1,1-Diphenyl-2-picrylhydrazyl radical scavenging activity of novel dihydropyridine derivatives

Thirteen dihydropyridine analogues 1-13 were synthesized and evaluated for their DPPH radical scavenging activity. A good to moderate antioxidant activity ranging from 127.4 to 284.5 μM was observed and structure-activity relationship was established. The 3'-fluoro derivative 8 (IC50 = 127.4±3.5 μM) was found to exhibit highest activity among the dihydro pyridine derivatives 1-13, while the other derivatives 11 (IC50 = 132.5±3.32 μM), 6 (IC50 = 142.2±0.60 μM), 10 (IC50 = 144.7±2.46 μM), 12 (IC50 = 153.7±0.50 μM), 5 (IC50 = 161.4±2.81 μM) and 5 (IC50 = 164.4±2.50 μM) possess moderate activity, depends upon the C-4 and C-6 substituted groups. The compounds 7, 13, 4, 3 and 2 have lowest IC50 values, ranging between 172.8 and 284.5 μM. Dihydropyridine analogues were characterized by spectroscopic techniques

Alkaloid inspired spirocyclic oxindoles from 1,3-dipolar cycloaddition of pyridinium ylides

Cycloaddition reactions between pyridinium ylides and 3-alkenyl oxindoles that proceed in high yield and with very good regio- and diastereoselectivity are reported. The resulting cycloadducts have the same stereochemistry of biologically active oxindole alkaloids, such as strychnofoline

Nyctanthes arbor-tristis

Nyctanthes arbor-tristis (NAT) is commonly used traditionally for the treatment of rheumatism and inflammatory diseases. Current study evaluates the antiarthritic potential of NAT using Freund’s adjuvant-induced arthritic rat model. Treatments with methanolic, ethyl acetate, and n-hexane extracts were continued for consecutive 20 days. Macroscopic arthritic scoring and water displacement plethysmometry were used to evaluate arthritic development. Hematological and biochemical parameters were investigated and ankle joints were processed for histopathological evaluation. Qualitative phytochemical analysis and GC-MS analysis were conducted for identification of constituents. NAT extracts suppressed arthritic scoring, paw edema, infiltration of inflammatory cells, pannus formation, and bone erosion. The plant extracts ameliorated total leukocytes and platelet counts and nearly normalized red blood cells (RBC) counts and hemoglobin (Hb) content. The extracts were found safe in terms of hepatotoxicity and nephrotoxicity as determined by aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and urea levels. Comparative analysis showed that ethyl acetate extract produced the highest inhibition of paw edema. The major constituents found in ethyl acetate extract can be classified into three major classes, that is, terpenes, terpenoids, fatty acids, and iridoid glycosides. Current study showed that Nyctanthes arbor-tristis ameliorated experimental rheumatoid arthritis and ethyl acetate extract possessed the highest inhibitory activity

Synthesis, characterization of flavone, isoflavone, and 2,3-dihydrobenzofuran-3-carboxylate and density functional theory studies

We describe the oxidation of flavanones by employing phenyliodonium diacetate to form the flavone (15), isoflavone (8) and 2,3-dihydrobenzofurane (18) in this study. The oxidative method was found to be regioselective and dependent on the substitution pattern present on the two aromatic rings of the starting flavanone. The structures of products obtained were fully characterized by using IR, 1H and 13C NMR spectroscopy and Mass spectrometry. X-ray crystallography further confirms the structures of flavones and isoflavone. The density field theory calculations have also been performed to get more insight about the structures, electronic and spectroscopic properties of synthetic flavonoid derivatives. The geometrical parameters such as bond lengths and angels showed a good correlation with the values obtained through X-ray crystallography. Moreover, the theoretically simulated vibrational and UV-vis spectral values are in agreement with the experimental results

Calculating singlet excited states: comparison with fast time-resolved infrared spectroscopy of coumarins

In contrast to the ground state, the calculation of the infrared (IR) spectroscopy of molecular singlet excited states represents a substantial challenge. Here we use the structural IR fingerprint of the singlet excited states of a range of coumarin dyes to assess the accuracy of density functional theory based methods for the calculation of excited state IR spectroscopy. It is shown that excited state Kohn-Sham density functional theory provides a high level of accuracy and represents an alternative approach to time-dependent density functional theory for simulating the IR spectroscopy of the singlet excited states

Total synthesis of aritasone, cymbodiacetal and progress towards dihypoestoxide

This thesis describes the synthetic studies towards dihypoestaxide, accompanied by total syntheses of aritasone and (+)-cymbodiacetal. These are all terpene derived natural products that share a common spirochroman core structure. The introduction details the isolation, biological significance and proposed biosynthesis of the aforementioned natural products, followed by a review of the previous work towards them. The key step in OUf synthesis is a heteTo-Diels-Alder dimerisation reaction of the corresponding monomeric exocyclic enane for the formation of a common tricyclic spirochroman core structure. The hetero-Diels-Alder cycloaddition reaction is reviewed. with special regard to its stereochemical outcomes, which suggest a preference for the endo-cyclOtiddition pathway in this reaction. The results and discussion section gives a detailed account of the preliminary studies undertaken to explore the hetero-Diels-Alder dimerisation. Our attempts to synthesise aritasone via the dimerisation of pinocarvone are described, which resulted in a total synthesis of aritasone and X -ray analysis confirmed the stereochemistry of the natural product.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Synthesis and Characterization of Waste Eggshell-Based Montmorillonite Clay Catalyst for Biodiesel Production from Waste Cooking Oil

The depletion of resources and increase in demand for fossil fuel raise concerns as it is natural and non-renewable. Therefore, it will cause limitation on its availability and continuous reduction. This issue has led to the search for more economic, sustainable, and environmentally friendly alternatives which is biodiesel. The major drawback that reduces the possibility of biodiesel commercialization is the high cost of oil feedstock as it covers 75% of its total production cost. The waste cooking oil is used as feedstock in continuous transesterification as it is the primary option to lower the cost of biodiesel production. Biodiesel can be prepared using waste cooking oil and catalyst through transesterification reaction. In this research, the focus is on the utilization of chicken and quail waste eggshell to synthesize highly active Calcium Oxide (CaO)-based heterogenous catalyst with montmorillonite clay to catalyze efficient conversion of waste cooking oil to biodiesel. The formation of CaO/montmorillonite catalyst was confirmed based on the outputs from X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM). The physio-chemically characteristics of catalysts exhibited a BET surface area from the ranging from 9.2-9.5 m2/g and presence of around 87% of elemental calcium as constituent through XRF characterization. In addition to this, high-performance liquid chromatography (HPLC) analysis is used to determine the conversion of biodiesel using conventional and microwave heating method which revealed a maximum biodiesel production yield of 98%. This optimum biodiesel yield was obtained at reaction temperature, molar ratio of waste cooking oil to methanol, and catalyst amount of 60 ºC, 2 h, 1:12, 2.5 wt.% and 5 wt.% for both eggshells, respectively

Total synthesis of (−)-aritasone via the ultra-high pressure hetero-Diels–Alder dimerisation of (−)-pinocarvone

This paper describes a total synthesis of the terpene-derived natural product aritasone via the hetero-Diels-Alder [4+2] cyclodimerisation of pinocarvove, which represents the proposed biosyntheic route. The hetero-Diels-Alder dimerisation of pinocarvone did not proceed under standard conditions, and ultra-high pressure (19.9 kbar) was required. As it seems unlikely that these ultra-high pressures are accessible within a plant cell, we suggest that the original biosynthetic hypothesis be reconsidered, and alternatives are discussed