In vitro evaluation of anti-methylglyoxal/glyoxal activity of three phytosterols using glycated bovine serum albumin models

Reactive intermediate dicarbonyls, such as methylglyoxal (MGO) and glyoxal (GO), have received extensive attention recently due to their high reactivity and capability to form advanced glycation end products (AGEs) in foods, which have been implicated in the progression of age-related complaints. We aimed to investigate the effects of three structurally different phytosterols (PS), including stigmasterol (SS), β-sitosterol (βS), and γ-oryzanol (γO), on AGEs-formation by measuring their anti-GO/MGO activity. The glycoxidation-based products, SDS-PAGE intensity, free lysine, protein thiols, fluorescence microscopy clicks, scavenging of dicarbonyl activity, and protein aggregation in bovine serum albumin (BSA) models were therefore measured. The results showed that PS could strongly inhibit fluorescent-AGEs, lysine residues, intermediate di-carbonyls, beside their disaggregation effects in a dose and structure dependent manner. Additionally, γ-oryzanol strongly inhibited AGEs more than the other PS, mostly due to its distinctive structure. Our results will provide a new foundation for development of different structure of PS as natural AGEs-inhibitors.

Spray-dried olive mill wastewater reduces Maillard reaction in cookies model system

The network of the Maillard reaction can be influenced by the presence of polyphenols. In this paper, we evaluated the ability of secoiridoids to interact with asparagine and lysine tuning the formation of dietary advanced glycation end-products (d-AGEs), dicarbonyls and acrylamide. Olive oil mill wastewater polyphenol powders (OMWP) were added to glucose and lysine or asparagine in silica model systems to mimic water activity present in cookies. Results revealed that acrylamide, Amadori compounds and N-ε-carboxyethyllysine (CEL) were reduced to 50%, after 13 min at 180 °C; for the reduction of N-ε-carboxymethyllysine (CML), secoiridoids were effective only in model systems with the addition of acacia fiber and maltodextrin as coating agents. In cookies, OMWP at three different concentrations decreased the concentration of protein bound Amadori compounds, CML, CEL and dicarbonyls. Acrylamide and 5-hydroxymethylfurfural were reduced to 60% and 76% respectively, highlighting the ability of secoiridoids-based functional ingredients in controlling d-AGEs formation.

Formation kinetics of Maillard reaction intermediates from glycine-ribose system and improving Amadori rearrangement product through controlled thermal reaction and vacuum dehydration

Amadori rearrangement product (ARP) is an ideal flavor precursor. The formation kinetics of ARP from glycine-ribose system, 3-deoxyribosone (3-DR) and 1-deoxyribosone (1-DR) were evaluated, and then controlled thermal reaction (CTR) coupled with vacuum dehydration was proposed to improve the ARP yield. As key factors controlling the formation of byproducts, CTR temperature and time were optimized as 100 °C, 60 min based on the formation kinetics of the ARP and deoxyribosones. Vacuum dehydration was further used to increase the ARP yield from 0.77% to 64.50%, which was improved by 82.8 times, while 3-DR and 1-DR yield increased only by 1.5 and 3.7 times, respectively. The formation of ARP was the dominant reaction during vacuum dehydration. Under optimal conditions, CTR coupled with vacuum dehydration was an effective method to control byproducts formation and improve the ARP yield simultaneously. This method may offer a potential application in flavor enhancement of light-color food.

Effect of hydroxytyrosol and olive leaf extract on 1,2-dicarbonyl compounds, hydroxymethylfurfural and advanced glycation endproducts in a biscuit model

The antiglycative activity of hydroxytyrosol (HT) and olive leaf extract (OLE) was investigated in wheat-flour biscuits. Quercetin (QE) and gallic acid (GA) were used as reference of antiglycative activity of phenolic compounds. HT, OLE, QE and GA were added in the range of 0.25-0.75% (w/w). Samples were compared against a control recipe baked at 180°C/20min. HT biscuit was able to inhibit efficiently the formation of hydroxymethylfurfural (HMF) and 3-deoxyglucosone (3-DG), as well as reduced the formation of overall free fluorescent AGEs and pentosidine. The inhibition of the 3-DG and HMF formation was directly and significantly correlated under controlled baking conditions. However, samples formulated with OLE exerted similar antiglycative capacity against pentosidine and Nε-carboxyethyl-lysine, although the amount of HT in the biscuit was 100-fold lower than the biscuit formulated with HT. Methylglyoxal, 3-DG, and glyoxal were the predominant 1,2-dicarbonyl compounds after baking but only 3-DG was significantly reduced by HT.

Mechanism of reactive carbonyl species trapping by hydroxytyrosol under simulated physiological conditions

This investigation reveals that hydroxytyrosol (HT) could compete with lysine, arginine and histidine to bind methylglyoxal (MGO) and reducing the formation of advanced glycation end products. Kinetic of the degradation of HT in presence/absence of MGO under simulated physiological conditions is monitored by HPLC coupled to a QTOF spectrometer. HT should previously be oxidized to DOPAC (3,4-dihydroxyphenylacetic acid) which reacts with MGO by electrophilic aromatic substitution of the ortho-diphenyl ring. DOPAC was detected as the major degradation product of HT under simulated physiological conditions. Ortho-hydroxyl groups are necessary to promote the nucleophilic addition of MGO by HT and related compounds. The formation of four adducts were described by mass spectrometry, but monoDOPAC-monoMGO adduct (C11H12O6) was predominant. Results suggest that HT and its degradation product DOPAC could have a relevant role in preventing the formation of advanced glycation end products and therefore potentially mitigate the diabetic complications.

Methylglyoxal is associated with bacteriostatic activity of high fructose agave syrups

Three α-ketoaldehydes, potentially present in high fructose agave syrups (HFASs) as intermediates of the Maillard reaction, were determined. A previously reported HPLC-FLD procedure based on pre-column derivatisation with 4-methoxy-o-phenylenediamine was adopted, yielding the method quantification limits 0.11 mg/kg, 0.10mg/kg, 0.09 mg/kg for glyoxal, methylglyoxal (MGo) and diacetyl, respectively. The obtained results revealed high concentrations of methylglyoxal in HFASs (average 102 ± 91 mg/kg, range 15.6-315 mg/kg) as compared to commercial Mexican bee honeys or corn syrups. Hydrogen peroxide was generated in all HFASs upon dilution, yet to less extent than in bee honeys. HFASs presented bacteriostatic activity against Bacillus subtilis and Escherichia coli; catalase addition had minimum effect on the assay results in syrups with elevated MGo. Principal component analysis revealed direct association between growth inhibition and MGo. It is concluded that elevated concentration of MGo in HFASs is at least in part responsible for their non-peroxide bacteriostatic activity.