Regulation of the differentiation of osteoblasts and osteoclasts by a hot-water extract of adzuki beans (Vigna angularis)

Cholesterol-lowering activity of adzuki bean (Vigna angularis) polyphenols

BACKGROUND

Adzuki beans (ABs; Vigna angularis) were reported to show potential for prevention of cholesterol absorption and lowering of the blood cholesterol level. However, the main active compounds and some cellular effects remain unknown. In this study, we evaluated the potential cholesterol-lowering effects of (+)-catechin 7-O-β-D-glucopyranoside (C7G) and (+)-epicatechin 7-O-β-D-glucopyranoside (E7G), identified as abundant polyphenols in ABs.

METHODS AND RESULTS

To investigate the cholesterol-lowering activity in vitro, cholesterol micelles, bile acids, and Caco-2 cells as an intestinal model were used in the study. C7G and E7G each inhibited micellar solubility in a dose-dependent manner, and their inhibitory activity was as strong as that of (+)-catechin (IC₅₀ values: C7G, 0.23 ± 0.03 mg/ml; E7G, 0.22 ± 0.02 mg/ml; (+)-catechin, 0.26 ± 0.11 mg/ml). The AB polyphenols showed binding activity toward bile acids and changed them into an insoluble form. When Caco-2 cells were treated with C7G or E7G, the amount of incorporated cholesterol was significantly decreased compared with vehicle-treated control cells, and no cytotoxicity was observed under the experimental conditions used. Meanwhile, quantitative real-time PCR revealed that the mRNA level of the cholesterol transporter NPC1L1 remained unchanged in the treated cells.

CONCLUSIONS

Taken together, the present findings suggest that C7G and E7G are the main active compounds in ABs, and have the ability to inhibit micellar solubility, bind to bile acids, and suppress cholesterol absorption. The present study supports the health benefits of ABs as a medicinal food and the application of AB polyphenols as medicinal supplements to suppress cholesterol elevation.

Adzuki bean (Vigna angularis): Chemical compositions, physicochemical properties, health benefits, and food applications

Adzuki bean (Vigna angularis), also called red bean, is a legume of Fabaceae (Leguminosae) family. This crop is native to East Asia and is also commercially available in other parts of the world. It is becoming a research focus owing to its distinct nutritional properties (e.g., abundant in polyphenols). The diverse health benefits and multiple utilization of this pulse are associated with its unique composition. However, there is a paucity of reviews focusing on the nutritional properties and potent applications of adzuki beans. This review summarizes the chemical compositions, physicochemical properties, health benefits, processing, and applications of adzuki beans. Suggestions on how to better utilize the adzuki bean are also provided to facilitate its development as a functional grain. Adzuki bean and its components can be further developed into value-added and nutritionally enhanced products.

Isolation and Characterization of Antihyperglycemic Compounds from Vigna angularis Extracts

Functional foods that inhibit α-amylase and α-glucosidase activity are effective for regulating the blood glucose level and preventing hyperglycemia. Extracts of adzuki beans (ABs, Vigna angularis), widely eaten in East Asia, can inhibit α-amylase and α-glucosidase activity. In this study, we identified and evaluated the components in an AB water extract (ABWE) after boiling, which is an essential process for cooking ABs. The ABWE before boiling inhibited α-amylase and α-glucosidase activity and the boiled ABWE showed slightly stronger inhibitory effects. High-performance liquid chromatography, liquid chromatography-mass spectrometry, and nuclear magnetic resonance analyses identified (+)-catechin 7-O-β-d-glucopyranoside (C7G), (+)-epicatechin 7-O-β-d-glucopyranoside (E7G), and (+)-catechin as the bioactive components in boiled ABWE. Interestingly, the quantity of E7G significantly increased after boiling (from 0% to 17.1 ± 1.3%). E7G showed stronger inhibition of α-amylase and α-glucosidase than C7G; the IC₅₀ values for α-amylase were 0.74 ± 0.04 mg/mL (C7G) and 0.40 ± 0.09 mg/mL (E7G), and for α-glucosidase the IC₅₀ values were 0.085 ± 0.032 mg/mL (C7G) and 0.051 ± 0.007 mg/mL (E7G). Our findings suggest that C7G and E7G are the main active components in ABWE as they inhibit α-amylase and α-glucosidase and their inhibitory effect is not lost after boiling. These results support the effectiveness of boiled ABs in the promotion of health. PRACTICAL APPLICATION: We identified (+)-catechin 7-O-β-d-glucopyranoside (C7G), (+)-epicatechin 7-O-β-d-glucopyranoside (E7G), and (+)-catechin in adzuki bean extracts and commercially available boiled adzuki bean products. Interestingly, the E7G content was increased by boiling, and this compound showed strong inhibitory activity toward α-amylase and α-glucosidase. These results support the consumption of boiled adzuki beans to prevent acute rises in blood glucose level.

