Browsing by Author "Cao, Hui"

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    Advance toward isolation, extraction, metabolism and health benefits of kaempferol, a major dietary flavonoid with future perspectives
    (Francis and Taylor, 2021-09-23) Yang, Li; Gao, Yongchao; Bajpai, Vivek K.; El-Kammar, Heba A.; Simal-Gandara, Jesus; Cao, Hui; Cheng, Ka-Wing; Wang, Mingfu; Arroo, R. R. J.; Zou, Liang; Farag, Mohamed A.; Zhao, Yonghua; Xiao, Jianbo
    As a major ubiquitous secondary metabolite, flavonoids are widely distributed in planta. Among flavonoids, kaempferol is a typical natural flavonol in diets and medicinal plants with myriad bioactivities, such as anti-inflammatory activity, anti-cancer activity, antioxidant activity, and anti-diabetic activity. However, the natural sources, absorption and metabolism as well as the bioactivities of kaempferol have not been reviewed comprehensively and systematically. This review highlights the latest research progress and the effect of kaempferol in the prevention and treatment of various chronic diseases, as well as its protective health effects, and provides a theoretical basis for future research to be used in nutraceuticals. Further, comparison of the different extraction and analytical methods are presented to highlight the most optimum for PG recovery and its detection in plasma and body fluids. Such review aims at improving the value-added applications of this unique dietary bioactive flavonoids at commercial scale and to provide a reference for its needed further development.
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    Amination of Flavonoids Possessing a Pyrogallol Group in Cell Culture Medium at 37◦C
    (Wiley, 2025-02-18) Zhang, Haolin; Zhang, Jingjing; Cao, Hui; Högger, Petra; Arroo, Randolph; Farag, Mohamed A.; Shpigelman, Avi; Xiao, Jianbo; Li, Chunlin
    A class of flavonoid aminated derivatives that had been consistently overlooked in literaturewas shown to be formed as artefacts in cell culturemedium. In this study, 34 flavonoids from different subclasses were incubated in Dulbecco’s modified Eagle’sMedium (DMEM) at 37◦C for 2 h to identify the reaction mechanism behind aminated derivatives formation from flavonoids. Baicalein, scutellarein, dihydromyricetin, (−)-gallocatechin (GC), (−)-epigallocatechin (EGC), (−)-GC gallate, and (−)-EGC gallate were found to yield corresponding nitrogenous derivatives in both DMEM and amino acid solution. The nitrogen source of these seven flavonoid -aminated derivatives was revealed to be amino acids in DMEM. The pyrogallol group of the flavonoids was a key structural motif, being first oxidized into quinone and then further reacting with amino acids (Strecker degradation) to yield aminated flavonoids and corresponding aldehydes. A slightly alkaline environment accelerated the amination of flavonoids, possibly via the formation of flavonoid quinone. These results provide the mechanistic evidence for the in vitro generation of flavonoid -aminated derivatives, yet to be tested using in vivo assays.
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    Flavonols with a catechol or pyrogallol substitution pattern on ring B readily form stable dimers in phosphate buffered saline at four degrees Celsius.
    (Elsevier, 2019-11-14) Cao, Hui; Högger, Petra; Arroo, R. R. J.; Xiao, Jianbo
    Phosphate buffered saline (PBS) is a buffer commonly used in biological research. The stability of a series of flavonoids, i.e. myricetin, kaempferol, baicalein, luteolin and quercetin in PBS was assessed. Apigenin proved very stable when incubated with PBS and was used as a control. Kaempferol and baicalein were less stable, and small amounts of oxidized and hydroxylated products could be detected. Flavonols with catechol or pyrogallol structure in ring B are unstable in PBS (pH=7.4) at 4 ºC and were converted into their stable dimers and oxidized products within 5 seconds. The chosen experimental conditions improved the stability of dimers and allowed their detection.
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    Stability and antioxidant capacity of epigallocatechin gallate in Dulbecco’s modified eagle medium.
    (Elsevier, 2021-07-05) Wang, Minglong; Zhang, Haolin; Yi, Lunzhao; Högger, Petra; Arroo, R. R. J.; Bajpal, Vivek K.; Prieto, Miguel-Angel; Simel-Gandara, Jesus; Wang, Shengpeng; Cao, Hui
    Though the instability of polyphenols in cell culture experiment has been investigated previously, the underlying mechanism is not completely clear yet. Therefore, in this study, the stability of epigallocatechin gallate (EGCG) in cell culture medium DMEM was investigated at 4 ◦C and 37 ◦C via UPLC-MS-MS analysis followed by determination of the antioxidant capacity of EGCG. EGCG was instable in DMEM and formed various degradation products derived from its dimer with increasing incubation time with many isomers being formed at both temperatures. The dimer products were more stable at 4 ◦C than at 37 ◦C. The structure and formation mechanism of five products were analyzed with four unidentified. Ascorbic acid significantly improved the stability of EGCG by protecting EGCG from auto-oxidation in DMEM, particularly at 4 ◦C. The antioxidative activity of EGCG in DMEM was determined by DPPH, ABTS and FRAP assay. The antioxidative properties of EGCG continuously decreased over 8 h in DMEM, which was consistent with its course of degradation.