Comprehensive Analysis of Physicochemical Properties and Volatile Compounds in Different Strawberry Wines under Various Pre-Treatments.

Pre-fermentation treatment has an important impact on the color, aroma, taste, and other characteristics of fruit wine. To discover suitable pre-treatment techniques and conditions that yield strawberry wine of excellent quality, the influences of juice fermentation, pulp maceration, thermovinification, and enzymatic hydrolysis pre-treatments on the basic chemical composition, color, antioxidant capacity, and volatile organic compounds in strawberry wines were investigated. The results showed that the color, antioxidant properties, and volatile aroma of strawberry wines fermented with juice were different from those with pulp. Strawberry wines fermented from juice after 50 °C maceration had more desirable qualities, such as less methanol content (72.43 ± 2.14 mg/L) compared with pulp-fermented wines (88.16 ± 7.52 mg/L) and enzymatic maceration wines (136.72 ± 11.5 mg/L); higher total phenolic content (21.78%) and total flavonoid content (13.02%); enhanced DPPH (17.36%) and ABTS (27.55%) free radical scavenging activities; richer essential terpenoids and fatty acid ethyl esters, such as linalool (11.28%), ethyl hexanoate (14.41%), ethyl octanoate (17.12%), ethyl decanoate (32.49%), and ethyl 9-decenoate (60.64%); pleasant floral and fruity notes compared with juice-fermented wines macerated at normal temperatures; and a lighter color. Overall, juice thermovinification at 50 °C is a potential pre-treatment technique to enhance the nutrition and aroma of strawberry wine.

Virtual Cold Chain Method to Evaluate the Effect of Rising Temperature on the Quality Evolution of Peach Fruit.

Poor temperature management along a cold chain leads to fruit quality deterioration and loss. In order to determine the threshold value of temperature fluctuation in a cold chain, peach fruits were stored in four different virtual cold chains applying different temperature-time scenarios. Core temperature profiling, the physicochemical qualities, and the activities of the peaches' antioxidant enzymes were monitored during cold storage and shelf life. Abusive temperature management (temperature increased to 20 and 15 °C three times) resulted in a significant increase in a peach's core temperature to the highest temperature measured: 17.6 °C. The ethylene production rate at the end of the shelf life of peaches under these temperatures was 21.03-28.16% higher than the constant-temperature group and accompanied by significantly lower levels of flesh firmness, titratable acid content, total phenol and flavonoid content, and peroxidase (POD) and catalase (CAT) activities (p < 0.05). The results of a principal component analysis (PCA) and heatmap confirmed the results. Limited temperature increases (10 °C) in a cold chain had little impact on the quality of the peaches, while temperature increases higher than 15 °C three times would negatively affect the quality of the peaches significantly. The temperature of a cold chain needs to be controlled precisely to reduce the loss of peaches.

Inhibition of Dipeptidyl Peptidase-4 by Flavonoids: Structure-Activity Relationship, Kinetics and Interaction Mechanism.

With the aim to establish a structure-inhibitory activity relationship of flavonoids against dipeptidyl peptidase-4 (DPP-4) and elucidate the interaction mechanisms between them, a pannel of 70 structurally diverse flavonoids was used to evaluate their inhibitory activities against DPP-4, among which myricetin, hyperoside, narcissoside, cyanidin 3-O-glucoside, and isoliquiritigenin showed higher inhibitory activities in a concentration-dependent manner. Structure-activity relationship analysis revealed that introducing hydroxyl groups to C3', C4', and C6 of the flavonoid structure was beneficial to improving the inhibitory efficacy against DPP-4, whereas the hydroxylation at position 3 of ring C in the flavonoid structure was unfavorable for the inhibition. Besides, the methylation of the hydroxyl groups at C3', C4', and C7 of the flavonoid structure tended to lower the inhibitory activity against DPP-4, and the 2,3-double bond and 4-carbonyl group on ring C of the flavonoid structure was essential for the inhibition. Glycosylation affected the inhibitory activity diversely, depending on the structure of flavonoid aglycone, type of glycoside, as well as the position of substitution. Inhibition kinetic analysis suggested that myricetin reversibly inhibited DPP-4 in a non-competitive mode, whereas hyperoside, narcissoside, cyanidin 3-O-glucoside, and isoliquiritigenin all reversibly inhibited DPP-4 in a mixed type. Moreover, the fluorescence quenching analysis indicated that all the five flavonoid compounds could effectively quench the intrinsic fluorescence of DPP-4 by spontaneously binding with it to form an unstable complex. Hydrogen bonds and van der Waals were the predominant forces to maintain the complex of myricetin with DPP-4, and electrostatic forces might play an important role in stabilizing the complexes of the remaining four flavonoids with DPP-4. The binding of the tested flavonoids to DPP-4 could also induce the conformation change of DPP-4 and thus led to inhibition on the enzyme. Molecular docking simulation further ascertained the binding interactions between DPP-4 and the selected five flavonoids, among which hyperoside, narcissoside, cyaniding 3-O-glucoside, and isoliquiritigenin inserted into the active site cavity of DPP-4 and interacted with the key amino acid residues of the active site, whereas the binding site of myricetin was located in a minor cavity close to the active pockets of DPP-4.

