Phenolic compounds and antioxidant activity in red-fleshed apples

Bioassay-guided evaluation of antimicrobial properties and profile of bioactive compounds from leaf, peel and mesocarp of four apple cultivars (Malus domestica Borkh.) grown in Serbia: Application of HPTLC-EDA and UHPLC Q-ToF MS techniques

The aim of this study was to evaluate the antimicrobial properties and profile of bioactive compounds from mesocarp, peel and leaves of four autochthonous apple cultivars against human pathogens, Escherichia coli, Staphylococcus aureus and Bacillus subtilis and the apple pathogen Erwinia amylovora by direct detection on HPTLC plates and subsequent chemometric analysis. UHPLC Q-ToF MS was used for detailed characterization of the bioactive compounds with antimicrobial properties. Leaf extracts showed the highest antibacterial activity against all bacterial strains, followed by peel extracts, while the mesocarp extracts showed only weak and selective inhibition zones for E. coli and B. subtillis. The apple cultivars, 'Kadumana' and 'Kopaoničanka' showed the best antimicrobial properties. The active compounds were triterpenoids, coumaroylquinic acid and caffeoylquinic acid isomers and methyl derivatives, naringenin, kaempferol and quercetin aglycones and glycosides, phloretin and its glycosides and acylated derivatives that detected for the first time in the apple leaves and fruits.

Investigation of the impact of cold plasma pretreatments, long term storage and drying on physicochemical properties, bioactive contents and microbial quality of 'Keitt' mango

There is heightened demand for dried mango fruits with desired nutritional and physicochemical qualities, microbiologically stable and chemical residue free. This has led to the exploration of innovative preservation technologies for the extension of storability prior to processing. This study investigated the impact of cold plasma (CP) treatment on physicochemical properties and microbial stability in fresh and dried 'Keitt' mango during long term storage. Freshly harvested 'Keitt' mangoes were subjected to: CP treatment (for 5 min (CP5) and 10 min, CP10), dipping in "Chronos Prochloraz" for 30 s (industry practice), and untreated group (control). All samples were stored at 11 °C for 30 days, prior to minimal processing and hot air drying at 60 °C. Results after 30 days of storage demonstrated that untreated samples (control) had the highest TSS (15.06 ± 0.32 °Brix), while CP10 pretreated samples had the lowest TSS (13.80 ± 0.06 °Brix) value (p ≤ 0.05). In comparison to the fresh samples post storage, all pretreated dried mango slices retained lower total flavanols with CP5 (13.49 ± 1.64 mg GAE 100/g), CP10 (20.12 ± 1.42 mg GAE 100/g) and SMB (23.89 ± 3.35 mg GAE 100/g), but higher than the dried untreated samples (6.68 ± 0.53 mg GAE 100/g). Yellowness (b∗) of the fresh pulp (38.53 ± 1.73) increased significantly (p ≤ 0.05) with the long-term storage (39.88-46.74) and drying (55.01-64.90). CP pre-treatment combined with drying resulted in ≥2 Log reduction in microbial count. This study shows the potential of cold plasma as a pretreatment for extending storability and maintaining the quality of 'Keitt' mangoes.

The Changes in Color and Image Parameters and Sensory Attributes of Freeze-Dried Clones and a Cultivar of Red-Fleshed Apples

The target of breeding red-fleshed apples is to increase their potential health benefits related to red flesh coloration and consumer acceptance. The objective of this study was to determine the usefulness of four clones (90, 120, 156, and 158) of red-fleshed apples for freeze-drying compared to the cultivar 'Trinity'. Red-fleshed apples were dried in the form of slices using a laboratory freeze-dryer. The changes in color features and image texture parameters after drying and the sensory quality of freeze-dried samples were assessed. Trends of increase in the value of the L* parameter and decrease in the a* and b* parameters after freeze-drying were observed. Furthermore, freeze-drying caused statistically significant changes in analyzed image textures named XHMean, RHMean, SHMean, VHMean, LHMean, and UHMean. Machine learning models developed based on the color parameters L*, a*, and b* distinguished raw and freeze-dried red-fleshed apples with an average accuracy of 84% for clone 90 up to 99.0% for clone 156, and models based on twenty selected image textures exhibited an accuracy of 98.5% for clone 156 to 100% for clones 90 and 158 and the cultivar 'Trinity'. The very attractive external appearance, medium-intense fruity smell, crunchiness, and intense fruity taste of all the apple slices were revealed. The innovative aspect of this study included the comparison of the drying behavior and sensory quality of the new clones and a standard cultivar of red-fleshed apples. Moreover, innovative methods and results were used to determine the effect of freeze-drying on red-fleshed apple quality, considering novel models involving thousands of image textures and machine learning algorithms.

Biofunctionality of a new vinegar rich in anthocyanin from red-fleshed Niedzwetzky's apple: An ornamental plant

In recent years, red-fleshed apple has attracted a lot of attention due to its pleasant appearance, taste, and being a valuable source of anthocyanins. Generally, different types of this apple are known as ornamental apple plants that are rarely found in various regions around the world like New Zealand, Kazakhstan, Kyrgyzstan, Australia, China, and Turkey. This study focused on the accumulation and changes of the bioactive and aroma-related volatile components at different production stages of a red-fleshed apple vinegar. The aim of this study is to produce an anthocyanin- and vitamin C-rich vinegar (NAV) from red-fleshed Niedzwetzky's apple for the first time. According to the results, in this vinegar, it was determined high concentrations of total phenolic content (904.8 mg-GAE/mL), total flavonoid content (0.25 mg-EGCE/mL), vitamin C content (3024.3 mg-AAE/mL), and 1,1-diphenyl-2-picrylhydrazyl (8.33 mmol-TE/mL), as well as FRAP (13.57 mmol-ISE/mL), respectively. Moreover, total anthocyanin content value was found to be 6.46 mg/g. One of the components that provide the specified functional effect in this vinegar is chlorogenic acid, which constitutes the main phenolic compound, and the other one is cyanidin-3-glucoside, which is the major anthocyanin in this vinegar. The main volatile components associated with the aroma of vinegar are -acetic acid, -phenylacetic acid (5067.7 µg/100 mL), -phenethyl alcohol (3096.1 µg/100 mL), and -nonanoic acid (2939.0 µg/100 mL) compounds. Consequently, it is recommended to expand the range of Niedzwetzky's apples in the production and consumption of food products such as functional vinegar. Thus, a new vinegar with high functional properties will be introduced to the worldwide food industry. PRACTICAL APPLICATION: In this study, vinegar was produced from the small and dark-red-flesh-colored fruits of Niedzwetzky's apple tree, which is known in a small part of the world and is generally used as an ornamental plant due to its red-pink flowers. It has been determined that the produced vinegar has high bioavailability due to the apples with red inner flesh and high anthocyanin content and has a desirable aromatic content. Thus, a food product with high functional quality and desirable aroma, accessible to consumers all over the world, has been produced from a little-known fruit.

