Nonenzymatic Transglycosylation Reactions Induced by Roasting: New Insights from Models Mimicking Coffee Bean Regions with Distinct Polysaccharide Composition.

Three mixtures containing different molar proportions of (ß1→4)-D-mannotriose and (α1→5)-L-arabinotriose, oligosaccharides structurally related to coffee polysaccharides (galactomannans and arabinogalactans), were roasted at 200 °C for different periods. Electrospray ionization mass spectrometry (ESI-MS) and tandem mass spectrometry (ESI-MS(n)) analyses of labeled ((18)O) and unlabeled samples allowed identification of not only nonhybrid oligosaccharides but also hybrid oligosaccharides composed of both hexose and pentose units. The identification of hybrid oligosaccharides allowed us to infer the occurrence of nonenzymatic transglycosylation reactions involving both oligosaccharides in the starting mixtures. Also, it was observed that using different proportions of the oligosaccharides in the starting mixtures and extents of thermal treatment led to a variation in the composition of the compounds formed. These results have led to the conclusion that, depending on the distribution of the polysaccharides in the bean cell walls and the roasting conditions, different nonhybrid and hybrid structures can be formed during coffee roasting.

Transglycosylation reactions between galactomannans and arabinogalactans during dry thermal treatment.

Aiming to investigate the possible occurrence of transglycosylation reactions between galactomannans and side chains of arabinogalactans during coffee roasting, mixtures of ß-(1 → 4)-D-mannotriose and α-(1 → 5)-L-arabinotriose were subjected to dry thermal treatments at 200 °C. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) analysis allowed identifying polysaccharides composed by pentose and hexose residues with a degree of polymerization up to 18 residues. Methylation analysis showed the occurrence of new types of glycosidic linkages in all thermally treated mixtures, as well as the occurrence of terminally and 5-linked ribose, possibly formed from arabinose isomerization. Also, xylose and lyxose were identified and proposed to be formed from mannose. These results support the occurrence of transglycosylation reactions promoted by roasting involving both oligosaccharides in the starting mixtures, resulting in arabinan and mannan chimeric polysaccharides. These structural features were also found in roasted coffee polysaccharide samples.

Thermal stability of spent coffee ground polysaccharides: galactomannans and arabinogalactans.

In order to better understand the thermal stability of spent coffee grounds (SCG) galactomannans and arabinogalactans and the reactions that can occur upon roasting, long term isothermal exposures, up to 3h, were performed at 160, 180, 200, 220, and 240 °C. The resultant products were analysed according to the sugars and linkage composition and also by electrospray mass spectrometry. Galactomannans did not loss mass at T ≤ 200 °C during exposures up to 3h whereas the arabinogalactans showed that thermal stability only for T ≤ 180 °C. This was in accordance with the estimated activation energies of their thermal decomposition of 138 kJ/mol and 94 kJ/mol, respectively. The roasting of galactomannans promoted the formation of new glycosidic linkages, with occurrence of 2-, 6-, 2,3-, 2,6-, 3,6-, 2,3,6-, 3,4,6-linked mannose residues, 3,4,6-linked galactose residues, and terminally-linked glucose residues, observed by methylation analysis. Depolymerisation and formation of anhydrohexose residues at the reducing end and mannose-glucose isomerisation were also observed. The roasting of galactomannans at 200 °C promoted their solubility in water upon alkali extraction and neutralisation.

[A cutaneous infection by Mycobacterium chelonae in a patient with rheumatoid arthritis]. / Infecção cutânea por Mycobacterium chelonae numa doente com artrite reumatóide.

There are no pathognomonic findings for cutaneous infection caused by Mycobacterium chelonae. The type and duration of therapy varies considerably among reports and no single antibiotic is considered the treatment of choice. A 61-year-old patient, suffering from rheumatoid arthritis (treated with metotrexate and salazopyrine), presented with violaceous nodules of the right leg that had been evolving for 6 months. She was underwent several skin biopsies. Tissue culture of the last showed an atypical mycobacteria, identified as M. chelonae. Despite improvement after a two-week course of treatment with clarithromycin, a switch to ciprofloxacin was made because of gastrointestinal intolerance. After 3 months, only slight improvement of the lesions was achieved and clarithromycin was reintroduced; significant clinical improvement occurred by the third month. Clarithromycin was continued a further two months until the patient quit on her own and. no recurrence was observed. Infections caused by M. chelonae frequently occur in the setting of immunological impairment. Contaminated water is the natural reservoir, but we were unable to establish the source of contamination. As was previously described, there was a significant delay between clinical presentation and diagnosis. Thus, a high index of suspicion and multiple biopsies with culture are of paramount importance to confirming the diagnosis.

Immunostimulatory properties of coffee mannans.

Coffee infusion mannans are acetylated polysaccharides containing single Galp and Araf residues as side chains of a beta-(1 --> 4)-Manp backbone. These mannans are structurally similar to the bioactive acetylated mannans from Aloe vera (AV). In this study, acetylated mannans were obtained from two coffee infusions prepared from light and dark roasted beans. These samples were tested for their immunostimulatory activity and compared with an extract of AV mannan and with locust bean gum (LBG) galactomannans. The coffee samples, as well as the AV extract, stimulated murine B- and T-lymphocytes, as evaluated by the in vitro expression of the surface lymphocyte activation marker CD69, more marked on B- than on T-lymphocytes. In coffee samples, contrarily to the AV, no proliferative effect was noticed. LBG sample did not show any immunostimulatory activity. Because the material that remains in the residue of the hot water extraction was still very rich in mannans, a sequential extraction was performed and a main fraction was recovered with a 4 M NaOH solution. Because this material was insoluble in water, a partial acetylation was performed. These polysaccharides also showed immunostimulatory activity, opening the possibility of exploitation of coffee infusion and coffee residue as sources of bioactive polysaccharides.