Our previous study found that Stenotrophomonas maltophilia CGMCC 1.1788 could hydroxylate imidacloprid (IMI) to 5-hydroxy IMI. Here we first report that S. maltophilia CGMCC 1.1788 can demethylate acetamiprid (AAP) to form IM 2-1 that was characterized by HPLC-MS/MS and NMR. IM 2-1 retained only 10.5% contact activity and 13.1% oral activity of AAP against horsebean aphid. Time course of biotransformation under existing of sucrose revealed that 58.9% of AAP disappeared, but only 16.7% of reduced AAP was transformed to IM 2-1, after 8 days. Both demethylation and degradation of AAP contribute to the weak bioefficacy of AAP in soil application. The differences in metabolism and detoxification pathways between AAP and IMI are probably originated from the structural differences of these insecticides.

Microbacterium oxydans strain NJ 6 isolated from soil samples converted puerarin into two novel compounds, puerarin-7-O-glucoside and puerarin-7-O-isomaltoside, via an unreported O-glycosylation of the phenolic hydroxyl group at the 7-position of puerarin. Sucrose, maltotriose, and maltose could be used as glucosyl donors for glycosylation of puerarin, but uridine-diphosphate glucose, glucose, fructose, lactose, cyclodextrin, and starch could not. Regardless of the position of B-ring in the (iso)flavonoids core structure, the glycosylation of the phenolic hydroxyl group at the 7-position of (iso)flavonoids was governed by the presence or absence of a glucosyl residue at 8-C. The apparent solubility of puerarin-7-O-glucoside and puerarin-7-O-isomaltoside was approximately 18 and 100 times that of natural puerarin, respectively. Like parent puerarin, puerarin-7-O-glucoside maintained its physiological ability to relax the contractions of isolated rat thoracic aortic rings in vitro induced by phenylephrine. However, puerarin-7-O-glucoside was able to maintain higher plasma concentrations and have a longer mean residence time in the blood than the parent puerarin.

Separation of Puerarin-7-O-glucoside from its precursor, puerarin, using a common chromatography column packed with AB-8 macroporous resin was unsuccessful. Therefore, in this study a 8 m super-long flexible reinforced PVC column was externally added to the common column in order to improve the chromatography efficiency by increasing the number of theoretical plates. Both the PVC and common columns were separately packed with AB-8 macroporous resin slurry. The packed PVC column was coiled after washing and stored until use. The microbial transformation mixture with puerarin-7-O-glucoside and puerarin (250 mL) was loaded onto the common column, followed by washing with 2000 mL H(2)O. After attaching the coiled external PVC column to the common column, a linear gradient of 10-30% ethanol was applied to elute the target compound. Two peaks appeared: peak I contained puerarin-7-O-glucoside at 97.9% purity and 88.1% recovery rate, and peak II was puerarin at 98.7% purity and 87.0% recovery rate. The use of the coiled external flexible reinforced PVC column avoided spatial restriction for long columns, which made it much more convenient for column packing and chromatography operations. Furthermore, this method eliminated the resin blockage problem caused by stationary water pressure in a rigid vertical long column. Using an external super-long column, the PVC tube was connected with the common column only during elution, which avoided delay in time period during sample loading and column washes associated with the use of long external columns.