Comparison of microwave‐assisted and conventional extraction of mangiferin from mango (Mangifera indica L.) leaves

Mangiferin is the main bioactive component in mango leaves, which possesses anti‐inflammatory, antioxidative, antidiabetic, immunomodulatory, and antitumor activities. In the present study, a microwave‐assisted extraction method was developed for the extraction of mangiferin from mango leaves. Some parameters such as ethanol concentration, liquid‐to‐solid ratio, microwave power, and extraction time were optimized by single‐factor experiments and response surface methodology. The optimal extraction conditions were 45% ethanol, liquid‐to‐solid ratio of 30:1 (mL/g), and extraction time of 123 s under microwave irradiation of 474 W. Under optimal conditions, the yield of mangiferin was 36.10 ± 0.72 mg/g, significantly higher than that of conventional extraction. The results obtained are beneficial for the full utilization of mango leaves and also indicate that microwave‐assisted extraction is a very useful method for extracting mangiferin from plant materials.     

Glycosidases of turnip leaf tissues

Four myrosinase (β-thioglucosidase EC. 3.2.3.1) and seven disaccharase (β-fructofuranosidase, EC. 3.2.1.26) isoenzymes were isolated from turnip leaves. The most active enzymes were isolated in pure form. Myrosinase and disaccharase mol wt was 62.0 × 10³ and 69.5 × 10³ dalton, respectively, on the basis of gel filtration on Sephadex G-200. Myrosinase pH profile showed high activity between pH 5 and 7 with the optimum at pH 5.5. The purified enzyme was heat-stable for 60 min at 30°C with only loss of 24% of activity. Its activity is strongly inhibited (100%) by Pb²⁺, Ba²⁺, Cu²⁺ and Ca²⁺ ions, and activated (70%) by EDTA at 0.04M. The pure enzyme failed to hydrolyze amylose, glycogen, lactose, maltose, and sucrose. TheK _m andV _max values of myrosinase using sinigrin as specific substrate was 0.045 mM and 2.5 U, respectively. The maximal activity of disaccharase enzyme was obtained at pH 4–5 and 35–37°C. The enzyme was heat-stable at 30°C for 30 min with only 10% loss of its activity. Its activity is strongly activated (70–240%) by Ca²⁺, Ba²⁺, Cu²⁺, and EDTA at 0.01M. The enzyme activity is specific to the disaccharide sucrose and failed to hydrolyze other disaccharides (maltose and lactose). TheK _m andV _max of disaccharase were 0.123 mM and 3.33 U, respectively.     

Antioxidant and toxicological evaluation of a Tamarindus indica L. leaf fluid extract

In the scientific community, there is a growing interest in Tamarindus indica L. leaves, both as a valuable nutrient and as a functional food. This paper focuses on exploring its safety and antioxidant properties. A tamarind leaf fluid extract (TFE) wholly characterised was evaluated for its anti-DPPH activity (IC₅₀ = 44.36 μg/mL) and its reducing power activity (IC₅₀ = 60.87 μg/mL). TFE also exhibited a high ferrous ion-chelating capacity, with an estimated binding constant of 1.085 mol L^? 1 while its influence over nitric oxide production in human leucocytes was irregular. At low concentrations, TFE stimulated NO output, but it significantly inhibited it when there was an increase in concentration. TFE was also classified as a non-toxic substance in two toxicity tests: the acute oral toxicity test and the oral mucous irritability test. Further toxicological assays are needed, although results so far suggest that TFE might become a functional dietary supplement.     

电感耦合等离子体原子发射光谱法测定杨树叶中铜锌铅镍

研究了电感耦合等离子体原子发射光谱法(ICP-AES)的仪器工作参数,溶液提升速率为2.4 mL.min-1,雾室压力为2.07×105Pa,观测高度为16 mm。用浓硝酸1 mL作样品的消化剂。用此方法测定杨树叶标准物质(GBW 07604)中铜、锌、铅、镍,相对误差在0.54%~9.3%之间,加标回收率在97.9%~101.0%之间。     

荧光法猝灭测定木槿叶中混合氨基酸的总量

在乙酸-乙酸钠缓冲介质中,氨基酸能猝灭壳聚糖-茚三酮体系荧光,基于此,对木槿叶中混合氨基酸进行测定,并对该方法的测定条件进行了讨论.线性范围为0.5～3.0 mmol/L,检出限为0.1 mmol/L.木槿叶干粉中游离氨基酸的质量分数为10.18%,相对标准偏差为1.3%,回收率为102.5%～94.3%.     

苎麻叶中绿原酸的分光光度法测定

探讨了采用分光光度法测定苎麻叶中绿原酸的含量的方法。12.5%的醋酸用量为0.1mL,7%尿素2.0mL,0.5%亚硝酸钠0.25mL,3min后加入5%氢氧化钠0.5mL,绿原酸与试剂形成鲜红色络合物,通过在510nm处测定溶液的吸光度确定绿原酸的含量。绿原酸浓度在0.01~0.12g/L范围内与吸光度值有良好的线性关系,回收率为95%~107%,相对标准偏差(RSD)为2.4%。该方法简便、快速。     

Conformal geometry of foliations

In this article, we begin a systematic study of conformal properties of codimension-1 foliations. We first define and study local conformal invariants. A case of particular interest is that of harmonic foliations of the plane. Then we study existence of totally umbilical and “Dupin” foliations on compact 3-manifolds of constant curvature.      

Antifeedant effects of mixed methylphenyl hexaorganoditin compounds of the type PhnMe6–nSnSn on larvae of Spodoptera littoralis and Epilachna varivestis

Compounds of the series Ph_nMe_6–nSn₂ were prepared and tested for their antifeedant effects against Spodoptera littoralis (Boisduval) and Epilachna varivestis (Mulsant) larvae. In addition, phytotoxicity towards bean seedlings was measured. The most active compound against both Spodoptera and Epilachna was Ph₃Me₃Sn₂. The compound at 50 mg dm^?3 was comparatively innocuous in phytotoxicity tests against bean seedlings.     

原子吸收光谱法测定粽叶中微量元素

用火焰原子吸收光谱法直接测定了粽叶中Fe、Cu、Zn、K、Ca、Na 6种微量元素的含量。结果表明,粽叶中含有丰富的人体必需微量元素。该法简单、准确,回收率在95.0%~105.0%之间,相对标准偏差(RSD)小于2.68%,结果令人满意。     

Determination and quantification of active phenolic compounds in pigeon pea leaves and its medicinal product using liquid chromatography–tandem mass spectrometry

A novel method using liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS) has been optimized and established for the qualitative and quantitative analysis of ten active phenolic compounds originating from the pigeon pea leaves and a medicinal product thereof (Tongluo Shenggu capsules). In the present study, the chromatographic separation was achieved by means of a HiQ Sil C18V reversed-phase column with a mobile phase consisting of methanol and 0.1% formic acid aqueous solution. Low-energy collision-induced dissociation tandem mass spectrometry (CID-MS/MS) using the selected reaction monitoring (SRM) analysis was employed for the detection of ten analytes which included six flavonoids, two isoflavonoids and two stilbenes. All calibration curves showed excellent coefficients of determination (r(2) ≥ 0.9937) within the range of tested concentrations. The intra- and inter-day variations were below 5.36% in terms of relative standard deviation (RSD). The recoveries were 95.08-104.98% with RSDs of 2.06-4.26% for spiked samples of pigeon pea leaves. The method developed was a rapid, efficient and accurate LC-MS/MS method for the detection of phenolic compounds, which can be applied for quality control of pigeon pea leaves and related medicinal products.