In this study, the effects of chain length distribution and drying methods on the structural properties and in vitro digestibility of resistant starch (RS) are investigated. Rice starch is debranched at 10% w/w solid concentrations, incubated at 60 °C, and further subjected to freeze drying and oven drying treatment to obtain debranched starch (DBS). The chain length distribution shows that DBS (the degree of polymerization [DP] = 19.52 ± 0.13) has a high proportion of B1 and B2 chains (DP13-36) and a narrow chain length distribution. In addition, the results of scanning electron microscopy (SEM) show that the oven-dried samples have denser structures and larger particle morphology compared to samples prepared by freeze-drying. In FTIR, LCM-Raman and X-ray diffraction patterns, debranched starch supernatant fraction 1 (DBSS1) exhibit higher short-range molecular order and crystallinity than other samples. Digestibility analysis shows that DBSS1 with narrow chain length distribution (DP13-36) promotes the high content of RS formation and oven drying is more favorable for RS formation than freeze drying (RS DBSFS1 = 79.69 ± 5.09% and RS DBSOS1 = 84.17 ± 0.17%). This suggests that the proper narrow chain length distribution is conducive to the formation of ordered structure and an increase in resistance. Oven drying provides a larger starch particle size, which facilitates resistance to digestion.
Quercetin is a kind of polyphenolic flavonoid compounds which has perfect antioxidant properties. However, quercetin is not available in many situations due to its poor bioavailability. In this work, the QAEs with better solubility and even stronger antioxidant properties were synthesized, through the esterification between quercetin and the chlorinated cinnamic acid or its derivatives, whose chlorination were achieved by using SOCl 2 . The protective effects of the QAEs were evaluated by the H 2 O 2 -induced apoptosis experiment in rat adrenal pheochromocytoma cells (PC12 cells) and its ability to remove ROS generated by oxidative stress. Compared with the original quercetin group, the QAEs groups showed much improved cell viability and capability of removing ROS, which means their higher bioavailability than the parent.
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