Phytohemagglutinin isolectins extracted and purified from red kidney beans and its cytotoxicity on human H9 lymphoma cell line

Aptamer-functionalized stir bar sorptive extraction for selective isolation, identification, and determination of concanavalin A in food by MALDI-TOF-MS

An aptamer-functionalized stir bar sorptive extraction (SBSE) coating is described for the first time devoted to selective isolation and preconcentration of an allergenic food protein, concavanalin A (Con A), followed by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF-MS) determination. For this purpose, the polytetrafluoroethylene surface of commercial magnetic stir bars was properly modified and vinylized to immobilize a thiol-modified aptamer against Con A via straightforward "thiol-ene" click chemistry. The aptamer-functionalized stir bar was employed as SBSE sorbent to isolate Con A, and several parameters that can affect the extraction efficiency were investigated. Under the optimized conditions, Con A was extracted and desorbed during 30 and 45 min, respectively, at 25 °C and 600 rpm. The SBSE MALDI-TOF-MS method provided limits of detection of 0.5 μg mL^-1 for Con A. Furthermore, the SBSE coating was highly selective to Con A compared to other lectins. The developed method was successfully applied to the determination of low levels of Con A in several food matrices (i.e., white beans as well as chickpea, lentils, and wheat flours). Recoveries ranged from 81 to 97% with relative standard deviations below 7%. The aptamer-based stir bars presented suitable physical and chemical long-term stability (1 month) and a reusability of 10 and 5 extraction cycles with standards and food extracts, respectively. The developed aptamer-affinity extraction devices open up the possibility of developing novel highly selective SBSE coatings for the extraction of proteins and peptides from complex samples.

Intracellular inflammatory signalling cascades in human monocytic cells on challenge with phytohemagglutinin and 2,4,6-trinitrophenol

Phytohemagglutinin (PHA) is a plant mitogen that can agglutinate human leukocytes and erythrocytes. PHA is mainly derived from red kidney beans and can act as an exogenous pyrogen. When entering into the blood circulation, exogenous pyrogens principally interact with monocytes and macrophages and induce the release of pro-inflammatory cytokines. Monocytes and macrophages are the cells that fight against foreign invaders and acts as a primary line of immune defence. Similar to PHA, the chemical 2,4,6-trinitrophenol (TNP) also acts as an exogenous pyrogen. The study focused on the in vitro interaction of PHA and TNP with the human monocyte/macrophage cell model THP-1. The exposure and associated change in cellular morphology, organelle function, mechanism of cell death, inflammatory signalling and expression of inflammation-related genes were analyzed in different time periods. It was observed that PHA and TNP induce dose and time-dependent toxicity to monocytes/macrophages where the mechanism of cell death was different for PHA and TNP. Both PHA and TNP can evoke immune signalling with increased expression of inflammatory genes and associated activation of intracellular signalling cascades.

Antioxidant activity and sensory characteristics of Maillard reaction products derived from different peptide fractions of soybean meal hydrolysate

Four peptide fractions PF1 (>5;kDa), PF2 (3-5;kDa), PF3 (1-3;kDa), PF4 (<1;kDa) were isolated from soybean hydrolysate using the ultrafiltration method. Then, d-xylose and l-cysteine were reacted with specific peptide solution at 120;°C for 2;h, and the molecular weight distribution (MWD), pH, colour, browning intensity, DPPH radical-scavenging activity, free amino acids and sensory characteristics of corresponding Maillard reaction products (MRPF1, MRPF2, MRPF3 and MRPF4) were evaluated, respectively. Peptides with low molecular weight showed higher contribution to the changes of pH, colour and browning intensity during Maillard reaction. The DPPH radical-scavenging activity of PF4 was significantly improved after Maillard reaction. Aroma volatiles and PLSR analysis suggested MRPF3 had the best sensory characteristics with higher contents of umami amino acids and lower of bitter amino acids, therefore it could be deduced that the umami and meaty characteristics were correlated with the peptides of 1-3;kDa.