Isolation of (E)-9,10-dihydroxy-2-decenoic acid from royal jelly and determination of the absolute configuration by chemical synthesis

Optimization of ultrasound-assisted extraction of fatty acids from royal jelly and its effect on the structural and antioxidant property

Fatty acids are the key active components in royal jelly (RJ) with various biological activities. In this study, a novel ultrasound-assisted extraction (UAE) method was established to extract fatty acids from RJ and their structural and antioxidant property were further evaluated. The optimum extraction conditions were as follows: liquid-to-solid ratio of 10:1, ultrasonic power of 450 W and ultrasonic duration of 20 min, resulting in a better extraction yield of 16.48 % and 10-hydroxy-2(E)-decenoic acid (10-HDA) content of 4.12 %. Furthermore, compared with the solvent extraction method, the antioxidant activity of extract by ultrasound was enhanced significantly by at least 448 %. GC-MS showed that ultrasound didn't change the chemical composition of fatty acids, while it significantly increased the content of fatty acids. SEM image illustrated that extracts by UAE showed a rougher, looser microstructure compared to the solvent method. Overall, UAE is a promising method to obtain fatty acids in RJ with high efficiency.

Acetylcholine and Royal Jelly Fatty Acid Combinations as Potential Dry Eye Treatment Components in Mice

Dry eye is a multifactorial disease characterized by ocular discomfort and visual impairment. Our previous studies have shown that royal jelly (RJ) has restored the capacity for tear secretion by modulating muscarinic calcium signaling. RJ contains acetylcholine, which is a major cholinergic neurotransmitter, and a unique set of fatty acids with C 8 to 12 chains, which are expected to be associated with health benefits. The purpose of the present study was to investigate the active components involved in tear secretion capacity, focusing on acetylcholine and fatty acids in RJ. Using the stress-induced dry-eye model mice, it was confirmed that acetylcholine with three fatty acids (10-hydroxydecanoic acid, 8-hydroxyoctanoic acid, and (R)-3,10-dihydroxydecanoic acid) was essential for tear secretion. In ex vivo Ca2+ imaging, these three fatty acids suppressed the decrease in intracellular modulation of Ca2+ in the lacrimal gland by acetylcholine when treated with acetylcholinesterase, indicating that the specific type of RJ fatty acids contributed to the stability of acetylcholine. To our knowledge, this study is the first to confirm that a specific compound combination is important for the pharmacological activities of RJ. Our results elucidate the active molecules and efficacy mechanisms of RJ.

Gas chromatographic-mass spectrometric investigation of volatile and extractable compounds of crude royal jelly

Using headspace solid-phase microextraction (HS-SPME) followed by diethyl ether and methanol extraction, it was possible to isolate as many as 185 organic compounds out of 17 samples of crude royal jelly (RJ). Of the above compound number, 169 compounds were positively identified by means of gas chromatography-mass spectrometry. The volatile fraction of RJ consists of 25 different compounds where approximately 47% of the total ion current (TIC) of volatile compound chromatograms were composed of substances characterized by bactericidal (phenols) and repelling (octanoic acid and 2-heptanone) activities. Preliminary investigations have shown that RJ stored for 10 months at -18°C and 4°C keeps its composition of volatile compounds unchanged, however, at the same time at room temperature RJ phenol contents is decreased twice, whereas the fraction of aliphatic acids is increased 2.8 times due to the presence of both acetic and butyric acids. The chromatogram of RJ ether extracts showed 85 different compounds, however about 88% of TIC consisted exclusively of 8 compounds, i.e. 10-hydroxy-2-decenoic, 10-hydroxydecanoic, 3,10-dihydroxydecanoic, 8-hydroxyoctanoic, 2-decene-1,10-dioc and (Z)-9-hydroxy-2-decenoic acids. Nine aliphatic acids, which were detected for the first time, are the homologues of hydroxy- and oxo-acids identified earlier in RJ. In the RJ methanol extracts 82 compounds were identified, mainly carbohydrates and their derivatives. Approximately 87% of TIC consisted of fructose, glucose and sucrose. Special attention was paid to discrepancies between obtained and literature data concerning the presence of free amino acids in RJ. It was suggested that these inconsistencies can be explained by the differences in the methods of RJ collection and/or sample preparation.