydrophilic interaction liquid chromatography-high-resolution mass spectrometry. Metabolite abundance, water content, and antibacterial activity were found largely unchanged between both bee strains, indicating that a similar RJ quality was achieved. Notably, the observed 10-hydroxy-2-decenoic acid content in RJBs (1.98%) and ITBs (2.41%) meet the standard for premium RJ in China. RJ harvested at 48 h and 72 h had similar metabolic profiles, indicating little influence of the two harvesting times on RJ quality. The harvesting at 24 h could lead to a higher RJ quality with higher abundance levels of many bioactive compounds and lower water content. Our data based mainly on RJ metabolic composition constitute evidence for mass production of high-quality RJ.