Kiwifruit (Actinidia spp.): A review of chemical diversity and biological activities

Unveiling the polyphenol profile and bioactive potential of kiwi berry (Actinidia arguta): Antioxidant capacity and enzyme inhibition activities

Kiwi berry (Actinidia arguta (Sieb & Zucc) Planch. ex Miq. cv 'Longcheng No.2') is rich in polyphenols and has gained popularity in recent years. However, there is a lack of information on the specific polyphenol composition and antioxidant and enzyme inhibition activities of kiwi berries. This study aimed to analyze the anthocyanin and non-anthocyanin polyphenol profiles of kiwi berry using HPLC-HR TOF MS2, compare their antioxidant capacity, and assess inhibition activity of digestive enzymes. Molecular docking was employed to investigate the interaction between cyanidin 3-O-sambubioside and digestive enzymes. The results revealed twenty non-anthocyanin polyphenols and ten anthocyanins, with seven anthocyanins and eight non-anthocyanins newly identified in kiwi berry. Kiwi berry exhibited potent antioxidant capacity and excellent α-glucosidase inhibition activity, suggesting its potential as a functional ingredient for managing early type-II diabetes through dietary interventions.

Eco-friendly biocontrol strategies for management of postharvest fungal decays in kiwifruit: A review

Kiwifruit is known for its rich content of nutrients and significant economic value. Global cultivation of kiwifruit has been increasing along with the amount of land being dedicated to its production. Regrettably, postharvest fungal decays, such as those caused by Botrytis cinerea, Penicillium expansum, Alternaria alternata, Botryosphaeria dothidea, Nigrospora oryzae, and others, pose a significant challenge to the kiwifruit industry, and are responsible for substantial losses during storage, transportation, and local marketing. Biological control of postharvest diseases is seen as a safe and sustainable strategy and as a result has received considerable interest for its potential in disease management. The present review provides an overview of the research conducted on the major postharvest diseases of kiwifruit and the use of biocontrol agents to manage these diseases. It also reviews the status of microbial formulations and the impact of environmental factors on biocontrol efficacy. The need for further research on the utilization of microbial consortia to manage postharvest diseases of kiwifruit is discussed as a major new approach to biological control.

Genome-Wide Identification and Expression Profiling of the Invertase Genes Involved in Sugar Metabolism and Accumulation in Actinidia arguta

Invertase (INV, EC3.2.1.26) is widely recognized as an indispensable enzyme for catalyzing sucrose degradation and plays a central role in plant growth as well as fruit quality improvement. However, no systematic study has been performed in kiwifruit. Here, we identified 102 AaINV genes in the Actinidia arguta "M1" genome. Their physical and chemical properties, subcellular localizations, phylogenetic relationships and expression profiles were characterized. Phylogenetic analysis showed that the INV members were clustered into three groups (vacuole invertases (VINVs) and cell wall invertases (CWINVs) in Group I, alkaline/neutral invertase (NINVs) in Group II and Group III), demonstrating evolutionary conservation in the INV family across Arabidopsis and Actinidia species. Gene replication analysis revealed that many AaINV genes were derived from gene duplication events. Molecular evolution analysis based on Ka/Ks ratios indicated that the INV members have experienced extensive purifying selection during evolution. To explore the potential gene functions, we integrated RNA-seq and metabolomics to analyze AaINV gene expression patterns and sugar accumulation in three A. arguta varieties ("Kukuwa", "Qinhuang", "Xianziguang"), respectively. The expression analysis of the 102 genes showed that the expression patterns varied among the three kiwifruit varieties at fruit maturity stage. The expression levels of AaINVs were also investigated via qRT-PCR in these varieties. Specifically, we constructed a complex regulatory network that regulates sugar metabolism in kiwifruit based on the correlation between 42 AaINV genes and 14 sugar metabolites. These findings provide insights into physiological functions of AaINVs in kiwifruit, especially roles in governing sugars accumulation in fruits.

RNA-Seq Analysis Reveals Potential Genes Involved in Plant Growth Regulator-Induced Ovary Development in Male Kiwifruit (Actinidia eriantha)

Kiwifruit is a dioecious woody liana fruit tree, and the non-fruitfulness of male plants leads to a great deal of blindness in the selection of male plants in crossbreeding. In this study, we induced the development of male plant ovary by externally applying plant growth regulators (PGRs) and performed histological observation, phytohormone content determination and transcriptome analysis on the abortive ovary of the male kiwifruit (Con), the ovary of the female kiwifruit (Fem) and the PGR-induced developing ovary of the male kiwifruit (PT). Histological analysis showed that the Con ovary was devoid of ovules and the carpels were atrophied, the Fem ovary had ovules and the PT ovary was devoid of ovules, but the carpels developed normally and were not atrophied. Endogenous phytohormone content measurements displayed higher levels of trans-zeatin (tZT) in PT and Fem than Con, and lower levels of gibberellin (GA3) and abscisic acid (ABA) than Con. Transcriptome analysis revealed significant differences in many key genes in the cytokinin and auxin pathways, which were consistent with the results of phytohormone content measurements. Meanwhile, the genes related to carpel development, SPT (DTZ79_04g03580) and SK41 (DTZ79_19g04340), were highly expressed in PT, suggesting that they may play a key role in PGR-induced development of the ovary in male kiwifruit. These results provide information for elucidating the potential regulatory network of PGR-induced ovary development in male flowers and contribute to further identification of valuable target genes.

