Lemon oils are broadly used as flavoring agents in beverages, foods, cosmetics and pharmaceuticals, yet the adulteration of natural, particularly cold pressed lemon oils is very common in the industry due to its unmet demand and high cost. Nowadays, most quality control (QC) analysis of lemon oils is conducted by gas chromatography (GC) analysis, which is far from a reliable method. Oxygen heterocyclic compounds (OHCs) in non-volatile fraction are gaining increasing attention in authentication process because of the nearly finger-printing profiles of OHCs in cold pressed citrus essential oils. Our goal in this study was to identify OHCs using high performance liquid chromatography (HPLC) in lemon oils, establish OHC profiles, perform stepwise logistic regression analysis (SLRA) and build effective predicting model and further determine adulterated lemon oils by referencing the OHC profiles and established models. After HPLC analyses, profiling and SLRA modeling of 154 OHCs samples of industrial lemon oils, we found that the combination of isopimpinellin and total OHC concentration are essential and robust predictors to differentiate authentic samples from adulterated lemon oils with a success rate of 98% from the 5-fold cross validation. This study provided a reliable and efficient method in determining the authenticity of lemon oils.

As the body’s internal clock, the circadian rhythm regulates the energy expenditure, appetite, and sleep. There exists a close relationship between the host circadian rhythm and gut microbiota. In this work, a circadian disorder mouse model induced by constant darkness (CD) was constructed to investigate the regulating effects of capsaicin (CAP) on disturbances of metabolism homeostasis and gut microbiota in the respect of circadian rhythm-related mechanisms. Our results indicated that CAP reduced weight gain induced by circadian rhythm disorder in mice by inhibiting fat accumulation in liver and adipose tissue. The rhythmic expressions of circadian clock genes and lipid-metabolism related genes in liver were also recovered by CAP. Microbial study using 16S rRNA sequencing revealed that CAP modulated the gut microbiota richness, diversity and composition, and restored diurnal oscillations of gut microbes at the phylum and family level. These results indicated that CAP could alleviate CD-induced hepatic clock gene disruption and gut microbiota dysbiosis in mice, providing theoretical basis for CAP to be used as a muti-functional ingredient with great health-promoting effects.

The interaction between host circadian rhythm and gut microbes through the gut-brain axis provides new clues for tea polyphenols to improve host health. Our present research showed that oolong tea polyphenols (OTP) improved the structural disorder of the intestinal flora caused by continuous darkness, thereby modulating the production of metabolites related to pyruvate metabolism, glycolysis/gluconeogenesis, and tryptophan metabolism to alleviate the steady-state imbalance. After fecal microbiota transplantation from the OTP group, the single-cell transcriptomic analysis revealed that OTP significantly increased the number of hypothalamus cell clusters, up-regulated the number of astrocytes and fibroblasts, and enhanced the expression of circadian rhythm genes Cry2, Per3, Bhlhe41, Nr1d1, Nr1d2, Dbp and Rorb in hypothalamic cells. Our results confirmed that OTP can actively improve the intestinal environmental state as well as internal/peripheral circadian rhythm disorders and cognitive impairment, with potential prebiotic functional characteristics to notably contribute to host health.

Although a certain number of amino acid-Amadori rearrangement products (ARPs) have been studied, there is still a lack of knowledge of small peptide-ARPs. Filling the gap should be a great step in the potential usage of ARP as future flavor additives. This study illustrated that small peptides (diglycine and triglycine) exhibited better relative reactivity of ARP formation than an amino acid (glycine) at relatively low temperature such as 80 and 100 ℃ and in a wide range of pH from acidic to neutral conditions, but the result reversed at high temperatures for severer instability of small peptide-ARPs. The relative reactivity of ARP formation of amino compounds in a competing Maillard systems results from dynamic systems with various factors including the chemical characterization and composition of intrinsic reactants, and parameters of matrix conditions like pH, temperature and thermal treatment time among others. Further research should be conducted to investigate peptide-ARPs, for which are ubiquitous in real food systems and worth to pay more attention.

In 2021, there are approximately 537 million adults ageing 2079 years affected by diabetes worldwide and the number is rising rapidly, hence it is important to manage and control diabetes mellitus and its associated complications. Food is one of the key factors in preventing and combating diseases such as diabetes. Both as a food and an herbal medicine, Polygonum multiflorum (PM) has been used as an anti-aging tonic, for hair darkening in traditional Chinese medicine for several centuries. The recent research effort of PM has been focused on antioxidant, anti-ageing and anti-tumor properties. In the present study, we utilized the traditional processing of harvested raw PM, and identified several stilbene components and then evaluated the potential anti-diabetic effects of the processed PM extract (PME). PME (0.075%) was given to diabetic mice (KK CgAy/J) in drinking water and after 7 weeks, PME-treated mice had significantly lower glucose levels than mice in the diabetic control group (P < 0.01). The mechanism was explored with ELISA and Western blotting and results suggested that the effect was through maintaining β-cell function.

