Optimization of Vacuum-Microwave-Assisted Extraction of Natural Polyphenols and Flavonoids from Raw Solid Waste of the Orange Juice Producing Industry at Industrial Scale

Orange pomace (OP) is a solid waste produced in bulk as a byproduct of the orange juice industry and accounts for approximately 50% of the quantity of the fruits processed into juice. In numerous literature references there is information about diverse uses of orange pomace for the production of high-added-value products including production of natural antioxidant and antimicrobial extracts rich in polyphenols and flavonoids which can substitute the hazardous chemical antioxidants/antimicrobials used in agro-food and cosmetics sectors. In this work and for the first time, according to our knowledge, the eco-friendly aqueous vacuum microwave assisted extraction of orange pomace was investigated and optimized at real industrial scale in order to produce aqueous antioxidant/antimicrobial extracts. A Response Surface Optimization methodology with a multipoint historical data experimental design was employed to obtain the optimal values of the process parameters in order to achieve the maximum rates of extraction of OP total polyphenols and/or total flavonoids for economically optimum production at industrial scale. The three factors used for the optimization were: (a) microwave power (b) water to raw pomace ratio and (c) extraction time. Moreover, the effectiveness and statistical soundness of the derived cubic polynomial predictive models were verified by ANOVA.     

Enhancement of the Anti-Inflammatory Activity of NSAIDs by Their Conjugation with 3,4,5-Trimethoxybenzyl Alcohol

The synthesis of derivatives of three nonspecific COX-1 and COX-2 inhibitors, ibuprofen, ketoprofen, naproxen is presented. These acids were connected via an amide bond with an amino acid (L-proline, L-tyrosine, and beta-alanine) used as a linker. The amino acid carboxylic group was esterified with 3,4,5 trimethoxybenzyl alcohol. The activity of the novel derivatives was examined in vivo on carrageenan-induced inflammation, and in vitro, as cyclooxygenase and lipoxygenase inhibitors. It was found that the new compounds were more potent anti-inflammatory agents than the parent drugs. Thus, the ibuprofen (21) and ketoprofen (16) derivatives reduced rat paw edema by 67 and 91% (the reduction by the relevant NSAIDs was 36 and 47%, respectively). They inhibited COX-2 more than the starting drugs (21 by 67%, ibuprofen 46%, 19 by 94%, ketoprofen 49%). Docking of compounds on the active sites of COX-1 and COX-2 reflects their in vitro activity. Thus, 19 adopts an unfavorable orientation for COX-1 inhibition, but it binds effectively in the binding pocket of COX-2, in agreement with the absence of activity for COX-1 and the high inhibition of COX-2. In conclusion, the performed structural modifications result in the enhancement of the anti-inflammatory activity, compared with the parent NSAIDs.     

Polyoxomolybdenum(V/VI)-sulfite compounds: synthesis, structural, and physical studies

Reaction of Na(2)Mo(VI)O(4) x 2H(2)O with (NH(4))(2)SO(3) in the mixed-solvent system H(2)O/CH(3)CN (pH = 5) resulted in the formation of the tetranuclear cluster (NH(4))(4)[Mo(4)(VI)SO(16)] x H(2)O (1), while the same reaction in acidic aqueous solution (pH = 5) yielded (NH(4))(4)[Mo(5)(VI)S(2)O(21)] x 3H(2)O (2). Compound {(H(2)bipy)(2)[Mo(5)(VI)S(2)O(21)] x H(2)O}(x) (3) was obtained from the reaction of aqueous acidic solution of Na(2)Mo(VI)O(4) x 2H(2)O with (NH(4))(2)SO(3) (pH = 2.5) and 4,4'-bipyridine (4,4'-bipy). The mixed metal/sulfite species (NH(4))(7)[Co(III)(Mo(2)(V)O(4))(NH(3))(SO(3))(6)] x 4H(2)O (4) was synthesized by reacting Na(2)Mo(VI)O(4) x 2H(2)O with CoCl(2) x 6H(2)O and (NH(4))(2)SO(3) with precise control of pH (5.3) through a redox reaction. The X-ray crystal structures of compounds 1, 2, and 4 were determined. The structure of compound 1 consists of a ring of four alternately face- and edge-sharing Mo(VI)O(6) octahedra capped by the trigonal pyramidal sulfite anion, while at the base of the Mo(4) ring is an oxo group which is asymmetrically shared by all four molybdenum atoms. Compound 3 is based on the Strandberg-type heteropolyion [Mo(5)(VI)S(2)O(21)](4-), and these coordinatively saturated clusters are joined by diprotonated 4,4'-H(2)bipy(2+) through strong hydrogen bonds. Compound 3 crystallizes in the chiral space group C2. The structure of compound 4 consists of a novel trinuclear [Co(III)Mo(2)(V)SO(3)(2-)] cluster. The chiral compound 3 exhibits nonlinear optical (NLO) and photoluminescence properties. The assignment of the sulfite bands in the IR spectrum of 4 has been carried out by density functional calculations. The cobalt in 4 is a d(6) octahedral low-spin metal atom as it was evidenced by magnetic susceptibility measurements, cw EPR, BVS, and DFT calculations. The IR and solid-state UV-vis spectra as well as the thermogravimetric analyses of compounds 1-4 are also reported.     