Geographical origin traceability of kiwifruit products using stable isotope and multi-element analysis with multivariate modeling: Feature extraction, selection of model and variable, and discrimination

The mislabeling of kiwifruit origin frequently disturbs market competition and governmental supervision, significantly undermines brand reputation and consumer rights. In this work, a total of 370 kiwifruits from 8 different countries in global were collected, and 6 stable isotope ratios (SIRs), 10 mineral elements (MEs), and 16 rare earth elements (REEs) were determined for origin traceability study. One-way analysis of variance (ANOVA) showed that regional differences of 32 variables are at significant level (P value =0.00). Supervised methods, partial least squares-discriminant analysis (PLS-DA) and its derivative algorithm (OPLS-DA), linear discriminant analysis (LDA), enhanced identification performance and finally elevated the accuracies to 100 % for all kiwifruit origins. Lu, Tb, Eu, Ho, Pm, Y, δ34S, δ2H, δ15N, Mg, Se were main contributive variables for LDA modeling (AUC value >0.5). A blind test was conducted using 63 samples randomly selected from Chinese market. The predicted result indicated a significantly high probability of origin mislabeling of imported kiwifruit products, with percentages ranging from 30.0 % to 90.0 %. This study may provide technical supports for combating origin mislabeling conduct, and ensuring food authenticity of kiwifruit in global trade.

The diversity and disparity of mineral elements in global kiwifruits

Mineral elements in fruits are essential for various physiological functions and offer significant health benefits. While kiwifruit is valued for its vitamin C and nutritional content, the role of its mineral composition and distribution in fruit safety and disease remains unclear. This study analyzed the mineral composition of kiwifruits from 12 cultivars across 4 countries, identifying 20 mineral elements. Notably, potassium and magnesium concentrations were significantly higher compared to those in most commonly consumed fruits. The mineral profiles varied by flesh color: red-fleshed kiwifruits had more iron and phosphorus, green-fleshed varieties contained more calcium and manganese, and yellow-fleshed fruits had higher levels of potassium, chlorine. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was optimized to visualize mineral distribution, revealing heterogeneous patterns of potassium, calcium, chlorine, sodium and boron in kiwifruits affected by soft rot. These findings underscore the potential of LA-ICP-MS as an effective tool for studying the distribution of nutrients in fruit and assessing its physiological disorders. The target hazard quotient (THQ) values of the mineral contents in all kiwifruit samples were below 1, indicating no significant risk of heavy metal contamination. Furthermore, agricultural practices such as fertilization and fungicide application influenced mineral content, with red-fleshed kiwifruits showing elevated copper and lead levels, likely from heavy metal-based disease and pest control agents. This study provides a comprehensive analysis of mineral diversity in kiwifruits and introduces a novel visual mapping technique, offering valuable insights into both the nutritional profile and safety of kiwifruit.

Biological and Health-Promoting Potential of Fruits from Three Cold-Hardy Actinidia Species

Fruits are essential components of the human diet, valued for their diverse bioactive compounds with potential health-promoting properties. This study focuses on three cold-hardy Actinidia species, namely A. arguta, A. kolomikta, and A. polygama, examining their polyphenolic content, antioxidant/antiradical activities, scavenging capacity and effects on intestinal cell viability (Caco-2 and HT29-MTX). A comprehensive profile of their phenolic compounds was identified, in descending order of total polyphenol content: A. kolomikta > A. arguta > A. polygama. Across species, 16 phenolic acids, 2 flavanols, 2 flavanones, 11 flavonols, and 3 flavones were quantified, with caffeine as a prominent compound. A. kolomikta achieved the highest antioxidant activity, with 'Vitakola' cultivar showing almost double the antioxidant activity compared to 'Tallinn' and 'Pozdni'. By contrast, A. arguta 'Geneva' and A. polygama 'Pomarancheva' exhibited significantly lower activity in both FRAP and DPPH assays. Notably, A. kolomikta cultivars showed distinct radical-scavenging capacities, particularly for superoxide, wherein 'Tallinn' and 'Pozdni' achieved the highest values. Cell viability tests on Caco-2 and HT29-MTX cells revealed a dose-dependent reduction in viability, notably stronger in Caco-2 cells. Overall, this study underscores the therapeutic potential of Actinidia species.

Agrobacterium-Mediated Stable Transformation of Actinidia deliciosa (Kiwi)

Actinidia deliciosa, commonly known as kiwi, is a woody perennial species recognized for its commercially relevant fruits with high levels of vitamin C, potassium, and dietary fiber. This chapter explores an efficient Agrobacterium-mediated stable transformation method for Actinidia, focusing on A. deliciosa cv Hayward, coupled with a somatic organogenesis regeneration protocol serving as a foundational tool for manipulating the kiwifruit genome. Beyond technical details, this contribution aims to advance both fundamental understanding and practical applications in kiwifruit genetics, providing a valuable resource for researchers.

