A review on the latest advances in extraction and analysis of artemisinin

Introduction: Artemisinin (1), a well-known natural antimalarial drug, is a sesquiterpene lactone that contains a unique peroxide bridge. Since its discovery, the amount of research into the analysis of artemisinin has increased considerably, and it has been further intensified since the Noble Prize win by Tu Youyou in the year 2015 for the discovery of artemisinin. Objective: To review published literature on the extraction and analysis of artemisinin, published during 2017-present, and to present an appraisal of those methods. Methodology: Extensive literature search was carried out which involved, but not limited to, the use of, various databases, like Web of Knowledge, PubMed and Google Scholar, and relevant published materials including published books. The keywords used, in various combinations, with artemisinin being present in all combinations, in the search were artemisinin, Artemisia annua, analysis, extraction, quantitative, qualitative and quality control. Results: During the period covered in this review, there are several methods of analysis of artemisinin have been reported, the most of which were LC-based methods. However, the use of new methods like near infrared analysis, fluorometirc analysis and molecular imprinting, and a significant increase in the use of computational tools have been observed. Mainly several methods involving supercritical fluid extraction and ultrasound-assisted extraction of artemisinin have dominated the extraction area. Conclusions: Newer analytical tools, as well as improved protocols for the known analytical tools, for qualitative and quantitative determination of artemisinin (1), have been made available by various researchers during the period covered by this review. Supercritical fluid extraction and ultrasound-assisted extraction are still the methods of choice for extraction of artemisinin

Boundaries can steer active Janus spheres

The advent of autonomous self-propulsion has instigated research towards making colloidal machines that can deliver mechanical work in the form of transport, and other functions such as sensing and cleaning. While much progress has been made in the last 10 years on various mechanisms to generate self-propulsion, the ability to steer self-propelled colloidal devices has so far been much more limited. A critical barrier in increasing the impact of such motors is in directing their motion against the Brownian rotation, which randomizes particle orientations. In this context, here we report directed motion of a specific class of catalytic motors when moving in close proximity to solid surfaces. This is achieved through active quenching of their Brownian rotation by constraining it in a rotational well, caused not by equilibrium, but by hydrodynamic effects. We demonstrate how combining these geometric constraints can be utilized to steer these active colloids along arbitrary trajectories

Selenium- and tellurium-containing fluorescent molecular probes for the detection of biologically important analytes

As scientists in recent decades have discovered, selenium is an important trace element in life. The element is now known to play an important role in biology as an enzymatic antioxidant. In this case, it sits at the active site and converts biological hydrogen peroxides to water. Mimicking this reaction, chemists have synthesized several organoselenium compounds that undergo redox transformations. As such, these types of compounds are important in the future of both medicinal and materials chemistry. One main challenge for organochalcogen chemists has been to synthesize molecular probes that are soluble in water where a selenium or tellurium center can best modify electronics of the molecule based on a chemical oxidation or reduction event. In this Account, we discuss chemists’ recent efforts to create chalcogen-based chemosensors through synthetic means and current photophysical understanding. Our work has focused on small chromophoric or fluorophoric molecules, in which we incorporate discrete organochalcogen atoms (e.g., R-Se-R, R-Te-R) in predesigned sites. These synthetic molecules, involving rational synthetic pathways, allow us to chemoselectively oxidize compounds and to study the level of analyte selectivity by way of their optical responses. All the reports we discussed here deal with well-def ined and small synthetic molecular systems. With a large number of reports published over the last few years, many have notably originated from the laboratory of K. Han (P. R. China). This growing body of research has given chemists new ideas for the previously untenable reversible reactive oxygen species detection. While reversibility of the probe is technically important from the stand-point of the chalcogen center, facile regenerability of the probe using a secondary analyte to recover the initial probe is a very promising avenue. This is because (bio)chalcogen chemistry is extremely rich and bioinspired and continues to yield important developments across many scientific fields. Organochalcogen (R-E-R) chemistry in such chemical recognition and supramolecular pursuits is a fundamental tool to allow chemists to explore stable organic-based probe modalities of interest to develop better spectroscopic tools for (neuro)biological applications. Chalcogen donor sites also provide sites where metals can coordinate, and facile oxidation may extend to the sulfone analogues (R-EO2-R) or beyond. Consequently, chemists can then make use of reliable reversible chemical probing platforms based on the chemical redox properties valence state switching principally from 2 to 4 (and back to 2) of selenium and tellurium atoms. The main organic molecular skeletons have involved chemical frames including boron-dipyrromethene (BODIPY) systems, extended cyanine groups, naphthalimide, rhodamine, and fluorescein cores, and isoselenazolone, pyrene, coumarin, benzoselenadiazole, and selenoguanine systems. Our group has tested many such molecular probe systems in cellular milieu and under a series of conditions and competitive environments. We have found that the most important analytes have been reactive oxygen species (ROS) such as superoxide and hypochlorite. Reactive nitrogen species (RNS) such as peroxynitrite are also potential targets. In addition, we have also considered Fenton chemistry systems. Our research and that of others shows that the action of ROS is often reversible with H2S or biothiols such as glutathione (GSH).11011011sciescopu