In vitro digestion and antioxidant activity of Xuan-Mugua (Chaenomeles fruit) peel and pulp phenolics

Since time immortal, people have used the well-known Chinese Chaenomeles fruit Xuan-Mugua for both traditional medicine and nourishment. With an aim to explore the digestive and antioxidant properties of the phenolics, Xuan-Mugua peel and pulp were extracted, digested and analyzed in vitro. Our results indicated that the total phenolics content (TPC), total flavonoids content (TFC) and the antioxidant activity of the peel were 3.24-8.89 times higher than that of pulp. The contents and activity of the peel and pulp consistently dropped in the sequence of oral, gastric, and small intestine digestions, from 22.78 % to 52.16 %. With a level of 1.590 ± 0.060 and 0.395 ± 0.015 mg g-1 dried weight in the peel and pulp, respectively, chlorogenic acid was the primary phenolic ingredient in Xuan-Mugua, with a promising recovery (81.39-82.23 %) during the digestion. According to these results, Xuan-Mugua exhibited an appreciable level of phenolic content and antioxidant activity during digestion, making it a suitable ingredient for use in functional foods.

Morphological and biochemical characteristics of wild red-fleshed apples (Malus sieversii f. niedzwetzkyana) in the North and Northeast of Iran

BACKGROUND

Red-flesh apples (Malus sieversii f. niedzwetzkyana) have attracted attention from consumers and researchers due to their pleasant appearance and taste. These exotic apples are rich sources of nutrients and health-promoting polyphenols and phenolics. This study aimed to investigate morphological (40 quantitative and 13 qualitative traits) and biochemical (5 traits) characteristics of four socioeconomically important red-fleshed apple populations in North and Northeast region of Iran, which are understudied and under serious extinction risk.

RESULTS

The examined characters exhibited wide and statistically significant variations, especially in leaf color (68.86%) and the number of seeds per fruit (61.61%), and more dramatically in the total flavonoids (146.64%) and total phenolics contents (105.81%). There were also strong variations in fresh fruit weight and fruit length, diameter, and flesh thickness. Red, with 34 accessions, was the dominant ripe fruit skin color. All biochemical traits also showed high variations, particularly in total flavonoid content. Red-fleshed Gavramak and Kalateh Khij apples contained the highest biochemical and morphological values, respectively. Principal component analysis (PCA) revealed that the first five principal components together accounted for more than 60.83% variation of the total observed variations. Moreover, the cluster dendrogram analysis based on Ward's method indicated three different clusters based on the characters measured, indicating high variation among the accessions.

CONCLUSION

red-flesh apples can be considered suitable sources of natural antioxidants with great potential as healthy foods and nutraceutical applications. Based on the commercial characters, Red-fleshed Gavramak and Kalateh Khij apples showed the highest fruit quality with proper size and thus can be suggested as superior for cultivation or use in breeding programs due to having higher quality fruits.

The elicitation effects of diode and He-Ne laser irradiations on the alleviation of nutrient-deficiency induced damage in anthocyanin-producing red-fleshed apple cell suspension

PURPOSE

We explored the elicitation role of the laser irradiations on the alleviation of nutrient-deficiency induced damage in anthocyanin-producing red-fleshed apple cell suspension in continuous production of anthocyanin.

METHODS

Anthocyanin-producing red-fleshed apple cells were irradiated by 4 intensity levels of red He-Ne (RHNL) and blue diode (BDL) lasers for 20 min.

RESULTS

Nutrient deficiency indicated negative effect on total soluble proteins (TSP), superoxidase dismutase (SOD) activity, and total phenolics content (TPC) while it displayed a positive effect on malondialdehyde (MDA), total flavonoids content (TFC), O2-, H2O2-, and lipoxygenase (LOX) and polyphenol oxidase (PPO) activities in light controls, illustrating oxidative stress. The laser irradiations on suspension cells indicated variable effects on measured parameters and were time of growth-, levels of intensity-, and laser type-dependent. Likewise, the elicitation effects of lasers relied on a critical threshold among ROS generation and antioxidative system which determines the fate of cells against oxidative stress. The same trend was displayed by RHNL at 6.46 mWcm-2 intensity and BDL at 13.73 mWcm-2. These intensities resulted in a significant increase in SOD, APX, POD, and CAT activities and TSP, TPC, TFC, proline, and glycine betaine accumulation, while induced decrease in LOX, and PPO activities and MDA, and ROS generation, alleviating cellular injury from prolonged nutrient deficiency by diminishing lipid peroxidation and oxidative damages of cell membrane.

CONCLUSION

Results suggested that lasers application on mitigating nutrient deficiency stress relied on establishing a suitable balance between ROS generation and antioxidative system, which enables the nutrient-starved anthocyanin-producing cells to continuously produce anthocyanin.

Physiological and biochemical mechanisms underlying the role of anthocyanin in acquired tolerance to salt stress in peanut (Arachis hypogaea L.)

Anthocyanin is an important pigment that prevents oxidative stress and mediates adaptation of plants to salt stress. Peanuts with dark red and black testa are rich in anthocyanin. However, correlation between salt tolerance and anthocyanin content in black and dark red testa peanuts is unknown. In this study, three peanut cultivars namely YZ9102 (pink testa), JHR1 (red testa) and JHB1 (black testa) were subjected to sodium chloride (NaCl) stress. The plant growth, ion uptake, anthocyanin accumulation, oxidation resistance and photosynthetic traits were comparatively analyzed. We observed that the plant height, leaf area and biomass under salt stress was highly inhibited in pink color testa (YZ9102) as compare to black color testa (JHB1). JHB1, a black testa colored peanut was identified as the most salt-tolerance cultivar, followed by red (JHR1) and pink(YZ9102). During salt stress, JHB1 exhibited significantly higher levels of anthocyanin and flavonoid accumulation compared to JHR1 and YZ9102, along with increased relative activities of antioxidant protection and photosynthetic efficiency. However, the K+/Na+ and Ca2+/Na+ were consistently decreased among three cultivars under salt stress, suggesting that the salt tolerance of black testa peanut may not be related to ion absorption. Therefore, we predicted that salt tolerance of JHB1 may be attributed to the accumulation of the anthocyanin and flavonoids, which activated antioxidant protection against the oxidative damage to maintain the higher photosynthetic efficiency and plant growth. These findings will be useful for improving salt tolerance of peanuts.