Identification of Six Flavonoids as Novel Cellular Antioxidants and Their Structure-Activity Relationship.

This study is aimed at determining the relationship of flavonoid structures to their chemical and intracellular antioxidant activities. The antioxidant activities of 60 flavonoids were investigated by three different antioxidant assays, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorption capacity (ORAC), and cellular antioxidant activity (CAA) assays. The result showed 6 flavonoids as good cellular antioxidants evaluated for the first time. The cellular antioxidant activities of compounds 7-methoxy-quercetin, 3-O-methylquercetin, 8-hydroxy-kaempferol, quercetin-3-O-α-arabinofuranose, kaempferol-7-O-glucopyranoside, and luteolin6-C-glucoside were linked with the upregulation of antioxidant enzyme activities (superoxide dismutase, catalase, and glutathione peroxidase). A structure-activity relationship suggested that 2,3-double bond, 4-keto groups, 3',4'-catechol structure, and 3-hydroxyl in the flavonoid skeleton played important roles in the antioxidant behavior. Furthermore, the cell proliferative assay revealed a low cytotoxicity for 3-O-methylquercetin. The present results provide valuable information for the dietary application of flavonoids with different structures for high antioxidant.

Effect of dehydration techniques on bioactive compounds in hawthorn slices and their correlations with antioxidant properties.

Hawthorn fruits are rich in nutrients and antioxidant compounds. Dehydration is the major processing and preservation method for hawthorn fruits. The rates of moisture loss; polyphenol, flavonoid and triterpenoid acid contents; and antioxidant activities and their relationships were investigated in hawthorn slices that were dried by four dehydration techniques (microwave drying, solar drying, hot air drying and freeze drying) under different operation conditions. The results showed that both the drying method and the processing parameter affected the antioxidants. Microwave drying and hot air drying at high temperatures (≥ 80 °C) resulted in the degradation of the polyphenols, flavonoids and triterpenoid acids in the hawthorn slices. These antioxidant compounds were best preserved by freeze drying and hot air drying at 60 °C. Epicatechin and chlorogenic acid were the major phenolic compounds identified in this research, and these compounds were significantly affected during processing. The antioxidant activities of the hawthorn fruits were significantly related to the total polyphenol, flavonoid and triterpenoid acid contents. Hot air drying at proper temperatures could be suitable for hawthorn slice dehydration processing that conserves the antioxidant properties of the fruit.

Experimental and molecular docking investigations on the inclusion mechanism of the complex of phloridzin and hydroxypropyl-ß-cyclodextrin.

Phloridzin is a nutraceutical. Its use in food, medicine and cosmetics is limited because of its low aqueous solubility and stability limits, but it can be improved by complexing with cyclodextrins. In this study, we investigated the inclusion mechanism between phloridzin and hydroxylpropyl-ß-cyclodextrin (HP-ß-CD) using isothermal titration calorimetry (ITC), ultraviolet-visible spectrometry (UV), infrared spectrometry (IR), proton nuclear magnetic resonance spectroscopy ((1)H NMR) and molecular docking simulations. The ITC results found that the equilibrium binding constant of HP-ß-CD with phloridzin was higher than that of ß-CD. Their inclusion was a spontaneous process with negative ΔG, ΔH and ΔS values. UV spectra showed that the aqueous solubility of phloridzin was enhanced by HP-ß-CD. Our IR analysis verified the inclusion complexation of phloridzin into the HP-ß-CD cavity. The Autodock determined that the substitution distribution of HP-ß-CD influenced not only the orientation and depth degree of phloridzin within the cavity, but also the binding energies.

Variation in Phenolics, Flavanoids, Antioxidant and Tyrosinase Inhibitory Activity of Peach Blossoms at Different Developmental Stages.

Peach blossoms were harvested and classified into six developmental stages: (I) bud emerging stage; (II) middle bud stage; (III) large bud stage; (IV) initial-flowering stage; (V) full-flowering stage; and (VI) end-flowering stage. The contents of total phenolics, flavanoids, individual phenolic compounds as well as antioxidant and tyrosinase inhibitory activity of peach blossoms at different developmental stages were investigated. The total phenolic contents varied from 149.80 to 74.80 mg chlorogenic acid equivalents/g dry weight (DW), and the total flavanoid contents ranged from 93.03 to 44.06 mg rutin equivalents/g DW. Both the contents of total phenolics and flavanoids decreased during blossom development. Chlorogenic acid was the predominant component, accounting for 62.08%-71.09% of the total amount of identified phenolic compounds in peach blossom. The antioxidant capacities determined by different assays and tyrosinase inhibitory activity also showed descending patterns during blossom development. Significant correlations were observed between antioxidant capacities with contents of total phenolics and total flavanoids as well as chlorogenic acid, cinnamic acid and kaempferol-3-O-galactoside, while the tyrosinase inhibitory activity had lower correlations with total phenolics and total flavanoids as well as chlorogenic acid, quercetin-3-O-rhamnoside, kaempferol-3-O-galactoside and cinnamic acid. The antioxidant activities of peach blossom seemed to be more dependent on the phenolic compounds than tyrosinase inhibitory activity.