Peter C.K. Cheung

Antioxidant activity and total phenolics of edible mushroom extracts

Abstract Methanol and water crude extracts from Shiitake mushroom (Lentinus edodes) and straw mushroom (Volvariella volvacea) were investigated for their antioxidant capacity in three different assays, namely, the β-carotene and linoleic acid system, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity, and inhibition of hemolysis of rat erythrocyte induced by peroxyl radicals. Among the four mushroom extracts, the water extract from L. edodes showed the most potent radical scavenging activity in each assay, showing 75.9% (at 20 mg/ml) in the β-carotene bleaching method, 55.4% in the DPPH radical scavenging method (at 6 mg/ml) and 94.9% of inhibition of erythrocyte hemolysis (at 5 mg/ml). Total phenolics in the water extracts were higher than that of the methanol ones. Positive correlations were found between total phenolic content in the mushroom extracts and their antioxidant activities. Edible mushrooms may have potential as natural antioxidants.

Nutritional evaluation of some subtropical red and green seaweeds: Part I — proximate composition, amino acid profiles and some physico-chemical properties

Abstract The proximate composition, amino acid profile and some physico-chemical properties of two subtropical red seaweeds (Hypnea charoides and Hypnea japonica) and one green seaweed (Ulva lactuca) were investigated. The total dietary fiber [ranged from 50.3 to 55.4% dry weight (DW)] and ash (ranged from 21.3 to 22.8% DW) were the two most abundant components in these seaweeds but their crude lipid contents were very low (ranged from 1.42 to 1.64% DW). Although the crude protein content of the red seaweeds was significantly (p

Nutritional evaluation of some subtropical red and green seaweeds Part II. In vitro protein digestibility and amino acid profiles of protein concentrates

Abstract The nutritional values of seaweed protein concentrates (PCs) isolated from two red seaweeds (Hypnea charoides and Hypnea japonica) and one green seaweed (Ulva lactuca) were evaluated by determining their in vitro protein digestibility and amino acid profiles. Both protein extractability and in vitro protein digestibility of the red seaweed PCs (88.7–88.9%) were significantly (P

Antitumor activities of heteropolysaccharides of Poria cocos mycelia from different strains and culture media.

Ten water-soluble heteropolysaccharide fractions were isolated from Poria cocos mycelia cultured from one wild and one cultivated strain in two identical culture media differing only in one component: either corn steep liquor or bran extract. The chemical compositions, including monosaccharide profile, protein content, and molecular mass M(w) of the mycelial polysaccharides were determined. Both the in vitro and in vivo antitumor activities of the heteropolysaccharides were evaluated and compared. The heteropolysaccharides from Poria cocos mycelia cultured with the wild strain in a medium containing corn steep liquor exhibited the highest antitumor activities against Sarcoma 180 in vivo.

The hypocholesterolemic effect of two edible mushrooms: Auricularia auricula (tree-ear) and Tremella fuciformis (white jelly-leaf) in hypercholesterolemic rats1

The effect of two edible mushrooms, namely Auricularia auricula (Tree-ear) and Tremella fuciformis (White jelly-leaf) of the Heterobasidiae, on serum and liver lipids, fecal neutral steroids and bile acid excretion was investigated in rats. Male Sprague-Dawley rats were fed two semisynthetic hypercholesterolemic diets (1.5% cholesterol, 5% fat) each containing 5% dried powder of the two mushrooms. After 4 wk of mushroom diet consumption, the serum total cholesterol concentration was significantly decreased in both A. auricula and T. fuciformis diet groups (17 and 19%, respectively). Similar significant decrease in serum LDL cholesterol level was observed (24 and 31%, respectively). There was no significant difference found in serum HDL cholesterol concentration and the amount of liver total cholesterol and total lipids among the two mushroom diet groups and the control group. Only animals fed T. fuciformis diet had a significant decrease in serum triacylglycerol level. Animals fed A. auricula diet had a significant increase in the levels of fecal neutral steriods and bile acids by 39 and 46%, respectively. T. fuciformis diet also increased significantly the fecal excretion of neutral steroids and bile acids in rats by 51 and 36%, respectively. In the present study, both mushrooms had effective hypocholesterolemic activity in rats.

Temperature and pressure effects on supercritical carbon dioxide extraction of n-3 fatty acids from red seaweed

Lipids were extracted with supercritical carbon dioxide (SC-CO2) from a subtropical red seaweed (Hypnea charoides) within the temperature range 40–50°C and the pressure range 24.1–37.9 MPa. In general, the extraction rates of algal lipids increased with pressure and temperature except when the pressure was at 24.1 MPa. The combined effect of pressure and temperature on the solubility of individual n-3 fatty acids in the SC-CO2 varied with its carbon chain length. The concentrations of C18, C20 and C22 n-3 fatty acids, extracted under different pressure and temperature conditions, were significantly different (p<0.05). Proportions of total polyunsaturated fatty acids increased significantly (p<0.05) and proportions of total saturated fatty acids decreased significantly (p<0.05) with increasing pressure as shown by the saturated/unsaturated and saturated/polyunsaturated ratios.