Fruits of Wild-Grown Shrubs for Health Nutrition

Cultivated fruits and berries, such as raspberries, strawberries, black currants, cherries, blueberries, are generally recognized sources of antioxidants, vitamins, minerals, and other substances beneficial to human health and well-being. However, there are also wild berries and fruits that are of undoubted interest as food products having valuable medicinal properties due to the presence of phenolic compounds, antioxidants, and vitamins. These fruits have a great potential to be used in functional food making. The present review is dedicated to fruits of wild-grown shrubs Bird cherry (Prunus padus L.), Rowan berry (Sorbus aucuparia L.), Guelder rose (Viburnum opulus L.), Black elderberry (Sambucus nigra L.), and Barberry (Berberis vulgaris L.) The chemical compositions of these wild berries are described as well as their effects on the improvement of human health proved by clinical trials and epidemiological studies. The possibilities of using the fruits of wild-grown shrubs in the preparation of functional foods and examples of their implementation for the manufacturing of dairy, bakery and meat products are considered.

Solid-state fermentation with Zygomycetes fungi as a tool for biofortification of apple pomace with γ-linolenic acid, carotenoid pigments and phenolic antioxidants

In the last few years, there has been a growing interest in the more efficient utilization of agricultural and food by-products. Apples are among the most processed fruits in the world that generate huge quantities of processing waste biomasses. Therefore, the objective of this study was to improve the nutritional value of apple pomaces with γ-linolenic acid (GLA) and carotenoid pigments by solid-state fermentation (SSF) using two Zygomycetes fungi (Actinomucor elegans and Umbelopsis isabellina). The impact of fermentation periods on the polyphenol content and antioxidant capacity of the bioprocessed apple pomace was also investigated. The accumulated lipids were composed primarily of neutral fractions (mostly triacylglycerols). SSF with U. isabellina yielded a 12.72% higher GLA content than with A. elegans (3.85 g GLA/kg DW of pomace). Contrary to the lipogenic capacity, A. elegans showed higher carotenoids and phenolic antioxidants productivity than U. isabellina. The maximum concentrations for β-carotene (433.11 μg/g DW of pomace-SSF with A. elegans and 237.68 μg/g DW of pomace-SSF with U. isabellina), lutein (374.48 μg/g DW- A. elegans and 179.04 μg/g DW- U. isabellina) and zeaxanthin (247.35 μg/g DW- A. elegans and 120.41 μg/g DW- U. isabellina) were registered on the 12th day of SSFs. In the case of SSF with A. elegans, the amount of total phenolics increased significantly (27%) by day 4 from the initial value (2670.38 μg of gallic acid equivalents/g DW) before slowly decreasing for the remaining period of the fungal growth. The experimental findings showed that a prolonged fermentation (between 8 and 12 days) should be applied to obtain value-added apple pomaces (rich in GLA and carotenoids) with potential pharmaceutical and functional food applications. Moreover, the SSF processes of simultaneous bioaccumulation of valuable fatty acids, carotenoids and phenolic antioxidants proposed in the present study may open up new challenges for biotechnological production of industrially important biomolecules using abundant and unexploited apple pomaces.

Characterization of polyphenols compounds extracted from stressed apple peel and their interaction with β-lactoglobulin

This paper proposes to apply a postharvest environmental stress to red apples, Malus domestica, variety Red Delicious in order to increase the polyphenols compounds (PP) content in their peels. The possibility of enhancing extractable PP provides a useful alternative for the use of discarded crops in the food industry. A great increase in PP was observed in response to light damage produced by the environmental stress applied in this work. Flavonols > anthocyanins > flavanols > dihydrochalcones > phenolic acids is the order in PP content. The interaction of the extracted PP from unstressed and stressed apple peels with beta-lactoglobulin (β-LG) was characterized. A PP/β-LG complex which was formed with one single binding site in the protein was determined. The interaction was spontaneous and enthalpy driven. PP extracted from unstressed samples had greater affinity for the protein than PP extracted from stressed samples, possibly due to the polar characteristic of anthocyanins. The results of this last study could provide a better understanding of the interaction between PP and β-LG to incorporate them into functional foods.

Exogenous melatonin enhances low-temperature stress of jute seedlings through modulation of photosynthesis and antioxidant potential

Developing new varieties of natural fibers that can grow throughout the year is very crucial to replace and avoid the bad effect of synthetic fiber. As a result of its beneficial role in protecting plants from abiotic stressors, melatonin (N-acetyl-5-methoxytryptamine) has gained recognition as a novel plant growth regulator. This study aimed to investigates the role of exogenous melatonin (200 μM) on two varieties of Corchorous olitorius and Corchorous capsularis in response to low-temperature stress (8 °C) for different periods of treatment (0, 24, 36, and 48 h) based on biochemical properties, and antioxidant system. The results demonstrated that exogenous melatonin had inhibitory effects of low-temperature stress on seedlings at different period of treatment when compared to non-melatonin treated seedlings, potentially improved photosynthetic apparatus (total chlorophyll up to 29.93 and 33.37%; total carotenoid up to 29.93 and 19.05%; anthocyanin up to 40.47 and 31.94% in M33 and Y49, respectively), reduced oxidative damage (MDA up to 53.59 and 44.28%; H2O2 up to 41.04 and 16.88% in M33 and Y49, respectively) by boosting the antioxidant enzymes (SOD up to 12.75 and 4.65%; POD up to 39.08 and 81.39%; total phenolic up to 43.38 and 56.48% in M33 and Y49, respectively) reduced electrolyte leakage (EL) up to 15.37 and 13.64% in M33 and Y49, respectively) and increased osmoregulation (soluble sugars up to 25.86 and 25.86%; proline up to 105.19 and 172.07%; FAA up to 48.50 and 30.06% in M33 and Y49, respectively) content. Thus, this study showed that exogenous melatonin effectively mitigated the low-temperature-induced oxidative in C. olitorius and C. capsularis seedlings by regulating the antioxidant system and improving the low-temperature resistance.

Identification and characterisation of MdUGT78T2 as a galactosyltransferase with dual activity on flavonol and anthocyanidin substrates in red-skinned apple fruit (Malus domestica L.)

Anthocyanidin and flavonol glycosides have been linked to the health-promoting effects associated with apple consumption. However, very few enzymes involved in flavonoid glycosylation have been characterised to date. Here, we present the identification and phylogenetic analysis of 234 putative glycosyltransferases involved in flavonoid biosynthesis, and detail the biochemical and structural characterisation of MdUGT78T2 as a strict galactosyltransferase involved in the formation of quercetin-3-O-galactoside and cyanidin-3-O-galactoside, the major glycoconjugates of flavonoids in apple. The enzyme is also active on other flavonoids but with a lower catalytic efficiency. Our data, complemented with gene expression analysis suggest that MdUGT78T2 synthesises the glycoconjugates at both the early and late stages of fruit development. This newly discovered type of catalytic activity can potentially be exploited for in vitro modification of flavonoids to increase their stability in food products and to modify apple fruits and other commercial crops through breeding approaches to enhance their health benefits.