Comparative analysis of phenolic compounds in different thinned unripe kiwifruits and their biological functions

Thinned unripe kiwifruits (TUK) are considered the major agro by-products in kiwifruit production. To promote their potential applications, polyphenols and biological effects of unripe fruits from nine commercial kiwifruit cultivars were compared. Our findings showed that TUK were rich in bioactive polyphenols, which varied greatly by different cultivars. Indeed, catechin, epicatechin, procyanidin PB1, procyanidin B2, protocatechuic acid, neochlorogenic acid, and gallic acid were measured as the major phenolic components in most TUK, with the highest levels observed in 'Hongao' and 'Cuiyu' cultivars. Furthermore, TUK exerted strong in vitro antioxidant capacities, inhibitory effects on digestive enzymes, and anti-inflammatory activities. Particularly, their stronger antioxidant effects and inhibitory effects on digestive enzymes were probably attributed to their higher contents of phenolic compounds, especially procyanidin B2. Collectively, our findings reveal that TUK are potential resources of valuable polyphenols, which can be exploited as natural antioxidants and natural inhibitors of α-glucosidase and α-amylase.

Valorizing Agro‐Food Waste for Nutraceutical Development: Sustainable Approaches for Managing Metabolic Dysfunction‐Associated Steatotic Liver Disease and Related Co‐Morbidities

This comprehensive investigation delves into the interconnectedness of different features of cardiometabolic syndrome, such as metabolic dysfunction‐associated steatotic liver disease (MASLD), atherosclerotic cardiovascular disease (ASCVD), and gut dysbiosis, highlighting the crucial role of nutraceuticals in their management and prevention. Given the significant overlap in the pathophysiology of these conditions, the treatment with nutraceuticals, especially those derived from agro‐food waste, offers a promising, sustainable, and innovative approach to healthcare. The 2030 Agenda for Sustainable Development and the One Health concept are key frameworks for selecting the most interesting supply chain for the production of nutraceuticals from agro‐food waste, ensuring environmental sustainability, and innovative agricultural practices. In this review, the therapeutic potential of kiwifruit and apples has been explored, detailing how their bioactive compounds, like polyphenols, fiber, pectin, kaempferol, phloretin, and phlorizin, may contribute to the management of MASLD, ASCVD, and gut dysbiosis. Various extraction methods for active ingredients, including chemical, water, and enzyme extractions, are analyzed for their respective benefits and drawbacks. By integrating scientific research, sustainable agricultural practices, and innovative extraction methods, we can develop effective strategies to combat these pervasive health issues. This holistic approach not only enhances individual health outcomes but also supports broader environmental and societal goals, promoting a healthier future for all.

Design, Synthesis, and Biological Activity Studies of Myricetin Derivatives Containing a Diisopropanolamine Structure

A series of myricetin derivatives containing diisopropanolamine were designed and synthesized. The in vitro inhibitory effects of the target compounds on 9 fungal pathogens and 3 bacterial pathogens were also evaluated. A12 had the best inhibitory effect against Xanthomonas oryzae pv. oryzae (Xoo), with an EC50 value of 4.9 μg/mL, which was better than zinc-thiazole (ZT: EC50 = 7.3 μg/mL) and thiodiazole-copper (TC: EC50 = 65.5 μg/mL); A25 had the best inhibitory effect against Phomopsis sp. (Ps), with an EC50 value of 17.2 μg/mL, which was better than azoxystrobin (Az: EC50 = 22.3 μg/mL). In vivo inhibition tests were performed on kiwifruit for A25 and rice leaves for A12. At 200 μg/mL, the curative activity of A12 against rice leaf blight was 40.7%, which was better than that of ZT (37.2%) and TC (32.9%), and the protective activity of A12 was 44.8%, which was better than that of ZT (39.5%) and TC (34.6%). The curative activity of A25 against kiwi soft rot disease was 70.1%, which was better than that of Az (62.8%). Preliminary elucidation of the possible mechanisms of action was carried out by experiments on fluorescence microscopy, scanning electron microscopy, formation of biofilms, density functional theory calculations, and so on.

Exploring Lectin Bioactivity and Total Phenolic Compounds in Kiwifruit (Actinidia deliciosa var. Hayward)

BACKGROUND

The consumption of kiwifruit (Actinidia deliciosa var. Hayward) is recognized for its health benefits due to its high vitamin C content and bioactive secondary metabolites, such as phenolic compounds with antioxidant properties. These compounds may help prevent chronic noncommunicable diseases, currently the leading cause of death. Additionally, plants and fruits contain proteins like lectins, which contribute to plant defense and may also have health-promoting effects, including antitumor and hypoglycemic activities.

OBJECTIVES

The objective of this work was to evaluate and identify the phenolic compounds in this variety of kiwifruit, as well as to investigate the lectin activity and the potential dietary benefits of this combination.

METHODS

This study quantified and identified total phenolic compounds and flavonoids in a kiwifruit extract using HPLC-DAD-MS/MS, and assessed their antioxidant activity through the DPPH method.

RESULTS

Novel lectin activity was also investigated, with polypeptide characterization and glycoprotein profiling performed. The affinity of lectins for glycans was evaluated using a hemagglutination inhibition assay. Results indicated that kiwifruit lectins bind to glycoreceptors on tumor cell membranes, with a specific affinity for sialic acid, an important glycan in tumor-associated glycomic aberrations.

CONCLUSIONS

These findings suggest that the bioactive components of kiwifruit may offer multiple health benefits through a synergistic effect.

