Ultrasound and heating treatments improve the antityrosinase ability of polyphenols

Potassium chloride-assisted heat treatment enhances the de-glycosylation efficiency and xanthine oxidase inhibitory activity of Sophora japonica L. flavonoids

Salt-assisted heat treatment is considered an effective way to enhance the bioactivities of flavonoids in Flos Sophorae Immaturus tea (FSIt). Herein, sodium chloride (NaCl)- and potassium chloride (KCl)-assisted heat treatment was employed to process FSIt, the components, xanthine oxidase (XO) inhibitory activity, and degradation or conversion kinetics of FSIt flavonoids were recorded. Results showed that KCl-assisted heat treatment significantly increased the XO inhibition rate of FSIt from 28.05 % to 69.50 %. The de-glycosylation of flavonoids was the crucial reason for enhancing XO inhibitory activity. Notably, KCl exhibited a better catalytic effect on the de-glycosylation reaction than NaCl. Meanwhile, conversion kinetics showed that the generation rate of quercetin, kaempferol, and isorhamnetin reached the maximum at 180, 160, 160 °C, respectively. Furthermore, the established artificial neural network model could accurately predict the changes of FSIt flavonoids during salt-assisted heat treatment. Thus, KCl can be used as a valuable food processing adjuvant to enhance the bioactivities of food materials.

Reducing the oil absorption and oil deterioration in fried apple slices by ultrasound integrated in infrared frying

The effects of integrated ultrasonic infrared frying (USIF) on the oil absorption of apple slices and the oil deterioration were studied with frequency of 28 and 40 kHz, respectively. Results showed that the heat transfer and moisture migration was accelerated by the integrated ultrasound in IF. The soluble Gal-A content and esterification degree of pectin was increased, the damages of pectin crystal structure and chemical structure in side chain was aggravated. These damages to pectin were intensified with higher frequency (40 kHz) of ultrasound. Lower retention of phenols was found in USIF apple slices, but the flavonoids content had no significant change compared to CF samples. USIF samples showed a smoother morphology, and the pore volume and porosity were reduced by ultrasonication applied with 28 kHz but increased with 40 kHz. The largest volume fraction of pores was changed from 100-250 μm in IF to 0.02-10 μm and 10-100 μm by the integrated ultrasound at 28 kHz and 40 kHz samples, respectively. The total oil uptake in USIF samples was reduced by 24.9 %-33.2 % compared to the conventional fried (CF) samples, and achieved the lowest with the frequency of 40 kHz. The surficial and structural oil were also decreased by 39.2 %-51.3 % and 20.9 %-32.3 %, respectively. The peroxide value, acid value, carbonyl value, polar component, and the saturated fatty acids ratio of oil in repeated frying for 16 h was reduced in USIF, especially with ultrasonication 40 kHz. These results indicate that USIF is a promising method for producing novel low-oil apple fries.

Treatments of heating and ultrasound improve the inhibition of gallocatechin gallate on tyrosinase

BACKGROUND

Gallocatechin gallate (GCG), a catechin of tea polyphenols, possesses inhibitory ability against tyrosinase, but few studies have reported how common processing methods affect it. In this research, the influence of heating and ultrasound treatments on the inhibition of GCG against tyrosinase was explored by ultraviolet-visible absorption, fluorescence spectroscopy, high-performance liquid chromatography and liquid chromatography-tandem mass spectrometry.

RESULTS

Both heating and ultrasound treatments of GCG alone improved GCG's inhibitory ability against tyrosinase compared with the untreated, and a combination of heating and ultrasound treatment (100 °C, 20 min + 630 W, 20 min) further decreased the relative tyrosinase activity to 26.8%. The treated GCG exhibited a stronger fluorescence quenching effect on tyrosinase, but did not have any influence on the static quenching mechanism. Compared to the untreated GCG, the binding constants of treated GCG by heating, ultrasound and their combination with tyrosinase significantly increased, but the number of binding sites was still approximately one and the main driving force of the treated GCG was still hydrophobic interaction. After treatments of heating, ultrasound and their combination, the composition of GCG solutions was changed.

CONCLUSION

The enhanced inhibition of treated GCG on tyrosinase may be due to partial conversion of GCG into epigallocatechin-3-gallate (EGCG) and gallic acid (GA), which may cooperate with GCG to better inhibit the enzyme activity. This study has provided some valuable information for the application of catechins against tyrosinase in food processing and cosmetic industry. © 2022 Society of Chemical Industry.

Insights into the interaction of cyclooxygenase and lipoxygenase with natural compound 3,4',5,7-Tetrahydroxyflavone based on multi-spectroscopic and metabolomics

Hypoxia induce right ventricular dysfunction in human heart, but the molecular mechanism remains limited. As known, cyclooxygenases (COX) and lipoxygenases (LOX) play a key role in the cardiovascular system under hypoxia. 3,4',5,7-Tetrahydroxyflavone (THF), which widely exists in a variety of plants and vegetables, is famous for good ability to relieve cardiac injury, but the mechanism remains to be further understood. In this study, we firstly estimated the preventive role of THF against hypoxia-induced right ventricular dysfunction. Metabolomics analysis showed there were differential metabolites involved in above process, which helped us to screen the crucial regulated enzymes of these metabolites. Molecular docking and multi-spectroscopic revealed the molecular mechanism of interaction between THF and COX/LOX. Results suggested that THF bound to COX/LOX through static quenching and these bindings were driven by hydrogen bonds. After binding with THF, the secondary structure of COX/LOX was changed. In general, this study indicated that THF inhibited COX/LOX by spontaneously forming complexes with them.