Synthesis, structure, and solution dynamics of UO22+-hydroxy ketone compounds [UO2(ma)2(H2O)] and [UO2(dpp)(Hdpp)2(H2O)]ClO4 [ma = 3-hydroxy-2-methyl-4-pyrone, Hdpp = 3-hydroxy-1,2-dimethyl-4(1H)-pyridone

Reaction of [UO(2)(NO(3))(2)] with the hydroxy ketones 3-hydroxy-2-methyl-4-pyrone (Hma) and 3-hydroxy-1,2-dimethyl-4(1H)-pyridone (Hdpp) in aqueous acidic solutions (pH approximately 3) yields the compounds [UO(2)(ma)(2)(H(2)O)].H(2)O (1.H(2)O) and [UO(2)(dpp)(Hdpp)(2)(H(2)O)]ClO(4) (2), respectively. X-ray diffraction shows that the geometry around the metal ion in both complexes is pentagonal bipyramid. Uranium ion in the crystal structure of 1 were found to be ligated with two chelate ma(-) groups and one unidentate H(2)O molecule (C coordination mode) at the equatorial plane, while in 2 with two single-bonded Hdpp there were one chelate dpp(-) and one H(2)O molecule (P coordination mode). Crystal data (Mo Kalpha; 293(2) K) are as follows: (1) monoclinic space group C2/c, a = 14.561(7) A, b = 14.871(9) A, c = 7.250(4) A, beta = 95.40(4) degrees , Z = 4; (2) monoclinic space group P2(1)/c, a = 19.080(2) A, b = 9.834(1) A, c = 15.156(2) A, beta = 104.62(1) degrees , Z = 4. (1)H NMR measurements indicate that complex 2 retains its structure in CD(3)CN solution; however, in DMSO-d(6) both complexes adopt the C structure. Line-shape analysis for the (1)H NMR peaks of 2 at various temperatures shows a fast intramolecular exchange process between the chelate dpp(-) and one of the single bonded Hdpp ligands and one slower exchange between all three ligands. The activation parameters and the decrease of the exchange rate by replacing unidentate ligand with DMSO indicate the dissociation of the unidentate ligand as the rate-determining step for the former exchange. Density functional calculations (DFT) support this mechanism and give a quantitative interpretation of the electronic structure of the two ligands and the geometries adopted by the complexes.     

p-Hydroquinone-metal compounds: synthesis and crystal structure of two novel VV-p-hydroquinonate and VIV-p-semiquinonate species

Reaction of the p-hydroquinone derivative H2Na4bicah.4H2O with either VIVOSO(4).3H2O and NaVVO3 in equivalent quantities or with NaVVo3 yields the tetranuclear VIVO2+ macrocycle-semiquinonate compound Na6[(VIVO)4-(mu2-O)2[mu2-bicas.(-5)-N,O,O,O]2].Na2SO(4).20H2O (1.Na2SO(4).20H2O) and the dinuclear cis-VVO2(+)-hydroquinone species Na4[(VVO2)2[mu2-bicah(-6)-N,O,O,O]].11H2O (2.11H2O) respectively. Compounds 1.Na2SO(4).20H2O and 2.11H2O were characterized by X-ray structure analysis and ab initio calculations.     

