Qilan Wang

Methane emissions by alpine plant communities in the Qinghai-Tibet Plateau

For the first time to our knowledge, we report here methane emissions by plant communities in alpine ecosystems in the Qinghai–Tibet Plateau. This has been achieved through long-term field observations from June 2003 to July 2006 using a closed chamber technique. Strong methane emission at the rate of 26.2±1.2 and 7.8±1.1 μg CH4 m−2 h−1 was observed for a grass community in a Kobresia humilis meadow and a Potentilla fruticosa meadow, respectively. A shrub community in the Potentilla meadow consumed atmospheric methane at the rate of 5.8±1.3 μg CH4 m−2 h−1 on a regional basis; plants from alpine meadows contribute at least 0.13 Tg CH4 yr−1 in the Tibetan Plateau. This finding has important implications with regard to the regional methane budget and species-level difference should be considered when assessing methane emissions by plants.

Optimization of polysaccharides from Lycium ruthenicum fruit using RSM and its anti-oxidant activity

Dynamic microwave-assisted extraction (DMAE) technique was employed for the extraction of polysaccharides from Lycium ruthenicum (LRP). The extracting parameters were optimized by using three-variable-three-level Box-Behnken design and response surface methodology (RSM) based on the single-factor experiments. RSM analysis indicated good correspondence between experimental and predicted values. The optimum extraction parameters for the yield of polysaccharide were ratio of water to raw material 31.5 mL/g, extracting time 25.8 min and microwave power 544.0 W. Polysaccharide was analyzed by chemical methods and Fourier-transform infrared (FT-IR). The antioxidant activities of LRP were investigated including scavenging activity of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide and free radicals of superoxide anion in vitro. The results of antioxidant activity exhibited LRP had the potential to be explored as novel natural antioxidant for using in functional foods or medicine.

Separation and purification of water-soluble iridoid glucosides by high speed counter-current chromatography combined with macroporous resin column separation

Four iridoid glucosides, shanzhiside methyl ester, phloyoside II, chlorotuberside, and penstemonoside, were isolated and purified from an herbal medicinal plant for the first time by high-speed counter-current chromatography (HSCCC) using a two-phase solvent system composed of ethyl acetate-n-butanol-water (5:14:12, v/v/v). A total of 37mg of shanzhiside methyl ester, 29mg of phloyoside II, 27mg of chlorotuberside, and 21mg of penstemonoside with the purity of 99.2%, 98.5%, 97.3%, and 99.3%, respectively, were obtained in one-step separation within 4h from 150mg of crude extract. To the best of our knowledge, this is the first report of separation and purification of iridoid glucosides from natural sources by HSCCC. The chemical structures of all the four compounds were identified by ESI-MS, (1)H NMR, and (13)C NMR.

Culturable actinomycetes from desert ecosystem in northeast of Qinghai-Tibet Plateau

In this study, 53 actinomycetes strains were isolated from desert ecosystems located in northeast of Qinghai-Tibet Plateau and grouped into four RFLP patterns. Twenty-six actinomycetes with obvious morphology differences were chosen for phylogenetic diversity study and antimicrobial testing. As a result, the 16S rRNA gene sequencing showed that these strains belonged to Streptomyces, Micromonospora, Saccharothrix, Streptosporangium and Cellulomonas, and that most of the strains had antimicrobial bioactivity. The PKS and NRPS genes detection indicated diversified potential bioactive products of actinomycetes in this ecosystem. Among these strains, Sd-31 was chosen to study the bioactive products using HPLC-MS because of its optimum antimicrobial bioactivity. The result showed that it might produce Granatomycin A, Granatomycin C, and an unknown compound.

Two-dimensional hydrophilic interaction chromatography × reversed-phase liquid chromatography for the preparative isolation of potential anti-hepatitis phenylpropanoids from Salvia prattii.

