Effects of ultrasonic treatment on the molecular weight and anti-inflammatory activity of oxidized konjac glucomannan

The ultrasound-degraded oxidized konjac glucomannan (U-OKGM) was manufactured and its immune activity in RAW264.7 macrophages was examined. Results showed that ultrasound treatment, which was an effective method to obtain low molecular weight OKGM, did not change the main structure of polysaccharides under the test conditions. Molecular weights (MW) of OKGM and U-OKGM are about 1.58 x 10(6) g/mol and 5.64 x 10(5) g/mol, respectively. We showed that U-OKGM could inhibit NO secretion and augment phagocytotic activity of RAW264.7 cell, and 0.8 mg/mL U-OKGM reached significant level (p < 0.05). Meanwhile, TNF-alpha and IL-1 beta secretion levels were significantly (p < 0.05) decreased by U-OKGM treatments in LPS-stimulated RAW264.7 cells. Moreover, the mRNA transcription of IL-1 beta, TNF-alpha, IL-6 and iNOS were significantly (p < 0.05) inhibited by U-OKGM in LPS-activated RAW264.7 macrophages. The results suggest that ultrasonic treatment provides a viable modification to obtain low-molecular-weight polysaccharide, and U-OKGM has strong anti-inflammatory effects on LPS-stimulated RAW264.7 macrophages.