Composition of the Essential Oil of Coristospermum cuneifolium and Antimicrobial Activity Evaluation

AbstractFor the first time, the chemical composition and antimicrobial evaluation of Coristospermum cuneifolium (previously named Ligusticum lucidum subsp. cuneifolium) essential oil obtained from the aerial parts are reported in this work. Approximately 85% of the total constituents were identified by GC-MS analysis, evidencing the presence of 12 chemical components which belong to several classes of natural compounds. Most of them are reported for the first time in the Ligusticum genus (s.l.) and in the Apiaceae family. Their presence was able to provide a rationale for essential oil use in the field similar to those obtained from other species of the Ligusticum genus (s.l.). Moreover, the huge presence of aromatizing and flavoring components, accounting for 44.4% of the essential oil composition, might make C. cuneifolium a useful natural source of aromatic components for the food and cosmetic fields. In addition to this, a deep comparison of the essential oil of this species with that of other entities within the Ligusticum genus (s.l.) was performed and discussed on a chemotaxonomic basis.The essential oil was tested for its antimicrobial activity at both high and low inoculum (~5×105 and ~ 5×103 cfu/mL, respectively) against several bacterial and fungal strains, including methicillin-susceptible Staphylococcus aureus (ATCC 29213), Escherichia coli (ATCC 25922), Candida albicans (ATCC 14053), methicillin-resistant S. aureus (clinical strain), carbapenem-susceptible Klebsiella pneumoniae (clinical strain), carbapenem-resistant K. pneumoniae (clinical strain), and carbapenem-resistant Acinetobacter baumannii (clinical strain).A high potency against C. albicans was shown, with an absence of growth at the concentration of 3.01 mg/mL; similarly, for methicillin-susceptible S. aureus and methicillin-resistant S. aureus, a reduction of 1.73 and 2 log10 cfu/mL at the concentration of 3.01 mg/mL was observed. With regard to gram-negative microorganisms, only slight potency against A. baumannii was shown, whereas no activity was found against E. coli and K. pneumoniae

Phytochemical analysis and biological activities of the ethanolic extract of Daphne sericea Vahl flowering aerial parts collected in Central Italy

In this paper, the first phytochemical analysis of the ethanolic extract of Daphne sericea Vahl flowering aerial parts collected in Italy and its biological activities were reported. Eleven compounds were identified i.e., -linolenic acid (1), tri-linoleoyl-sn-glycerol (2), pheophorbide a ethyl ester (3), pilloin (4), sinensetin (5), yuanhuanin (6), rutamontine (7), syringin (8), p-coumaric acid (9), p-anisic acid (10) and caffeic acid (11). To the best of our knowledge, compounds (1-4, 7-8 and 10) were isolated from D. sericea for the first time during this work, whereas sinensetin (5) represents a newly identified component of the entire Thymelaeaceae family. The extract was found to possess radical scavenging against both DPPH and 2,20-azino-bis(3-thylbenzothiazoline-6-sulfonic acid (ABTS.+) radicals, with at least a 40-fold higher potency against the latter. Moreover, chelating abilities against both ferrous and ferric ions have been highlighted, thus suggesting a possible indirect antioxidant power of the extract. Although the precise bioactive compounds remain to be discovered, the polyphenolic constituents, including phenolic acids, tannins and flavonoids, seem to contribute to the antioxidant power of the phytocomplex. In addition, the extract produced cytotoxic effects in MDA-MB-231 and U87-MG cancer cell lines, especially at the concentration of 625 g/mL and after 48–72 h. Further studies are required to clarify the contribution of the identified compounds in the bioactivities of the extract and to support possible future applications

Representation of the continuous spectrum excited by a dipole in a multilayer configuration through weighted cylindrical leaky waves

In this work, an original closed-form approximate evaluation is performed for the continuous-spectrum field excited by a dipole source in substrate-superstrate configurations, often employed in planar antennas and integrated passive components. By extending a recently-developed asymptotic approach, previously applied to the one-dimensional TE case of a line-source excitation, we first derive a suitable closed-form expression for the residual-wave field: this allows us to represent the continuous-spectrum field also in the neighbourhood of the transition region between leaky-wave and bound-wave ranges in the form of angular-dependent cylindrical leaky waves of TE or TM type, weighted by an appropriate transition function. The proposed formulation makes clear in a simple way the characteristics of the continuous-spectrum field excited by practical sources. Numerical results which show the accuracy of this approach are provided for different configurations and frequency ranges