Synthesis of novel 5,6-dehydrokawain analogs as osteogenic inducers and their action mechanisms

An imbalance between bone resorption by osteoclasts and bone formation by osteoblasts can cause bone loss and bone-related disease. In a previous search for natural products that increase osteogenic activity, we found that 5,6-dehydrokawain (1) from Alpinia zerumbet promotes osteoblastogenesis. In this study, we synthesized and evaluated series of 5,6-dehydrokawain analogs. Our structure-activity relationships revealed that alkylation of para or meta position of aromatic ring of 1 promote osteogenic activity. Among the potential analogs we synthesized, (E)-6-(4-Ethylstyryl)-4-methoxy-2H-pyran-2-one (14) and (E)-6-(4-Butylstyryl)-4-methoxy-2H-pyran-2-one (21) both significantly up-regulated Runx2 and Osterix mRNA expression at 10µM. These osteogenic activities could be mediated by bone morphogenetic protein (BMP) and activation of p38 MAPK signaling pathways. Compounds 14 and 21 also inhibited RANKL-induced osteoclast differentiation of RAW264 cells. These results indicated that novel 5,6-dehydrokawain analogs not only increase osteogenic activity but also inhibit osteoclast differentiation, and could be potential lead compounds for the development of anti-osteoporosis agents.

5,6-Dehydrokawain from Alpinia zerumbet promotes osteoblastic MC3T3-E1 cell differentiation

Bone homeostasis is maintained by balancing bone formation and bone resorption, but an imbalance between them is associated with various bone-related diseases such as osteoporosis and rheumatoid arthritis. We found that 5,6-dehydrokawain (DK) and dihydro-5,6-dehydrokawain (DDK), which were isolated as promising compounds from Alpinia zerumbet rhizomes, promote differentiation of osteoblastic MC3T3-E1 cells. DK and DDK increased the alkaline phosphatase activity and matrix mineralization of MC3T3-E1 cells. DK exerts larger effects than DDK. The gene expression of runt-related transcription factor 2 and osterix, which are essential transcription factors in the early period of osteoblast differentiation, was significantly increased by DK treatment. The mRNA level of distal-less homeobox 5 was also enhanced by DK treatment, and DK activated the p38 mitogen-activated protein kinase pathway. Therefore, DK may have clinical potential for preventing osteoporosis, and could be considered as a potential anabolic therapeutic agent.

Antiangiogenic Effect of Ethanol Extract of Vigna angularis via Inhibition of Phosphorylation of VEGFR2, Erk, and Akt

Though dietary azuki bean (Vigna angularis) seed containing antioxidant proanthocyanidins was known to have multibiological activities including antioxidant, hypotensive, anti-inflammatory, and immunomodulatory activities, the antiangiogenic activity of ethanol extract of Vigna angularis (EVA) was never reported so far. In the present study, the antiangiogenic mechanism of EVA was examined in human umbilical vein endothelial cells (HUVECs). EVA showed weak cytotoxicity in HUVECs, while it significantly suppressed the VEGF induced proliferation of HUVECs. Consistently, wound healing assay revealed that EVA inhibited the VEGF induced migration of HUVECs. Also, EVA abrogated the VEGF induced tube formation of HUVECs in a concentration dependent fashion. Furthermore, Matrigel plug assay showed that EVA significantly reduced the hemoglobin level of Matrigel plug in mice compared to untreated control. Of note, EVA effectively attenuated the phosphorylation of VEGFR2, Erk, and Akt in VEGF-treated HUVECs. Overall, our findings suggest that EVA inhibits angiogenesis in VEGF-treated HUVECs via inhibition of phosphorylation of VEGFR2, ERK, and Akt.

Coupling Hydroxyapatite Nanocrystals with Lactoferrin as a Promising Strategy to Fine Regulate Bone Homeostasis

Lactoferrin (LF) is an interesting glycoprotein in the field of bone biology for its regulatory effect on cells involved in bone remodeling, that results compromised in several pathological conditions, as osteoporosis. In a previous study we observed that the coupling of LF and biomimetic hydroxyapatite nanocrystals (HA), a material well-known for its bioactivity and osteoconductive properties, leads to a combined effect in the induction of osteogenic differentiation of mesenchymal stem cells. On the basis of this evidence, the present study is an extension of our previous work aiming to investigate the synergistic effect of the coupling of HA and LF on bone homeostasis. Biomimetic HA nanocrystals were synthesized and functionalized with LF (HA-LF) and then pre-osteoblasts (MC3T3-E1) and monocyte/macrophage cells lines (RAW 264.7), using as osteoclastogenesis in vitro model, were cultured separately or in co-culture in presence of HA-LF. The results clearly revealed that HA and LF act in synergism in the regulation of the bone homeostasis, working as anabolic factor for osteoblasts differentiation and bone matrix deposition, and as inhibitor of the osteoclast formation and activity.

Genistein from Vigna angularis Extends Lifespan in Caenorhabditis elegans

The seed of Vigna angularis has long been cultivated as a food or a folk medicine in East Asia. Genistein (4',5,7-trihydroxyisoflavone), a dietary phytoestrogen present in this plant, has been known to possess various biological properties. In this study, we investigated the possible lifespan-extending effects of genistein using Caenorhabditis elegans model system. We found that the lifespan of nematode was significantly prolonged in the presence of genistein under normal culture condition. In addition, genistein elevated the survival rate of nematode against stressful environment including heat and oxidative conditions. Further studies demonstrated that genistein-mediated increased stress tolerance of nematode could be attributed to enhanced expressions of stress resistance proteins such as superoxide dismutase (SOD-3) and heat shock protein (HSP-16.2). Moreover, we failed to find genistein-induced significant change in aging-related factors including reproduction, food intake, and growth, indicating genistein exerts longevity activity independent of affecting these factors. Genistein treatment also led to an up-regulation of locomotory ability of aged nematode, suggesting genistein affects healthspan as well as lifespan of nematode. Our results represent that genistein has beneficial effects on the lifespan of C. elegans under both of normal and stress condition via elevating expressions of stress resistance proteins.