Metabolome and Whole-Transcriptome Analyses Reveal the Molecular Mechanisms Underlying Hypoglycemic Nutrient Metabolites Biosynthesis in Cyclocarya paliurus Leaves During Different Harvest Stages

Combined metabolomic and transcriptomic analysis reveals the key genes for triterpenoid biosynthesis in Cyclocarya paliurus

BACKGROUND

Cyclocarya paliurus is a high-value tree, and it contains a variety of bioactive secondary metabolites which have broad application prospects in medicine, food and health care. Triterpenoids can improve the bioactive function of C. paliurus health tea and also improve the efficacy of health care tea.

RESULTS

The results of this study showed that there were 69 kinds were terpenoids, and triterpenoids accounted for more than 80%. We excavated 5 kinds of triterpenoid metabolites with high content and significant difference dynamics, namely, corosolic acid, asiatic acid, maslinic acid, ursolic acid and oleanolic acid. The co-expression analysis identified CYP71D8 and CYP716A15 co-expressed with β-AS may generate oleanane type triterpenoids by modifying β-amyrin, while CYP71AN24 and CYP98A2 co-expressed with LUS may play a key role in lupine type triterpenoids biosynthesis. MYB,Whirly,WRKY and bHLH families, which showed strong correlation with function genes, may play an important role in the regulation of P450 and OSC expression. A total of 20 modules were identified by WGCNA analysis, and CYP71AU50 and CYP716A15 in tan and orange modules may play a major role in the synthesis of oleanolic acid, ursolic acid and asiatic acid, while CYP82D47 in lightcyan 1 module may be the hub gene for the biosynthesis of corosolic acid and maslinic acid.

CONCLUSIONS

Our findings mined candidate genes closely related to triterpenoid synthesis in C. paliurus. The results of this paper can provide scientific reference for breeding high-content triterpenoid varieties of C. paliurus.

Analysis of Volatile Components in Rosa roxburghii Tratt. and Rosa sterilis Using Headspace-Solid-Phase Microextraction-Gas Chromatography-Mass Spectrometry

Volatile organic compounds (VOCs) and flavor characteristics of Rosa roxburghii Tratt. (RR) and Rosa sterilis (RS) were analyzed using headspace solid-phase microextraction coupled with gas chromatography-mass spectrometry (HS-SPME-GC-MS). The flavor network was constructed by combining relative odor activity values (ROAVs), and the signature differential flavor components were screened using orthogonal partial least squares discriminant analysis (OPLS-DA) and random forest (RF). The results showed that 61 VOCs were detected in both RR and RS: 48 in RR, and 26 in RS. There were six key flavor components (ROAVs ≥ 1) in RR, namely nonanal, ethyl butanoate, ethyl hexanoate, (3Z)-3-hexen-1-yl acetate, ethyl caprylate, and styrene, among which ethyl butanoate had the highest contribution, whereas there were eight key flavor components (ROAVs ≥ 1) in RS, namely 2-nonanol, (E)-2-hexenal, nonanal, methyl salicylate, β-ocimene, caryophyllene, α-ionone, and styrene, among which nonanal contributed the most to RS. The flavor of RR is primarily fruity, sweet, green banana, and waxy, while the flavor of RS is primarily sweet and floral. In addition, OPLS-DA and RF suggested that (E)-2-hexenal, ethyl caprylate, β-ocimene, and ethyl butanoate could be the signature differential flavor components for distinguishing between RR and RS. In this study, the differences in VOCs between RR and RS were analyzed to provide a basis for further development and utilization.

