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

[Display omitted] 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 maritima maltosyl transferase (TMMT), Thermus scotoductus 4-α-glucanotransferase (TS4αGTase), and Bacillus sp. I-5 cyclodextrin glucanotransferase (BSCGTase). TMMT and TS4αGTase 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 5 U/100 μL BSMA at 55 °C 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 α- d-glucosyl-(1→6)-puerarin and α- d-maltosyl-(1→6)-puerarin using ESI + TOF MS–MS and 13C NMR spectroscopy. The solubility of the transfer products was 14 and 168 times higher than that of puerarin, respectively.