The effect of Vaccinium bracteatum Thunb. leaves addition on antioxidant capacity, physicochemical properties, and in vitro digestibility of rice extrudates

Mechanisms of rice protein hydrolysate regulating the in vitro digestibility of rice starch under extrusion treatment in terms of structure, physicochemical properties and interactions

The effect of protein hydrolysates on starch digestibility has been observed in other heat treatments but has yet to be extensively researched under extrusion. This study aimed to analyze the physicochemical properties, structure, and starch digestibility of extruded rice starch-protein hydrolysate (ERS-RPH) complexes prepared by extrusion treatment. The resistant starch contents of ERS-RPH (12.30 %-19.36 %) were higher than those of extruded starch alone (6.33 %). The interaction forces, physical barrier effects, and enzyme inhibition indicated that RPHs at varying hydrolysis degrees hindered starch digestibility by reducing its contact with enzyme and via adhesion and hydrogen bonding with starch. RPHs with higher hydrolysis exhibited greater inhibition of starch digestibility, limiting the swelling power of starch and the leaching of amylose, thereby improving the thermal stability of starch. Fourier transform infrared spectroscopy results revealed the presence of hydrogen bonding interactions between RPHs and starch in complexes, intensifying the ordered structure of starch. Extrusion caused an increase of 6.8 %-10.8 % in the relative crystallinity of ERS-RPH compared to extruded starch alone. Moreover, the strength of V-type structure was reinforced after extrusion. These results enhanced comprehension of how PRHs regulate starch digestibility under extrusion, and offer direction for producing slow-digesting foods.

Validation of reference genes for gene expression analysis in fruit development of Vaccinium bracteatum Thunb. using quantitative real-time PCR

Vaccinium bracteatum Thunb. (VBT) is widely distributed in the mountainous areas in eastern and southern China. VBT leaves have great medical value and can be used to stain rice to produce "Wumifan". Its fruits also contain rich nutrients. However, there has been limited attention to exploring the molecular content of VBT. Previously, we performed RNA-seq on three typical VBT fruits that were at various stages of ripening, although a reliable reference gene was lost in validation.In this study, we selected ten candidate reference genes based on previous studies and transcriptomics analyses. Subsequently, these genes were evaluated using a combination of methods, including geNorm, NormFinder, and Bestkeeper, with a comprehensive ranking assessment. As a result, we found that the actin2, NADH, and ADK genes have high reliability for analysing the expression levels of genes involved in fruit development. Furthermore, the transcript levels of 15 DEGs from transcriptomic analysis were assessed using NADH as a reference gene, and RT-qPCR data were highly consistent with the transcriptomic data. These results provide reliable reference genes for further studying gene expression, which will be beneficial for comprehensively exploring VBT.

In Vitro Inhibitory Effects of Viburnum opulus Bark and Flower Extracts on Digestion of Potato Starch and Carbohydrate Hydrolases Activity

One of the effective treatments for diabetes is to reduce and delay the absorption of glucose by inhibition of α-amylase and α-glucosidase in the digestive tract. Currently, there is a great interest in natural inhibitors from various part of plants. In the present study, the phenolic compounds composition of V. opulus bark and flower, and their inhibitory effects on in vitro potato starch digestion as well as on α-amylase and α-glucosidase, have been studied. Bark and flower phenolic extracts reduced the amount of glucose released from potato starch during tree-stage simulated digestion, with IC50 value equal to 87.77 µg/mL and 148.87 µg/mL, respectively. Phenolic bark extract showed 34.9% and 38.4% more potent inhibitory activity against α-amylase and α-glucosidase, respectively, but the activity of plant extracts was lower than that of acarbose. Chlorogenic acid (27.26% of total phenolics) and (+)-catechin (30.48% of total phenolics) were the most prominent phenolics in the flower and bark extracts, respectively. Procyanidins may be responsible for the strongest V. opulus bark inhibitory activity against α-amylase, while (+)-catechin relative to α-glucosidase. This preliminary study provides the basis of further examination of the suitability of V. opulus bark compounds as components of nutraceuticals and functional foods with antidiabetic activity.