Determination of anthraquinones in Rhamnus purshiana using high-performance liquid chromatography coupled to diode array detector and simple ultraviolet spectroscopic analysis

A new method based on Ultraviolet spectrophotometry was developed and compared with that based on high-performance liquid chromatography for the determination and quantification of anthraquinones in the extracts of Rhamnus purshiana bark. A validated quantitative analysis of cascaroside A, cascaroside B, emodin, and aloe-emodin in these herbal products has been previously performed using high-performance liquid chromatography coupled with a diode array detector. In the high-performance liquid chromatography analysis, all the anthraquinones showed satisfactory regression (r² > 0.98) within the test ranges, and the recovery was in the range of 94–117%. The limits of detection and quantification were 0.008–0.010 and 0.029–0.035 μg/mL, respectively. Hierarchical cluster analysis and principal component analysis showed differences in the anthraquinones determined from herbal samples. Subsequently, a simple and low-cost ultraviolet spectrophotometric methodology for the quantitative analysis of the same compounds in the extracts was applied, and all the contents were determined. A paired t-test confirmed that there were no significant differences between the two methods. Our results revealed that the developed method is simple and provides the ability to discriminate and control the quality of anthraquinones in herbal products.     

Physicochemical characterization of a new raw material obtained from leaves of <Emphasis Type="Italic">Syzygium cumini</Emphasis> (L.) Skeel (Myrtaceae)

The aim of this study was to determine the physicochemical characteristics of leaves of Syzygium cumini L. Skeels plant and characterize the extract of this plant by analytical techniques. Pharmacopeial methods of physicochemical analysis were used, including morphological characterization of the particle, thermal analysis, infrared spectroscopy and X-ray diffraction. The plant drug was presented as a coarse powder, within the appropriate Brazilian Pharmacopoeia parameters. The X-ray diffraction, optical microscopy and scanning electron microscopy suggested that the extract particles are amorphous and have irregular shapes, so that clusters of different sizes and morphologies are displayed. Thermal decomposition of the organic components in the sample started in a step that occurred between 151.64 and 209.27 °C with mass loss of 9.08 %, followed by another step with more significant mass loss (28.16 %). The infrared spectrum, in turn, showed many functional groups of compounds present in the lyophilized extract in different absorption bands. The results showed that the analytical techniques allowed us to characterize the physicochemical properties of the plant leaves, which may be useful in the production of new herbal medicines.     

Contribution of air pollution to the fouling of heat exchangers in cooling water circuits

In an open recirculating system with a cooling tower, there are favorable conditions for the development of corrosion and fouling problems. These problems arise from the operating conditions and constant contamination of cooling water. A deep analysis of the system should provide the solutions for those problems. In the Sociedade Portuguesa de Oxigénio, SA, plant, a phosphate-based cooling water treatment ensures low corrosion rates. However, the fouling of heat exchange surfaces is promoted by the cooling water contamination. This contamination may result from the makeup water or from the air scrubbed in the tower. The fouling lowers the process efficiency and makes shutdowns for cleaning necessary. The air pollution produced by a neighboring plant is the main cause for fouling. To solve this problem, a decision was made to invest in equipment for makeup water treatment and reduce the stagnation conditions in the heat exchangers. It was also decided to hold negotiations to persuade the polluting company to reduce the particle emission to the atmosphere.     

Dynamics of flexible mechanical systems with contact-impact and plastic deformations

A computer based formulation for the analysis of mechanical systems is investigated as a feasible method to predict the impact response of complex structural systems. A general methodology for the dynamic analysis of rigid-flexible multibody systems using a number of redundant Cartesian coordinates and the method of the Lagrange multipliers is presented. The component mode synthesis is then used to reduce the number of flexible degrees of freedom. In many impact situations, the individual structural members are overloaded giving rise to plastic deformations in highly localized regions, called plastic hinges. This concept is used by associating revolute nonlinear actuators with constitutive relations corresponding to the collapse behavior of the structural components. The contact of the system components is described using a continuous force model based on the Hertz contact law with hysteresis damping. The effect and importance of structural damping schemes in flexible bodies are also addressed here. Finally, the validity of this methodology is assessed by comparing the results of the proposed models with those obtained in different experimental tests where: a beam collides transversally with a rigid block; a torque box impacts a rigid barrier.     

Microwave-assisted synthesis and antimicrobial activity of novel spiro 1,3,4-thiadiazolines from isatin derivatives

This work describes the synthesis of spiro 1,3,4-thiadiazolines from isatin-β-thiosemicarbazone acetylation, using microwave irradiation as a source of heating the reaction medium. N-substituted isatin derivatives were used as substrates to obtain thiosemicarbazones by adding thiosemicarbazide to the isatin ketone carbonyl. The final synthetic step was the reaction of thiosemicarbazones with acetic anhydride under microwave irradiation to get the spiro compounds. Reaction times ranged from 6 to 18 minutes resulting in yields of up to 90%. Biological assays have shown promising antibacterial and antifungal activity, especially spiro thiadiazolines derived from allylated isatins. All the proposed molecules proved to be potential drug candidates based on the results of the in silico investigation, with satisfactory drug-likeness and drug-score, respecting Lipinski's rule. The use of the microwave reactor was efficient for the synthesis of thiosemicarbazones and spiro compounds, resulting in a significant reduction in reaction times with conventional heating. Taking into account the threat of antimicrobial resistance, this work presents a series of bioactive molecules that are easily obtained via microwave reaction.     

