In vitro enzymatic modification of puerarin to puerarin glycosides by maltogenic amylase

Puerarin (daidzein 8-C-glucoside), the most abundant isoflavone in Puerariae radix, is prescribed to treat coronary heart disease, cardiac infarction, problems in ocular blood flow, sudden deafness, and alcoholism. However, puerarin cannot be given by injection due to its low solubility in water. To increase its solubility, puerarin was transglycosylated using various enzymes. Bacillus stearothermophilus maltogenic amylase (BSMA) was the most effective transferase used compared with Thermotoga maritinta maltosyl transferase (TMMT), Thermus scotoductus 4-alpha-glucanotransferase (TS4alphaGTase), and Bacillus sp. 1-5 cyclodextrin glucanotransferase (BSCGTase). TMMT and TS4alphaGTase lacked acceptor specificity for puerarin, which lacks an O-glucoside linkage between D-glucose and 7-OH-daidzein. The yield exceeded 70% when reacting 1% puerarin (acceptor), 3.0% soluble starch (donor), and 5U/100muL BSMA at 55degreesC for 45 min. The two major transfer products of the BSMA reaction were purified using C-18 and GPC chromatography. Their structures were identified as alpha-D-glucosyl-(1-->6)-puerarin and alpha-D-maltosyl-(1-->6)-puerarin using ESI* TOF MS-MS and C-13 NMR spectroscopy. The solubility of the transfer products was 14 and 168 times higher than that of puerarin, respectively. (C) 2004 Elsevier Ltd. All rights reserved.