Integral Valorization of Grape Pomace for Antioxidant Pickering Emulsions

Full harnessing of grape pomace (GP) agricultural waste for the preparation of antioxidant Pickering emulsions is presented herein. Bacterial cellulose (BC) and polyphenolic extract (GPPE) were both prepared from GP. Rod-like BC nanocrystals up to 1.5 µm in length and 5-30 nm in width were obtained through enzymatic hydrolysis (EH). The GPPE obtained through ultrasound-assisted hydroalcoholic solvent extraction presented excellent antioxidant properties assessed using DPPH, ABTS and TPC assays. The BCNC-GPPE complex formation improved the colloidal stability of BCNC aqueous dispersions by decreasing the Z potential value up to -35 mV and prolonged the antioxidant half-life of GPPE up to 2.5 times. The antioxidant activity of the complex was demonstrated by the decrease in conjugate diene (CD) formation in olive oil-in-water emulsions, whereas the measured emulsification ratio (ER) and droplet mean size of hexadecane-in-water emulsions confirmed the physical stability improvement in all cases. The synergistic effect between nanocellulose and GPPE resulted in promising novel emulsions with prolonged physical and oxidative stability.

Autophagic and phytochemical aspects of color changes in white petals of snapdragon flower during development and senescence

Color change in petals is a clever strategy to attract more pollinators and one of the attractive features of edible flowers for consumers. Several physiological, phytochemical, and ultrastructural factors are involved in this process. However, this phenomenon is well underexplored in white petals. In this study, we investigated the color changes of the white petals of the snapdragon (Antirrhinum majus 'Legend White') flower from different aspects during development and senescence. In the ultrastructural analysis, both epidermal and mesophyll cells were examined. During flower development, plastid transition and autophagy processes led to the fading of the green color of young petals and the reduction of starch content, chlorophyll, and carotenoids. The piecemeal chlorophagy was observed in the degradation of starch granules. Leucoplasts were converted into autophagosome-like structures and then disappeared. The presence of these structures was evidence of the transformation of the plastid to the vacuole. As the green color faded, phytochemical compounds were synthesized. With partial flower opening and progression of senescence, pH and phenolic compounds were responsible for color changes. The highest amount of phenolic compound was observed after the flower opening stages. However, Phenolic colored compounds or total anthocyanins became colorless under the influence of low pH. The decrease in starch content caused an increase in the lightness parameter, and the petal color changed to pale yellow.

Apple polyphenol biotransformation using probiotics in vitro and dynamic simulated digestion by bionic rats

BACKGROUND

The present study investigated the effects of fermentation by Lactobacillus rhamnosus zrx01 (LR-zrx01), Lactobacillus acidophilus zrx02 (LA-zrx02), and Lactobacillus plantarum zrx03 (LP-zrx03), as well as dynamic simulated digestion by bionic rats, on the biotransformation and antioxidant potential of apple polyphenols. Polyphenols were determined by ultra-high-performance liquid chromatography-mass spectrometry, the dynamic simulated digestion of fermented apple pulp was determined by bionic rats, and the antibacterial and antioxidant activities were analyzed.

RESULTS

The polyphenol content of apple pulp fermented using the three strains was respectively 1.41, 1.38, and 1.36 times that of non-fermented pulp. The antibacterial activity of apple pulp improved dramatically after fermentation. Moreover, the antioxidant potential of apple pulp increased after fermentation and digestion. After dynamic simulated digestion by bionic rats, the polyphenol content in unfermented and the three fermented groups increased significantly by 1.19, 1.23, 1.20, and 1.19 times compared to that before digestion, respectively. The major polyphenols in each group with obvious changes were epicatechin, rutin, kaempferol, quercetin-3 galactoside, p-coumaric acid, and two unknown substances, 1 and 2.

CONCLUSION

Fermented and digested apple polyphenols showed better biotransformation effects and mostly existed in the form of small molecules, which was conducive to the improvement of polyphenol bioavailability and beneficial to the absorption of active substances by the human body. These findings build a foundation for the development of functional food beverages. © 2023 Society of Chemical Industry.

Distribution and Stability of Polyphenols in Juices Made from Traditional Apple Cultivars Grown in Bosnia and Herzegovina

The present research was undertaken to investigate polyphenolic profiles of peel, pulp and juices made from two standard commercial and five traditional apple cultivars from Bosnia and Herzegovina. The main goal of the study was to monitor the distribution and changes of polyphenolic profiles through different phases of apples' processing into cloudy and clear juices, with regard to L-ascorbic acid pretreatment. Quantitative determination of phenolic compounds was carried out by using high-performance liquid chromatography with diode-array detection. The obtained results showed that traditional cultivars, namely 'Paradija' and 'Prijedorska zelenika', displayed significantly higher content of these compounds compared to commercial ones. Flavan 3-ols and flavonol glycosides were mostly found in peels of all cultivars (21.2-44.1 and 5.40-33.3%, respectively), while phenolic acids along with flavan 3-ols were predominant in the pulp (8.20-30.8 and 5.10-13.9%, respectively). Apples' processing into juices caused decrease (more than 90%) in the content of all polyphenols and the distribution of these compounds from fruits to final products had a negative trend, particularly evident in clear juices. The most drastic loss occurred in the flavonol glycosides and dihydrochalcones content, while chlorogenic acid displayed quite stable distribution from apples to final products due to its good solubility. Apple mash pretreatment with L-ascorbic acid had a positive impact on the preservation and retention of polyphenols.

Phytochemical Properties and In Vitro Biological Activities of Phenolic Compounds from Flower of Clitoria ternatea L

Phenolic compounds from the flower of Clitoria ternatea L. (PCFCTL) were extracted using a high-speed shearing extraction technique and purified by AB-8 macroporous resins, and the phytochemical composition of the purified phenolic compounds from the flower of Clitoria ternatea L. (PPCFCTL) was then analyzed. Subsequently, its bioactivities including antioxidant properties, enzyme inhibitory activities, and antiproliferative activities against several tumor cell lines were evaluated. Results indicated that the contents of total phenolics, flavonoids, flavonols, flavanols, and phenolic acids in PPCFCTL were increased by 3.29, 4.11, 2.74, 2.43, and 2.96-fold, respectively, compared with those before being purified by AB-8 macroporous resins. The results showed PPCFCTL have significant antioxidant ability (measured by reducing power, RP, and ferric reducing antioxidant power method, FRAP) and good DPPH, ABTS+, and superoxide anion radical scavenging activities. They can also significantly inhibit lipase, α-amylase, and α-glucosidase. In addition, morphological changes of HeLa, HepG2, and NCI-H460 tumor cells demonstrated the superior antitumor performance of PPCFCTL. However, the acetylcholinesterase inhibitory activity was relatively weak. These findings suggest that PPCFCTL have important potential as natural antioxidant, antilipidemic, anti-glycemic and antineoplastic agents in health-promoting foods.