Facile meso-BODIPY annulation and selective sensing of hypochlorite in water

Annulated BODIPY chalcogenide (Se, Te) systems were synthesized from their respective bis(oformylphenyl) dichalcogenide intermediates. The annulated BODIPY selenide product was confirmed by X-ray diffraction. The red-shifted telluride version was found to be sensitive and selective for hypochlorite detection, reversible upon treatment with biothiols. © 2013 American Chemical Society.183911sciescopu

Fluorescence probing of the ferric Fenton reaction via novel chelation

A new probe-chelator PET dyad was synthesised, which can be used to detect Fe3+via fluorescence enhancement to discriminate between Fe 2+ and Fe3+via Fenton chemistry involving hydrogen peroxide. This is the first BODIPY which works as a 2:1 multiplexer for Fe 3+, Fe2+ and H2O2. © 2013 The Royal Society of Chemistry.118171sciescopu

Solvent-controlled novel Cu+ and Cu+/2+ fluorescent turn-ON probing

Anovel Schiff base probe, carbamoyl salicylimine benzothiazole hydrazine, was prepared and measured for its probing ability. High sensitivity was shown for Cu+and Cu2+. When solvent polarity was regulated through a combination of H2O and acetonitrile, selective sensing ofCu+or the total amount of Cu+andCu2+ was possible. In addition, a linear hypsochromic fluorescent shift of about 30 nm was shown. A binding stoichiometry of 1:1 exists at low concentration. Time-dependent emission measurement showed an exponential decay curve (τ1 = 2.99 × 103s, 10 equiv of Cu+) and a linear decay line (slope = -0.0216, 5 equiv of Cu+). Interference experiments in 50% acetonitrile inH2Oshowed that the emission produced by Cu+and Cu2+ was not disturbed by other metal ions or by acidity or basicity. Peroxynitrite changed the emission trends; Cu+emission decreased (78%) and Cu2+ fluorescence increased (28-fold). Biothiols, L-cysteine, DL-homocysteine, reduced glutathione, and N-acetyl-L-cysteine affected the complete reversibility of Cu+-induced emission in 50% (v/v) acetonitrile in H2O, relative to partial reversibility of Cu2+ emission. Thus, by regulating the ratio between acetonitrile and H2O, Cu+and Cu+/2+ can be probed selectively. © 2015 Korean Chemical Society, Seoul & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim1111sciescopuskc

H+-Assisted fluorescent differentiation of Cu+ and Cu2+: Effect of Al3+-induced acidity on chemical sensing and generation of two novel and independent logic gating pathways

A novel Schiff base probe exhibited strong 'turn-ON' fluorescence for Cu2+ at 345 nm, Al3+ at 445 nm, and Cu+ at 360 nm in the presence of Al3+ in organic solvent (acetonitrile), which allowed for construction of molecular logic gates 'INH' and '1:2 DEMULTIPLEXING.' H+ generated from Al3+ contributed greatly to Cu+ chemosensing based on a redox non-innocence mechanism. © The Royal Society of Chemistry 20151991sciescopu