Comparison of Protective Effects of Polyphenol-Enriched Extracts from Thinned Immature Kiwifruits and Mature Kiwifruits against Alcoholic Liver Disease in Mice

Alcoholic liver disease (ALD) is regarded as one of the main global health problems. Accumulated evidence indicates that fruit-derived polyphenols can lower the risk of ALD, this attributed to their strong antioxidant capacities. Thinned immature kiwifruits (TIK) are the major agro-byproducts in the production of kiwifruits, which have abundantly valuable polyphenols. However, knowledge about the protective effects of polyphenol-enriched extract from TIK against ALD is still lacking, which ultimately restricts their application as value-added functional products. To promote their potential applications, phenolic compounds from TIK and their corresponding mature fruits were compared, and their protective effects against ALD were studied in the present study. The findings revealed that TIK possessed extremely high levels of total phenolics (116.39 ± 1.51 mg GAE/g DW) and total flavonoids (33.88 ± 0.59 mg RE/g DW), which were about 7.4 times and 4.8 times greater than those of their corresponding mature fruits, respectively. Furthermore, the level of major phenolic components in TIK was measured to be 29,558.19 ± 1170.58 μg/g DW, which was about 5.4 times greater than that of mature fruits. In particular, neochlorogenic acid, epicatechin, procyanidin B1, and procyanidin B2 were found as the predominant polyphenols in TIK. In addition, TIK exerted stronger in vitro antioxidant and anti-inflammatory effects than those of mature fruits, which was probably because of their higher levels of polyphenols. Most importantly, compared with mature fruits, TIK exhibited superior hepatoprotective effects on alcohol-induced liver damage in mice. The administration of polyphenol-enriched extract from TIK (YK) could increase the body weight of mice, reduce the serum levels of ALP, AST, and ALT, lower the levels of hepatic TG and TC, and diminish lipid droplet accumulation and hepatic tissue damage. In addition, the treatment of YK could also significantly restore the levels of antioxidant enzymes (e.g., SOD and CAT) in the liver and lower the levels of hepatic proinflammatory cytokines (e.g., IL-6, IL-1β, and TNF-α), indicating that YK could effectively ameliorate ALD in mice by reducing hepatic oxidative stress and hepatic inflammation. Collectively, our findings can provide sufficient evidence for the development of TIK and their extracts as high value-added functional products for the intervention of ALD.

Analysis of the liver-gut axis including metabolomics and intestinal flora to determine the protective effects of kiwifruit seed oil on CCl4-induced acute liver injury

The hepatoprotective effects of kiwifruit seed oil (KSO) were evaluated on acute liver injury (ALI) induced by carbon tetrachloride (CCl4) in vivo. Network pharmacology was used to predict active compounds and targets. Metabolomics and gut microbiota analyses were used to discover the activity mechanism of KSO. KSO improved the liver histological structure, significantly reduced serum proinflammatory cytokine levels, and increased liver antioxidant capacity. The metabolomics analysis showed that KSO may have hepatoprotective effects by controlling metabolites through its participation in signaling pathways like tryptophan metabolism, glycolysis/gluconeogenesis, galactose metabolism, and bile secretion. The gut microbiota analysis demonstrated that KSO improved the composition and quantity of the gut flora. Network pharmacological investigations demonstrated that KSO operated by altering Ptgs2, Nos2, Ppara, Pparg and Serpine1 mRNA levels. All evidence shows that KSO has a hepatoprotective effect, and the mechanism is connected to the regulation of metabolic disorders and intestinal flora.

Characterization, Antioxidant Capacity, and Anti-Inflammatory Activity of Polyphenol-Enriched Extracts Obtained from Unripe, Mature, and Overripe Fruits of Red-Fleshed Kiwifruit Cultivars

Discarded unripe kiwifruits (DUKs) are regarded as the major agro-byproducts in the production of kiwifruits, which have abundantly valuable secondary metabolites. Nevertheless, owing to the limited knowledge about the differences in phytochemicals and bioactivity between DUKs and mature kiwifruits, the utilization of DUKs in the food industry remains scarce. Hence, to promote their food applications, the phenolic compounds and bioactivity of discarded unripe, mature, and overripe fruits from three red-fleshed kiwifruit cultivars were studied and compared. The results revealed that the levels of total phenolics, total flavonoids, and total procyanidins in kiwifruits varied significantly by maturity stage. In addition, our findings demonstrated that DUKs possessed much higher contents of valuable phenolic compounds (e.g., chlorogenic acid (CHA), neochlorogenic acid (NCHA), gallic acid (GA), protocatechuic acid (PA), procyanidin B1 (ProcB1), procyanidin B2 (ProcB2), procyanidin C1 (ProcC1), quercetin 3-O-glucoside (QueG), and quercetin 3-O-rhamnoside (QueR)) than mature and overripe kiwifruits. Furthermore, DUKs exerted much stronger in vitro antioxidant capacity, inhibitory effects on α-glucosidase, and anti-inflammatory activity than mature and overripe kiwifruits, which were mainly attributed to their higher contents of total polyphenols and individual phenolic components, such as GA, CHA, NCHA, PA, ProcB1, ProcB2, ProcC1, and QueR. Overall, these findings provide sufficient evidence for the development and utilization of DUKs in the food/functional food industry.