Isolation and characterization culturable microbes on the surface of ‘Granny Smith’ apples treated with electrolyzed water during cold storage

Response of culturable microbes on the surface of apples treated with slightly alkaline electrolyzed water (SAIEW) is largely unexplored. Thus, the aim of this study was to characterize culturable microbes on the surface of SAIEW treated 'Granny Smith' apples using conventional and molecular approach. Results showed that SAIEW treatments and storage duration influenced culturable microbes isolated from the surface of 'Granny Smith' apples stored at 5 °C for 21 days. Enterobacterial repetitive intergenic consensus (ERIC-PCR) analysis distinctively identified 27 groups of bacteria from 56 plate isolates. Using random amplified polymorphic DNA (RAPD-PCR) typing and RAPD1283 primers, 10 distinct band patterns were identified from 30 fungal isolates. Sequencing of 16S rRNA and intergenic spacer (ITS1 and ITS4) region, identified eight bacteria and four fungi, respectively, to species level. Study showed that SAIEW treatment inhibited growth of Staphylococcus epidermidis, S. capitis, Ochrobactrum soli, and Aspergillus inuii on the surface apples during storage.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01148-2.

New red-fleshed apple cultivars: a comprehensive review of processing effects, (poly)phenol bioavailability and biological effects

Red-fleshed apple cultivars with an enhanced content of anthocyanins have recently attracted the interest of apple producers and consumers due to their attractive color and promising added health benefits. In this paper, we provide the first comprehensive overview of new hybrid red-fleshed apples, mainly focusing on their (poly)phenolic composition, the effect of processing, the (poly)phenolic bioavailability and the biological effects. Evidence so far from in vitro and in vivo studies supports their added beneficial effects compared to common apples on health outcomes such as cancer, cardiovascular disease, inflammation and immune function, which are mainly related to their specific (poly)phenol composition.

"An apple a day keeps the doctor away": The potentials of apple bioactive constituents for chronic disease prevention

Apples are rich sources of selected micronutrients (e.g., iron, zinc, vitamins C and E) and polyphenols (e.g., procyanidins, phloridzin, 5′‐caffeoylquinic acid) that can help in mitigating micronutrient deficiencies (MNDs) and chronic diseases. This review provides an up‐to‐date overview of the significant bioactive compounds in apples together with their reported pharmacological actions against chronic diseases such as diabetes, cancer, and cardiovascular diseases. For consumers to fully gain these health benefits, it is important to ensure an all‐year‐round supply of highly nutritious and good‐quality apples. Therefore, after harvest, the physicochemical and nutritional quality attributes of apples are maintained by applying various postharvest treatments and hurdle techniques. The impact of these postharvest practices on the safety of apples during storage is also highlighted. This review emphasizes that advancements in postharvest management strategies that extend the storage life of apples should be optimized to better preserve the bioactive components crucial to daily dietary needs and this can help improve the overall health of consumers.

Analysis of Apple Fruit (Malus × domestica Borkh.) Quality Attributes Obtained from Organic and Integrated Production Systems

The aim of this study was to compare total phenolic content (TPC), radical-scavenging activity (RSA), total anthocyanin content (TAC), sugar and polyphenolic profiles of two apple cultivars (‘Discovery’ and ‘Red Aroma Orelind’) from organic and integrated production systems in climatic conditions of Western Norway. Sixteen sugars and four sugar alcohols and 19 polyphenols were found in the peel, but less polyphenols were detected in the pulp. The peel of both apples and in both production systems had significantly higher TPC and RSA than the pulp. The peel from integrated apples had higher TPC than the peel from organic apples, while organic apples had higher TAC than the integrated. Sucrose and glucose levels were higher in organic apples; fructose was cultivar dependent while minor sugars were higher in integrated fruits. The most abundant polyphenolic compound in the peel of the tested cultivars was quercetin 3-O-galactoside, while chlorogenic acid was most abundant in the pulp. Regarding polyphenols, phloretin, phloridzin, protocatechuic acid, baicalein and naringenin were higher in organic apple, while quercetin 3-O-galactoside, kaempferol 3-O-glucoside, chlorogenic acid and syringic acid was higher in integrated fruits. In conclusion, organic ‘Discovery’ and integrated ‘Red Aroma Orelind’ had higher bioavailability of health related compounds from the peel and the pulp.

Comparative Evaluation of Juices from Red-Fleshed Apples after Production with Different Dejuicing Systems and Subsequent Storage

In this work, two vintages (2019 and 2020) of red-fleshed ‘Weirouge’ apples were processed with the innovative spiral filter press technology to investigate juice production in an oxygen-reduced atmosphere. After pressing, a more brilliant red color and appreciably higher amounts of oxidation-sensitive constituents (ascorbic acid, anthocyanins, and colorless (poly)phenols) were seen in spiral filter pressed juices compared to those produced with conventional systems (horizontal filter press and decanter). In a subsequent stability study (24 weeks storage at 4, 20, and 37 °C), the color and phenolic compounds were monitored and differences in the juices produced with the different pressing-systems were widely maintained during the storage period. The analyses of the anthocyanins and colorless (poly)phenols were conducted by UHPLC-DAD-ESI-QTOF-HR-MS/MS and UHPLC-DAD. The spiral filter press emerged as a promising technology for the production of juices with a more attractive color and a better retention of oxidation-sensitive constituents during processing and storage compared to conventional juices.

Impact of Storage Controlled Atmosphere on the Apple Phenolic Acids, Flavonoids, and Anthocyanins and Antioxidant Activity In Vitro

Apples are seasonal fruits, and it is important to prepare them adequately for storage and ensure proper storage conditions. In this study, we used ten different apple cultivars: ‘Alva’, ‘Auksis’, ‘Connell Red’, ‘Cortland’, ‘Ligol’, ‘Lodel’, ‘Noris’, ‘Rubin’, ‘Sampion’, and ‘Spartan’. We studied the qualitative and quantitative composition of phenolic compounds in the apple and apple extracts antioxidants activity before placing them in the controlled atmosphere chambers and again at the end of the experiment, eight months later. Different concentrations of O2, CO2, and N2, constant temperature, relative humidity, and removal of endogenous ethylene were continually maintained. HPLC analysis showed that the highest amount of 2265.7 ± 152.5 µg/g of chlorogenic acid was found in apple samples of the ‘Auksis’ cultivar stored under variant IV conditions. Different concentrations of gas in the controlled atmosphere chambers caused changes in antioxidant activity in whole apple and apple peel extracts. In our study, we found that the antioxidant activity of apple extracts varied between samples of different apple cultivars and depended on the composition of the controlled atmosphere. Determining the optimal storage conditions is beneficial to providing the consumers with apples that have a known and minimally altered chemical composition of phenolic compounds and the strongest antioxidant activity, which determine the use of apples in the healthy food chain.

