Jinjin Chen

Extraction, purification and antioxidant activities of the polysaccharides from maca (Lepidium meyenii)

Water-soluble polysaccharides were separated from maca (Lepidium meyenii) aqueous extract (MAE). The crude polysaccharides were deproteinized by Sevag method. During the preparation process of maca polysaccharides, amylase and glucoamylase effectively removed starch in maca polysaccharides. Four Lepidium meyenii polysaccharides (LMPs) were obtained by changing the concentration of ethanol in the process of polysaccharide precipitation. All of the LMPs were composed of rhamnose, arabinose, glucose and galactose. Antioxidant activity tests revealed that LMP-60 showed good capability of scavenging hydroxyl free radical and superoxide radical at 2.0mg/mL, the scavenging rate was 52.9% and 85.8%, respectively. Therefore, the results showed that maca polysaccharides had a high antioxidant activity and could be explored as the source of bioactive compounds.

Responses of typical grasslands in a semi-arid basin on the Qinghai-Tibetan Plateau to climate change and disturbances

Alpine grassland ecosystems on the Qinghai-Tibetan Plateau (QTP) are vulnerable to climate change and anthropogenic disturbances, which may have significant effects on the QTP’s carbon budgets. In this study, vegetation and soil characteristics were compared among alpine grassland ecosystems in a semi-arid basin on the northeast ridge of the QTP (1) among alpine swamp meadow, meadow, steppe meadow and steppe soils, which represent the direction of succession under climate-warming conditions, and (2) among alpine, degraded and tilled meadow soils to investigate the effects of human disturbance. The results showed that (1) if the alpine grassland ecosystems succeed in this direction, climate warming will cause a loss of carbon, and (2) tilling activity also results in carbon loss. Therefore, these results indicate that anthropogenic disturbance regimes that change more rapidly than climate may exert a more profound influence on carbon dynamics and balance. However, the plots that were set in the present study represented only part of the basin due to road accessibility. Relationships between leaf area index (biomass and soil carbon) and fractional vegetation coverxa0×xa0vegetation height from this study are fairly good, which can be applied at regional scale to estimate carbon pools. In combination with detailed information of grassland types, climate and human activities, the effects of climate change and disturbances can be estimated using remote sensing datasets.

Effect of drying methods on physicochemical properties and antioxidant activities of wolfberry (Lycium barbarum) polysaccharide.

In this study, an efficient drying process of Lycium barbarum L. polysaccharide (LBP) suitable for industrial production was developed and optimized. Three drying methods, including hot air drying (40-80°C), vacuum drying (40-60°C) and spray drying were test and compared. Hot air drying and vacuum drying cost long time and produced a brown product which needs further process due to the agglomeration or alveolation form. The condition of spray drying (without any excipient) was optimized by orthogonal experiment, which gave different optimum conditions based on LBP recovery rate (LBP solution concentration 1.06 g/mL, inlet air temperature 170°C, sample flow rate 15 mL/min and air speed 4.2m(3)/min) or LBP transparency (LBP solution concentration 1.04 g/mL, inlet air temperature 170°C, sample flow rate 20 mL/min and air speed 2.8m(3)/min). Pilot scale experiments showed preferable stability of LBP product quality and process parameters. Sample of spray drying (SD) had the highest scavenging free radical effects, the best appearance (LBP transparency), and uniform morphology with hollow sphere which are important properties for the reconstitution of the powder product. Considering the product appearance and product activity, the spray drying was selected to apply in industrial production.

Physicochemical and functional properties of dietary fiber from maca (Lepidium meyenii Walp.) liquor residue

Using maca (Lepidium meyenii) liquor residue as the raw material, dietary fiber (DF) was prepared by chemical (MCDF) and enzymatic (MEDF) methods, respectively, of which the physicochemical and functional properties were comparatively studied. High contents of DF were found in MCDF (55.63%) and MEDF (81.10%). Both fibers showed good functional properties, including swelling capacity, water holding capacity, oil holding capacity, glucose adsorption capacity and glucose retardation index. MEDF showed better functional properties, which could be attributed to its higher content of DF, more irregular surface and more abundant monosaccharide composition. The results herein suggest that maca DF prepared by enzymatic method from liquor residue is a good functional ingredient in food products.

