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5-Demethylnobiletin (5-DMN), a hydroxylated polymethoxyflavone (OH-PMF) identified in aged citrus peels, has demonstrated health benefiting effects in previous studies. 5-DMN undergoes biotransformation in vivo, yielding 5,3'-didemethylnobiletin (5,3'-DDMN), 5,4'-didemethylnobiletin (5,4'-DDMN) and 5,3',4'-tridemethylnobiletin (5,3',4'-TDMN). However, the anti-cancer effects of 5-DMN and its in vivo metabolites against HepG2 cells remain unclear. In this study, an efficient chemical synthetic method was developed to obtain 5-DMN and its 3 metabolites, and their molecular structures were confirmed by 1H NMR and LC-MS. Cytotoxicity, cell cycle arrestment, apoptosis and caspase-3 expression were investigated to evaluate the anti-liver cancer effects of these OH-PMFs on HepG2 cells. The results showed that all 4 compounds inhibited the proliferation of HepG2 cells in a concentration-dependent manner. Their anti-proliferative activity was exerted through inducing G2/M phase arrestment, cell apoptosis and promoting expression of a key apoptotic protein called cleaved caspase-3. Our results indicated that 5,3'-DDMN and 5,3',4'-TDMN showed a stronger inhibitory activity on cell proliferation than 5-DMN, followed by 5,4'-DDMN. The expression of cleaved caspase-3 was the highest in cells treated with 5,4'-DDMN, implying that the apoptosis induced by other OH-PMFs might be mediated by other apoptotic execution proteins. Our research reveals the application potential and scientific evidence for the production and functionality of OH-PMFs.


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5-Demethylnobiletin and its major metabolites: efficient preparation and mechanism of their anti-proliferation activity in HepG2 cells

Show Author's information Yanping Xina,b,c,1Ting Zhengc,1Man ZhangcRuiqiang ZhangaSiyue ZhucDongli Lia,b( )Denggao Zhaoa,bYanyan Maa,bChi-Tang HocQingrong Huangc( )
School of Biotechnology and Health Sciences, Wuyi University, Jiangmen 529020, China
International Healthcare Innovation Institute (Jiangmen), Jiangmen 529020, China
Department of Food Science, Rutgers University, New Jersey 08901, USA

1 These two authors contribute equally.

Peer review under responsibility of KeAi Communications Co., Ltd.

Abstract

5-Demethylnobiletin (5-DMN), a hydroxylated polymethoxyflavone (OH-PMF) identified in aged citrus peels, has demonstrated health benefiting effects in previous studies. 5-DMN undergoes biotransformation in vivo, yielding 5,3'-didemethylnobiletin (5,3'-DDMN), 5,4'-didemethylnobiletin (5,4'-DDMN) and 5,3',4'-tridemethylnobiletin (5,3',4'-TDMN). However, the anti-cancer effects of 5-DMN and its in vivo metabolites against HepG2 cells remain unclear. In this study, an efficient chemical synthetic method was developed to obtain 5-DMN and its 3 metabolites, and their molecular structures were confirmed by 1H NMR and LC-MS. Cytotoxicity, cell cycle arrestment, apoptosis and caspase-3 expression were investigated to evaluate the anti-liver cancer effects of these OH-PMFs on HepG2 cells. The results showed that all 4 compounds inhibited the proliferation of HepG2 cells in a concentration-dependent manner. Their anti-proliferative activity was exerted through inducing G2/M phase arrestment, cell apoptosis and promoting expression of a key apoptotic protein called cleaved caspase-3. Our results indicated that 5,3'-DDMN and 5,3',4'-TDMN showed a stronger inhibitory activity on cell proliferation than 5-DMN, followed by 5,4'-DDMN. The expression of cleaved caspase-3 was the highest in cells treated with 5,4'-DDMN, implying that the apoptosis induced by other OH-PMFs might be mediated by other apoptotic execution proteins. Our research reveals the application potential and scientific evidence for the production and functionality of OH-PMFs.

Keywords: Chemical synthesis, Apoptosis, Cell cycle, HepG2, Hydroxylated polymethoxyflavones

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Received: 27 May 2021
Revised: 03 June 2021
Accepted: 09 June 2021
Published: 02 June 2022
Issue date: September 2022

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© 2022 Beijing Academy of Food Sciences.

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