Asymptotic analysis of bound-mode and free-space residual-wave currents excited by a delta-gap source on a microstrip line

In this work, an asymptotic analysis is presented for bound-mode and free-space residual-wave currents, with the aim of obtaining an analytical representation of the continuous-spectrum current excited by a delta-gap source on a microstrip line. The proposed approach is valid in a frequency region which extends through the entire spectral gap of the dominant leaky mode. The analysis proves in a rigorous way the different asymptotic behaviors of the TM0 bound-mode and free-space residual-wave currents. The relevance of the nature of the involved branch points to these asymptotic behaviors is also discussed. An explicit expression for the numerical coefficient arising in the asymptotic expansion obtained through Watson's Lemma is provided in a simple closed form for both types of residual-wave current. Analytical details are supplied, together with numerical results which confirm the predicted asymptotic behaviors and the accuracy of the closed-form representation also in proximity of the source, if the presence of singularities of the relevant spectral integrands is properly taken into account

Analisi dello spettro continuo della corrente eccitata in microstrisce aperte e schermate nella regione di spectral gap del modo leaky dominante

In this work, the problem of obtaining a closed form representation for the continuous-spectrum current excited by a finite source along open and covered microstrip lines is addressed inside the frequency range (the so-called spectral-gap region) in which the dominant leaky mode is not physical. In particular, the lowest asymptotic order of such continuous spectrum at large distances from the source is rigorously derived and the accuracy of such representation close to the source is further increased by properly taking into account the relevant spectral Green’s function singularities. Numerical results for different structures and frequencies inside the spectral gap region are provided which confirm the accuracy of the proposed formulatio

Novel analytical representations of the continuous spectrum current on multilayer stripline structures

We consider a multilayer stripline structure excited by a delta-gap source and we study the continuous-spectrum current, which may be responsible of several spurious transmission effects such as interference with the quasi-TEM mode, undesired radiative effects, and crosstalk. In particular, a uniform asymptotic analysis of such continuous spectrum is presented, based on two alternative closed-form representations. Both representations are accurate also very close to the source and are valid inside a wide frequency range starting from DC. One formulation has a direct implementation, since it needs only knowledge of the spectral Green's function of the background structure. The other formulation requires knowledge of the exact complex (leaky) poles of the stripline Green's function and of their residues, but provides more physical insight since it gives quantitative information on the role of leaky waves in the continuous-spectrum representation in the entire considered frequency range. Numerical results which validate the accuracy and efficiency of the proposed approaches are provided at different frequencies for covered-microstrip structures with different strip widths

An accurate analytical representation of the continuous spectrum excited on multilayer stripline structures in spectral-gap regions

In this work, an approximate asymptotic closed-form representation is derived for the continuous-spectrum current excited by a delta-gap source in a multilayer stripline. The proposed representation is accurate also very close to the source and is valid inside the low-frequency spectral-gap region of the dominant leaky mode supported by this structure, where the main contribution to the continuous-spectrum current is given by the residual-wave current. Numerical results which confirm the accuracy and numerical efficiency of the proposed approach are provided at different frequencies

Analytical investigation on the continuous spectrum in the spectral gap of the dominant leaky mode for open and covered microstrip lines

In this work, a rigorous analysis is carried out in order to characterize the behaviour of the continuous-spectrum current excited by a delta-gap source along open and covered microstrip lines at large distances from the source. The proposed analysis is valid and particularly efficient in the neighbourhood of the spectral gap of the dominant leaky mode. In particular, a closed-form representation for the continuous-spectrum current is obtained at the lowest asymptotic order; the accuracy of such representation close to the source can be further increased by properly taking into account the role of the singularities of the involved spectral integrands, which directly influence the behaviour of such continuous spectrum. Numerical results for different structures and frequencies are provided, which confirm the accuracy and the efficiency of the proposed approach

Approximate analytical evaluation of the continuous spectrum in a substrate-superstrate dielectric waveguide

In this work, an original closed-form approximate evaluation is performed for the continuous-spectrum field excited by an electric-current line source in a substrate-superstrate configuration, optimized for leaky-wave radiation. The validity of these results is shown for the near and the far field at different frequencies, including the frequency range in which the leaky wave is physical and the entire transition region through the spectral gap. This new closed-form result shows explicitly the nature of the continuous-spectrum field in the transition region, and provides insight into the nature of the fields on more complicated structures such as microwave integrated circuits