Natural Products from Tongan Marine Organisms

The islands of the South Pacific Ocean have been in the limelight for natural product biodiscovery, due to their unique and pristine tropical waters and environment. The Kingdom of Tonga is an archipelago in the central Indo-Pacific Ocean, consisting of 176 islands, 36 of which are inhabited, flourishing with a rich diversity of flora and fauna. Many unique natural products with interesting bioactivities have been reported from Indo-Pacific marine sponges and other invertebrate phyla; however, there have not been any reviews published to date specifically regarding natural products from Tongan marine organisms. This review covers both known and new/novel Marine Natural Products (MNPs) and their biological activities reported from organisms collected within Tongan territorial waters up to December 2020, and includes 109 MNPs in total, the majority from the phylum Porifera. The significant biological activity of these metabolites was dominated by cytotoxicity and, by reviewing these natural products, it is apparent that the bulk of the new and interesting biologically active compounds were from organisms collected from one particular island, emphasizing the geographic variability in the chemistry between these organisms collected at different locations.     

Fault Tolerant Sorting—Theoretical and Empirical Analyses of the Randomized QuickMergesort Algorithm

This paper introduces a new paradigm in the design of sorting algorithms, viz., fault tolerance. Fault tolerance is an important concept in modern day computing and design workflows must accommodate this need. In general, there are a number of avenues for faults to occur and techniques to address the same; this paper focusses on only one source of faulty behavior, viz., process termination. Process termination, as a cause of faulty behavior, is important from the perspective of various applications in real-time scheduling. In order to measure the effectiveness of a fault tolerant protocol, it is necessary to define a suitable metric and analyze the performance of the protocol with respect to that metric. We measure the “unsortedness” of an array, as characterized by the number of inversion pairs that remain when the sorting algorithm (process) terminates. This paper proposes a new algorithm for sorting called the Randomized QuickMergesort (RQMS) algorithm. RQMS has a higher degree of fault tolerance than either Randomized Quicksort (RQS) or Mergesort (MS), in that fewer inversion pairs remain when it terminates. Likewise, RQMS has a lower comparison overhead than RQS and is more space-efficient than MS. Our empirical analysis, which was conducted over a wide variety of distributions, conclusively establishes that RQMS is the algorithm of choice, when fault tolerance is paramount in the application. This research was supported in part by the Air Force Office of Scientific Research under Contract FA9550-06-1-0050.     

Development of a flow-sheet for the radiochemical processing of irradiated sulphate targets for the production of carrier-free 32P

Carrier-free ³²P was produced in KAlpakkam MINI reactor (KAMINI) via ³²S (n, p) ³²P using its small fast flux component. This method has established the flow-sheet for the production of ³²P from sulphate targets such as magnesium sulphate and strontium sulphate which can withstand high temperatures of fast reactors unlike the conventionally used sulphur powder. The chemical processing involved (i) struvite precipitation method for magnesium sulphate and (ii) co-precipitation with ferric hydroxide method for strontium sulphate.     

One-pot synthesis of symmetrical and unsymmetrical acridine sulfonamide derivatives catalyzed by p-TSA

Research on Chemical Intermediates - Synthesis of a series of symmetrical and unsymmetrical 1,8-dioxo-octahydroacridine benzenesulfonamide derivatives has been achieved by one-pot, multicomponent...     

Synthesis and biological evaluation of 3-hydroxypyrazoles as aquaporin 9 inhibitors

A series of 3-hydroxypyrazole derivatives have been synthesized by a base-promoted reaction of nitro-substituted donor–acceptor cyclopropanes with hydrazines. The synthesized compounds have been investigated for their ability to inhibit aquaporin 9 (AQP9) in rat Leydig cells (LC-540). The protein data bank structure for AQP9 was predicted using homology modeling; and the protein–ligand interaction for the synthesized hydroxyl pyrazole derivatives were analyzed using molecular modeling and docking studies. The results of in silico analyses showed that compound 5b had a higher binding affinity with AQP9 than other compounds. Further, in vitro studies conducted in LC-540 cells confirmed that compound 5b effectively inhibits AQP9. Hence, compound 5b may be used as an inhibitor in enhancing our understanding of AQP9 function, and in the treatment of several diseases.     

