Extraction of acyclovir from pharmaceutical creams for HPLC assay. Optimization and validation of pretreatment protocols

Three simple protocols for the extraction of acyclovir from its pharmaceutical creams based on ultrasonication, ultrasonication with heating and magnetic stirring were evaluated and compared. Extraction kinetics were studied at different time intervals (5, 10, 15, 30 and 60 min) and the extraction efficiency was determined by HPLC. The effect of concentration of aqueous NaOH as the extraction medium and the stirring speed were also studied and optimized. Best results were obtained with 50 mL of 0.01 mol L⁻¹ aqueous NaOH with magnetic stirring speed of 500 r.p.m. HPLC analysis involved rapid separation of acyclovir from the cream matrix using a 100 × 4.6 mm i.d. monolithic column and UV detection at 254 nm. Magnetic stirring produced the best results in terms of extraction efficiency with an average extraction yield of 100.8%, n = 16 at an optimum extraction time of 15 min. The selected protocol was validated for within and day-to-day precision and ruggedness.      

On the origin of ferromagnetism in oximato-based [Mn3O]7+ triangles

DFT calculations reveal the unusual ferromagnetic exchange observed in an oxo-centered Mn(III) triangle may originate from a combination of the 'non-planarity' of the bridging oxime ligands and the non-parallel alignment of the Jahn-Teller axes.     

The dramatic effect of NH3 co-ligation on the Fe+-assisted activation of carbon dioxide in the gas phase: from bare metal ions to complexes

The catalytic efficiency of Fe(+) ion over the CO(2) decomposition in the gas phase has been extensively investigated with the help of electronic structure calculation methods. Potential-energy profiles for the activation process Fe(+) + CO(2) --> CO + FeO(+) along two rival potential reaction paths, namely the insertion and addition pathways, originating from the end-on kappa(1)-O and kappa(2)-O,O coordination modes of CO(2) with the metal ion, respectively, have been explored by DFT calculations. For each pathway the potential energy surfaces of the high-spin sextet (S = 5/2) and the intermediate-spin quartet (S = 3/2) spin-states have been explored. The complete energy reaction profile calculated by a combination of ab initio and density functional theory (DFT) computational techniques reveals a two-state reactivity, involving two spin inversions, for the decomposition process and accounts well for the experimentally observed inertness of bare Fe(+) ions towards CO(2) activation. Furthermore, the coordination of up to three extra ancillary NH(3) ligands with the Fe(+) metal ion has been explored and the geometric and energetic reaction profiles of the CO(2) activation processes Fe(+) + n x NH(3) + CO(2) --> [Fe(NH(3))(n)(CO(2))](+) --> [Fe(NH(3))(n)(O)(CO)](+) --> CO + [Fe(O)(NH(3))(n)](+) (n = 1, 2 or 3) have thoroughly been scrutinized for both the insertion and the addition mechanisms. Inter alia, the geometries and energies of the various states of the [Fe(NH(3))(n)(CO(2))](+) and [Fe(NH(3))(n)(O)(CO)](+) complexes are explored and compared. Finally, a detailed analysis of the coordination modes of CO(2) in the cationic [Fe(NH(3))(n)(CO(2))](+) (n = 0, 1, 2 and 3) complexes is presented.     

Selective monocyclization of epoxy terpenoids promoted by zeolite NaY. A short biomimetic synthesis of elegansidiol and farnesiferols B-D

Epoxy terpenes cyclize readily, by confinement within zeolite NaY, to form exomethylenic cyclohexanols as the major products. The selective monocyclization of 10,11-epoxyfarnesyl acetate within NaY provides a short and efficient biomimetic route to (+/-)-elengasidiol and (+/-)-farnesiferols B-D. [reaction: see text].     

