Glycation of proteins and DNA forms advanced glycation end products (AGEs) causing cell and tissue dysfunction and subsequent various chronic diseases, in particular, metabolic and age-related diseases. Targeted AGE inhibition includes scavengers of reactive carbonyl species (RCS) such as methylglyoxal (MG), glyoxalase-1 enhancers, Nrf2/ARE pathway activators, AGE/RAGE formation inhibitors and other antiglycatng agents. Citrus flavonoids have demonstrated antioxidant and anti-inflammatory effects and are also found to be effective antiglycating agents. Herein, we reviewed the up to date progress of the antiglycation effects of citrus flavonoids and associated mechanisms. Major citrus flavonoids, hesperedin and its aglycone, hesperetin, inhibited glycation by scavenging MG forming mono- or di-flavonoid adducts with MG, enhanced the activity of glyoxase-1, activated Akt/Nrf2 signal pathway while inhibiting AGE/RAGE/NF-κB pathway, reduced the formation of N^ε-(carboxylmethyl)lysine (CML) and pentosidine, inhibited aldol reductase activity and decreased the levels of fructosamine. The antiglycating activity and mechanisms of other flavonoids was also summarized in this review. In conclusion, citrus flavonoids possess effective antiglycating activity via different mechanisms, yet there are many challenging questions remaining to be studied in the near future such as in vivo testing and human study of citrus flavonoids for efficacy, effectiveness and adverse effects of citrus flavonoids as a functional food in managing high levels of AGEs and controlling AGE-induced chronic diseases, diabetic complications in particular.

Polygonati Rhizoma, a functional food and a traditional Chinese medicine broadly used in China and several Southeast Asia countries, possesses effective health-promoting activities. Prepared from three plants in Polygonatum family (P. kingianum, P. sibiricum, and P. cyrtonema), Polygonati Rhizoma has drawn increasing attention due to its remarkable immune-enhancing and metabolic regulatory activities in recent years. In this review, we summarized the updated research of chemical constituents and biological activities of Polygonati Rhizoma, especially the metabolic regulation, immunomodulatory effects, and anti-fatigue activities, aiming to provide a comprehensive understanding, broaden the usage and promote more in-depth exploration of Polygonati Rhizoma as a functional food.

Coreopsis tinctoria Nutt (C. tinctoria) or a common name ‘Snow chrysanthemum’ because of its growing condition at high altitude,is one of the popular medicinal-food plants, mainly grows in the northwest area of China. Because of its rich nutrients, particularly polyphenols (majorly flavonoids), and volatile oils among others, C. tinctoria has become a research hotspot in recent years. In addition, the flavonoids of C. tinctoria, especially the flavanomarein, marein, okanin and other bioactive phytochemicals, have effective biological activity. They possess good antioxidant and anti-inflammatory effects, also have significant effects on lowering blood pressure, hypoglycemia and reducing levels of triglycerides and cholesterol. However, at present, studies on the bioactivity of C. tinctoria are mainly focused on crude extracts or total flavonoids. The study of monomer components is largely limited to the isolation and purification process, which is difficult for a systematic study because of the chemical-physical nature of marein, flavanomarein and other compounds in C. tinctoria. Therefore, to have an updated isolation of C. tinctoria bioactive components, this paper reviewed the current research status of the separation and purification methods of flavonoids from C. tinctoria, by analyzing and comparing the technical characteristics of these methods, and providing prospects on the development and application of the separation and purification methods of C. tinctoria.

Sinensetin is one of the polymethoxyflavones existed in citrus peels. The effective antioxidant, inhibitory effect of inflammation, anti-diabetic and anti-cancer activity of sinensetin has been revealed recently. However, the amount of sinensetin isolated from the nature source is extremely low relating to the needs for its in vivo and efficacy study. Herein we summarized the alternative routes, i.e. the organic synthesis of sinensetin and its associated derivatives to provide a complete but concise reference in the preparation of this class of compounds as an effective source for in-depth study of sinensetin and related molecules.

Oxyresveratrol (ORes, trans-2,4,3′,5′-tetrahydroxy stilbene) naturally exists in mulberry, grapes, peanuts and other plants. It belongs to stilbene polyphenolic family and has an extra hydroxyl group at 2-position comparing with resveratrol (Res). Hence, ORes has stronger antioxidant activity than resveratrol. In present study, we employed a rat hepatic fibrosis model induced by carbon tetrachloride (CCl₄) and administrated ORes via gavage feeding to study the protective effects and potential mechanisms of ORes against hepatic fibrosis. We demonstrated that rat liver oxidative damage induced by CCl₄ was significantly alleviated after ORes feeding. Furthermore, the mRNA transcription levels of α-smooth muscle actinn (α-SMA), desmin, and two MMPs (MMP2 and MMP9) were reduced and the expression levels of transforming growth factor β1 (TGF-β1), p- small mother against decapen-taplegic protein (Smad)1/2 and p-extracellular signal-regulated kinases (ERK)1/2 in the liver tissue down-regulated dramatically. In a parallel study with Res, ORes showed more efficacious protective effect than Res against rat liver fibrosis, which is attributed to extended conjugation system due to the extra hydroxyl group at 2-position on ORes making it more electron-rich and susceptible to oxidation than Res. Therefore, dietary consumption of mulberry and other fruits containing ORes may be beneficial in the prevention of liver fibrosis.

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.

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.

Theaflavins in black tea and other fermented tea have attracted many studies because of their stronger antioxidant and anti-inflammatory effects among bioactives other than catechins. However, within the four major theaflavins, namely theaflavin, theaflavin-3-O-gallate, theaflavin-3'-O-gallate and theaflavin-3, 3'-O, O-digallate, their biological properties are different. A method to efficiently and selectively synthesize targeted theaflavins with desired property is a key condition for further evaluation. Herein, we have summarized the sources of polyphenol oxidase (PPO) and the yields of total and individual theaflavins based on some available publications. This overview lays the foundation for a comprehensive review in this area of researchin the near future.

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.

Oolong tea, partially fermented from Camellia sinensis leaves, exhibits significant antioxidative, anti-inflammatory, and anti-cancer activities as indicated in several in vitro and in vivo studies. However, studies on health promoting effects of oolong tea and its characteristic compounds are limited. The potential efficacy of bioactives derived from oolong tea and their roles as promising anticancer agents, their cardio-protective benefits during hypoxic conditions, effects in treating allergic disorders, potential prebiotic activities, improvement of blood lipid status in human beings, effectivity as oral hypoglycemic agent in the treatment of type 2 diabetes, and their potentials to reduce the risk of obesity have been discussed in this review. These promising studies mainly gained from animal studies might broaden the consumption and usage of the phenolic-enriched oolong tea and its products in food and pharmaceutical industries. However, potential health beneficial effects of oolong tea in humans should be further complemented by large-sized, randomized double-blind and placebo-controlled trials to consolidate potential therapeutic applications.