High resistive ferrite films by a solution process for electromagnetic compatible (EMC) devices

Mn-Zn ferrite films with high resistivity and good noise suppressing ability for use as ‘coupling-type noise suppressors’ have been prepared by the spin-spray ferrite plating. The as-prepared films were crystalline and exhibited single-phase spinel structure. The films had an ‘integrated nano-columnar’ morphology that resulted in a very high resistivity. Further, by varying the chemical composition, films with varying resistivity were prepared and then heat treated at 260 °C for 3 min, similar to that of the reflow soldering process. The reflection and transmission coefficients, S₁₁ and S₂₁ parameters, on coplanar micro-strip line (50 Ω) were measured for the as-prepared and heat-treated films in order to study the effect of heat treatment. When the resistivity was above 2×10⁵ Ω/sq, S₁₁ and S₂₁ exhibited uniform profiles throughout the measurement frequency (50 MHz-10 GHz), which is ideal for the ‘coupling-type’ noise suppressor. These films retain a moderately high resistivity and hence do not show the downshift in the stopband frequency even after the heat treatment (reflow soldering process).     

Kinetic Resolution of Tertiary 2‐Alkoxycarboxamido‐Substituted Allylic Alcohols by Chiral Phosphoric Acid Catalyzed Intramolecular Transesterification

A highly enantioselective kinetic resolution of tertiary 2‐alkoxycarboxamido allylic alcohols has been achieved through a chiral phosphoric acid catalyzed intramolecular transesterification reaction. Both alkyl,aryl‐ and dialkyl‐substituted tertiary allylic alcohols were resolved with excellent efficiencies, affording both the recovered tertiary alcohols and the carbamate products with high enantioselectivities (with s factors up to 164.6). A gram‐scale reaction with 1 mol % catalyst loading and the facile conversion of the enantioenriched products into useful chiral building blocks, such as chiral oxazolidinones and β‐amino alcohols, demonstrate the value of this reaction.     

Carrier-free separation of 22Na from magnesium by chromatographic techniques

Carrier-free ²²Na was separated from bulk quantities of magnesium by both ion exchange and extraction chromatographic techniques. An extraction chromatographic procedure based on di-(2-ethylhexyl) phosphoric acid (HDEHP) coated on to an inert support (Amberlite XAD-7) was developed for the first time for separation of sodium from magnesium. The sorption behavior for sodium and magnesium was studied as a function of percentage of HDEHP loaded on to the inert support as well as pH of aqueous phase. These data were used to arrive at the optimum conditions of separation. In addition, carrier free ²²Na was also separated from magnesium using ion exchange chromatographic technique.     

Synthesis and characterizations of silylated polyurethane from methyl ethyl ketoxime-blocked polyurethane dispersion

Water-dispersible blocked polyurethane dispersions (BPUD) were synthesized by prepolymer mixing process using toluene 2,4-diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), poly(tetramethylene glycol) (PTMG), dimethylol propionic acid (DMPA), and methyl ethyl ketoxime (MEKO). The particle size, viscosity, pH and storage stability of the BPUDs were studied and compared. The aqueous dispersions were characterized by FT-IR, GPC, DSC and TGA techniques. De-blocking temperatures of the BPUDs were measured and end-capped with phenylamino propyl trimethoxysilane (PAPTMS) at different de-blocking temperatures. The thermal analysis revealed that both MDI- and TDI-based BPUDs started to de-block at about 60–85 °C. The average molecular weights of the MDI-BPUDs were higher than that of the TDI-BPUDs due to the high reactivity of MDI. It was noticed that the tensile strength increased and elongation at break decreased in the silylated BPUD compared to pure BPUDs, which confirmed that the BPUDs were de-blocked and end-capped with PAPTMS. The T_g values of the silylated BPUD were higher than the BPUD and pure PTMG as well as thermal stability. Storage stability results showed that all BPUDs containing PAPTMS were stable. Water and xylene resistance tests and gel content studies confirmed that silylated PU cross-linked well after silylation of blocked PUDs.