Revealing the mechanisms of the bioactive ingredients accumulation in Polygonatum cyrtonema by multiomics analyses

Polygonatum cyrtonema is a medicinal and edible herb rich in polysaccharides, steroidal saponins, and flavonoids that has been widely used as a food, vegetable, and medicine over the years. Although previous studies have preliminarily explored the metabolic and transcriptional regulatory mechanisms of the main secondary metabolites in P. cyrtonema, the complex mechanism of microRNA (miRNA)-mediated posttranscriptional regulation remains unclear. Metabolome analysis showed that iso-ophiopogonanone B, (25S)-pratioside D1, disporopsin, and isodiosgenin-Glc-Glc, which are associated with intermediates in the flavonoids and saponins pathways, were significantly upregulated in the stem and leaf compared with the rhizome, and most saccharides, including arabinose, cellobiose, maltotetraose, and panose, showed the opposite trend, suggesting that they may contribute to the formation and accumulation of the main active ingredients in P. cyrtonema. We found that 4-hydroxymandelonitrile have a relatively good inhibitory effect on α-glucosidase, indicating that it may play a role in hypoglycemic functions. Transcriptome and weighted gene coexpression network analysis (WGCNA) were combined to reveal several candidate genes involved in the accumulation of polysaccharides, saponins, and flavonoids, including PcSQLE, PcCYP71A1, PcSUS, PcFK, and PcMYB102. Integrated analyses of miRNAs and messengerRNAs (mRNAs) showed that novel_miR14, novel_miR49, novel_miR75, and aof_miR164 were negatively correlated with alpha-linolenic acid metabolism and the mitogen activated protein kinase (MAPK) signaling pathway, including PcAOS, PcSPLA2, PcFRK1, and PcDELLA, indicating that these miRNAs may coordinately regulate the biosynthesis of other secondary metabolites in P. cyrtonema. These findings will facilitate in-depth research on the functions of these miRNAs and mRNAs related to the main active substances for pathological and biological regulation, which will be beneficial to provide theoretical guidance for the molecular breeding of P. cyrtonema.

The chemical composition and toxic effects of aqueous extracts of Cyclocarya paliurus leaves

Cyclocarya paliurus leaves, which possess various bioactivities, have been widely used in dietary supplements or as ingredients in functional foods. However, limited information is available about the toxicity or safety concerns. In the present work, the maximum tolerated dose (MTD) and potential toxicity of the aqueous extracts of C. paliurus leaves (AECPL) were evaluated. Our results indicated that AECPL was rich in phenolics, flavonoids, and polysaccharides, which might be responsible for the health benefits of C. paliurus leaves. The MTD of AECPL was considered to be > 10,000 mg/kg BW in both male and female rats. The acute toxicity study was carried out by a 14-day repeat dose oral toxicity study. The results showed that the rats were all well-tolerated. No treatment-related mortality, abnormal clinical signs, body weight, or food consumption changes were reported during the study. Moreover, AECPL showed no adverse changes in the hematology, serum chemistry, urinalysis parameters, organ weights, gross finding, and histopathology. In this study, the non-observed-adverse-effect level of AECPL was 5,000 mg/kg BW/day, indicating AECPL was safe and can be used in the food industry.

Progress in Research on the Alleviation of Glucose Metabolism Disorders in Type 2 Diabetes Using Cyclocarya paliurus

Globally, the incidence of diabetes is increasing annually, and China has the largest number of patients with diabetes. Patients with type 2 diabetes need lifelong medication, with severe cases requiring surgery. Diabetes treatment may cause complications, side-effects, and postoperative sequelae that could lead to adverse health problems and significant social and economic burdens; thus, more efficient hypoglycemic drugs have become a research hotspot. Glucose metabolism disorders can promote diabetes, a systemic metabolic disease that impairs the function of other organs, including the heart, liver, and kidneys. Cyclocarya paliurus leaves have gathered increasing interest among researchers because of their effectiveness in ameliorating glucose metabolism disorders. At present, various compounds have been isolated from C. paliurus, and the main active components include polysaccharides, triterpenes, flavonoids, and phenolic acids. C. paliurus mainly ameliorates glucose metabolism disorders by reducing glucose uptake, regulating blood lipid levels, regulating the insulin signaling pathway, reducing β-cell apoptosis, increasing insulin synthesis and secretion, regulating abundances of intestinal microorganisms, and exhibiting α-glucosidase inhibitor activity. In this paper, the mechanism of glucose metabolism regulation by C. paliurus was reviewed to provide a reference to prevent and treat diabetes, hyperlipidaemia, obesity, and other metabolic diseases.