Traditional Tibetan medicine is important for discovery of drug precursors. However, knowledge of the chemical composition of traditional Tibetan medicines is very limited due to the lack of appropriate chromatographic purification methods. In the present work, Salvia prattii was taken as an example, and an off-line hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography preparative method was developed for the purification of phenylpropanoids with high purity from a crude sample of Salvia prattii. Based on the separation results of four different chromatographic stationary phases, the first-dimensional preparation was performed on an XAmide preparative column with the crude sample concentration of 62.0 mg/mL, and five main fractions were obtained from the 12.4 g crude sample with a recovery of 54.8%. An XCharge C18 preparative column was applied in the second-dimensional preparation to further isolate the phenylpropanoids from the redissolved first-dimensional fractions with concentration of approximately 50.0 mg/mL. The purities of the phenylpropanoids isolated from the crude sample of Salvia prattii were higher than 98%, indicating that the method was efficient for the purification of phenylpropanoids with high purity from Salvia prattii. Additionally, this method showed great potential in the preparation of phenylpropanoids and can serve as a good example for the purification of phenylpropanoids from other plant materials.

Two-dimensional chromatography based on on-line HPLC-DPPH bioactivity-guided assay for the preparative isolation of analogue antioxidant compound from Arenaria kansuensis.

Traditional Tibetan medicine is important for discovery of drug precursors. However, information about the chemical composition of traditional Tibetan medicine is very limited due to the lack of appropriate chromatographic purification methods. In the present work, A. kansuensis was taken as an example and a novel two-dimensional reversed-phase/hydrophilic interaction liquid chromatography(HILIC) method based on on-line HPLC-DPPH bioactivity-guided assay was developed for the purification of analogue antioxidant compounds with high purity from the extract of A. kansuensis. Based on the separation results of many different chromatographic stationary phases, the first-dimensional (1D) preparation was carried on a RP-C18HCE prep column, and 2 antioxidant fractions were obtained from the 800mg crude sample with a recovery of 56.7%. A HILIC-XAmide prep column was selected for the second-dimensional (2D) preparation. Finally, a novel antioxidant β-carboline Alkaloids (Glusodichotomine AK) and 4 known compounds (Tricin, Homoeriodictyol, Luteolin, Glucodichotomine B) were purified from A. kansuensis. The purity of the compounds isolated from the crude extract was >98%, which indicated that the method built in this work was efficient to manufacture single analogue antioxidant compounds of high purity from the extract of A. kansuensis. Additionally, this method showed great potential in the preparation of analogue structure antioxidant compounds and can serve as a good example for the purification of analogue structure antioxidant carboline alkaloids and flavonoids from other plant materials.

Isolation and identification of antioxidant and α-glucosidase inhibitory compounds from fruit juice of Nitraria tangutorum

Nitraria tangutorum Bor., having edible berries, is valued for reputed health benefits in Qinghai-Tibet plateau. The phytochemical research on the fruit juice of N. tangutorum led to the isolation of twenty-six compounds including five new compounds, tangutorids A-D (1, 2, 3a, and 3b), and (3E,5E)-7-O-β-glucosyl-4-(2-methoxy-2-oxoethyl)hepta-3,5-dienoic acid (15). The structures of these compounds were elucidated through comprehensive spectroscopic analyses. Tangutorids A-F were the first examples of glucose-derived β-carbolines from natural products. The biogenetic pathways of 1-8 were proposed to involve Pictet-Spengler reactions and described starting from the co-isolated tryptophan (10) and corresponding aldehydes. All isolates were evaluated for their antioxidant and α-glucosidase inhibitory activities. Compounds 21, 22, and 24 showed antioxidant activity with SC50 values ranging from 12.2±1.9 to 30.4±2.7μg/mL, and compound 1 showed strong α-glucosidase inhibitory effect with IC50 value of 63.3±4.6μg/mL.

Protective Effects of Dracocephalum heterophyllum in ConA-Induced Acute Hepatitis

Dracocephalum heterophyllum (DH) is a Chinese herbal medicine used in treating hepatitis. However, the protective effects and pharmacological mechanisms of DH in hepatitis are unknown. In this study, we found that pretreatment with DH extract significantly ameliorated liver injury and suppressed the production of inflammatory cytokines, including tumor necrosis factor (TNF-α) and interferon-γ (IFN-γ) in Concanavalin A- (ConA-) induced hepatitis (CIH). DH recruited more CD11b+ Gr1+ myeloid-derived suppressor cells (MDSCs) to the liver and suppressed infiltration of macrophages (Kupffer cells) in the liver. The present work explores DH as an effective hepatoprotective medicine to inhibit inflammation and liver injury caused by hepatitis.

