Ugo M. Pagnoni

In vitro comparison of the prebiotic effects of two inulin-type fructans

Faecal cultures were used to compare the prebiotic effects of a new fructan containing high solubility inulin (HSI) and of a well-established prebiotic containing oligofructose (OF) with a negative control (CT). Changes in the intestinal microbiota, pH, ammonia, volatile organic acids and lactic acid were monitored during incubation. Molecular techniques for microbial enumeration indicated that both HSI and OF led to a significant increase in bifidobacteria (P< or =0.05) and lactobacilli (P< or =0.05) compared to the control. Significant changes in the pH and levels of ammonia with both inulin-type fructans were observed, as well as higher levels of acetic, lactic and formic acids (P< or =0.05). The fermentative metabolism appeared to be faster on OF than on HSI. Both OF and HSI showed clear prebiotic effects, but had differences in fermentation kinetics because of to the different degree of polymerization (DP). This study provides proof for the prebiotic effectiveness of HSI, and shows that inulin-type fructans with higher DP might have a prolonged bifidogenic effect, thus could extend the saccharolytic metabolism and low pH to the distal parts of the colon.

Bioconversion of soy isoflavones daidzin and daidzein by Bifidobacterium strains

Twenty-two strains of Bifidobacterium, representative of eight major species of human origin, were screened for their ability to transform the isoflavones daidzin and daidzein. Most of the strains released the aglycone from daidzin and 12 gave yields higher than 90%. The kinetics of growth, daidzin consumption, and daidzein production indicated that the hydrolytic activity occurred during the growth. The supernatant of the majority of the strains did not release the aglycone from daidzin, suggesting that cell-associated β-glucosidases (β-Glu) are mainly responsible for the metabolism of soybean glyco-conjugates. Cell-associated β-Glu was mainly intracellular and significantly varied among the species and the strains. The lack of β-Glu was correlated with the inability to hydrolyze daidzin. Although S-equol production by anaerobic intestinal bacteria has been established, information on S-equol-producing bifidobacteria is contradictory. In this study, 22 bifidobacteria failed to transform daidzein into reduced metabolites under all the experimental conditions, excluding any role in the reductive pathway of daidzein toward the production of S-equol. These results suggest that selected probiotic strains of Bifidobacterium can be used to speed up the release of daidzein, improving its bioavailability for absorption by colonic mucosa and/or biotransformation to S-equol by other intestinal microorganisms.

Volatile components of Grana Parmigiano-Reggiano type hard cheese

Abstract GC–MS analysis of volatile components of Grana Parmigiano-Reggiano type Italian hard cheese was performed by solid phase micro extraction (SPME) and Purge & Trap (PT) methods. Half of the 24 samples analysed were produced in flat land (

Growth, lipid accumulation, and fatty acid composition in obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts

Obligate psychrophilic, facultative psychrophilic, and mesophilic yeasts were cultured in a carbon-rich medium at different temperatures to investigate whether growth parameters, lipid accumulation, and fatty acid (FA) composition were adaptive and/or acclimatory responses. Acclimation of facultative psychrophiles and mesophiles to a lower temperature decreased their specific growth rate, but did not affect their biomass yield (Y(X/S)). Obligate and facultative psychrophiles exhibited the highest Y(X/S). Acclimation to lower temperature decreased the lipid yield (Y(L/X)) in mesophilic yeasts, but did not affect Y(L/X) in facultative psychrophilic ones. Similar Y(L/X) were found in both groups of psychrophiles, suggesting that lipid accumulation is not a distinctive characteristic of adaptation to permanently cold environments. The unsaturation of FAs was one major adaptive feature of the yeasts colonizing permanently cold ecosystems. Remarkable amounts of alpha-linolenic acid were found in obligate psychrophiles at the expense of linoleic acid, whereas it was scarce or absent in all the other strains. Increased unsaturation of FAs was also a general acclimatory response of facultative psychrophiles to a lower temperature. These results improve the knowledge of the responses enabling psychrophilic yeasts to cope with the cold and may be of support for potential biotechnological exploitation of these strains.

