Starch and non-starch polysaccharides (NSPs) are two important nutrients, which cause different blood glucose responses after ingestion. To develop novel starchy-based food with low glycemic index values, the introduction of NSPs into starchy system is one of the promising methods. However, in our previous study, NSPs from jicama root (named as PEP-6P) unexpectedly reduced the digestive resistance of jicama starch (PES). To unravel the underlying mechanisms, PEP-6P was treated by three amylolytic enzyme systems. Results showed that PEP-6P could be rapidly digested by α-amylase, indicating the possible existence of α-(1→4)-glucosyl bonds. Further structural analysis confirmed this deduction, and a proposed galactoglucan main chain of PEP-6P was deduced based on the methylation-GC/MS and NMR data. Conformation analysis suggested that PEP-6P presented spherical and aggregated structures in water and 0.1M NaNO₃. These findings revealed that the unexpected pro-digestive effect of jicama NSPs on starch is attributable to the presence of α-(1→4)-glucosyl linkages in the galactoglucan backbone, providing a molecular basis for formulating low-GI jicama-based foods.

The unripe palmleaf raspberry, namely Fupenzi (FPZ), is an important medicinal and edible food. This study aims to evaluate the potential of FPZ extracts prepared with different approaches in attenuating hyperglycemia, gout, Alzheimer's disease, and pigmentation, to obtain the enriching fraction and to identify the major active compounds. Results indicated that FPZ extracts showed weak activity against acetylcholinesterase, considerable ability against tyrosinase and xanthine oxidase, but excellent inhibition on α-glucosidase. Ultrasound-assisted 40 % ethanol extract (40EUS) gave the highest phenolics content, and the best α-glucosidase inhibition (IC₅₀ = 0.08 μg/mL), which is 877-fold higher than that of positive control acarbose. The 40 % ethanol eluting fraction of 40EUS showed the strongest a-glucosidase inhibition with the IC₅₀ value of 37.79 ng/mL, it could also effectively attenuate the fasting blood glucose level and oral glucose tolerance of C57BL/6 mice. Twenty-six compounds were identified from 40 % ethanol fraction by using HPLC-QTOF-MS/MS, hydrolysable tannins (including 11 ellagitannins and 4 gallotannins) were the major compounds, phenolic acids came to the second. Above results could provide important technical supporting for the further application and research of FPZ in health foods and drugs against diabetes.