The fruit of Ziziphus jujuba Mill., known as Hongzao (or Hong-Zao) in Chinese and cultivated in China for more than 4000 years, has shown to have hepatoprotective property. In previous study, we have isolated and identified 27 known compounds from Z. jujuba fruits, which demonstrated anti-tumor activity. In this study, a high-performance liquid chromatography-diode-array detection-mass spectrometry (HPLC-DAD-MS) method was successfully applied to the simultaneous characterization and quantitation of 18 constituents in 28 Z. jujuba samples, comprised of 12 cultivars from different regions in China, by comparing their HPLC retention times, MS spectra, UV spectra, and NMR data with those of reference compounds. The quantitative method was validated with excellent linearity (R² > 0.999 1), preferable intra- and inter-day precisions (RSD < 2.78%), and good recoveries (94.96%–102.65%). The content variation of 18 compounds was analyzed by a chemometric method (hierarchical cluster analysis). In addition, these constituents showed protection against carbon tetrachloride (CCl₄) intoxicated HepG2 cell lines by decreasing lactic dehydrogenase (LDH) levels. Results in this study illustrated that the content of all 18 compounds examined has significant difference and variation among cultivars and extracts. The proposed method can serve as a prerequisite for quality control of bioactive compounds in Z. jujuba products.

Human beings have consumed lemon (Citrus limon) and lime (Citrus aurantifolia or Citrus latiflia) for thousands of years. Among the variety of citrus families, lemon and lime are originated from the hybridization of citron with primitive papeda, hence they are similar from the nutritional and organoleptic standpoints, whereas very different from other citrus species such as orange and mandarin. Except for fresh produce, a significant percentage of lemon and lime are processed and separated as juice, essential oils, pulps and other products. Lemon and lime juice or fruit itself is rich in vitamins, minerals and flavonoids which are rich sources for human nutrition. Consumption of lemon and lime fruit or juice are beneficial for human health in the scope of urinary citrate increase, oxidative stress relief, improvement in lipid profiles and inflammation markers, neuroprotective effects among others. These beneficial effects of lemon and lime are not only because of their high vitamin C content but also other bioactive micronutrients such as flavonoids. Essential oils from lemon and lime have fresh and zesty aroma for perfumery and flavor applications for centuries. Compared with orange or mandarin, the integrated review for lemon and lime dietary bioactive compounds and essential oils is scarce. Therefore, in this review, we introduced the historical cultivation, consumption and process of lemon and lime, discussed the chemical and biological activities of phytochemicals in lemon and lime fruits and juice, and summarized volatile and non-volatile components in lemon and lime oil. This review may provide a comprehensive perspective for entire lemon and lime industry as well as their scientific values.

Myriad evidence attests to the health-promoting benefits of tea drinking. While there are multiple factors of tea influencing the effective biological properties, tea polyphenols are the most significant and valuable components. The chemical characterization and physical characteristics of tea polyphenols have been comprehensively studied over the previous years. Still the emergence of new chemistry in tea, particularly the property of scavenging reactive carbonyl species (RCS) and the newly discovered flavoalkaloid compounds, has drawn increasing attention. In this review, we summarize recent findings of a new class of compounds in tea - flavonoid alkaloids (flavoalkaloids), which exist in fresh tea leaves and can be generated during the process of post-harvesting, and also postulate the formation mechanism of flavoalkaloids between catechins and theanine-derived Strecker aldehyde. Additionally, we detail the up-to-date research results of tea polyphenols regarding their ability to trap RCS and their in vivo aminated metabolites to suppress advanced glycation ends products (AGEs). We further raise questions to be addressed in the near future, including the synthetic pathways for the generation of flavoalkaloids and AGEs in fresh tea leaves before processing and the concentrations of tea polyphenols that affect their RCS scavenging capability due to their pro-oxidant nature. More intensive research is warranted to elucidate the mechanisms of action underlying the biological activity of flavoalkaloids and the pharmacological application of tea polyphenols in scavenging RCS and impeding detrimental AGEs.

Tea is a widespread functional plant resource. Phytochemicals such as tea polyphenols (TP) can interact with the intestinal flora and participate in regulating the expression and rhythm of biological clock genes. Circadian rhythm controls a variety of behaviors and physiological processes, and circadian misalignment has been found to be closely related to multiple metabolic diseases. Interestingly, the gut microbiota also has diurnal fluctuations, which can be affected by diet composition and feeding rhythm, and play a role in maintaining the host's circadian rhythm. The two-way relationship between the host's circadian rhythm and intestinal microbiota confirms the possibility that prebiotics or probiotic can be used to adjust the intestinal environment and microbiome composition to improve the host health. This article reviews the relationship between the host's circadian rhythm and microbiota and its influence on metabolic diseases. The beneficial effects of the interaction between TP and gut microbiota on diseases related to rhythm disorders are emphasized to improve the theories of disease prevention and treatment.

Tea as the most consumed beverage in the world has received enormous attention for its promoting health benefits. The deleterious effect of α-dicarbonyls and AGEs formed in Maillard reaction is also a long-term challenge. The connection between the two topics was the main aim of this review, to address and update the antiglycation effect and mechanism of tea and tea polyphenols. By analyzing recent publications, we have covered across chemistry models, cell lines and animal studies. Tea polyphenols, particularly catechins, showed outstanding antiglycation effect by trapping α-dicarbonyl compounds and impeding AGEs formation. Reduction of carbonyl stress brought alleviation to aging, diabetes, and collagen related diseases or complications through regulation of RAGE expression and subsequent MAPK and TGF-β pathway. Therefore, tea polyphenols can serve as promising natural candidates in the treatment and/or prevention of nephropathy, retinopathy, hepatopathy, hyperglycemia and obesity among others, by their potent antiglycation effect. Further studies need to address on aspects like exact mechanisms, solution of detection obstacles, balance of practical usage and harmful effects such as potential flavor damage and toxicity in food, to gain a comprehensive understanding of antiglycation activities of tea polyphenols and its actual application.