Studio fitochimico di Clerodendrum splendens G. Don (Verbenaceae)

Oggetto della presente tesi è lo studio fitochimico delle parti aeree di Clerodendrum splendens G. Don, un arbusto rampicante sempreverde appartenente alla famiglia delle Verbenaceae, originaria dell’ Africa occidentale ed acclimatato presso El Zoharia Research Garden del Cairo in Egitto. Lo studio di piante provenienti da tale giardino botanico rientra in un progetto di ricerca in collaborazione con la Faculty of Pharmacy, Al Azhar University del Cairo, Egitto, progetto che prevede l’isolamento e la caratterizzazione chimica di metaboliti secondari presenti in diverse specie vegetali mediante tecniche cromatografiche e spettroscopiche. L’ interesse verso questa specie nasce in primo luogo dall’esiguo numero di studi svolti su di essa ed inoltre, sulla base di dati presenti in letteratura sul genere, allo scopo di isolare e caratterizzare nuovi composti di natura diterpenica quali possibili prodotti di interesse biologico. Il materiale vegetale (parti aeree) è stato sottoposto a essiccazione all’aria, macinazione e successiva estrazione a temperatura ambiente con solventi a polarità crescente: n-esano, cloroformio, cloroformio–metanolo (9:1) e metanolo. In questo studio sono stati presi in considerazione gli estratti: cloroformico (RCHCl3), cloroformio–metanolo (RC-M), e metanolico (RMeOH). Il residuo RC-M è stato è stato sottoposto a cromatografia su colonna Sephadex LH-20 ad esclusione molecolare e, successivamente, le frazioni di interesse sono state studiate tramite cromatografia ad alta pressione su fase inversa (RP-HPLC), giungendo alla purificazione di 2 derivati fenolici, il composto flavonoidico ispidulina 7-O- β-D-glucopiranoside (1), ed il fenilpropanoide phlinoside B (2). Il residuo RMeOH è stato ripartito in una frazione acquosa ( RW ) ed in una n-butaolica ( RBu ) che è stata sottoposta a cromatografia su colonna Sephadex LH-20 ad esclusione molecolare. In seguito le frazioni di interesse sono state studiate tramite RP-HPLC giungendo all’ isolamento di 8 metaboliti secondari tra cui un nuovo fenilpropanoide (3), (3,4-diidrossifenil)etil-O-β-D-xilopiranosil-(1→2)-α-L-ramnopiranosil-(1→3)-6-O-t-caffeoil-β-D-glucopiranoside , i composti (1) e (2) già isolati nel residuo RCM , ed altri composti fenolici tra cui ispidulina 7-neoesperidoside (4), verbascoside (5), isoacteoside (6), luteolina 7-neoesperidoside (7), ed infine acido rosmarinico (8) . Il residuo RCHCl3 è stato sottoposto a cromatografia flash su colonna di gel di silice e, in seguito, le frazioni di interesse sono state studiate tramite cromatografia ad alta pressione su fase inversa RP-HPLC giungendo alla purificazione di composti di origine terpenica, fra cui un composto sesquiterpenico 2β-angeloilossi-5β-idrossi-7αH,10β-metil-eudesm-3-en-1-one (9), il diterpene 14,15-diidro-15-idrossi-3-epicarioptina (10), e 4 composti diterpenici mai precedentemente isolati, il 2-acetossi-3-(2’,3’-diacetossi-2’-metil)-butanoilossi-14-idro-15-idrossiclerodina (11), il 3,15-diidrossi-14-idro-clerodina (12), il 2,15-diidrossi-3-(2’-idrossi-2’-metil-3’-acetossi)-butanoilossi-6α,18-diacetossi-4α,17-epossi-clerodan-11,16-lattone (13), ed infine il diterpene 3,14,15-tridrossi-6α,18-diacetossi-4α,17-epossi-clerodan-11,16-lattone (14) . La determinazione strutturale di tutti i composti è stata effettuata con l’ausilio di tecniche spettroscopiche NMR mono e bidimensionali, fra cui 1H-NMR, 13C-NMR, HSQC, HMBC, 1D-TOCSY sono state le principali, e tecniche di spettrometria di massa ESI-MS. L’indagine fitochimica condotta su Clerodendrum splendens G. Don ha quindi portato all’isolamento totale di 14 composti tra cui 4 diterpeni mai caratterizzati in precedenza, 1 nuovo fenilpropanoide ed altri derivati fenolici nel completo accordo con quanto trovato negli studi riportati nella letteratura appartenente al genere Clerodendrum

Transitive Triangle Tilings in Oriented Graphs

In this paper, we prove an analogue of Corr\'adi and Hajnal's classical theorem. There exists $n_0$ such that for every $n \in 3\mathbb{Z}$ when $n \ge n_0$ the following holds. If $G$ is an oriented graph on $n$ vertices and every vertex has both indegree and outdegree at least $7n/18$, then $G$ contains a perfect transitive triangle tiling, which is a collection of vertex-disjoint transitive triangles covering every vertex of $G$. This result is best possible, as, for every $n \in 3\mathbb{Z}$, there exists an oriented graph $G$ on $n$ vertices without a perfect transitive triangle tiling in which every vertex has both indegree and outdegree at least $\lceil 7n/18\rceil - 1.$Comment: To appear in Journal of Combinatorial Theory, Series B (JCTB

Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range

This paper analyses the behaviour of the gas-to-dust mass ratio (G/D) of local Universe galaxies over a large metallicity range. We combine three samples: the Dwarf Galaxy Survey, the KINGFISH survey and a subsample from Galametz et al. (2011) totalling 126 galaxies, covering a 2 dex metallicity range, with 30% of the sample with 12+log(O/H) < 8.0. The dust masses are homogeneously determined with a semi-empirical dust model, including submm constraints. The atomic and molecular gas masses are compiled from the literature. Two XCO are used to estimate molecular gas masses: the Galactic XCO, and a XCO depending on the metallicity (as Z^{-2}). Correlations with morphological types, stellar masses, star formation rates and specific star formation rates are discussed. The trend between G/D and metallicity is empirically modelled using power-laws (slope of -1 and free) and a broken power-law. We compare the evolution of the G/D with predictions from chemical evolution models. We find that out of the five tested galactic parameters, metallicity is the galactic property driving the observed G/D. The G/D versus metallicity relation cannot be represented by a power-law with a slope of -1 over the whole metallicity range. The observed trend is steeper for metallicities lower than ~ 8.0. A large scatter is observed in the G/D for a given metallicity, with a dispersion of 0.37 dex in metallicity bins of ~0.1 dex. The broken power-law reproduces best the observed G/D and provides estimates of the G/D that are accurate to a factor of 1.6. The good agreement of the G/D and its scatter with the three tested chemical evolution models shows that the scatter is intrinsic to galactic properties, reflecting the different star formation histories, dust destruction efficiencies, dust grain size distributions and chemical compositions across the sample. (abriged)Comment: 23 pages, 12 figures, accepted in Astronomy & Astrophysic

On dominating and spanning circuits in graphs

An eulerian subgraph of a graph is called a circuit. As shown by Harary and Nash-Williams, the existence of a Hamilton cycle in the line graph L(G) of a graph G is equivalent to the existence of a dominating circuit in G, i.e., a circuit such that every edge of G is incident with a vertex of the circuit. Important progress in the study of the existence of spanning and dominating circuits was made by Catlin, who defined the reduction of a graph G and showed that G has a spanning circuit if and only if the reduction of G has a spanning circuit. We refine Catlin's reduction technique to obtain a result which contains several known and new sufficient conditions for a graph to have a spanning or dominating circuit in terms of degree-sums of adjacent vertices. In particular, the result implies the truth of the following conjecture of Benhocine et al.: If G is a connected simple graph of order n such that every cut edge of G is incident with a vertex of degree 1 and d(u)+d(v) > 2(1/5n-1) for every edge uv of G, then, for n sufficiently large, L(G) is hamiltonian

On fractionality of the path packing problem

In this paper, we study fractional multiflows in undirected graphs. A fractional multiflow in a graph G with a node subset T, called terminals, is a collection of weighted paths with ends in T such that the total weights of paths traversing each edge does not exceed 1. Well-known fractional path packing problem consists of maximizing the total weight of paths with ends in a subset S of TxT over all fractional multiflows. Together, G,T and S form a network. A network is an Eulerian network if all nodes in N\T have even degrees. A term "fractionality" was defined for the fractional path packing problem by A. Karzanov as the smallest natural number D so that there exists a solution to the problem that becomes integer-valued when multiplied by D. A. Karzanov has defined the class of Eulerian networks in terms of T and S, outside which D is infinite and proved that whithin this class D can be 1,2 or 4. He conjectured that D should be 1 or 2 for this class of networks. In this paper we prove this conjecture.Comment: 18 pages, 5 figures in .eps format, 2 latex files, main file is kc13.tex Resubmission due to incorrectly specified CS type of the article; no changes to the context have been mad

Non-skeletal activities of vitamin d: From physiology to brain pathology

Vitamin D is a secosteroid hormone regulating the expression of almost 900 genes, and it is involved in the regulation of calcium and phosphate metabolism, immune response, and brain development. Low blood vitamin D levels have been reported in patients affected by various diseases. Despite a large amount of literature data, there is uncertainty surrounding the role of vitamin D as a serum biomarker in Alzheimer’s disease (AD) and Parkinson’s disease (PD). Indeed, the lack of internationally recognized 25(OH)D3 reference measurement procedures and standard materials in the past led to unstandardized serum total 25(OH)D3 results among research and clinical care laboratories. Thus, most of the literature studies reported unstandardized data, which are of little use and make it difficult to draw conclusions of the role of vitamin D in AD and PD. This review summarizes the extra-skeletal actions of vitamin D, focusing its role in immunomodulation and brain function, and reports the issue of lacking standardized literature data concerning the usefulness of vitamin D as a biomarker in AD and PD

FGGE/SMMR-30 tape specification and shipping letter description

The Nimbus-7 FGGE/SMMR-30 tape which contains sea ice concentration data in 30 km resolution which are extracted and reformatted from Nimbus-7 SMMR PARM-30 tapes in accordance with the FGGE level II International Exchange Format Specification is outlined. There are three types of files on a FGGE/SMMR-30 tape. The first file on the tape is a test file. The second file on the tape is a tape header file. The remaining one or more files are data files. All files are terminated with a single end of file (EOP) tape mark. The last file is terminated with two EOF tape marks. All files are made up of one or more physical records. Each physical record contains 2960 bytes. Each data file contains all available values for a 6 hour synoptic time period