Honeybee caste development is nutritionally regulated by royal jelly (RJ). Major royal jelly protein 1 (MRJP1), the most abundant glycoprotein among soluble royal jelly proteins, plays pivotal roles in honeybee nutrition and larvae development, and exhibits broad pharmacological activities in humans. However, its structure has long remained unknown. Herein, we identify and report a 16-molecule architecture of native MRJP1 oligomer containing four MRJP1, four apisimin, and eight unanticipated 24-methylenecholesterol molecules at 2.65 Å resolution. MRJP1 has a unique six-bladed β-propeller fold with three disulfide bonds, and it interacts with apisimin mainly by hydrophobic interaction. Every four 24-methylenecholesterol molecules are packaged by two MRJP1 and two apisimin molecules. This assembly dimerizes to form an H-shaped MRJP1₄-apisimin₄-24-methylenecholesterol₈ complex via apisimin in a conserved and pH-dependent fashion. Our findings offer a structural basis for understanding the pharmacological effects of MRJPs and 24-methylenecholesterol, and provide insights into their unique physiological roles in bees.

Propolis is an important hive product and considered beneficial to health. However, evidence of its potential for improving gut health is still lacking. Here we use rats to examine whether dietary supplementation with propolis could be used as a therapy for ulcerative colitis. Rats were fed with a Western style diet alone (controls) or supplemented with different amounts of Chinese propolis (0.1%, 0.2%, and 0.3%) to examine effects on acute colitis induced by 3% dextran sulphate sodium (DSS) in drinking water. Propolis at 0.3%, but not lower levels, significantly improved colitis symptoms compared with the control group, with a less pronounced disease activity index (DAI) (p < 0.001), a significant increase in colon length/weight ratio (p < 0.05) and an improved distal colon tissue structure as assessed by histology. Although short chain fatty acid levels in digesta were not altered by propolis supplementation, 16S rRNA phylogenetic sequencing revealed a significant increase in gut microbial diversity after 21 days of 0.3% propolis supplementation compared with controls including a significant increase in bacteria belonging to the Proteobacteria and Acidobacteria phyla. This is the first study to demonstrate that propolis can attenuate DSS-induced colitis and provides new insight into diet-microbiota interactions during inflammatory bowel disease.

This study aimed to evaluate the influence of fermentation on the levels of free amino acids (FAAs) and variations of volatile odorants in four groups of chickpea milk. Electronic nose (E-nose) and gas chromatography–mass spectrometry (GC-MS) data were subjected to mutual validation. W2S and W3S sensors of E-nose were sensitive to volatile constituents in the four groups of unfermented and fermented specimens. After fermentation, the levels of FAAs in the four groups of specimens decreased to varying degrees. Additionally, there were remarkable differences in the types and contents of volatile odor substances in all specimens before and after fermentation. The principal component analysis findings based on E-nose identified the changes of volatile odorants in all specimens before and after fermentation. GC-MS identified 35 and 55 volatile flavor substances in unfermented and fermented specimens, respectively. The varieties of volatile odor substances in fermented chickpea milk (FCM) with papain treatment plus yam addition (38) were more than those in FCM (24), indicating that the coupled treatment of enzymolysis and yam addition could enrich the volatile odorants in fermented specimens. After probiotic fermentation, the contents of off-flavor substances decreased to a certain extent, and key aroma substances such as 2,3-pentanedione, 2,3-butanedione, and heptyl formate were detected. These results demonstrated that lactic acid bacterial fermentation on the basis of enzymolysis and yam addition could be utilized as a feasible approach to improve the flavor of plant-based products adopting chickpea as the original ingredient.