Hydrogen sulfide enhances kiwifruit resistance to soft rot by regulating jasmonic acid signaling pathway

As the third active gas signal molecule in plants, hydrogen sulfide (H2S) plays important roles in physiological metabolisms and biological process of fruits and vegetables during postharvest storage. In the present study, the effects of H2S on enhancing resistance against soft rot caused by Botryosphaeria dothidea and the involvement of jasmonic acid (JA) signaling pathway in kiwifruit during the storage were investigated. The results showed that 20 μL L-1 H2S fumigation restrained the disease incidence of B. dothidea-inoculated kiwifruit during storage, and delayed the decrease of firmness and the increase of soluble solids (SSC) content. H2S treatment increased the transcription levels of genes related to JA biosynthesis (AcLOX3, AcAOS, AcAOC2, and AcOPR) and signaling pathway (AcCOI1, AcJAZ5, AcMYC2, and AcERF1), as well as the JA accumulation. Meanwhile, H2S promoted the expression of defense-related genes (AcPPO, AcSOD, AcGLU, AcCHI, AcAPX, and AcCAT). Correlation analysis revealed that JA content was positively correlated with the expression levels of JA biosynthesis and defense-related genes. Overall, the results indicated that H2S could promote the increase of endogenous JA content and expression of defense-related genes by regulating the transcription levels of JA pathway-related genes, which contributed to the inhibition on the soft rot occurrence of kiwifruit.

Genome sequencing and CAZymes repertoire analysis of Diaporthe eres P3-1W causing postharvest fruit rot of 'Hongyang' kiwifruit in China

Postharvest rot caused by various fungal pathogens is a damaging disease affecting kiwifruit production and quality, resulting in significant annual economic losses. This study focused on isolating the strain P3-1W, identified as Diaporthe eres, as the causal agent of 'Hongyang' postharvest rot disease in China. The investigation highlighted cell wall degrading enzymes (CWDEs) as crucial pathogenic factors. Specially, the enzymatic activities of cellulase, β-galactosidase, polygalacturonase, and pectin methylesterases peaked significantly on the second day after infection of D. eres P3-1W. To gain a comprehensive understanding of these CWDEs, the genome of this strain was sequenced using PacBio and Illumina sequencing technologies. The analysis revealed that the genome of D. eres P3-1W spans 58,489,835 bp, with an N50 of 5,939,879 bp and a GC content of 50.7%. A total of 15,407 total protein-coding genes (PCGs) were predicted and functionally annotated. Notably, 857 carbohydrate-active enzymes (CAZymes) were identified in D. eres P3-1W, with 521 CWDEs consisting of 374 glycoside hydrolases (GHs), 108 carbohydrate esterase (CEs) and 91 polysaccharide lyases (PLs). Additionally, 221 auxiliary activities (AAs), 91 glycosyltransferases (GTs), and 108 carbohydrate binding modules (CBMs) were detected. These findings offer valuable insights into the CAZymes of D. eres P3-1W.

Impact of must clarification treatments on chemical and sensory profiles of kiwifruit wine

This study examined the effect of various clarification treatments on the physicochemical properties, volatile compounds, and sensory attributes of kiwi wines produced from five different kiwifruit (Actinidia deliciosa) varieties. The degree of clarification had a minimal impact on physicochemical parameters, including the content of residual sugar, ethanol, volatile acid, titratable acidity (except for the kiwifruit variety 'Qinmei'), and the pH value. However, wines made from unclarified juices (muddy juice and pulp) displayed a higher glycerol content than those made from clarified juices. The cluster heat map and principal component analyses (PCA) demonstrated that kiwi wines produced from clarified kiwi juices possessed a higher ester content, whereas muddy juice and pulp wines contained elevated levels of higher alcohols. Quantitative descriptive analysis (QDA) indicated that clarified juice wines outperformed muddy juice and pulp wines in terms of purity, typicality, harmony, intensity, and freshness, with negligible differences in terms of palate acidity. Moreover, the clarified juice wines featured more characteristic kiwi wine aromas (kiwifruit, passionfruit, and pineapple) compared with that of the muddy juice and pulp wines, which exhibited an increased grassy flavour. Although the 100-NTU kiwifruit juice-fermented wine did not show an advantage in the cluster heat map and PCA, it presented better freshness, typicality, and intensity in the QDA, as well as a more passionfruit aroma. Based on the orthogonal partial least-squares discriminant analysis, A. deliciosa 'Xuxiang' was deemed to be the most suitable variety for vinification. This study provides crucial insights for enhancing the production of high-quality kiwi wine.

Antioxidant properties and changes in vitro digestion of the fermented kiwifruit extract prepared by lactic acid bacteria and yeasts

The health benefits of fermented fruits have attracted consumers' attention. High levels of antioxidant ability in the fermented kiwifruit extract were found at the early stage of fermentation. The co-fermention with Lactobacillus paracasei LG0260 and Kluyveromyces marxianus J2853 showed the highest ABTS radical scavenging ability (ABTS⋅+-SA) and superoxide dismutase (SOD) activity. Also, the typical antioxidant components of SOD activity, vitamin C concentration and total phenol content were highly correlated with ABTS⋅+-SA. Obviously, polyphenols in the fermented kiwifruit extract evolved into monophenols during fermentation. Compared to undigested samples, the activity of ABTS⋅+-SA and reducing power capacity (RP-CA) after the final intestinal digestion decreased and ranged 387.44-531.89 VCμg/mL, 650.95-981.63 VCμg/mL, respectively (P < 0.05). Meanwhile, SOD activity on the 10th day of fermentation were still remained 222.82 U/mL, 206.98 U/mL and 217.23 U/mL, respectively. These results suggested that the fermented kiwifruit extract could exhibit antioxidant activity through tolerance to the digestive environment.