Evaluation of the activity of the sponge metabolites avarol and avarone and their synthetic derivatives against fouling micro- and macroorganisms

The sesquiterpene hydroquinone avarol (1) was isolated from the marine sponge Dysidea avara, whereas the corresponding quinone, avarone (2), was obtained by oxidation of avarol, and the significantly more lipophilic compounds [3'-(p-chloro-phenyl)avarone (3), 3',4'-ethylenedithioavarone (4), 4'-isopropylthioavarone (5), 4'-tert-butylthioavarone (6), 4'-propylthioavarone (7), 4'-octylthioavarone (8)] were obtained by nucleophilic addition of thiols or p-chloroaniline to avarone. All these compounds were tested, at concentrations ranging from 0.5 to 50 microg/mL, for their effect on the settlement of the cyprid stage of Balanus amphitrite, for toxicity to both nauplii and cyprids and for their growth inhibitory activity on marine bacteria (Cobetia marina, Marinobacterium stanieri, Vibrio fischeri and Pseudoalteromonas haloplanktis) and marine fungi (Halosphaeriopsis mediosetigera, Asteromyces cruciatus, Lulworthia uniseptata and Monodictys pelagica).     

"Switching on" the properties of single-molecule magnetism in triangular manganese(III) complexes

The reaction between oxide-centered, triangular [MnIII3O(O2CR)6(py)3](ClO4) (R = Me (1), Et (2), Ph (3)) compounds and methyl 2-pyridyl ketone oxime (mpkoH) affords a new family of Mn/carboxylato/oximato complexes, [MnIII3O(O2CR)3(mpko)3](ClO4) [R = Me (4), Et (5), and Ph (6)]. As in 1-3, the cations of 4-6 contain an [MnIII3(mu3-O)]7+ triangular core, but with each Mn2 edge now bridged by an eta1:eta1:mu-RCO2- and an eta1:eta1:eta1:mu-mpko- group. The tridentate binding mode of the latter causes a buckling of the formerly planar [MnIII3(mu3-O)]7+ core, resulting in a relative twisting of the three MnIII octahedra and the central O2- ion now lying approximately 0.3 A above the Mn3 plane. This structural distortion leads to ferromagnetic exchange interactions within the molecule and a resulting S = 6 ground state. Fits of dc magnetization data for 4-6 collected in the 1.8-10.0 K and 10-70 kG ranges confirmed S = 6 ground states, and gave the following D and g values: -0.34 cm(-1) and 1.92 for 4, -0.34 cm(-1) and 1.93 for 5, and -0.35 cm(-1) and 1.99 for 6, where D is the axial zero-field splitting (anisotropy) parameter. Complexes 4-6 all exhibit frequency-dependent out-of-phase (chi" M) ac susceptibility signals suggesting them possibly to be single-molecule magnets (SMMs). Relaxation rate vs T data for complex 4 down to 1.8 K obtained from the chi" M vs T studies were supplemented with rate vs T data measured to 0.04 K via magnetization vs time decay studies, and these were used to construct Arrhenius plots from which was obtained the effective barrier to relaxation (Ueff) of 10.9 K. Magnetization vs dc field sweeps on single-crystals of 4.3CH2Cl2 displayed hysteresis loops exhibiting steps due to quantum tunneling of magnetization (QTM). The loops were essentially temperature-independent below approximately 0.3 K, indicating only ground-state QTM between the lowest-lying Ms = +/-6 levels. Complexes 4-6 are thus confirmed as the first triangular SMMs. High-frequency EPR spectra of single crystals of 4.3CH2Cl2 have provided precise spin Hamiltonian parameters, giving D = -0.3 cm(-1), B40 = -3 x 10(-5) cm(-1), and g = 2.00. The spectra also suggest a significant transverse anisotropy of E > or = 0.015 cm(-1). The combined work demonstrates the feasibility that structural distortions of a magnetic core imposed by peripheral ligands can "switch on" the properties of an SMM.     

Enhancing SMM properties in a family of [Mn6] clusters

The complex [Mn(6)O(2)(Et-sao)(6)(O(2)C(11)H(15))(2)(EtOH)(6)] has U(eff) = 80 K.     

Turning up the spin, turning on single-molecule magnetism: from S = 1 to S = 7 in a [Mn(8)] cluster via ligand induced structural distortion

The spin ground state of a [Mn(III)(6)Mn(II)(2)] cluster has been deliberately switched from S = 1 to S = 7 upon designed ligand substitution.