Structural Characterization of Mannoglucan Isolated from Ophiocordyceps sobolifera and Its Antioxidant Activities.

A novel polysaccharide structure (PS-T80) was collected from Ophiocordyceps sobolifera biomass and characterized via a combination of chemical and spectral analyses. Employing high-performance gel permeation chromatography (HPGPC), the average molecular weight is proven to be 7.4 × 104 Da. Furthermore, a sugar composition analysis of the obtained polysaccharide suggests two main sugars, ß-d-glucose and α-d-mannose, at a molar ratio of 2:1, respectively, in the backbone. The structure analysis unveils that PS-T80 is a mannoglucan, possessing the repeating unit of [→3)-ß-d-Glcp-(1 → 3)-α-d-Manp-(1 → 3)-ß-d-Glcp-(1→] n . Such a configuration could be considered a novel polysaccharide. Impressively, in vitro antioxidant tests revealed that PS-T80 has a promising antioxidant activity. These results demonstrate that the obtained PS is a potential bioactive material for biomedical applications.

Dissipation of the pesticides fipronil, cypermethrin, and tebuconazole in vegetables: A case study in Thua Thien-Hue province, Central Vietnam.

This study was designed to understand the dissipation of fipronil, cypermethrin, and tebuconazole in green onions and mustard greens grown in Central Vietnam. A field trial on ca. 400 m2 was implemented for two months with three different cropping regimes (natural plot-fully exposed to natural conditions; bed plot-fenced in by plastic sheets with an open roof; and protected plot-fully covered by plastic sheets) for each vegetable. A first-order kinetic model was successfully employed to interpret the dissipation data of each studied pesticide. A comparing the dissipation rate constants obtained under the same crop and growing regime between chemicals suggested that, among the chemicals examined, fipronil dissipated most readily. The pesticides were also proven to be more persistent in crops grown in protected plots than those grown in natural plots. The half-lives for fipronil, cypermethrin, and tebuconazole fluctuated, occurring at 0.4-2.2 days, 2.0-6.0 days, and 0.9-3.3 days, respectively.

Multi-residue analytical method for trace detection of new-generation pesticides in vegetables using gas chromatography-tandem mass spectrometry.

A GC-MS/MS method with low solvent consumption and easy operation was developed to simultaneously determine ten new-generation pesticides, namely fenobucarb, acetochlor, pretilachlor, fipronil, trifloxystrobin, fluazifop-p-butyl, isoprothiolane, tebuconazole, cypermethrin and difenoconazole in leafy vegetables. Influences from ultrasonic sample extraction and the clean-up steps to reduce matrix effects were investigated. Under suitable conditions, good linearity (deviation of back calculated concentration from true concentration lower than 20%) was achieved for all studied pesticides; the method detection limits (MDLs) ranged from 1.4 to 3.6 ng g-1 wet weight. For mustard green and green onion the method yielded good recoveries at two spiking levels (201 and 100 ng g-1) ranging from 80% to 111% (n = 5). The repeatability, expressed as relative standard deviation (RSD), was lower than 11% (n = 5). The method was successfully used to quantify pesticide residues in 207 vegetable samples (green onions, mustard greens, and lettuce) collected in Thua Thien Hue and Quang Binh Provinces, Central Vietnam. The insecticide cypermethrin was found at critical levels in 98% of the vegetable samples. Green onions had high pesticide residues with a significant number of samples containing pesticides at concentrations exceeding the maximum residue levels (MRLs).