Enhancement of Antitumor Activities in Sulfated and Carboxymethylated Polysaccharides of Ganoderma lucidum

Two water-soluble derivatives, sulfated and carboxymethylated Ganoderma lucidem polysaccharides, coded as S-GL and CM-GL, were prepared using derivatization of water-insoluble polysaccharides (GL-IV-I) extracted from the fruit body of G. lucidem . The degree of substitution (DS) of S-GL and CM-GL was 0.94 and 1.09, respectively. The weight-average molecular mass (Mw) of GL-IV-I, S-GL, and CM-GL was determined with light scattering to be 13.3x10(4), 10.1x10(4), and 6.3x10(4), respectively. S-GL and CM-GL inhibited the in vitro proliferation of Sarcoma 180 (S-180) tumor cells in a dose-dependent manner, with an IC50 value of 26 and 38 microg/mL, respectively. They also inhibited the growth of S-180 solid tumors implanted in BALB/c mice, with low toxicity to the animals. Flow cytometric studies revealed that treatment of S-GL and CM-GL with S-180 tumor cells could mediate the cell-cycle arrest in the G2/M phase. The expression of Bax increased, and the expression of Bcl-2 decreased dramatically, as shown by immuno-histochemical staining of S-180 tumor tissue excised from the animals. The sulfated and carboxmethylated groups in the polysaccharides played an important part in enhancing their antitumor activities, leading to the potential to be developed into antitumor drugs.

The hypocholesterolemic effect of extracellular polysaccharide from the submerged fermentation of mushroom

Male Sprague-Dawley rats were fed two semisynthetic diets supplemented with 2% cholesterol and 1% β-glucan type extracellular polysaccharide isolated from two liquid cultures of straw mushroom (Volvariella volvacea) mycelium containing different carbon sources. The experimental diets containing the two mycelial extracellular polysaccharides had induced a significant reduction in the levels of serum total cholesterol, LDL-cholesterol, and liver total cholesterol in the animals. There was no significant changes in the concentrations of serum triacylglycerol, HDL-cholesterol and liver total lipids. The fecal neutral steroid level was significantly increased while the fecal bile acid excretion was not significantly affected. Both mycelial extracellular polysaccharides exhibited hypocholesterolemic activity in rats with alimentary-induced hypercholesterolemia.

Chemical structure and chain conformation of the water-insoluble glucan isolated from Pleurotus tuber-regium

A water‐insoluble polysaccharide (TM8) was isolated from sclerotium of Pleurotus tuber‐regium by extraction with 0.5M NaOH aqueous solutions at 120°C. Its chemical structure was confirmed by infrared, high performance liquid chromatography, gas chromatography, and 13C NMR in dimethylsulfoxide (DMSO) to be composed of β‐(1 → 3)‐D‐glucan backbone chain linked with a branched glucose, one out of every three glycosyl units being substituted at C6 position. The glucan TM8 in DMSO was fractionated by nonsolvent addition method into ten fractions, and the solution properties were studied by size exclusion chromatography combined with multiangle laser light scattering (SEC‐MALLS) and viscometry in DMSO at 30°C. The dependencies of intrinsic viscosity [η] and radius of gyration 〈s2〉z1/2 on weight‐average molecular mass Mw for this glucan were found to be [η] = (9.24 ± 0.2) × 10−2Mw0.51 ± 0.02 (cm3g−1) and 〈s2〉z1/2 = (3.67 ± 0.3) × 10−2Mw0.56 ± 0.02 (nm) in the range of Mw from 1.07 × 104 to 77.4 × 104. Based on current theories for a wormlike chain, the conformational parameters of the glucan TM8 were found to be 408 (nm−1) for ML, 3.1 (nm) for q, and 16.8 for C∞, suggesting that the polysaccharide exists as a dense random‐coil chain in DMSO, due to branched structure.

Influence of drying treatment on three Sargassum species 2. Protein extractability, in vitro protein digestibility and amino acid profile of protein concentrates

The effects of different drying treatments (oven- andfreeze-drying) on protein extractability of three subtropical brownseaweeds, Sargassum hemiphyllum, S. henslowianum and S. patens, as well as in vitro protein digestibility and amino acid profileof their protein concentrates (PCs) were investigated. When comparedwith freeze-drying, oven-drying not only improved significantly (p <0.05, two-way ANOVA, Tukey-HSD) the protein extractability of thethree Sargassum species but also the protein quality (in vitroprotein digestibility) of their PCs. Therefore, oven-drying was found to bemore suitable for protein extraction of brown seaweeds. The relationshipsbetween the protein extractability and total phenolic content in seaweedsand between in vitro protein digestibility and total phenolic contentin PCs were also discussed.