Phytochemical Content and Antioxidant Activity of Malus domestica Borkh Peel Extracts

Apple is an important dietary source of carotenoids and phenolic compounds, and its regular consumption is associated with several health benefits. The aim of this study was to evaluate the phytochemical composition of fresh peels of four red-skinned (“Champion”, “Generos”, “Idared”, “Florina”) and two yellow-skinned (“Golden Delicious”, “Reinette Simirenko”) apple varieties. Antioxidant activity of apple peel extracts was determined by ferric reducing antioxidant power (FRAP) and ABTS radical scavenging capacity assays. Total carotenoid and polyphenolic contents were determined spectrophotometrically, while the profile of individual carotenoids and anthocyanins (in red-skinned varieties) was analyzed using high-performance liquid chromatography coupled to a photodiode array detector (HPLC-PDA). Carotenoid composition was specific for each variety, and total carotenoid content was slightly higher in yellow-skinned apple peels compared to red-skinned varieties. In contrast, total phenolic content was higher in the peels of red-skinned cultivars. Anthocyanin profile was predominated by cyanidin-3-O-galactoside. Antioxidant potential followed the trend of the total polyphenolic content, being highest in “Florina”, as measured by both FRAP and ABTS assays. Our results demonstrated apple peels have high phytochemical content with diverse compositions, and their regular consumption can be an excellent source of antioxidants.

Onco-Preventive and Chemo-Protective Effects of Apple Bioactive Compounds

Cancer is one of the leading causes of death globally. Epidemiological studies have strongly linked a diet high in fruits to a lower incidence of cancer. Furthermore, extensive research shows that secondary plant metabolites known as phytochemicals, which are commonly found in fruits, have onco-preventive and chemo-protective effects. Apple is a commonly consumed fruit worldwide that is available all year round and is a rich source of phytochemicals. In this review, we summarize the association of apple consumption with cancer incidence based on findings from epidemiological and cohort studies. We further provide a comprehensive review of the main phytochemical patterns observed in apples and their bioavailability after consumption. Finally, we report on the latest findings from in vitro and in vivo studies highlighting some of the key molecular mechanisms targeted by apple phytochemicals in relation to inhibiting multiple 'hallmarks of cancer' that are important in the progression of cancer.

A novel spatially resolved interactance spectroscopy system to estimate degree of red coloration in red-fleshed apple

Reliable information about degree of red coloration in fruit flesh is essential for grading and sorting of red-fleshed apples. We propose a spatially resolved interactance spectroscopy approach as a new rapid and non-destructive technique to estimate degree of red coloration in the flesh of a red-fleshed apple cultivar 'Kurenainoyume'. A novel measurement system was developed to obtain spatially resolved interactance spectra (190-1070 nm) for apple fruits at eight different light source-detector separation (SDS) distances on fruit surface. Anthocyanins in apple were extracted using a solvent extraction technique, and their contents were quantified with a spectrophotometer. Partial least squares (PLS) regression analyses were performed to develop estimation models for anthocyanin content from spatially resolved interactance spectra. Results showed that the PLS models based on interactance spectra obtained at different SDS distances achieved different predictive accuracy. Further, the system demonstrated the possibility to detect the degree of red coloration in the flesh at specific depths by identifying an optimal SDS distance. This might contribute to provide a detailed profile of the red coloration (anthocyanins) that is unevenly distributed among different depths of the flesh. This new approach may be potentially applied to grading and sorting systems for red-fleshed apples in fruit industry.

Antioxidant Activity and Discrimination of Organic Apples (Malus domestica Borkh.) Cultivated in the Western Region of Romania: A DPPH· Kinetics-PCA Approach

Apple (Malus domestica Borkh.) is one of the most used fruit for beverages in Romania. The goal of the study was to evaluate the antioxidant activity and discrimination of various parts of organic and non-organic apple varieties cultivated in the western region of Romania using the DPPH· kinetics–PCA (principal component analysis) approach. Organic and non-organic apples were subjected to solid–liquid ethanol extraction. Core and shell extracts were mixed with DPPH· and spectrophotometrically monitored at 517 nm. Antioxidant activity and mean DPPH· reaction rate at various time ranges reveal significant differences between organic and non-organic samples, as well as apple parts. Organic core and shell extracts had higher antioxidant activities than the corresponding non-organic samples (74.5–96.9% and 61.9–97.2%, respectively, 23.5–94.3% and 59.5–95.5%). Significant differences were observed for the DPPH· reaction rate for the first ½ min, especially in the presence of organic core extracts (3.7–4.8 μM/s). The organic samples were well discriminated by DPPH· kinetics–PCA, the most important variables being the DPPH· reaction rate for the first time range. This is the first DPPH· kinetics–PCA approach applied for discriminating between organic and non-organic fruits and can be useful for evaluating the quality of such type of fruits.

Evolution of typical aromas and phenolic compounds of a red-fleshed apple throughout different fruit developmental periods in Xinjiang, China

Red-fleshed apple is attracting more and more attentions from both consumers and researchers thanks to its pleasant appearance and flavor. Accumulation and development of aromas of apple fruit are important factors to understand the fruit quality of a new cultivated variety. However, knowledge on the key aroma components development and accumulation of red-fleshed apple (Malus sieversii f. neidzwetzkyana(Dieck) Langenf) in Xinjiang through the fruit developmental periods is insufficient. In this paper, free and bound form aromas of a red-fleshed apple since young fruit period through expansion period and conversion period to ripen period were comparatively studied. We classified aroma substances according to the compound category (esters, aldehydes, alcohols, terpenes, and aromatics), and to the odor types. The concentration of bound form aroma compounds were higher than that of free form throughout the 4 periods and showed different evolution trends. Among the 4 periods, the bound aroma was the most in the expansion period; and terpenoids showed the greatest potential to release free form aromas. Total aromas were found the lowest concentration in expansion period and the highest concentration in ripen period. The observations in this study will provide theoretical support for the research of typical aroma formation regularity of red-fleshed apple, and guide for the aroma enhancement regulation.