Halogen atom transfer radical cyclization of N-allyl-N-benzyl-2,2-dihaloamides to 2-pyrrolidinones, promoted by Fe0-FeCl3 or CuCl-TMEDA

Abstract The halogen atom transfer radical cyclization of a N-allyl-N-benzyl-2,2-dihaloamides to 2-pyrrolidinones has been carried out in high yields under mild conditions, in a reaction promoted by CuCl-TMEDA or Fe0-FeCl3 in acetonitrile or N,N-dimethylformamide, respectively.

The influence of benzylic protection and allylic substituents on the CuCl-TMEDA catalyzed rearrangement of N-allyl-N-benzyl-2,2-dihaloamides to gamma-lactams. Application to the stereoselective synthesis of pilolactam.

Abstract A number of N-benzylic protecting groups and allylic substituents have been investigated for the rearrangement, promoted by CuCl-TMEDA, of N-allyl-2,2-dihaloamides to 3,4-disubstituted γ-lactams. An appreciable chiral induction was observed at the C-4 site when α-phenylethylamine was used as a chiral protecting group, while an unexpected Diels-Alder reaction occurred when using a 2-furyl-methyl protection. This rearrangement has been applied to the synthesis of pilolactam, a drug with muscarinic activity.

Halogen atom transfer radical addition of α-polychloroesters to olefins promoted by Fe0 filings

Abstract The Kharasch addition of methyl 2,2-dichlorocarboxylates or trichloro acetic acid derivatives to alkenes, affording the corresponding 1:1 adducts, is promoted by the iron filings/N,N-dimethylformamide system.

A study on volatile organic compounds (VOCs) produced by tropical ascomycetous yeasts

As a part of a program aiming at the selection of strains which might be of interest as sources of natural flavouring molecules, the production of volatile organic compounds (VOCs) by 98 ascomycetous yeast strains (representative of 40 species belonging to 12 genera) isolated from tropical environments was investigated. Volatiles produced were sampled by means of headspace solid-phase microextraction (SPME) and the compounds were analysed and identified by gas chromatography–mass spectroscopy (GC–MS). The VOCs produced were found to be alcohols (amyl alcohol and isoamyl alcohol), aldehydes (2-methyl-2-hexenal and 2-isopropyl-5-methyl-2-hexenal) and esters (ethyl isobutyrate, isobutyl acetate, isoamyl acetate, 2-methylbutyl acetate, ethyl isovalerate, isoamyl propionate and phenylmethyl acetate). Differences in VOC profiles were used to cluster the yeast strains into 25 VOC phenotypes. The different frequency of VOC phenotypes in three specific habitats was correlated to the divergent environmental conditions, possibly affecting the selection of specific yeasts. From a biotechnological viewpoint, this study reveals the potentiality of ascomycetous yeasts isolated from tropical environments as a promising source of VOCs relevant in food and fragrance industry.

Biosynthesis of nepetalactone in Nepeta cataria

Abstract Iridodial is a key intermediate in the biosynthesis of nepetalactone. One of the steps on the pathway prior to the lactonization is a hydride shift from C-1 to C-10. 10-Hydroxycitronellol is a far more efficient precursor than the C-2/C-3 unsaturated analogue.

Synthesis of 5-methoxylated 3-pyrrolin-2-ones via the rearrangement of chlorinated pyrrolidin-2-ones

The reaction of N-substituted 4-methyl-2-pyrrolidinones or 4-diethoxyphosphoryl analogues, carrying at least two chlorine atoms between the C(3) and C(6) carbons, with alkaline methoxide in methanol afforded the corresponding 5-methoxylated 3-pyrrolin-2-ones, useful adducts for the preparation of agrochemicals or medicinal compounds.