3',4',5,5',6,7-Hexamethoxyflavone

International Journal of Oncology, 2017, 51(6):1685-1693.

5,6,7,3',4',5'-Hexamethoxyflavone inhibits growth of triple-negative breast cancer cells via suppression of MAPK and Akt signaling pathways and arresting cell cycle.[Reference: WebLink]

Natural components continue to be an important source for the discovery and development of novel anticancer agents. Polymethoxyflavones are a class of flavonoids found in citrus fruits and medicinal plants used in traditional medicine.
METHODS AND RESULTS:
In the present study, the anticancer activity of the well-known nobiletin (5,6,7,8,3',4'-hexamethoxyflavone) was compared against its less studied structural isomer 5,6,7,3',4',5'-hexamethoxyflavone（3',4',5,5',6,7-Hexamethoxyflavone）. These compounds were evaluated on the Hs578T triple-negative breast cancer cell line and its more migratory subclone Hs578Ts(i)8. 5,6,7,3',4',5'-hexamethoxyflavone was found to be less toxic than nobiletin, while a similar growth inhibitory effect was observed after 72 h. Additionally, 5,6,7,3',4',5'-hexamethoxyflavone arrested the cell cycle in the G2/M phase, while no effect was observed on apoptosis or the migratory behavior of these cells. Furthermore, mechanistic studies revealed that the growth inhibition was concomitant with reduced phosphorylation levels of signaling molecules in the MAPK and Akt pathways as well as cell cycle regulators, involved in regulating cell proliferation, survival and cell cycle.
CONCLUSIONS:
In summary, the present study is the first to report on the anticancer activities of 5,6,7,3',4',5'-hexamethoxyflavone（3',4',5,5',6,7-Hexamethoxyflavone） and to provide evidence that this flavone could have a greater potential than nobiletin for prevention or treatment of triple- negative breast cancer.

Acta Physiologica Sinica, 01 Apr 2015, 67(2):225-234.

Polymethoxylated flavonoids activate cystic fibrosis transmembrane conductance regulator chloride channel.[Reference: WebLink]

Cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-dependent chloride channel, plays key roles in fluid secretion in serous epithelial cells. Previously, we identified two polymethoxylated flavonoids, 3',4',5,5',6,7-Hexamethoxyflavone (HMF) and 5-hydroxy-6,7,3',4'-tetramethoxyflavone (HTF) which could potentiate CFTR chloride channel activities.
METHODS AND RESULTS:
The present study was aimed to investigate the potentiation effects of HMF and HTF on CFTR Cl(-) channel activities by using a cell-based fluorescence assay and the short circuit Ussing chamber assay. The results of cell-based fluorescence assay showed that both HMF and HTF could dose-dependently potentiate CFTR Cl(-) channel activities in rapid and reversible ways, and the activations could be reversed by the CFTR blocker CFTRinh-172. Notably, HMF showed the highest affinity (EC50 = 2 μmol/L) to CFTR protein among the flavonoid CFTR activators identified so far. The activation of CFTR by HMF or HTF was forskolin (FSK) dependent. Both compounds showed additive effect with FSK and 3-Isobutyl-1-methylx (IBMX) in the activation of CFTR, while had no additive effect with genistein (GEN). In ex vivo studies, HMF and HTF could stimulate transepithelial Cl(-) secretion in rat colonic mucosa and enhance fluid secretion in mouse trachea submucosal glands.
CONCLUSIONS:
These results suggest that HMF and HTF may potentiate CFTR Cl(-) channel activities through both elevation of cAMP level and binding to CFTR protein pathways. The results provide new clues in elucidating structure and activity relationship of flavonoid CFTR activators. HMF might be developed as a new drug in the therapy of CFTR-related diseases such as bronchiectasis and habitual constipation.

Korean Journal of Nutrition, 2009,42(3):278-290.

Composition of Flavonoids and Antioxidative Activity from Juice of Jeju Native Citrus Fruits during Maturation.[Reference: WebLink]

This study aims to evaluate the changes of flavonoid contents and antioxidants activity of Jeju native citrus fruits juice according to the harvest date.
METHODS AND RESULTS:
Flavonoids such as quercatagetin, narirutin, hesperidin and neohesperidin were contained most plentifully in the juice of Jigak (Citrus aur-antium) by 573.73 mg/100 mL, Sadoogam (C. pseudogulgul) by 393.99 mg /100 mL, Soyooja by 29.63 mg/100 mL and Jigak (C. aurantium) by 201.23 mg/100 mL in the late August, respectively. The highest contents of nob-iletin, sinensetin and tangeretin among polymethoxyflavones were found in the juice of Hongkyool (C. tachibana) by 7.39 mg/100 mL, 2.24 mg/100 mL, 0.63 mg/100 mL in the late August, respectively. 3,5,6,7,8,3',4'- Heptamet- hoxyflavone recorded the highest amount in Punkyool (C. tangerina) by 0.27 mg/100 mL in the late August, but the other polymethoxyflavones including 3',4',7,8-tetramethoxyflavone, 3',4'-dimethoxyflavone, 4'-methoxyflavone, 5,6,7,3',4',5'-hexamethoxyflavone（3',4',5,5',6,7-Hexamethoxyflavone ）, scutellarein tetramethylether were observed only trace amount in all the citrus fruits. Flavonoid contents in the citrus fruit juices were the highest during early maturation and decreased rapidly while ripening. Total polyphenol contents were the highest in the late August and decreased with ripening. However from the late December, the contents were increased again. Antioxidant activities of the fruits were evaluated as electron donating ability and were the lowest in the late September and increased with the fruit ripening.
CONCLUSIONS:
These results suggest that quercetagetin among all the flavonoids was most plentiful in Jigak and Dangyooja (C. grandis), so that the fruits could be used for industrial material of flavonoids and antioxidant agents.