Differential effects of phenolic extracts from red-fleshed apple peels and flesh induced G1 cell cycle arrest and apoptosis in human breast cancer MDA-MB-231 cells

Red-fleshedapples are preferredbecause of their high content of phenolics and antioxidants in peel and pulp. Herein, we evaluated the mechanisms of apple peel polyphenolic extracts (APP) and apple flesh polyphenolic extracts (AFP) from the new red-fleshed apple in inhibiting cell proliferation and inducing apoptosis on human breast cancer MDA-MB-231 cells. The antiproliferative activities were determined by the CCK8 assay. The expression of proteins was determined using Western blot. We found that the content of polyphenols and flavonoids in APP was significantly higher than that in AFP, and 14 main phenolic compounds in APP and AFP were quantified using UPLC-MS/MS techniques. Besides, the significant inhibition effects of APP and AFP were achieved through Akt pathway by inducing apoptosis (significantly upregulating reactive oxygen species [ROS] levels, and downregulating expression of pAkt, pBad, Bcl-2, promoting Cytochrome c release, activating Cle-Caspase 9, and inducing expressions of Cle-Caspase 3 and Cle-PARP), and inducing G0/G1 cell cycle arrest (increased expressions of p-p53 and p21 and decreased expressions of PCNA and Cyclin D1). And the inhibition effect of APP was stronger than that of AFP. These results suggest that AFP and APP may be excellent sources of natural chemicals for treating triple-negative breast cancer MDA-MB-231 cells. PRACTICAL APPLICATION: The effects of antiproliferation of phenolic extracts from red-fleshed apple peels and flesh on human breast cancer MDA-MB-231 cells were evaluated. The data may clarify the functional parts of red-fleshed apple and provide some basis for scientific researchers and consumers to recognize and exploit red-fleshed apple.

Antioxidant Activity and Healthy Benefits of Natural Pigments in Fruits: A Review

Natural pigments, including carotenoids, flavonoids and anthocyanidins, determine the attractive color of fruits. These natural pigments are essential secondary metabolites, which play multiple roles in the whole life cycle of plants and are characterized by powerful antioxidant activity. After decades of research and development, multiple benefits of these natural pigments to human health have been explored and recognized and have shown bright application prospects in food, medicine, cosmetics and other industries. In this paper, the research progress of natural fruit pigments in recent years was reviewed, including the structural characteristics and classification, distribution in fruits and analysis methods, biosynthetic process, antioxidant capacity and mechanism, bioaccessibility and bioavailability, and health benefits. Overall, this paper summarizes the recent advances in antioxidant activity and other biological functions of natural fruit pigments, which aims to provide guidance for future research.

Analysis of the postharvest storage characteristics of the new red-fleshed apple cultivar 'meihong'

This study examined the effects of postharvest storage conditions on the fruit quality of a new red-fleshed apple cultivar ('Meihong'). Mature 'Meihong' and 'Golden delicious' apples were exposed to room temperature, low temperature, and low temperature and 1-MCP, after which several fruit characteristics were evaluated (i.e., firmness, ethylene release rate, relative content of aroma components, phenolic compounds and antioxidant capacity, fruit softening-related enzyme activities, and related gene expression). Both 'Meihong' and 'Golden delicious' were ACS1-1/-2 heterozygotes, but the ethylene release rate in 'Meihong' fruits was lower than that in 'Golden delicious' fruits during storage. Therefore, 'Meihong' fruits are more conducive to storage. The low temperature storage with and without 1-MCP delayed fruit softening, decreased the ethylene release rate and ester aroma component content, and maintained total flavonoid and anthocyanin contents. Therefore, storage at low temperatures with 1-MCP or other preservatives may be useful for maintaining the 'Meihong' fruit quality.

Systematic Review of Phenolic Compounds in Apple Fruits: Compositions, Distribution, Absorption, Metabolism, and Processing Stability

As the most widely consumed fruit in the world, apple (Malus domestica Borkh.) fruits provide a high level of phenolics and have many beneficial effects on human health. The composition and content of phenolic compounds in natural apples differs according to the tissue types and cultivar varieties. The bioavailability of apple-derived phenolics, depending on the absorption and metabolism of phenolics during digestion, is the key determinant of their positive biological effects. Meanwhile, various processing technologies affect the composition and content of phenolic compounds in apple products, further affecting the bioavailability of apple phenolics. This review summarizes current understanding on the compositions, distribution, absorption, and metabolism of phenolic compounds in apple and their stability when subjected to common technologies during processing. We intend to provide an updated overview on apple phenolics and also suggest some perspectives for future research of apple phenolics.

Metabolomic and Transcriptomic Analyses of Anthocyanin Biosynthesis Mechanisms in the Color Mutant Ziziphus jujuba cv. Tailihong

The purplish-red color of "Tailihong" jujube fruit skins is caused primarily by anthocyanin accumulation, but the mechanisms that underlie anthocyanin biosynthesis in jujube fruit have rarely been studied. We performed metabolomic and transcriptomic analyses of jujube fruit skins at different developmental stages and identified a total of 158 flavonoids, among which cyanidin-3-O-rutinoside and peonidin-3,5-O-diglucoside were the primary anthocyanins. During fruit development and maturation, the anthocyanin content was strongly correlated with the expression of ZjANS and ZjUGT79B1, suggesting that these are key genes in the anthocyanin biosynthesis process. Transcriptomic analysis indicated that the transcription factors ZjMYB5, ZjTT8, and ZjWDR3 regulated anthocyanin biosynthesis in jujube fruit skins. Subcellular localization experiments confirmed that ZjANS and ZjUGT79B1 were localized to the nucleus and the endoplasmic reticulum. ZjMYB5 and ZjTT8 were found only in the nucleus, whereas strong fluorescence signals from ZjWDR3 were observed in the nucleus and cytoplasm. Prokaryotic expression and in vitro enzyme activity assays showed that the recombinant ZjANS protein catalyzed the formation of cyanidin from (+)-catechin. Secondary glycosylation by ZjUFGT79B1 modified cyanidin-3-O-glucoside to produce cyanidin-3-O-rutinoside, and ZjCCoAOMT readily catalyzed the production of the methylated anthocyanin peonidin-3,5-O-diglucoside from cyanidin 3,5-O-glucoside. Dual-Luciferase and GUS activity assays showed that the ZjANS and ZjUGT79B1 promoters were activated by ZjMYB5, ZjTT8, and ZjWDR3. All data indicated that these three transcription factors played important roles in anthocyanin biosynthesis in the color mutant Ziziphus jujuba cv. Tailihong, contributing to anthocyanin accumulation by enhancing the expression of ZjANS and ZjUGT79B1.

Development of red apple pomace extract/chitosan-based films reinforced by TiO2 nanoparticles as a multifunctional packaging material

A chitosan-based (CS) film was developed with nanosized TiO₂ and red apple pomace extract (APE). The intermolecular interactions of CS, TiO₂ and APE were evaluated by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. TiO₂ nanoparticles remarkably improved the water vapor and UV-Vis light barrier properties, mechanical strength and thermal stability of CS-APE films. The strong antioxidant abilities of CS-APE and CS-TiO₂-APE films were characterized. Nano-TiO₂ and APE showed a synergistic enhancement of the antimicrobial activity in CS matrix. The addition of TiO₂ nano-particles into CS-APE films resulted the sensitive color variations, which applied successfully as an indicator to monitor the freshness of salmon fillets. Consequently, the development of CS-APE-TiO₂ film provides a new solution to convert rad apple pomace to an active and multifunctional food packaging material with considerable mechanical, antibacterial, antioxidant and pH-responsive color-changing properties.