Preliminary characterizations, antioxidant and hepatoprotective activity of polysaccharide from Cistanche deserticola

To research the preliminary characterizations, antioxidant and hepatoprotective activity of polysaccharides from Cistanche deserticola (CDPs), three polysaccharide fractions, CDP-A, CDP-B and CDP-C, were obtained by successively membrane filtration (microfiltration, ultrafiltration and nanofiltration). Molecular weights, monosaccharide compositions, purities and IR spectra of the three fractions were analyzed. Results showed that CDP-C contained higher proportion of galacturonic acid (GalUA) than CDP-B and CDP-A. Antioxidant activities were also analyzed and the results revealed that CDP-C possessed the highest activity. Thus, hepatoprotective activity of CDP-C was studied further. In vitro research, CDP-C promoted viability of HepG2 cells. In vivo research, CDP-C ameliorated the alterations induced by alcohol, including serological indexes (alanine transaminase, acid phosphatase, γ-glutamyl transpeptidase and triglyceride) and hepatic indicators (superoxide dismutase, malondialdehyde, glutathione S-transferase and triglyceride) in model animals. The prominent microvesicular steatosis and mild necrosis in hepatic histopathology of model animals were also attenuated by CDP-C administration. These findings indicated that CDP-C possessed hepatoprotective activity against chronic hepatic injury induced by alcohol. The underlying mechanism might be that CDP-C can reduce the contents of MDA and TG, and modulate the activities of the relative enzyme. This property might associate with GalUA in CDP-C.

Identification of maca (Lepidium meyenii Walp.) and its adulterants by a DNA-barcoding approach based on the ITS sequence

Maca (Lepidium meyenii) is an herbaceous plant that grows in high plateaus and has been used as both food and folk medicine for centuries because of its benefits to human health. In the present study, ITS (internal transcribed spacer) sequences of forty-three maca samples, collected from different regions or vendors, were amplified and analyzed. The ITS sequences of nineteen potential adulterants of maca were also collected and analyzed. The results indicated that the ITS sequence of maca was consistent in all samples and unique when compared with its adulterants. Therefore, this DNA-barcoding approach based on the ITS sequence can be used for the molecular identification of maca and its adulterants.

Macamides present in the commercial maca (Lepidium meyenii) products and the macamide biosynthesis affected by postharvest conditions

Abstract Macamides are bioactive and marker compounds of maca (Lepidium meyenii). Thirty-five commercial maca products were surveyed for macamide composition and content by HPLC-UV/MS. Significant variations of macamide content were found in these products (69–2738 μg/g). Analysis of the macamide biosynthetic pathway suggests that: (a) glucosinolate catabolism, (b) lipid hydrolysis, and (c) amide formation are key steps controlling macamide accumulation in the tissues during the postharvest drying process. Therefore, we further investigated the effects of sample forms, drying temperatures, and storage times on macamide accumulation. Our results show that (1) powdered maca provided the largest macamide accumulation followed by sliced hypocotyls, while whole roots displayed a significantly reduced amide-generating potential; (2) the ideal temperature for macamide formation is about 30°C; (3) macamide content increases continuously along with storage time; (4) exposure to air results in the percentage of unsaturated macamides decreasing. These findings provide useful insights which can be applied in the industrial manufacture of maca products with higher content of bioactive amides.

Molecular weight controllable degradation of Laminaria japonica polysaccharides and its antioxidant properties

In this study, molecular weight controllable degradation of algal Laminaria japonica polysaccharides (LPS) was investigated by ultrasound combined with hydrogen peroxide. Three main factors, i.e., ultrasonic power (A), ultrasonic time (B), and H2O2 concentration (C) were chosen for optimizing parameters by employing three-factors, three-levels BBD. The influence of degradation on structure change and antioxidant activities was also investigated. A second-order polynomial equation including molecular weight (Y) of Laminaria japonica polysaccharides and each variable parameter, i.e., ultrasonic power (A), ultrasonic time (B), and H2O2 concentration (C), was established: Y=20718.67−4273.13A−4000.38B−1438.75C+2333.25AB+1511.00AC+873.00BC+2838.29A2 + 2490.79B2+873.04C2. The equation regression coefficient value (R2 = 0.969) indicated that this equation was valid. The value of the adjusted determination coefficient (adjusted R2 = 0.914) also confirmed that the model was highly significant. The results of selected experimental degradation conditions matched with the predicted value. FT-IR spectra revealed that the structures of LPS before and after degradation were not significantly changed. Antioxidant activities of LPS revealed that low Mws possessed stronger inhibitory than the original polysaccharides. The scavenging effects on superoxide radicals was the highest when IC50 of crude LPS was 4.92 mg mL−1 and IC50 of Mw 18.576 KDa was 1.02 mg mL−1, which was fourfold higher than initial polysaccharide.