Emanuele Arlandini

A rapid profiling of gallotannins and flavonoids of the aqueous extract of Rhus coriaria L. by flow injection analysis with high-resolution mass spectrometry assisted with database searching

Hydrolysable tannins appear to have some extremely important biological roles including antioxidant, antibacterial, anti-inflammatory, anti-hypoglycemic, anti-angiogenic, and anticancer activities. The aim of this work was to set up a flow injection high-resolution mass spectrometric approach combined with database searching to obtain rapidly a profiling of gallotannins and other phenolics in a crude extract from plant tissue. The flow injection analysis (FIA) takes place in an electrospray ionization source of an hybrid orbitrap high resolution mass spectrometry system (ESI-HR-MS/MS(2), resolution 100,000, negative ion mode) and polyphenols are tentatively identified by matching the monoisotopic masses of the spectra with those of polyphenols databases. This leads to the most probable molecular formulas and to the possible structures among those reported in the database. The structures confirmation occurs by the compliance of MS(2) fragments with those of a prediction fragment commercial database. With this method we identified in the aqueous extract of sumac leaves, with a maximum error of 1.7 ppm, a group of ten gallotannins from mono- to deca-galloyl glycosides of the class of hydrolysable tannins and a set of coextracted flavonoid derivatives including myricetin, quercetin-3-O-rhamnoside, myricetin-3-O-glucoside, myricetin-3-O-glucuronide, and myricetin-3-O-rhamnoglucoside. The separation of isomers of gallotannins and flavonoids present in the same extract occurred by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry (HPLC/ESI-HR-MS(2)); this approach allowed the structure resolution of the isobaric flavonoids quercetin-3-O-glucoside and myricetin-3-O-rhamnoside.

Acrolein sequestering ability of the endogenous tripeptide glycyl-histidyl-lysine (GHK): Characterization of conjugation products by ESI-MSn and theoretical calculations

Acrolein (ACR) is a well-known carbonyl toxin produced by lipid peroxidation of polyunsaturated fatty acids, which is involved in several life-threatening pathologies such as Alzheimer disease, arteriosclerosis, diabetes, and nephropathy. The aim of this work was to study the quenching ability of the endogenous tripeptide glycyl-histidyl-lysine (GHK), a liver cell growth factor isolated from human plasma, towards the electrophilic aldehyde ACR and to characterize the reaction products by electrospray mass spectrometry (ESI-MS/MS infusion experiments; positive ion mode). The reaction of ACR (30 microM) with GHK (0.1, 0.25, 0.5, 1.0 mM) was followed by measuring aldehyde consumption by reverse-phase HPLC (phosphate buffer, pH 7.4); after 4h, when the aldehyde had completely disappeared; the reaction products were checked by ESI-MS/MS. Several products were detected in the GHK+ACR reaction (1:1). This indicates a complex reaction cascade involving the sequential addition of ACR (up to 3 mol) to the tripeptide GHK and, in particular, to the epsilon-amino group of the lysine residue and to the N(tau) and N(pi) of the histidine moiety. The Michael addition of two molecules of ACR to the epsilon-amino group of the lysine residue is followed by aldol condensation and dehydration to give the N-(3-formyl-3,4-dehydropiperidino) derivative. The results confirm that the ESI-MS/MS approach in a direct infusion experiment permits rapid profiling of the products of the GHK+ACR reaction. They firstly point to the potential medicinal use of GHK in the prevention of carbonyl stress-linked pathologies, and--second--help shed light on the physiological role of this histidine-containing tripeptide which is claimed to be an endogenous growth factor, but has never been shown to be an ACR quencher.

Metal-catalyzed and -promoted cyclizations for the synthesis of cephalosporins: a possible DAOC/DAC synthetase biomimetic process.

Abstract A thiyl radical cyclization approach to the sulphur containing ring of cephams is described. The reaction was carried out using metals able to perform a single-electron oxidation process under stoichiometric [Fe(III), MN(OAc)3] or catalytic [Fe(III)] conditions. Furthermore, the FeCl3 or Mn(OAc)3/LiX promoted reactions afforded, by a double single-electron oxidation process, over oxidized compounds. The relationship with the mechanistic hypothesis proposed by Baldwin for the DAOC/DACS-catalyzed ring expansion from Penicillin N to Desacetoxy cephalosporin C is discussed.

NEW 13-AZA BACCATINS

Abstract Upon treatment of 7-triethylsilyl-10, 13-dideoxy-13-imino baccatin III (2) subsequently with diazomethane and m-chloroperbenzoic acid a few novel derivatives, namely methylimine 3 and oximes 4 and 5, were obtained. Interestingly, 4 is characterized by the hydroxyl at position 14.

Detection and mass spectrometric characterization of the major urinary and fecal metabolites of 9-methyl-1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]-quinolizine in the rat.

SummaryThe metabolic fate of 9-methyl 1,2,3,4,6,7,12,12b-octahydroindolo[2,3-a]quinolizine (MIQ), a compound with promising pharmacological action on the CNS system, was investigated in the rat after an oral dose of 200 mg/kg, the maximal tolerated dose. Urine and feces were collected, exhaustively extracted with organic solvents and the metabolites detected by TLC analysis.The structures of the isolated metabolites were characterized by several mass spectrometry techniques (FD, EI, CI) and, in some cases, confirmed by synthesis.The major metabolic pathways of MIQ in the rat involve: C-oxidation of the methyl group in position 9 to a primary alcohol and to a carboxylic acid, N-oxidation of basic nitrogen and C-oxidation of the quinolizidine nucleus, probably at position 7.