Spectrophotometric flow-injection determination of zinc in plant digests based on a spot test

A spot test was implemented in a flow-injection system for the spectrophotometric determination of zinc in digests of plant materials. It is based on the influence of Zn²⁺ on the oxidation rate of 1-naphthylethylenediamine (NED) by hexacyanoferrate(III) under acidic conditions. In order to control the precipitate formation and to maintain the resulting suspension, a micellar medium was established by adding Triton X-100. The proposed system handles about 65 samples per hour, meaning 72 μg NED and 9.0 mg K₃[Fe(CN)₆] per determination. Baseline drift is usually <0.01 absorbance per hour and the analytical signals for 0.5-2.5 mg l⁻¹ Zn range within ca. 0.07-0.45 absorbance. Linearity of the analytical curve is fair (r>0.999, n=6) and detection limit was estimated as 0.2 mg l⁻¹ Zn. Results are precise (R.S.D.<1%, n=10) and in agreement with flame atomic absorption spectrometry and with certified values of standard reference materials.     

Arbophylline, a novel heptacyclic indole with a cage skeleton incorporating an acetal moiety

A new indole alkaloid, arbophylline, possessing a novel heptacyclic cage skeleton, and incorporating an acetal function, was obtained from the Malayan Kopsia arborea. The structure was established by spectroscopic analysis and a possible biogenetic pathway from an akuammiline-type precursor is presented.     

SPME – A valuable tool for investigation of flower scent

A novel Headspace Solid Phase Microextraction (HS‐SPME) protocol is proposed for the analysis of floral scent. Volatile compounds emitted from the flower are collected on a Carboxen/PDMS fiber for 1 hour, transferred to the GC, and analyzed by GC/MS. The method completely eliminates the use of organic solvents, does not require special instrumentation, and may readily be performed in the field without access to mains electricity and other energy supplies. The method is robust, sensitive, and reduces the sampling stress on the investigated plant. Since enzymatic reactions in living flowers may cause changes in the composition of emitted fragrance, dried rosemary (Rosmarinus officinalis L.) was used as a stable standard for the method development and optimization. In addition, grape wine was also suggested as homogeneous, bio‐compatible, and relatively stable standard of pronounced and typical scent for the same purpose. The optimized method was used for the comparative investigation of the fragrances emitted by two different species – Lathyrus vernus (L.) and Orchis pallens (L.). Several monoterpenes (C10 compounds) were found as the main fragrance components of lathyrus, while sesquiterpenes (C15 compounds) were typical for the orchid.     

Unusual spirocyclic macroline alkaloids, nitrogenous derivatives, and a cytotoxic bisindole from Alstonia

The bark extract of the Malayan A. macrophylla provided several novel indoles with unprecedented carbon skeletons, an unusual nitrogenous compound, a cytotoxic bisindole, several new macroline alkaloids, in addition to other known alkaloids. The structures of the new compounds were established by spectroscopic analysis.     

Biogenic synthesis of gold and silver nanoparticles used in environmental applications: A review

Due to their physical, chemical, optical, and mechanical properties, metallic nanoparticles (MNPs) are increasingly being used, with an emphasis on silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs). In recent years, green synthesis has gained prominence for exploring the use of naturally available biological sources for the obtention of metallic nanoparticles. Among these, algae and plants stand out due to the presence of polysaccharides, proteins, polyphenols, and vitamins (among others) in their composition, which can act in the reduction and stabilisation of MNPs, and these biogenic materials have been characterised mainly by spectrometric and microscopic techniques. In addition, due to the numerous advantages of nanoparticles (NPs) synthetize from biogenic source, such as their simplicity and cost benefits, they have been used in the development of sensors applied in the determination of contaminants present in environmental samples and in the catalytic reduction of organic and inorganic contaminants. Therefore, this review describes the synthesis, mechanisms, characterization, and environmental analytical applications of NPs obtained by biogenic synthesis as well as the perspectives and challenges of these NPs.     