Efficient extraction of pectic polysaccharides from thinned unripe kiwifruits by deep eutectic solvent-based methods: Chemical structures and bioactivities

To promote the potentially industrial applications of thinned unripe kiwifruits, two deep eutectic solvent-based methods, including deep eutectic solvent-assisted extraction (DAE) and microwave-assisted deep eutectic solvent extraction (MDE), were optimized for the extraction of polysaccharides from thinned unripe kiwifruits (YKP). Results showed that the yields of YKP-D prepared by DAE and YKP-DM prepared by MDE were extremely higher than YKP-H prepared by hot water extraction. Furthermore, YKP-H, YKP-D, and YKP-DM were mainly composed of pectic polysaccharides, including homogalacturonan (HG) and rhamnogalacturonan I (RG I) domains. Besides, both YKP-D and YKP-DM exhibited stronger antioxidant, anti-glycosylation, and immunomodulatory effects than those of YKP-H, and their higher contents of uronic acids and bound polyphenols as well as lower molecular weights could partially contribute to their bioactivities. Overall, these results revealed that the developed MDE method could be utilized as a promising method for highly efficient extraction of YKP with superior beneficial effects.

A new source of starchy flour: Physicochemical and nutritional properties of starchy kiwifruit flour

The physicochemical and nutritional properties of three starchy kiwifruit flour (SKF) were systematically studied. The results revealed that the total starch content of SKF was 66.63-80.42%. SKF showed a B-type crystal structure with a grain size between 7.08 and 9.02 μm. In comparison to corn starch and potato starch, SKF possessed a lower pH (3.43-4.28), transparency (0.68-1.11%) and setback value (0.20-1.73 Pa·s) and a higher swelling power (9.42-15.02 g/g) and hot paste viscosity (1.73-2.10 Pa·s). Moreover, SFK was rich in protein and various mineral elements. It also contained high levels of total phenolics and exhibited a strong antioxidant capacity. The resistant starch content in SKF was as high as 67.19-73.22%, and the rapidly digestible starch content was remarkably lower than that of corn and potato starch. Overall, these unique physicochemical properties of SKF, coupled with its nutritional benefits, give it a good development potential in the food industry.

The genus Actinidia Lindl. (Actinidiaceae): A comprehensive review on its ethnobotany, phytochemistry, and pharmacological properties

ETHNOPHARMACOLOGICAL RELEVANCE

Actinidia Lindl. belongs to the family Actinidiaceae. Plants of this genus are popularly known as kiwifruits and are traditionally used to treat a wide range of ailments associated with digestive disorders, rheumatism, kidney problems, cardiovascular system, cancers, dyspepsia, hemorrhoids, and diabetes among others.

AIM

This review discusses the ethnobotanical uses, phytochemical profile, and known pharmacological properties of Actinidia plants, to understand their connotations and provide the scientific basis for future studies.

MATERIALS AND METHODS

The data were obtained by surveying journal articles, books, and dissertations using various search engines such as Google Scholar, PubMed, Science Direct, Springer Link, and Web of Science. The online databases; World Flora Online, Plants of the World Online, International Plant Names Index, and Global Biodiversity Information Facility were used to confirm the distribution and validate scientific names of Actinidia plants. The isolated metabolites from these species were illustrated using ChemBio Draw ultra-version 14.0 software.

RESULTS

Ten (10) species of Actinidia genus have been reported as significant sources of traditional medicines utilized to remedy diverse illnesses. Our findings revealed that a total of 873 secondary metabolites belonging to different classes such as terpenoids, phenolic compounds, alcohols, ketones, organic acids, esters, hydrocarbons, and steroids have been isolated from different species of Actinidia. These compounds were mainly related to the exhibited antioxidant, antimicrobial, anti-inflammatory, antidiabetic, antiproliferative, anti-angiogenic, anticinoceptive, anti-tumor, and anticancer activities.

CONCLUSION

This study assessed the information related to the ethnobotanical uses, phytochemical compounds, and pharmacological properties of Actinidia species, which indicate that they possess diverse bioactive metabolites with interesting bioactivities. Actinidia plants have great potential for applications in folklore medicines and pharmaceuticals due to their wide ethnomedicinal uses and biological activities. Traditional uses of several Actinidia species are supported by scientific evidences, qualifying them as possible modern remedies for various ailments. Nonetheless, the currently available data has several gaps in understanding the herbal utilization of most Actinidia species. Thus, further research into their toxicity, mechanisms of actions of the isolated bioactive metabolites, as well as scientific connotations between the traditional medicinal uses and pharmacological properties is required to unravel their efficacy in therapeutic potential for safe clinical application.

Understanding quality differences between kiwifruit varieties during softening

Research into variations between kiwifruit varieties particularly their softening quality during storage is important in improving kiwifruit quality. The potential reasons for ripening quality differences between 'Cuixiang' (CX) and 'Hayward' (HWD) kiwifruit were analyzed by physiology and metabolomic data combined with the random forests learning algorithm. The results showed that the storability difference between the two varieties mainly resulted from differences in polygalacturonase (PG) and β-galactosidase activities. The 1 °C slowed the fruit softening process of both varieties by decreasing their PG activities. A total of 368 metabolites were identified and amino acid, carbohydrate, cofactors and vitamins, as well as nucleotide metabolism are key metabolic modules that affect the ripening differences of CX and HWD kiwifruit. A total of 30 metabolites showed remarkable ability in distinguish the ripening quality of CX and HWD kiwifruit, in which d-glucose, d-maltose, 2-hydroxybutyric acid, phenyllactate, and vitamin B2 were noteworthy for their potential application on the evaluation of kiwifruit taste and nutritional value. These findings provide positive insights into the underlying mechanism of ripening quality differences between CX and HWD kiwifruit and new ideas for identifying key metabolic markers in kiwifruit.

