Biomimetic Modeling of Copper Complexes: A Study of Enantioselective Catalytic Oxidation on D-(+)-Catechin and L-( − )-Epicatechin with Copper Complexes

The biomimetic catalytic oxidations of the dinuclear and trinuclear copper(II) complexes versus two catechols, namely, D-(+)-catechin and L-( − )-epicatechin to give the corresponding quinones are reported. The unstable quinones were trapped by the nucleophilic reagent, 3-methyl-2-benzothiazolinone hydrazone (MBTH), and have been calculated the molar absorptivities of the different quinones. The catalytic efficiency is moderate, as inferred by kinetic constants, but the complexes exhibit significant enantio-differentiating ability towards the catechols, albeit for the dinuclear complexes, this enantio-differentiating ability is lower. In all cases, the preferred enantiomeric substrate is D-(+)-catechin to respect the other catechol, because of the spatial disposition of this substrate

Studi su rame: enzimi e modelli

Dottorato di ricerca in scienze chimiche. 12. ciclo. Relatore Michele GullottiConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Determination of Saffron Quality through a Multi-Analytical Approach

Currently, the specifications for the assessment of saffron quality are contained in the ISO 3632 technical standard. This norm evaluates saffron quality through a UV-Vis spectrophotometric method and grades the spice into three commercial categories. However, numerous studies have highlighted several weaknesses and limitations of the ISO method. For this reason, a new multi-analytical approach for the determination of saffron quality is proposed in this work. Different techniques were employed to assess saffron quality: UV-visible spectroscopy (UV-Vis), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDX) and inductively coupled plasma—optical emission spectroscopy (ICP-OES). The results show that the commercial grading based on the ISO 3632 methodology is not always in line with the observations made with the other techniques. Moreover, the use of two new techniques in the field of saffron quality determination, i.e., SEM-EDX and ICP-OES, proved to be effective for the determination of elemental composition and metal content, which are two important parameters to take into consideration when assessing the quality of the spice

Stereoselective catalytic oxidations of biomimetic copper complexes with a chiral trinucleating ligand derived from 1,1-binaphthalene.

The new octadentate ligand R-(−)-N,N-dimethyl-N,N-bis{3-[bis(1-methyl-2-benzimidazolyl)amino]propyl}1,1- binaphthalenyl-2,2-diamine (L) was employed for the synthesis of dinuclear and trinuclear copper(II) complexes. Two terminal binding sites with tridentate aminobis(benzimidazole) linkages (A sites) and one central binding site with the bidentate diamino-binaphthalenyl residue (B site) are used by the ligand to bind divalent metal centres in the trinuclear complex [Cu3L][ClO4]6. Spectroscopic measurements suggest that in the dinuclear complex [Cu2L][ClO4]4 the copper ions are five-coordinated, with ligation by the aminobis(benzimidazole) residues, one of the tertiary amine donors of the diamino-binaphthalenyl moiety, and one water molecule. The complexes bind azide in the -1,3 fashion at low concentration and in the terminal mode at high concentration. The copper(II) complexes derived from L are catalytically active in the oxidation of 3,5-di-tert-butylcatechol (DTBC) by dioxygen. The oxidations are biphasic, with a fast initial stoichiometric phase corresponding to reduction of a pair of copper(II) centres and oxidation of DTBC to quinone, followed by the catalytic reaction, that follows substrate saturation behaviour. The complexes act as stereoselective catalysts in the biomimetic oxidations of the optically active catechol derivatives l- and d-Dopa and their methyl esters. In all the cases, the preferred enantiomeric substrate has the L configuration. This preference is dictated by the chirality of the binaphthalenyl residue

Salvia verticillata: Linking glandular trichomes, volatiles and pollinators

Plants have developed a plethora of signals to interact with other organisms, finally building up a sophisticate language for communication. In this context, we investigated Salvia verticillata L. (Lamiaceae), with the primary goal to link secondary metabolites and actual biotic relationships. We specifically analysed the volatile organic compounds (VOC) spontaneously emitted by leaves and flowers and determined the composition of the essential oils obtained from the aerial parts across 2015 and 2016. We merged information of chemical analyses to a micromorphological investigation on the glandular indumentum and to focal observations on the pollinator assemblage. The VOC profiles were highly variable, with the floral bouquet being the most complex. Flowers and leaves showed 37 and 20 exclusive compounds, dominated by 1,8-cineole (10.4%) and germacrene D (38.4%), respectively. Sesquiterpene hydrocarbons prevailed (83.3% leaves; 73.7% flowers) and 19 common compounds were detected. The oil profiles proved to be consistent across the two years: sesquiterpene hydrocarbons invariably dominated, with germacrene D, bicyclogermacrene and β-caryophyllene as main compounds. The whole plant epidermis is thickly covered by two types of glandular hairs: peltates and small capitates, both responsible for the synthesis of terpenes, finally resulting in the VOC emission and in the essential oil production. S. verticillata attracted mainly bees belonging to two functional groups: medium-sized and large bees, notwithstanding the small size of its flowers. At the site, Apis mellifera and different Bombus species were recorded, mainly interested in feeding on nectar. The literature survey on the isolated volatile compounds confirmed the hypotheses on the seduction strategies towards Apoidea

Scutellaria brevibracteata subsp. subvelutina (Rech.f.) Greuter & Burdet: morphological and phytochemical characterization

