Dietary fibers fractionated from gardenia (Gardenia jasminoides Ellis) husk: Structure and in vitro hypoglycemic effect.

BACKGROUND Gardenia (Gardenia jasminoides Ellis) husk rich in dietary fiber is the by-product of fructus processing, and commonly discarded as waste. The husk was fractionated by sequential extraction into four fractions: water soluble fiber (W-SF), acid soluble fiber (Ac-SF), alkali soluble fiber (Al-SF) and insoluble residue fiber (IRF). The aim of this study was to investigate the differences in structure and in vitro hypoglycemic effect of these fibers. RESULTS Monosaccharide composition and FT-IR spectra showed that the major component might be pectin for W-SF and Ac-SF, xylan as well as pectin for Al-SF, and cellulose for IRF. These fibers offered excellent water holding capacity and swelling capacity, except that IRF was slight swellable in water. W-SF exhibited significantly higher capacities to adsorb glucose (2.408 mmol g-1 at the glucose concentration of 200 mmol L-1 ) and inhibit α-amylase activity (29.48-49.45% inhibition rate at concentration of 4-8 mg mL-1 ), probably caused by the higher viscosity and hydration properties; while Ac-SF, Al-SF and IRF (especially Al-SF) were more effective in retarding the glucose diffusion across dialysis membrane (34.97%-41.67% at 20-30 min), which might be attributed to particle size and specific surface area. All the fibers could quench the intrinsic fluorescence of α-amylase to some degree. CONCLUSION Dietary fiber from gardenia husk, especially W-SF, can be used as a potential hypoglycemic ingredient in diabetic functional foods. This article is protected by copyright. All rights reserved.