Arabinoxylans from rice bran and wheat immunomodulatory potentials: a review article

Wheat arabinoxylans: Insight into structure-function relationships

Arabinoxylan (AX), a key non-starch polysaccharide found in the cell walls of cereals like wheat, holds significant importance in the food industry. Recently, it has attracted attention due to its numerous health benefits. While the benefits of wheat arabinoxylans are well-established, a more comprehensive understanding of the relationship between their structure and functional properties is essential. This knowledge will be instrumental in addressing potential concerns in future research focusing on food products containing wheat arabinoxylan. Previous reviews predominantly focused on cereal arabinoxylans, and only a few have addressed wheat arabinoxylan. This review aims to consolidate recent research findings on wheat arabinoxylans, highlighting their health benefits and potential links to structural variations. This will aid future studies in this area. Feruloylated arabinoxylans and arabinoxylan oligosaccharides stand out as the most known for their health benefits. Modifying the chemical structure of arabinoxylans to yield low molecular weight oligosaccharides enhances their immunomodulatory and antioxidant activities, as well as promotes the growth and availability of beneficial gut microbes. The antioxidant activity is positively correlated with the ferulic acid content, whereas it has a negative correlation with arabinose substitution. Nevertheless, additional research using final products is necessary to delve into the potential underlying mechanisms.

Is there any hepatic impact associated with rice bran arabinoxylan compound supplementation? A systematic review and dose-response meta-analysis of randomized controlled trials

BACKGROUND & AIMS

Rice Bran Arabinoxylan Compound (RBAC) results from an enzymatic modification of rice bran, which is reported to have immunomodulatory, anti-oxidant, and anti-inflammatory effects by regulating the production of pro-inflammatory cytokines. The current systematic review and meta-analysis aimed to determine the hepatic adverse effects of RBAC by assessing the effect through liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST).

METHODS

In the present study, the Medline (PubMed), Web of Sciences, and Scopus databases were searched for relevant publications from the beginning to October 2022. The meta-analysis was based on the Mixed effect model to generate the mean effect sizes in weighted mean differences (WMD) and the 95% confidence intervals (95%CI). The heterogeneity was assessed using the Cochrane Chi-squared test, and the analysis of Galbraith plots was applied.

RESULTS

Subgroup meta-analysis on five eligible randomized controlled trials (n = 239) showed a significant decrease in serum AST regarding RBAC supplementation in powder form (WMD (95%CI) = -3.52 (-5.62, -1.42) U/L; P-value = 0.001, I2 (%) = 46.9; P heterogeneity = 0.170), three months and more supplementation duration (WMD (95%CI) = -3.71 (-5.95, -1.48) U/L; P-value = 0.001, I2 (%) = 29.9; P heterogeneity = 0.240) and studies with a good quality (WMD (95%CI) = -3.52 (-5.62, -1.42) U/L; P-value = 0.001, I2 (%) = 46.9; P heterogeneity = 0.170).

CONCLUSIONS

In conclusion, RBAC supplementation seems to not have any hepatic adverse effects and its supplementation as powder or for three months and more may decrease serum AST levels. However, we need further studies to confirm the results.

REGISTRY NUMBER FOR SYSTEMATIC REVIEWS OR META-ANALYZES

CRD42022361002, registration time: 29/09/2022.

Arabinoxylans as Functional Food Ingredients: A Review

The health benefits of fibre consumption are sound, but a more compressive understanding of the individual effects of different fibres is still needed. Arabinoxylan is a complex fibre that provides a wide range of health benefits strongly regulated by its chemical structure. Arabinoxylans can be found in various grains, such as wheat, barley, or corn. This review addresses the influence of the source of origin and extraction process on arabinoxylan structure. The health benefits related to short-chain fatty acid production, microbiota regulation, antioxidant capacity, and blood glucose response control are discussed and correlated to the arabinoxylan's structure. However, most studies do not investigate the effect of AX as a pure ingredient on food systems, but as fibres containing AXs (such as bran). Therefore, AX's benefit for human health deserves further investigation. The relationship between arabinoxylan structure and its physicochemical influence on cereal products (pasta, cookies, cakes, bread, and beer) is also discussed. A strong correlation between arabinoxylan's structural properties (degree of branching, solubility, and molecular mass) and its functionalities in food systems can be observed. There is a need for further studies that address the health implications behind the consumption of arabinoxylan-rich products. Indeed, the food matrix may influence the effects of arabinoxylans in the gastrointestinal tract and determine which specific arabinoxylans can be included in cereal and non-cereal-based food products without being detrimental for product quality.

Biological Functions and Activities of Rice Bran as a Functional Ingredient: A Review

Rice bran (RB) is a nutrient-rich by-product of the rice milling process. It consists of pericarp, seed coat, nucellus, and aleurone layer. RB is a rich source of a protein, fat, dietary fibers, vitamins, minerals, and phytochemicals (mainly oryzanols and tocopherols), and is currently mostly used as animal feed. Various studies have revealed the beneficial health effects of RB, which result from its functional components including dietary fiber, rice bran protein, and gamma-oryzanol. The health effects of RB including antidiabetic, lipid-lowering, hypotensive, antioxidant, and anti-inflammatory effects, while its consumption also improves bowel function. These health benefits have drawn increasing attention to RB in food applications and as a nutraceutical product to mitigate metabolic risk factors in humans. This review therefore focuses on RB and its health benefits.

Molecular modification, structural characterization, and biological activity of xylans

The differences in the source and structure of xylans make them have various biological activities. However, due to their inherent structural limitations, the various biological activities of xylans are far lower than those of commercial drugs. Currently, several types of molecular modification methods have been developed to address these limitations, and many derivatives with specific biological activity have been obtained. Further research on structural characteristics, structure-activity relationship and mechanism of action is of great significance for the development of xylan derivatives. Therefore, the major molecular modification methods of xylans are introduced in this paper, and the primary structure and conformation characteristics of xylans and their derivatives are summarized. In addition, the biological activity and structure-activity relationship of the modified xylans are also discussed.

The Health-Promoting Properties and Clinical Applications of Rice Bran Arabinoxylan Modified with Shiitake Mushroom Enzyme-A Narrative Review

Rice bran arabinoxylan compound (RBAC) is derived from defatted rice bran hydrolyzed with Lentinus edodes mycelial enzyme. It has been marketed as a functional food and a nutraceutical with health-promoting properties. Some research has demonstrated this rice bran derivative to be a potent immunomodulator, which also possesses anti-inflammatory, antioxidant, and anti-angiogenic properties. To date, research on RBAC has predominantly focused on its immunomodulatory action and application as a complementary therapy for cancer. Nonetheless, the clinical applications of RBAC can extend beyond cancer therapy. This article is a narrative review of the research on the potential benefits of RBAC for cancer and other health conditions based on the available literature. RBAC research has shown it to be useful as a complementary treatment for cancer and human immunodeficiency virus infection. It can positively modulate serum glucose, lipid and protein metabolism in diabetic patients. Additionally, RBAC has been shown to ameliorate irritable bowel syndrome and protect against liver injury caused by hepatitis or nonalcoholic fatty liver disease. It can potentially ease symptoms in chronic fatigue syndrome and prevent the common cold. RBAC is safe to consume and has no known side effects at the typical dosage of 2–3 g/day. Nevertheless, further research in both basic studies and human clinical trials are required to investigate the clinical applications, mechanisms, and effects of RBAC.