Kiwifruit Resistance to Sclerotinia sclerotiorum and Pseudomonas syringae pv. actinidiae and Defence Induction by Acibenzolar-S-methyl and Methyl Jasmonate Are Cultivar Dependent

Pathogen susceptibility and defence gene inducibility were compared between the Actinidia arguta cultivar 'Hortgem Tahi' and the two cultivars of A. chinensis 'Hayward' and 'Zesy002'. Plants were treated with acibenzolar-s-methyl (ASM) or methyl jasmonate (MeJA) one week before inoculation with Pseudomonas syringae pv. actinidiae (Psa biovar3) or Sclerotinia sclerotiorum, or secondary induction with chitosan+glucan (Ch-Glu) as a potential pathogen proxy. Defence expression was evaluated by measuring the expression of 18 putative defence genes. 'Hortgem Tahi' was highly susceptible to sclerotinia and very resistant to Psa, whereas 'Zesy002' was highly resistant to both, and 'Hayward' was moderately susceptible to both. Gene expression in 'Hayward' and 'Zesy002' was alike but differed significantly from 'Hortgem Tahi' which had higher basal levels of PR1-i, PR5-i, JIH1, NPR3 and WRKY70 but lower expression of RD22 and PR2-i. Treatment with ASM caused upregulation of NIMIN2, PR1-i, WRKY70, DMR6 and PR5-i in all cultivars and induced resistance to Psa in 'Zesy002' and 'Hayward' but decreased resistance to sclerotinia in 'Zesy002'. MeJA application caused upregulation of LOX2 and downregulation of NIMIN2, DMR6 and PR2-i but did not affect disease susceptibility. The Ch-Glu inducer induced PR-gene families in each cultivar, highlighting its possible effectiveness as an alternative to actual pathogen inoculation. The significance of variations in fundamental and inducible gene expression among the cultivars is explored.

In vitro anticholinergic and antiglycaemic properties of frost-hardy Actinidia fruit extracts and their polyphenol profile, L-ascorbic acid content and antioxidant capacity

The aim of this study was to investigate the inhibitory effects of Actinidia arguta ('Weiki', 'Skarlet September Kiwi') and Actinidia kolomikta ('Lande') fruit extracts against advanced glycation end-products (AGEs) formation and acetylcholinesterase (AChE) activity. The extracts were also tested regarding polyphenol profile and Lascorbic acid content (UHPLC-DAD-MS), and antioxidant capacity (DPPH, ABTS). 'Scarlet September Kiwi' showed the strongest anti-AGEs activity studied with BSAGLU (IC50 = 2.68) and BSA-MGO (IC50 = 18.06) models. The highest anti-AChE activity was found for the 'Lande' extract (IC50 = 4.56). 'Lande' showed the highest L-ascorbic acid content (8271.96 µg/g dw), ABTS (312.42 µmol TE/g dw) and DPPH (282.01 µmol TE/g dw) values. 'Scarlet September Kiwi' revealed the highest individual phenolics concentration (2321.43 µg/g dw). The contents of (+)-catechin and L-ascorbic acid were significantly correlated with anti-AChE activity. This research sheds new light on the bioactivity of Actinidia arguta and Actinidia kolomikta fruit elucidating the role of (+)-catechin and L-ascorbic acid in prevention of Alzheimer's disease.

Antifungal and elicitor activities of p-hydroxybenzoic acid for the control of aflatoxigenic Aspergillus flavus in kiwifruit

Aspergillus flavus not only reduces kiwifruit production but also synthesizes carcinogenic aflatoxins, resulting in a relevant threat to human health. p-Hydroxybenzoic acid (pHBA) is one of the most abundant phenolics in kiwifruit. In this study, pHBA was found to reduce A. flavus mycelial growth by blocking the fungal mitotic exit network (MEN) and cytokinesis and to inhibit the biosynthesis of aflatoxins B1 and B2. The application of pHBA promoted the accumulation of endogenous pHBA and induced oxidative stress in A. flavus-infected kiwifruit, resulting in an increase in H2O2 content and catalase (CAT) and superoxide dismutase (SOD) activities. Preventive and curative treatments with 5 mM pHBA reduced A. flavus advancement by 46.1% and 68.0%, respectively. Collectively, the antifungal and elicitor properties of pHBA were examined for the first time, revealing new insights into the role of pHBA in the defense response of kiwifruit against A. flavus infection.

