Immune-enhancing agents in autoimmune skin diseases – A review

Immunosuppressive drugs are the main stay of treatment for autoimmune dermatoses. The main disadvantage of these drugs is the increased susceptibility to life-threatening infections. Hence, in recent years, there has been an enthusiastic search for newer groups of drugs that can reduce this risk. Immune enhancing agents are considered as the key players of future. Immune enhancers function by activating various elements of the immune system and thereby amplifying the immune responses. They can be specific or non-specific in action. The main autoimmune dermatoses where the benefits of these drugs have so far been utilized include alopecia areata, vitiligo, psoriasis, lichen planus, and discoid lupus erythematosus. Immunostimulants are available in both topical and systemic forms. Topical immune- enhancing agents include contact sensitizers (diphenylcyclopropenone, dinitrochlorobenzene, and squaric acid dibutyl ester), anthralin, topical zinc, and interferons. Systemic agents include levamisole, zinc, probiotics, and so on. The exact mechanism of action of some of these drugs and other autoimmune conditions where they can be benefited is not completely understood. Another therapeutic agent that may come up in the future is individualized vaccines. Let us look forward to the days when individualized vaccines work wonders in the management of autoimmune diseases.

Chiral Aminoalcohols and Squaric Acid Amides as Ligands for Asymmetric Borane Reduction of Ketones: Insight to In Situ Formed Catalytic System by DOSY and Multinuclear NMR Experiments

A series of squaric acid amides (synthesized in 66–99% isolated yields) and a set of chiral aminoalcohols were comparatively studied as ligands in a model reaction of reduction of α-chloroacetophenone with BH3•SMe2. In all cases, the aminoalcohols demonstrated better efficiency (up to 94% ee), while only poor asymmetric induction was achieved with the corresponding squaramides. A mechanistic insight on the in situ formation and stability at room temperature of intermediates generated from ligands and borane as possible precursors of the oxazaborolidine-based catalytic system has been obtained by 1H DOSY and multinuclear 1D and 2D (1H, 10/11B, 13C, 15N) NMR spectroscopy of equimolar mixtures of borane and selected ligands. These results contribute to better understanding the complexity of the processes occurring in the reaction mixture prior to the possible oxazaborolidine formation, which play a crucial role on the degree of enantioselectivity achieved in the borane reduction of α-chloroacetophenone.

Polymeric Terbium(III) Squarate Hydrate as a Luminescent Magnet

Polymeric terbium(III) squarate hydrate [{Tb2(C4O4)3(H2O)8}n] was prepared from TbCl3 or Tb2O3 and squaric acid. The crystal structure was determined in a monoclinic Pc space group, and the whole molecular arrangement gives a sandwiched two-dimensional structure. The coordination polyhedra are described as a square antiprism. The solid complex emits green light under UV irradiation at room temperature with the quantum yield of 25%. Although Tb3+ is a non-Kramers ion, the alternating-current magnetic susceptibility showed frequency dependence in a 2000-Oe DC field, and the effective energy barrier for magnetization reorientation was 33(2) K. Thus, [{Tb2(C4O4)3(H2O)8}n] displayed functions of a potential luminescent magnet.

Nuclear Singlet Relaxation by Chemical Exchange

The population imbalance between nuclear singlet states and triplet states of strongly coupled spin-1/2 pairs, also known as nuclear singlet order, is well protected against several common relaxation mechanisms. We study the nuclear singlet relaxation of 13C pairs in aqueous solutions of 1,2-13C2 squarate, over a range of pH values. The 13C singlet order is accessed by introducing 18O nuclei in order to break the chemical equivalence. The squarate dianion is in chemical equilibrium with hydrogen-squarate (SqH−) and squaric acid (SqH2) characterised by the dissociation constants pKa1 = 1:5 and pKa2 = 3:4. Surprisingly, we observe a striking increase in the singlet decay time constants TS when the pH of the solution exceeds ~ 10, which is far above the acid-base equilibrium points. We derive general rate expressions for chemical-exchange-induced nuclear singlet relaxation and provide a qualitative explanation of the TS behaviour of the squarate dianion. We identify a kinetic contribution to the singlet relaxation rate constant which depends explicitly on kinetic rate constants. Qualitative agreement is achieved between the theory and the experimental data. This study shows that infrequent chemical events may have a strong effect on the relaxation of nuclear singlet order.

Synthesis and Characterization of Cr (III) Macrocyclic Schiff Base Complexes

Ninety Cr(III) macrocyclic Schiff base complexes of the type [CrL_n^(1-10) X_2 ]X(Where X = Cl- or NO-3 or CH3COO- and = macrocyclic Schiff base ligands derived from condensation of trimesic acid or p-phthalic acid or squaric acid with different aliphatic diamines) have been synthesised and characterised by elemental analysis; molar conductance; electronic spectra; IR; magnetic moment and XPS i.e. X-ray Photoelectron spectra data. An octahedral geometry was established for them.