Chemical Constituents of Incarvillea compacta

Incarvillea Juss. is notable for being a temperate and herbaceous genus of the primarily tropical and woody family Bignoniaceae. It is composed of 16 species, and most of the species occur in the Himalayas and S. W. China, whereas, a number of species are distributed through eastern and central Asia and into Mongolia [1, 2]. Many species of this genus are used as an ethnobotanical herb in China. For example, I. arguta has been widely used as a herbal medicine of the Yi nationality (an ethnic minority group of China) to treat hepatitis and diarrhea in China, and I. sinensis has been used in traditional Chinese medicine as a drug (“Tougucao”) to treat rheumatism and to relieve pain [3, 4]. Incarvillea compacta Maxim. is distributed in gravel slopes and grass brush, at 2600–4100 meters above sea level, in Gansu, Qinghai, Yunnan, and Tibet of China [5]. It is one of the four plant resources of red “Ou-Qv,” a common Tibetan medicine, commonly used for treating jaundice and stomachache, and especially as a major component in the prescription for otopathy like tympanitis and suppurative otitis media [6]. Previous work has been carried out on estimating the distribution area of I. compacta in Tibet, and the results showed that the distribution area of I. compacta was 4.75 105 km2, and the greatest resource amount of I. compacta was 2.17 105 tons in Tibet, which illustrated its abundant resources in Tibet [7]. However, its constituents are so far unknown. The aim of the study was to investigate the chemical constituents of I. compacta Maxim. through various chromatographic and spectroscopic methods. This study resulted in the identification of 23 known compounds, including five phenylpropanoid glycosides, three flavonoids, three iridoid glycosides, five triterpenes, two steroids, and four other compounds. The known compounds were identified as isoacteoside (1) [8], epimeridinoside A (2) [9], plantainoside C (3) [10], acteoside (4) [11], echinacoside (5) [12], citrusin C (6) [13], apigenin (7) [14], luteolin (8) [15], quercetin-3-O-L-(2 -galloyl)-arabinopyranoside (9) [16], sweroside (10) [17], swertiamarin (11) [18], 5-deoxystansioside (12) [19], -amyrin (13) [20], ursolic acid (14) [21], pololic acid (15) [22], roburic acid (16) [23], lupeol (17) [24], -sitosterol (18) [25], daucosterol (19) [26], caffeic acid (20) [27], 2,4-dihydroxy-6-methoxy-3-methylacetophenone (21) [28], palmitic acid (22) [29], and methyl gallate (23) [30] by comparison with authentic samples and by comparison of their spectroscopic and physical data with those previously reported. All of the isolates from Incarvillea compacta Maxim. were reported for the first time. The whole plant of Incarvillea compacta was bought from Lekang medicine market, Xining, Qinghai Province, P. R. China and identified by Prof. Li-Juan Mei (Northwest Institute of Plateau Biology, Chinese Academy of Science). The air-dried whole plants (5 kg) of I. compacta were extracted with 85% ethanol three times, each time for 3 h under reflux at 70 C. After concentration in vacuum, the combined extract (356 g) was suspended in H2O and partitioned with petroleum ether, EtOAc, and n-BuOH successively to give dried petroleum ether (50 g), EtOAc (118 g), n-BuOH (78 g), and H2O (106 g) fractions. The EtOAc soluble fraction was subjected to silica gel (200–300 mesh) column chromatography and eluted with a gradient solvent system of petroleum ether–EtOAc (5:1–1:1) to give six fractions (E1–E6). Compound 18 was crystallized from E3 and recrystallized to afford compound 18 (142 mg). The residue from E3 was subjected to CC over silica gel (CHCl3–Me2CO, 20:1–9:1) repeatedly to afford compounds 13 (19.2 mg) and 17 (50 mg). Compound 22 was crystallized from E4 and recrystallized to afford compound 22 (150 mg). The residue from E4 was subjected to column chromatography

A New Diarylheptanoid from Saxifraga tangutica

A new diarylheptanoid, (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptan-3-one-5-O-β-D-6-Oacetylglucoside (1), together with two known diarylheptanoids, (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptan-3-one-5-O-β-D-glucopyranoside (2) and hirsutanonol (3), were isolated from Saxifraga tangutica. The structures of 1–3 were elucidated using 1D and 2D NMR spectral data, including high-resolution mass spectra (HR-ESI-MS). It was found that the new compound was acetyl-substituted (5S)-1,7-bis-(3,4-dihydroxyphenyl)-5-hydroxyheptan-3-one-5-O-β-D-glucopyranoside.