连续流动注射法测定土壤和植物中全磷

应用AA3型连续流动分析仪测定了土壤和植物中全磷.结果表明:对于采用高氯酸-硫酸消解的土壤样品以及硫酸-过氧化氢消解的植物样品,在测定时调节反应混合液的酸度使其在显色的适宜范围内,磷的质量浓度在6 mg·L-1(土壤)和7.5 mg·L-1(植物)以内呈线性,相关系数分别为0.999 2(土壤)和0.999 6(植物);加标回收率98.5%～100.5%,相对标准偏差小于2%,检出限分别为0.010 mg·L-1(土壤)和0.013 mg·L-1(植物).     

Correction of iron interface in the spectrophotometric flow injection catalytic determination of molybdenum in plants

Iron interference in the spectrophotometric catalytic determination of molybdenum based on the iodide-hydrogen peroxide reaction can be corrected by using sulphosalicylic acid as masking and color-forming reagent. The catalytic influence of iron ions is circumvented to the extent of about 90% and correction of any remaining iron ions is possible by monitoring the colored iron(III)-salicylate complex at 490 nm. In this way, iron is also determined. With the proposed system, molybdenum can be determined in plant and food digests within the 0–100 μg Mo 1⁻¹ range in the presence of up to 25 mg Fe 1⁻¹, at a sampling rate of about 50 determinations h⁻¹. The relative standard deviation of 10 consecutive measurements was estimated as < 2%. Results for samples were comparable with those obtained by graphite furnace atomic absorption spectrometry. In addition, recoveries within the range 94–100% were calculated.     

Carbon and oxygen isotope working standards from C3 and C4 photosynthates

A preparation of organic working standards for the online measurement of ¹³C/¹²C and ¹⁸O/¹⁶O ratios in biological material is presented. The organic working standards are simple and inexpensive C₃ and C₄ carbohydrates (sugars or cellulose) from distinct geographic origin, including white sugar, toilet and XEROX papers from Switzerland, maize from Ivory Coast, cane sugar from Brazil, papyrus from Egypt, and the core of the stem of a Cyperus papyrus plant from Kenya. These photosynthetic products were compared with International Atomic Energy standards CH-3 and CH-6 and other calibration materials. The presented working standards cover a 15 ‰ range of ¹³C/¹²C ratios and 9 ‰ for ¹⁸O/¹⁶O, with a precision<±0.2 ‰ for n>10.     

Nature-inspired biogenic synthesis of silver nanoparticles for antibacterial applications

In recent decades, nanotechnology has been empowered as a new and developing interdisciplinary region of science and innovation that coordinates material science and biology. Nanoscience and nanotechnology open up new streets of examination that are helpful in synthesizing novel nanomaterials with remarkable applications. Among different metal nanomaterials, silver nanoparticles (AgNPs) attracted the attention of researchers due to their versatile antibacterial characteristics and biological properties. Biogenically synthesizing AgNPs from plants and microorganisms seems to be a highly promising alternative for developing a technology that is both environmentally benign and fast. Plants and microorganisms' ability to synthesize AgNPs has mostly remained untapped, and the lack of investigation is due to the vast variety of plants and microorganisms. This review aims to describe the current progress in various synthetic techniques for AgNPs and their potential for antibacterial applications. It discusses biogenic synthetic approaches, the role of various metabolites in the growth processes of AgNPs with antibacterial implications, bactericidal mechanisms, and the influence of operational parameters on AgNPs synthesis. Furthermore, the present status, critical challenges, and future outlook of AgNPs will be explored, which will definitely affect their present and future scenarios. We believe that by focusing readers' attention on nature-inspired, biogenically synthesized AgNPs and their bactericidal applications, this review will enable them to formulate a new perspective.     

Arboricine and arboricinine, unusual tetracyclic indole regioisomers from Kopsia

A pair of unusual regioisomeric tetracyclic indoles of the corynantheine-type, arboricine and arboricinine were obtained from the Malayan Kopsia arborea. The structures were established by spectroscopic analysis and a possible biogenetic link between the alkaloids is presented.