Comparing the effect of benzoic acid and cinnamic acid hydroxyl derivatives on polyphenol oxidase: activity, action mechanism, and molecular docking

BACKGROUND

Polyphenol oxidase (PPO) is considered to have a key role in the food industry because it initiates enzymatic browning in the processing and storage of fruit and vegetables. Increasing numbers of benzoic and cinnamic acid derivatives have been found to be efficient inhibitors of polyphenol oxidase, but a comparison study on activity and action mechanism is lacking. In this study, 18 benzoic acid and cinnamic acid hydroxy derivatives were selected and investigated.

RESULTS

Three substrates, four activators and 11 inhibitors were identified from benzoic and cinnamic acid derivatives. 2,4-Dihydroxycinnamic acid and benzoic acid showed the strongest inhibitory effect on PPO, with IC₅₀ of 0.092 and1.425 mmol L^-1 , respectively. Benzoic acid reversibly inhibited PPO in a competitive manner, while 2,4-dihydroxycinnamic acid showed a mixed-type inhibition. Both of them showed that static-type fluorescence quenching and electrostatic interaction were the main driving force in the bonding process. Compared with benzoic acid, 2,4-dihydroxycinnamic acid more easily formed hydrogen bonds in the active site of PPO, making the interaction more stable.

CONCLUSION

Comparative analysis showed that the inhibition effect of cinnamic acid hydroxyl derivatives on PPO was stronger than that of benzoic acid derivatives. Benzoic acid and 2,4-dihydroxycinnamic acid were the strongest inhibitors. PPO inhibitors identified from benzoic and cinnamic acid derivatives are expected to be promising inhibitors for controlling fruit and vegetable browning. © 2021 Society of Chemical Industry.

Angiotensin-Converting Enzyme (ACE) Inhibitory Activity and Mechanism Analysis of N-(1-Deoxy-d-fructos-1-yl)-histidine (Fru-His), a Food-Derived Amadori Compound

N-(1-Deoxy-d-fructos-1-yl)-histidine (Fru-His), one of the Amadori compounds, widely presents in processed foods, and its potential functional activities have attracted extensive attention in recent years. In this work, the angiotensin-converting enzyme (ACE) inhibitory activity and mechanism of Fru-His were investigated. The IC₅₀ value of Fru-His was 0.150 ± 0.019 mM, and there was no obvious degradation of Fru-His after digestion simulation, showing that Fru-His has good ACE inhibition and digestive stability. Fru-His was a competitive inhibitor according to the enzyme inhibition kinetic analysis. The interaction between ACE and Fru-His occurred spontaneously mainly through hydrogen bonding, and the process was accompanied by fluorescence quenching and the alteration of the secondary structure of ACE. The molecular docking data supported the above results. Fru-His was attached to ACE's S1 active pocket through hydrogen bonds and interacted with zinc ions in active sites. The present study demonstrates that food-derived Fru-His has the potential to relieve hypertension.

Drying methods influence the physicochemical and functional properties of seed-used pumpkin

The effects of far-infrared radiation drying (FIRD), freeze drying (FD), vacuum drying (VD), and hot air drying (HAD) on appearance, physicochemical properties, antioxidant activities, antityrosinase capacity using B16F10 melanoma cell from seed-used pumpkins (hull-less pumpkin and hull pumpkin) were evaluated. Results suggested that hull-less pumpkin (HLP) dehydrated by FIRD provided the highest total polyphenols content (37.11 ± 1.05 mg GAE/ g DW) and the ability of scavenging free radicals. HPLC analysis exhibited that coumaric acid was predominant phenolic acid in pumpkin. The correlation analysis demonstrated that polyphenolic compounds were related to antioxidant capacity. HLP-FD possessed better colour, higher preservation of β-carotene, ascorbic acid and higher sugar contents compared with HLP-HAD. The highest antityrosinase activity was recorded in HLP-VD with a concentration of 37.16%. The melanin inhibition increased to 76.61%, and intracellular tyrosinase activity in B16F10 melanoma cells decreased to 88.63% at 800 μg/mL of polyphenol extract.

Improving the bioactive ingredients and functions of asparagus from efficient to emerging processing technologies: A review

Historically, asparagus is a vegetable with abundant phytochemicals (polyphenols, saponins, asparagusic acid, and alkaloids) and crucial bioactivities (neuroprotective, antianxiety, antityrosinase, antioxidant, antibacterial, and antiasthma effects). Numerous investigations indicated that processing technologies have a significant influence on the physicochemical, functional, and microstructural characteristics of asparagus. This review presents an updated overview of novel applications of processing technologies, including ultrasound treatments (in terms of extraction, purification, and preservation), heating treatments (hydrothermal treatments, thermal treatments, and combination heating treatments), high-pressure processing, representative shelf-life extension technologies, and green extraction technologies. These physical technologies enhance the yields of bioactive substances, bioactivities and product quality. In addition, utilizing the novel technologies (ohmic heating, cold plasma, pulsed electric fields, membrane processing) and conventional technologies with novel effects to fully develop the potential of asparagus should also be taken into consideration in the future.