Synthesis, structure, magnetic properties and aqueous solution characterization of p-hydroquinone and phenol iminodiacetate copper(II) complexes

The reaction of Cu2+ acetate monohydrate with 2-[N,N'-bis(carboxymethyl)aminomethyl]-4-carboxyphenol (H4cacp), 2-[N,N-bis(carboxymethyl)aminomethyl]hydroquinone (H4cah) and the dinucleating 2,5-bis[N,N-bis(carboxymethyl)aminomethyl]hydroquinone (H6bicah) in water results in the formation of several Cu2+ species, which are in dynamic equilibrium in aqueous solution and their stability is pH dependent. A systematic crystallographic study of these species was pursued, resulting in the characterization of most of the species. Additional techniques were employed to characterize the molecules in the solid state (infrared spectroscopy) and in solution (UV-vis spectroscopy and electrochemistry). These measurements show that the Cu2+ ions are ligated mainly to the iminodiacetate at pH < 6, exhibiting only weak interactions with the phenol oxygen. At pH > 6, the phenol oxygen was deprotonated and dinuclear-bridged species, from the phenolate oxygen complexes exhibiting a Cu2+ 2O2 core, were isolated. The coordination environment around the copper ions varies between trigonal bipyramidal, tetragonal pyramidal and distorted octahedral geometries. The two unpaired electrons of the Cu2+ ions are found to be antiferromagnetically coupled. A survey of the magnetic and structural properties of the dinuclear phenoxide bridged Cu2+ complexes shows that the strength of the antiferromagnetic coupling is linearly dependent on the Cu-Ophenolate bond lengths, at bond distances below 1.98 angstroms. The effect of the Cu-O-Cu angles on the magnetic properties of the complexes is also discussed.     

Solid state and aqueous solution characterization of rectangular tetranuclear V(IV/V)-p-semiquinonate/hydroquinonate complexes exhibiting a proton induced electron transfer

Reaction of the non-innocent dinucleating ligand 2,5-bis[N,N-bis(carboxymethyl) aminomethyl]hydroquinone (H 6bicah) with VO (2+) and VO 4 (3-) salts in water in the pH range 2 to 4.5 provides a series of novel tetranuclear V (IV) and/or V (V) macrocycles with the main core consisting of the anions [V (V) 4O 4(mu-O) 2(mu-bicah) 2] (4-) isolated at pH = 2.5 and [V (IV) 2V (V) 2O 4(mu-O) 2(mu-bicas)(mu-bicah)] (5-) and [V (IV) 4O 4(mu-O) 2(mu-bicas) 2] (6-) isolated at pH = 4.5 (bicas (*5-) = 2,5-bis[N,N-bis(carboxymethyl) aminomethyl]- p-semiquinonate), whereas at pH = 2 the dinuclear [(V (IV)O) 2(OH 2) 2(mu-bicah)] (2-) was obtained. All vanadium compounds have been characterized, and the charge of the ligand has been assigned in solid state by X-ray crystallography and infrared spectroscopy. The structures of the tetranuclear anions consist of four vanadium atoms arranged at the corners of a rectangle with the two bridging bicas (*5-) and/or bicah (6-) ligands on the long and the two V (IV/V)-O-V (IV/V) bridges on the short sides of the rectangle. UV-vis, (51)V and (1)H NMR spectroscopy and electrochemistry showed that these complexes interconvert to each other by varying the pH. This pH induced redox transformation of the tetranuclear anions has been attributed to the shift of the reduction potential of the bicas (*5-) to higher values by decreasing the pH. The electron is transferred intramolecularly from the metal ion to the electron accepting semiquinones resulting in reduction of bicas (*5-) to bicah (6-) and concurrent oxidation of the V (IV) to V (V). The resulting complexes are further oxidized by atmospheric oxygen. This system as a model for the H (+) coupled redox reactions in metalloenzymes and its relevance is discussed briefly.     

Synthesis,spectroscopic, structural and magnetic studies of new binary Cr(III)–citrate pH-specific structural variants from aqueous media

In an attempt to understand the aqueous interactions of Cr(III) with the low molecular mass physiological ligand citric acid, the pH-specific synthesis in the binary Cr(III)–citrate system was pursued, leading to the new complexes Na₃[Cr(C₆H₅O₇)₂]·8.5H₂O (1) and (Hdmphen)₆[Cr(C₆H₅O₇)₂]·(NO₃)₃·14H₂O (2). Complexes 1 and 2 were characterized by elemental analysis, spectroscopic, structural, thermal, and magnetic susceptibility studies. The structures of 1 and 2 reveal a mononuclear octahedral complex of Cr(III) with two citrate ligands bound to it. Albeit of the same deprotonation state, the disposition of the two citrate ligands with respect to Cr(III) differs between 1 and 2 in the solid state, thus reflecting the presence of pH-structural variants in the requisite binary system. This conformational difference is lifted in aqueous solution, thus providing (a) comparative information on the distribution and diversity of species in the binary Cr(III)–citrate system, and (b) insight into the nature of interactions developing in the binary Cr(III)–hydroxycarboxylate systems in abiotic and biological applications.