Chun-Han Su

Changes of tocopherols, tocotrienols, γ-oryzanol, and γ-aminobutyric acid levels in the germinated brown rice of pigmented and nonpigmented cultivars.

This study examined the changes of tocopherols (Toc), tocotrienols (T3), γ-oryzanol (GO), and γ-aminobutyric acid (GABA) contents in germinated brown rice (GBR) of pigmented and nonpigmented cultivars under different germination conditions. Results showed that the Toc and T3 contents in GBR were significantly different between treatments in both rice cultivars. The pigmented GBR possessed higher total vitamin E, total Toc, total T3, and GO contents than the nonpigmented GBR; however, its level of GABA was lower. The order of the three highest vitamin E homologues in pigmented and nonpigmented GBR was γ-T3 > γ-Toc > α-Toc and α-Toc > γ-T3 > α-T3, respectively; β-Toc, β-T3, δ-Toc, and δ-T3 were present in only small amounts (≤1.0 mg/kg) in GBR of both cultivars. Although both cultivars showed an increase in GABA contents with increasing germination time, the GABA content in nonpigmented GBR was higher.

Inhibitory potential of fatty acids on key enzymes related to type 2 diabetes.

This study aimed to examine the inhibitory mechanisms of fatty acids on key enzymes related to type 2 diabetes, and their effects on starch digestion rate. Among the 10 fatty acids analyzed, oleic acid showed the strongest anti-α-glucosidase activity, followed by linoleic acid, and their activities were more potent than acarbose, but they possessed a weaker anti-α-amylase activity. Kinetic assays demonstrated that oleic acid and linoleic acid were competitive inhibitors, and their interactions with α-glucosidase exhibited a character of static quenching, which indicates that they would bind to α-glucosidase to form a complex. However, they had little effects on the secondary structures of α-glucosidase. In vitro study showed that oleic acid and linoleic acid were more potent than acarbose in inhibiting starch digestion. Taken together, these results conclude that oleic acid and linoleic acid possess potent inhibitory effects on α-glucosidase activity.

Effects of different extraction temperatures on the physicochemical properties of bioactive polysaccharides from Grifola frondosa

This study examined the effects of different extraction temperatures (70°C, 100°C and 121°C) on the physicochemical properties of water soluble polysaccharides (WSP; GF70, GF100 and GF121, respectively) from Grifola frondosa (GF) fruiting bodies, and evaluating their effects on nitric oxide (NO) production in lipopolysaccharide-stimulated RAW264.7 macrophages. Results showed that GF121 had the highest yield. GF70, GF100 and GF121 contained a similar monosaccharide composition and the predominant monosaccharide was glucose. These polysaccharides contained two major macromolecular populations; the high molecular weight population showed a clear trend of reduced molecular weight with increasing extraction temperature. GF121 contained the highest amount of (1→3, 1→6)-β-d-glucans, while the degree of branching in all samples was similar. GF WSP possessed NO inhibitory activity, and the strongest was GF121. This study concludes that WSP are good sources of food ingredients, and high temperature extraction could improve the quantity and quality of GF WSP.

Inhibitory potential of Grifola frondosa bioactive fractions on α‐amylase and α‐glucosidase for management of hyperglycemia

This study examined the inhibitory effects of Grifola frondosa (GF), a medicinal mushroom popularly consumed in traditional medicine and health food, on digestive enzymes related to type 2 diabetes; chemical profiles and inhibitory kinetics of its bioactive fractions were also analyzed. Results showed that all GF extracts showed weak anti‐α‐amylase activity; however, strong anti‐α‐glucosidase activity was noted on GF n‐hexane extract (GF‐H). Further fractionation confirmed that compared with acarbose (a commercial α‐glucosidase inhibitor), the nonpolar fraction of GF possessed a stronger anti‐α‐glucosidase activity but a weaker anti‐α‐amylase activity. These activities were not derived from ergosterol and ergosterol peroxide, two major compounds of this fraction. The inhibitory kinetics of GF‐H on α‐glucosidase was competitive inhibition. GF‐H was as good as acarbose in inhibiting the starch digestion in vitro. Oleic acid and linoleic acid could be the major active constituents that have contributed to the potency of GF in inhibiting α‐glucosidase activity.

Effects of Grifola frondosa non-polar bioactive components on high-fat diet fed and streptozotocin-induced hyperglycemic mice.

Abstract Context: Consumption of medicinal mushrooms for disease prevention and maintaining health has a very long history in Asia. Grifola frondosa (Fr) S.F. Gray (GF) (Meripilaceae) is a medicinal fungus popularly used for enhancing immune systems, lowering blood glucose, and improving spleen, stomach, and nerve functions. Objective: This study examines the hypoglycemic effects of GF in vitro and in vivo, and analyzes the chemical profiles of its bioactive components. Materials and methods: In vitro hypoglycemic effects of GF was evaluated enzymatically using α-amylase and α-glucosidase inhibition assays, whereas in vivo study was conducted on high-fat diet fed and streptozotocin (HFD + STZ)-induced hyperglycemic mice. GC-MS was used to determine the chemical profiles of bioactive components. Results: The non-polar fraction of GF exhibited a stronger anti-α-glucosidase activity (IC50: 0.0332 mg/ml) than acarbose, but its anti-α-amylase activity (IC50: 0.671 mg/ml) was weaker. Oral administration of GF at 600 mg/kg (GF600) significantly lowered the blood glucose, HbA1c, average blood glucose, and serum total cholesterol levels in hyperglycemic mice. Although GF was found to contain mainly oleic acid and linoleic acid, their levels in the fungus were low, suggesting that the effects of GF on HFD + STZ-induced hyperglycemic mice could be due to factors other than these fatty acids. Conclusion: These results conclude that GF possesses anti-α-glucosidase activity, and hypoglycemic effect in HFD + STZ-induced hyperglycemic mice.

Differences in water soluble non-digestible polysaccharides and anti-inflammatory activities of fruiting bodies from two cultivated Xylaria nigripes strains

Polysaccharides including β-glucans are important bioactive components of mushroom. Xylaria nigripes is a popular medicinal fungus that has been used for treating trauma, insomnia and mental illness. This study examined the physicochemical characteristics and anti-inflammatory activities of water soluble non-digestible polysaccharides (TXNP and CXNP) from fruiting bodies of two cultivated X. nigripes strains (TXN and CXN). Results showed that both TXNP and CXNP possessed relatively similar FT-IR spectra. TXNP had a triple helix conformation and molecular weight of 853.8 kDa, whereas the molecular weight of CXNP was 14.7 kDa. The monosaccharide composition of TXNP was predominantly glucose, whereas CXNP contained xylose, mannose and glucose. Although both TXNP and CXNP dose-dependently suppressed the production of NO, IL-1β, TNF-α and PGE2, as well as the expression of iNOS, COX-2 and NF-κB in the lipopolysaccharide-induced RAW264.7 macrophages, the potency of TXNP was stronger. This study reveals that under similar conditions of cultivation and extraction procedures, the different physicochemical characteristics of polysaccharides from TXN and CXN may have contributed to the differences in their anti-inflammatory potency.