Pharmacological Extracts and Molecules from Virola Species: Traditional Uses,Phytochemistry, and Biological Activity

Virola is the largest genus of Myristicaceae in America, comprising about 60 species of medium-sized trees geographically spread from Mexico to southern Brazil. The plant species of this genus have been widely used in folk medicine for the treatment of several ailments, such as rheumatic pain, bronchial asthma, tumors in the joints, intestinal worms, halitosis, ulcers, and multiple infections, due to their pharmacological activity. This review presents an updated and comprehensive summary of Virola species, particularly their ethnomedicinal uses, phytochemistry, and biological activity, to support the safe medicinal use of plant extracts and provide guidance for future research. The Virola spp.’s ethnopharmacology, including in the treatment of stomach pain and gastric ulcers, as well as antimicrobial and tryponosomicidal activities, is attributable to the presence of a myriad of phytoconstituents, such as flavonoids, tannins, phenolic acids, lignans, arylalkanones, and sitosterol. Hence, such species yield potential leads or molecular scaffolds for the development of new pharmaceutical formulations, encouraging the elucidation of not-yet-understood action mechanisms and ascertaining their safety for humans.     

Anthocyanins Recovered from Agri-Food By-Products Using Innovative Processes: Trends,Challenges, and Perspectives for Their Application in Food Systems

Anthocyanins are naturally occurring phytochemicals that have attracted growing interest from consumers and the food industry due to their multiple biological properties and technological applications. Nevertheless, conventional extraction techniques based on thermal technologies can compromise both the recovery and stability of anthocyanins, reducing their global yield and/or limiting their application in food systems. The current review provides an overview of the main innovative processes (e.g., pulsed electric field, microwave, and ultrasound) used to recover anthocyanins from agri-food waste/by-products and the mechanisms involved in anthocyanin extraction and their impacts on the stability of these compounds. Moreover, trends and perspectives of anthocyanins’ applications in food systems, such as antioxidants, natural colorants, preservatives, and active and smart packaging components, are addressed. Challenges behind anthocyanin implementation in food systems are displayed and potential solutions to overcome these drawbacks are proposed.     

Single-step,paper-based concentration and detection of a malaria biomarker

The lateral-flow immunoassay (LFA) is an inexpensive and rapid paper-based assay that can potentially detect infectious disease biomarkers in resource-poor settings. Despite its many advantages that make it suitable for point-of-care diagnosis, LFA is limited by its inferior sensitivity relative to sophisticated laboratory-based assays. Our group previously introduced the use of a micellar aqueous two-phase system (ATPS), comprised of the nonionic Triton X-114 surfactant, to concentrate biomarkers in a sample and enhance their detection with LFA. However, achieving complete phase separation and target concentration using the Triton X-114 system required many hours, and the concentrated sample needed to be manually extracted and applied to LFA. Here, we successfully integrated the concentration and detection steps into a single step that occurs entirely within a portable paper-based diagnostic strip. In a novel approach, we applied the micellar ATPS to a 3-D paper design and effectively reduced the macroscopic phase separation time from 8 h to approximately 3 min. The 3-D design was integrated with LFA to simultaneously concentrate and detect Plasmodium lactate dehydrogenase (pLDH), a malaria biomarker, in both phosphate-buffered saline and fetal bovine serum within 20 min at room temperature. Compared to a conventional LFA setup with a pLDH detection limit of 10 ng μL⁻¹, our single-step diagnostic successfully detected pLDH at 1.0 ng μL⁻¹, demonstrating a 10-fold detection limit improvement and resulting in a sensitive and user-friendly assay that can be used at the point-of-care. The integration of a micellar ATPS and LFA represents a new platform that can improve and promote the use of paper-based diagnostic assays for malaria and other diseases within resource-poor settings.     

Development of a versatile rotating ring-disc electrode for in situ pH measurements

There are some electrocatalytic reactions in which the key parameter explaining their behavior is a local change in pH. Therefore, it is of utter importance to develop an electrode that could quantify this parameter in situ, but also be customizable to be used in different systems. The purpose of this work is to build a versatile rotating ring/disc electrode (RRDE) with IrO_x deposited on a glass tube as a ring and any kind of material as disc. As the IrO_x is sensitive to pH variation, the reactions promoted on the disc can trigger proportional pH shifts on the ring. In such assembly, the IrO_x ring presents a fast response time even during the pH transients due to the small thickness of the ring (approximately 10 μm), which enables the detection of interfacial pH changes. The ring electrode was tested toward the interfacial pH shift observed during the electrolytic reduction of water on the disc and also characterized by acid–base titration to determine the response time. As the main conclusions, fast response and durable RRDE were obtained, and this assembly could be used to revisit many electrocatalytic reactions in order to test the importance of local pH on the process.     

Biosynthesis‐Assisted Structural Elucidation of the Bartolosides,Chlorinated Aromatic Glycolipids from Cyanobacteria

The isolation of the bartolosides, unprecedented cyanobacterial glycolipids featuring aliphatic chains with chlorine substituents and C‐glycosyl moieties, is reported. Their chlorinated dialkylresorcinol (DAR) core presented a major structural‐elucidation challenge. To overcome this, we discovered the bartoloside (brt) biosynthetic gene cluster and linked it to the natural products through in vitro characterization of the DAR‐forming ketosynthase and aromatase. Bioinformatic analysis also revealed a novel potential halogenase. Knowledge of the bartoloside biosynthesis constrained the DAR core structure by defining key pathway intermediates, ultimately allowing us to determine the full structures of the bartolosides. This work illustrates the power of genomics to enable the use of biosynthetic information for structure elucidation.