Effect of 6-hydroxy-7,4 '-dimethoxyflavone on antidiabetic effects in normal and streptozotocin-induced diabetic rats

Kaempferia parviflora is a famous endemic Thailand species of the family Zingiberaceae. MeOH extract of Kaempferia parviflora was consecutively partitioned with organic solvents such as CHCl3 EtOAc and BuOH. CHCl3 fractions were diluted with distilled water and extracted with n-hexane and CH2Cl2. Five methoxyflavone compounds were isolated from the CH2Cl2 fractions with column chromatography. The structures of the isolated compounds were identified as 3,5,7,3',4'-pentamethoxyflavone (KP1), 5,7-dimethoxyflavone (KP2), 5,7,4'-trimethoxyfiavone (KP3), 3,5-dihydroxy-3'-methoxyflavone (KP4) and 6-hydroxy-7,4'-dimethoxyflavone (KP5) by D-1 H-NMR spectral analysis and comparison of spectral data with literature values. KP5 showed significant hypoglycemic activity in streptozotocin-induced diabetic rats for 28 days. It significantly decreased the serum glucose and triglycerides while it increased the serum insulin in diabetic rats but not in normal rats (p < 0.05; at doses of 50, 100 and 150mg/kg for 28 days). It had no effect on C-peptide (ECLIA). Further structure-activity relationships of position 6 in the aromatic ring B will be reported in due course.