6 methoxyluteolin

Reference standards of apigenin, daidzein, daidzin, formononetin, genistein and genistin were obtained from Sigma-Aldrich Co. (St Louis, MO, USA); astragalin, calendoflavoside, cosmosiin, cynaroside, glycitin, hyperoside, isoquercitrin, isorhamnetin 3-O-glucoside, luteolin, narcissin, nicotiflorin and rutin as well as 6-methoxyluteolin and 6-methoxyflavone as internal standards were purchased from Extrasynthese (Genay, France); 6-O-malonyldaidzin and 6-O-malonylgenistin from Synthose Inc. (Ontario, Canada); kaempferol 3-O-gentiobioside, quercetin 3-O-gentiobioside and quercetin 3-O-sophoroside from PhytoLab GmbH & Co. (Vestenbergsgreuth, Germany); Cacticin and trifolin from MedChemExpress (Monmouth Junction, USA). LC–MS grade methanol, acetonitrile and water were supplied from Thermo Fisher Scientific Inc. (Waltham, MA, USA). Besides, formic acid (Junsei Chemical, Tokyo, Japan) was used as eluent additive in extraction and chromatographic separation of flavonoid derivatives.

Standards of 6-methoxyluteolin, apigenin, luteolin, luteolin7-O-glucoside, apigenin7-O-glucoside were purchased from Extrasynthese (Lyon, Genay Cedex, France); apiin, luteolin7-O-(2”-O-apiosyl)glucoside, caffeoyl-putrescine from ALB Technology(Hong Kong); 4-nitrophenyl-β-D-glucopyranoside (pNPG), α-glucosidase (yeast, EC 3.2.1.20), acarbose, sodium carbonate from Sigma Aldrich Co. (St. Louis, MO, USA); sodium phosphate buffer from Biosesang (Seongnam, Korea); methanol from MERCK (Damstadt, Germany); acetonitrile from Fisher Scientific (Fair Lawn, NJ, USA); and formic acid from Junsei Chemical (Tokyo, Japan).