A micromorphological and phytochemical survey was performed on Scutellaria brevibracteata subsp. subvelutina cultivated in Italy. The indumentum of the vegetative and reproductive organs was investigated: peltate, short-, medium- and long-stalked capitates were described. Histochemistry evidenced similar results for peltates and long-stalked capitates, differences for short and medium capitates. For the first time, this work reported the characterization of volatile organic compounds from leaves and flowers, along with the first analysis of the essential oil obtained from the aerial parts of Italian samples. The floral profile resulted more complex than the foliar one, due to the higher number of the total compounds (40 vs 27) and of the exclusive constituents (24 vs 11). 16 common compounds were detected, with β-caryophyllene as the most abundant. The essential oil was characterized by 23 compounds, with β-caryophyllene dominating. The peltates, the medium and the long-stalked capitates resulted the producers of the investigated compounds

A dinuclear biomimetic Cu complex derived from l-histidine: synthesis and stereoselective oxidations

A new dicopper(ii) complex with a histidine-derived N6 ligand performs a biomimetic stereoselective oxidation of catechols.</p

THE GHIRARDI BOTANIC GARDEN, BEYOND THE VISIBLE

Plants preserved in botanic gardens are primarily experienced for their aesthetic value, often losing their identity to give rise to a whole that welcomes visitors. However, beyond the visual display, each plant dialogues with the other living organisms through the production of a plethora of different secondary metabolites. In this perspective, botanic gardens become not only showcases of plant beauty, but also factories of molecules that drive multiple biotic interactions. Under this novel inquiring approach, botanic gardens may be explored for intrinsic features lying at a higher level than that visually perceived. In this framework, we planned a research project on 30 selected medicinal species preserved at the Ghirardi Botanic Garden (Toscolano Maderno, Bs) on the basis of their productivity in volatile compounds (VOCs), essential oils (EOs), epicuticular depositions and substances stored at tissue level. The project encompasses analyses on the: (i) micromorphology of the secretory structures; (ii) the chemistry of the secondary metabolites; (iii) the evaluation of their ecological roles and (iv) of their biological activity. By way of example, we presented hereafter the results of the investigations performed on some target-species for each of the three-scale analyses. (i) We addressed our attention on Cinnamomum camphora (L.) J.Presl. The structures responsible for oil synthesis and storage were secretory cells distributed in the foliar mesophyll, in the bark and in close association to the xylem medullary rays. (ii) We analysed the composition of the EOs obtained from the leaves of Myrtus communis L., following different preservation procedures: fresh, dried and stored at room temperature, dried and stored at -20°C, dried and stored at -80°C. A high level of chemical consistency emerged across the EOs, due to the occurrence of 11 common compounds that included the main constituents. (iii) We observed the peculiar handling strategies of the local insect visitors on the flowers of two Mexican sage species: Salvia blepharophylla Brandegee (ex Epling) and Salvia greggii A. Gray. (iv) We evaluated the antimalarial activity on Plasmodium falciparum chloroquine (CQ)-sensitive (D10) and CQ- resistant (W2) strains and the antileishmanial activity on Leishmania infantum and Leishmania tropica of the EO of Eugenia uniflora L. aerial parts. The cytotoxicity of the oils was evaluated on human cells to calculate the selectivity index. E. uniflora showed antimalarial and antileishmanial activity at micromolar concentrations, but exhibited high cytotoxicity. The overall results were discussed in the light of the most recent literature contributions

Micromorphological and phytochemical insights on Phlomis fruticosa L. cultivated at the G.E. Ghirardi Botanical Garden (Lombardy, Northern Italy)

A multi-level study was performed on the vegetative and reproductive organs of Phlomis fruticosa L. (Lamiaceae), cultivated at the G.E. Ghirardi Botanical Garden (Toscolano Maderno, Brescia, Northen Italy). This work is part of the project Ghirardi Botanical Garden, factory of molecules...work in progress, intended to preserve and enhance the plant heritage hosted at the study site. The multidisciplinary research combined four approaches: I) micromorphological, to describe the structures responsible for the productivity of secondary metabolites; II) histochemical, to define the chemical nature of the secretory products by Light Microscopy, Fluorescence Mi- croscopy, and Scanning Electron Microscopy; III) phytochemical, to characterize the Essential Oil obtained from the blooming aerial parts by hydrodistillation with a Clevenger-type apparatus, consequently analysed by Gas Chromatography-Mass Spectrometry; IV) biological, to assess the potential biological activity of the most abundant EO components based on literature data. Overall, P. fruticosa presented non-glandular and glandular trichomes. The former were multicellular stellate or simple uniseriate, the latter capitate belonging to three morphotypes: branched stalked with a one-celled head, simple short-stalked with a one(two)-celled head, simple medium-stalked with a four-celled head. For the first time, the histochemical survey reported digital images showing a predominant terpenes secretion by the branched-stalked and simple medium capitates, while the simple short hairs were responsible for the secretion of mucopolysaccharides and acid polysaccharides. The EO profile revealed 50 compounds and was dominated by sesquiterpene hydrocarbons (51.1 %) and oxygenated sesquiterpenes (33.6 %), with ar-curcumene (24.3 %), caryophyllene oxide (22.5 %) and α-cedrene (12.8 %) as most representative compounds. Finally, based on literature data, antimicrobial, antioxidant, and anti- inflammatory properties were hypothesized. In the context of Open Science, an original iconographic apparatus was drafted based on these results to make them accessible to the visitors of the G.E. Ghirardi BG, as an opportunity to discover the plant heritage from an unusual perspective