10-Hydroxy-2-decenoic acid, a natural fatty acid that has been extracted from royal jelly obtained from honeybees (Apis mellifera) and exhibits estrogenic action. 10-hydroxy-2-decenoic(10-HDA)dose-dependently inhibited the formation of the gastric ulcer induced by stress, pyloric ligation, and indomethacin selectively in rats. 10-HDA also accelerated the healing of gastric ulcer induced by acetic acid, by which the gastric acid output was decreased in a dose-dependent manner. A mechanism putatively linked to 10-HDA anti-inflammatory effect is the inhibition of LPS-induced NF-kB activation observed in the murine macrophage cell line RAW264. 10-HDA and 4-hydroperoxy-2-decenoic acid ethyl ester have been shown to inhibit histone deacetylase activity, thereby enhancing the expression of extracellular SOD release by leukemia THP-1 cells, and suggesting therapeutic potential against atherosclerosis. Various immunomodulatory activities have been reported for 10-HDA, including reduced T cell proliferation, inhibition of interleukin-12 production by spleen dendritic cells, and blocks of LPS- and IFN-b-induced NO production in macrophages. 10-HDA has been shown to increase collagen synthesis and production of the collagen promoting factor, transforming growth factor b1, in human skin fibroblasts. Such an effect is thought to mediate royal jelly skin protection against UVB-induced photoaging. 10-HDA and 10-hydroxydecanoic acid have been shown to act as potent agonists of the human TRPA1 and TRPV1 receptors. 10-HDA has stimulated neuron differentiation from rat embryo neural stem cells, possibly acting like the omega-3 docosahexaenoic acid, an essential diet component that is known to promote neurogenesis in the central nervous system.