5 research outputs found
Phytochemical Analysis of Acacia ehrenbergiana (Hayne) Grown in Qatar: Identification of Active Ingredients and Their Biological Activities
Acacia ehrenbergiana (Hayne), also known as Salam, is a highly drought resistant shrub distributed in North and East Africa, and the Arabian Peninsula. The plant is gathered for its gum and fiber, and is an important legume species for indigenous populations. In this study, the phytochemical analysis, antibacterial, and antioxidant properties of various alcoholic and aqueous extracts of Acacia ehrenbergiana grown in Qatar were investigated. The qualitative phytochemical screening of this species exhibited the presence of glycosides, tannins, flavonoids, terpenoids, saponins, phenol, and anthraquinones in various extracts. The agar diffusion method was performed to check the antibacterial activity. The acetone and ethanol extracts showed 85% antibacterial activity of the control against Gram-negative E. coli, while the acetone extract had 65% activity against the Bacillus Gram-positive species. The highest activity against Staphylococcus aureus was 65% for the butanol extract. The antioxidant capacities were evaluated by the DPPH method. Various extracts exhibited antioxidant activities similar to or higher than standard antioxidants, with the highest percent inhibition of 95% for the acetone and ethanol extracts. The acetone extracts were further purified by reverse phase combiflash chromatography followed by HPLC. Three of the pure compounds isolated were subjected to MS, FTIR, and NMR spectral analysis and were found to be stigmasterol, spinasterol, and theogallin. In conclusion, the observed antibacterial and antioxidant activities as well as the presence of secondary metabolites with potential medicinal activities makes Acacia ehrenbergiana a potent valuable endemic medicinal plant
Combined experimental and computational investigations of the fluorosolvatochromism of chromeno[4,3-b]pyridine derivatives: Effect of the methoxy substitution
Extensive research has been conducted on the spectral properties of chromeno[4,3-b]pyridine derivatives, owing to their potential applications in sensing, optoelectronic devices, and drug discovery. This study presents a comprehensive investigation into the fluorosolvatochromism of selected chromeno[4,3-b]pyridine derivatives, with a particular emphasis on the impact of methoxy substitution. Three derivatives were synthesized and subjected to spectral analysis: chromeno[4,3-b]pyridine-3-carboxylate (I) as the parent compound, and its 7-methoxy (II) and 8-methoxy (III) substituted derivatives. The UV–Vis absorption spectra of all derivatives exhibited a broad band with a maximum absorption wavelength that remained unaffected by the surrounding medium. However, distinct fluorescence properties were observed among them. Specifically, derivative II displayed notable fluorescence, while derivatives I and III exhibited no fluorescence properties. Furthermore, derivative II exhibited a fluorescence spectrum that is significantly influenced by the polarity of the medium. To investigate the fluorosolvatochromic behavior in depth, we conducted a comprehensive analysis using various neat solvents with different polarities and hydrogen bonding capabilities. The results obtained revealed a significant positive fluorosolvatochromism, with a bathochromic shift in the fluorescence spectrum as the solvent polarity increased. To understand how specific and non-specific interactions between the solute and the solvent affected the fluorosolvatochromism of II, we employed the four empirical scales model of Catalán. The obtained results demonstrated that intramolecular charge transfer played a crucial role in the fluorescence behavior of II. To provide a molecular-level explanation for the experimental spectral properties, we utilized the DFT and TD-DFT/B3LYP/6-31 + G(d) computational methods with the IEFPCM implicit solvation approach. The spectral differences between II and III were rationalized in terms of the frontier molecular orbitals (FMOs: the HOMO and LUMO), where distinct natures were observed among the examined derivatives. This study offers valuable insights into the impact of methoxy substitution on the physical and chemical properties of chromeno[4,3-b]pyridine derivatives, specifically concerning their spectral properties as elucidated by their fluorosolvatochromic behavior.The support from Qatar University is thankfully acknowledged. We thank the Central Laboratories Unit at Qatar University for their support in compounds analysis. Major aspects of the calculations were performed using the supercomputing facility at Texas A&M University in Qatar. Open Access funding provided by the Qatar National Library.Scopu