Thermal and non-thermal processing of red-fleshed apple: how are (poly)phenol composition and bioavailability affected?

The present study evaluated the impact of different thermal (infrared-drying, hot air-drying and purée pasteurization) and non-thermal (freeze-drying) processing technologies on red-fleshed apple (poly)phenolic compounds. We further investigated the processing effect on the (poly)phenol bioavailability in a crossover postprandial study where three subjects consumed three apple products (freeze-dried snack, hot air-dried snack and pasteurized purée). (Poly)phenolic compounds present in the apple products and their biological metabolites in urine were analyzed using liquid chromatography coupled to mass spectrometry (UPLC-MS/MS). When comparing different processes, infrared-drying caused important losses in most of the apple (poly)phenolics, while hot air-drying and purée pasteurization maintained approximately 83% and 65% of total (poly)phenols compared with the freeze-dried snack, respectively. Anthocyanins in particular were degraded to a higher extent, and hot air-dried apple and pasteurized purée maintained respectively 26% and 9% compared with freeze-dried apple snack. The acute intake showed that pasteurized purée exhibited the highest (poly)phenol bioavailability, followed by hot air-drying and freeze-dried snack, highlighting the impact of processing on (poly)phenols absorption. In conclusion, for obtaining affordable new red-fleshed apple products with enhanced (poly)phenol bioavailability, purée pasteurization and hot air-drying represent viable techniques. However, to obtain a red-fleshed apple snack with high anthocyanin content, freeze-drying is the technique that best preserves them.

Bioactive Compounds and Antioxidant Capacity of Moringa Leaves Grown in Spain Versus 28 Leaves Commonly Consumed in Pre-Packaged Salads

Total antioxidant capacity (TAC) evaluated by ferric ion reducing antioxidant power (FRAP) assay, ABTS, DPPH, and Oxygen radical absorbance capacity (ORAC) assay, and total polyphenol content (TPC) by Folin–Ciocalteu were determined in Moringa oleifera leaves (MO) grown in Spain, and compared with 28 different vegetable leaves pre-packaged for consumption as a salad. Total carotenoids, flavonoids, and chlorophylls were also determined in the samples with highest TAC. Two different extraction procedures were applied to obtain the methanolic fraction and the lipophilic and hydrophilic fractions. The highest TAC and TPC contents were found in MO. High values were also found in red chicory, “lollo rosso”, and oak lettuce. The lowest TAC and TPC values were obtained in iceberg lettuce. The correlations between the extraction procedures and methods assayed were high and statistically significant. In the light of these results, we suggest the addition of MO to the existing range of fresh-cut salad foods would increase their antioxidant content by up to six times.

Preharvest application of prohydrojasmon affects color development, phenolic metabolism, and pigment-related gene expression in red pear (Pyrus ussuriensis)

BACKGROUND

Peel color is an economically relevant trait that influences the appearance and quality of red pear, whose red color is due to anthocyanin accumulation. Prohydrojasmon (PDJ), which has similar effects to endogenous jasmonates, was developed as a commercial bioregulator, particularly to improve fruits coloring. However, little information is available about the effect of PDJ on pears. This study investigated the effects of preharvest PDJ treatments on color development, phenolic compounds accumulation, and related gene expression in the red pear cultivar 'Nanhong'. The treatments were performed during the pre-color-change period by spraying 50 or 100 mg L^-1 of PDJ on fruits.

RESULTS

Preharvest PDJ treatments had a significant effect on color development, without affecting other quality parameters such as total soluble solids and fruit acidity. Liquid chromatography-mass spectrometry analysis showed that concentrations of anthocyanins and flavonols were enhanced in the peel after PDJ treatments, particularly when a concentration of 100 mg L^-1 was used, whereas those of hydroxycinnamates and flavanols were decreased. After PDJ application, the transcription levels of anthocyanin biosynthesis genes PAL, CHS, CHI, ANS, F3H, and UFGT were enhanced, especially under the higher PDJ concentration tested. In addition, anthocyanin accumulation in the peels of PDJ-treated fruits was found to be positively correlated with the upregulation of the regulatory gene MYB114.

CONCLUSION

Preharvest treatments with PDJ could be a useful tool to improve fruits coloring and increase phenolic content in pear. These findings also improve our understanding of the molecular mechanisms associated with PDJ-regulated anthocyanin accumulation in pear fruits.

Antioxidant and hepatoprotective effects against acute CCl4 -induced liver damage in mice from red-fleshed apple flesh flavonoid extract

Apple (Malus domestica Borkh.) is an important fruit tree species worldwide. Apple fruits are favored by consumers because of their antioxidative, anti-inflammatory, and antitumor effects as well as their protective effects against cardiovascular diseases and other health benefits. There is considerable interest in red-fleshed apple fruits among breeders because of their high flavonoid and anthocyanin contents. However, the flavonoids extracted from red-fleshed apple fruits must still be functionally characterized, especially regarding their protective effects against certain pathologies. In this study, the flavonoid components and contents in the extracts prepared from red-fleshed apple cultivar "Meihong" were determined. Additionally, the in vitro antioxidant activities and protective effects of the extracts against CCl₄ -induced acute liver injury were investigated. The red-fleshed apple flesh flavonoid extract (RAFF) exhibited strong in vitro antioxidant activities. Compared with the model control mice treated with CCl₄ , the mice pretreated with high (800 mg/kg·bw), middle (400 mg/kg·bw), and low (200 mg/kg·bw) RAFF doses had significantly lower CCl₄ -induced serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase activities. Moreover, the RAFF pretreatment also significantly decreased the liver malondialdehyde activity and prevented the CCl₄ -induced decrease in liver superoxide dismutase, glutathione peroxidase, catalase, and reduced glutathione levels. Furthermore, a histopathological examination revealed that RAFF inhibited the inflammatory cell infiltration and cell boundary loss caused by CCl₄ in the liver. Thus, RAFF is a natural antioxidant with significant antioxidative activities and liver protective effects. The results of this study may be relevant for enhancing the application of the red-fleshed apple fruit extract as a food additive. PRACTICAL APPLICATION: We took the self-selected red-fleshed apple cultivar "Meihong" as the unique research material, and the active ingredients of its flavonoid extract, in vitro antioxidant activity and hepatoprotective effect were analyzed. It is of great significance to promote the development of the red-fleshed apple industry, and also provides an important reference for the development of natural antioxidants.