Phytochemical Analysis of <i>Anastatica hierochuntica</i> and <i>Aerva javanica</i> Grown in Qatar: Their Biological Activities and Identification of Some Active Ingredients
Plant-derived compounds and their extracts are known to exhibit chemo preventive (antimicrobial, antioxidant and other) activities. The levels of such chemo preventive compounds vary depending on environmental factors, including the regions where they grow. Described in this study are: (i) a phytochemical analysis of the two plants grown in the desert environment of Qatar, viz., Anastatica hierochuntica and Aerva javanica; (ii) the antibacterial, antifungal and antioxidant activities of various solvent extracts of these plants; (iii) a report on the isolation of several pure compounds from these plants. The phytochemical screening indicated the presence of glycosides, tannins, flavonoids, terpenoids, saponins, phenol and anthraquinones in various extracts of each of the plants. Antibacterial and antioxidant activities were studied using agar diffusion and DPPH methods, respectively. The extracts of Anastatica hierochuntica as well as Aerva javanica inhibit the growth of both gram-positive and gram-negative bacterial species. Various extracts of the two plants also exhibited higher or similar antioxidant activities as those of the standard antioxidants, α-tocopherol and ascorbic acid. The extracts of these plants were further purified by HPLC and characterized by IR and NMR techniques. This process has led to identification of β-sitosterol, campesterol and methyl-9-(4-(3,4-dihydroxy-1′-methyl-5′-oxocyclohexyl)-2-hydroxycyclohexyl)nonanoate from Anastatica hierochuntica, and lupenone, betulinic acid, lupeol acetate and persinoside A and B from Aerva javanica. The results reported herein suggests that Anastatica hierochuntica and Aerva javanica are potent sources of phytomedicines
l-Proline-Catalyzed Three-Component Reaction of 4-Chloro-3-formylcoumarin, Sodium Sulfide, and α-Halo Ketones: A Direct Approach to Thieno[3,2- c ]coumarins
A new protocol for the synthesis of thieno[3,2-c]coumarins is disclosed. In this method, a 3-formyl-2-oxo-2H-chromene-4-thiolate anion is generated in situ by treatment of 4-chloro-3-formylcoumarin with sodium sulfide. This chromene-4-thiolate undergoes an L-prolinecatalyzed substitution/Knoevenagel cascade with various α-halo ketones to afford the desired thienocoumarins in moderate to good isolated yields. This protocol eliminates the need for stoichiometric amounts of inorganic bases and the use of foul-smelling thiols. The reaction conditions tolerate a variety of α-halo ketones.This work was supported by a Qatar University Student Grant [QUST2-CAS-2020-8] and the Medical Research Center (MRC)/Academic
Health System (AHS) (Grant No. MRC-01-22-414
Picomolar or beyond Limit of Detection Using Molecularly Imprinted Polymer-Based Electrochemical Sensors: A Review
Over the last decades, molecularly imprinted polymers (MIPs) have emerged as selective synthetic receptors that have a selective binding site for specific analytes/target molecules. MIPs are synthetic analogues to the natural biological antigen–antibody system. Owing to the advantages they exhibit, such as high stability, simple synthetic procedure, and cost-effectiveness, MIPs have been widely used as receptors/sensors for the detection and monitoring of a variety of analytes. Moreover, integrating electrochemical sensors with MIPs offers a promising approach and demonstrates greater potential over traditional MIPs. In this review, we have compiled the methods and techniques for the production of MIP-based electrochemical sensors along with the applications of reported MIP sensors for a variety of analytes. A comprehensive in-depth analysis of recent trends reported on picomolar (pM/10−12 M)) and beyond picomolar concentration LOD (≥pM) achieved using MIPs sensors is reported. Finally, we discuss the challenges faced and put forward future perspectives along with our conclusion.This work was supported by the UREP grant # UREP28-063-1-008 from the Qatar National Research Fund (QNRF)