Antioxidant, Antiglaucoma, Anticholinergic, and Antidiabetic Effects of Kiwifruit (Actinidia deliciosa) Oil: Metabolite Profile Analysis Using LC-HR/MS, GC/MS and GC-FID

Determining the antioxidant abilities and enzyme inhibition profiles of medicinally important plants and their oils is of great importance for a healthy life and the treatment of some common global diseases. Kiwifruit (Actinidia deliciosa) oil was examined and researched using several bioanalytical methods comprehensively for the first time in this research to determine its antioxidant, antiglaucoma, antidiabetic and anti-Alzheimer's capabilities. Additionally, the kiwifruit oil inhibitory effects on acetylcholinesterase (AChE), carbonic anhydrase II (CA II), and α-amylase, which are linked to a number of metabolic illnesses, were established. Furthermore, LC-HRMS analysis was used to assess the phenolic content of kiwifruit oil. It came to light that kiwifruit oil contained 26 different phenolic compounds. According to the LC-HRMS findings, kiwifruit oil is abundant in apigenin (74.24 mg/L oil), epigallocatechin (12.89 mg/L oil), caryophyllene oxide (12.89 mg/L oil), and luteolin (5.49 mg/L oil). In addition, GC-MS and GC-FID studies were used to ascertain the quantity and chemical composition of the essential oils contained in kiwifruit oil. Squalene (53.04%), linoleoyl chloride (20.28%), linoleic acid (2.67%), and palmitic acid (1.54%) were the most abundant compounds in kiwifruit oil. For radical scavenging activities of kiwifruit oil, 1,1-diphenyl-2-picryl-hydrazil (DPPH•) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS•+) radicals scavenging techniques were examined. These methods effectively demonstrated the potent radical scavenging properties of kiwifruit oil (IC50: 48.55 μg/mL for DPPH•, and IC50: 77.00 μg/mL for ABTS•+ scavenging). Also, for reducing capabilities, iron (Fe3+), copper (Cu2+), and Fe3+-2,4,6-tri(2-pyridyl)-S-triazine (TPTZ) reducing abilities were studied. Moreover, kiwifruit oil showed a considerable inhibition effect towards hCA II (IC50: 505.83 μg/mL), AChE (IC50: 12.80 μg/mL), and α-amylase (IC50: 421.02 μg/mL). The results revealed that the use of kiwifruit oil in a pharmaceutical procedure has very important effects due to its antioxidant, anti-Alzheimer, antidiabetic, and antiglaucoma effects.

Comparative transcriptomic and plastid development analysis sheds light on the differential carotenoid accumulation in kiwifruit flesh

Carotenoids are colorful lipophilic isoprenoids synthesized in all photosynthetic organisms which play roles in plant growth and development and provide numerous health benefits in the human diet (precursor of Vitamin A). The commercially popular kiwifruits are golden yellow-fleshed (Actinidia chinensis) and green fleshed (A. deliciosa) cultivars which have a high carotenoid concentration. Understanding the molecular mechanisms controlling the synthesis and sequestration of carotenoids in Actinidia species is key to increasing nutritional value of this crop via breeding. In this study we analyzed fruit with varying flesh color from three Actinidia species; orange-fleshed A. valvata (OF), yellow-fleshed A. polygama (YF) and green-fleshed A. arguta (GF). Microscopic analysis revealed that carotenoids accumulated in a crystalline form in YF and OF chromoplasts, with the size of crystals being bigger in OF compared to YF, which also contained globular substructures in the chromoplast. Metabolic profiles were investigated using ultra-performance liquid chromatography (UPLC), which showed that β-carotene was the predominant carotenoid in the OF and YF species, while lutein was the dominant carotenoid in the GF species. Global changes in gene expression were studied between OF and GF (both tetraploid) species using RNA-sequencing which showed higher expression levels of upstream carotenoid biosynthesis-related genes such as DXS, PSY, GGPPS, PDS, ZISO, and ZDS in OF species compared to GF. However, low expression of downstream pathway genes was observed in both species. Pathway regulatory genes (OR and OR-L), plastid morphology related genes (FIBRILLIN), chlorophyll degradation genes (SGR, SGR-L, RCCR, and NYC1) were upregulated in OF species compared to GF. This suggests chlorophyll degradation (primarily in the initial ripening stages) is accompanied by increased carotenoid production and localization in orange flesh tissue, a contrast from green flesh tissue. These results suggest a coordinated change in the carotenoid pathway, as well as changes in plastid type, are responsible for an orange phenotype in certain kiwifruit species.

Characterization of Bioactivity of Selective Molecules in Fruit Wines by FTIR and NMR Spectroscopies, Fluorescence and Docking Calculations

Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H NMR) spectroscopies were applied to characterize and compare the chemical shifts in the polyphenols' regions of some fruit wines. The obtained results showed that FTIR spectra (1800-900 cm-1) and 1H NMR (δ 6.5-9.3 ppm) of different fruit wines can be used as main indices of the year of vintage and quality of fruit wines. In addition to the classical determination of antioxidant profiles and bioactive substances in wines, fluorometric measurements were used to determine the interactions of wine substances with the main human serum proteins. The results showed relatively high binding properties of wines with the highest one for pomegranate, followed by kiwifruit and persimmon wines. The interactions of vitamin C, catechin and gallic acid with human serum albumin (HSA) were also examined by docking studies. The docking calculations showed that gallic acid has a stronger binding affinity compared to catechin and vitamin C. The stronger binding affinity of gallic acid may be due to three hydrogen bonds and pi-pi interactions. The fluorescence and docking studies proved that only the bioactive compounds of wines and not the amount of alcohol have high binding properties to human serum proteins. The emphasis in this report was made on the utility of FTIR, NMR and fluorescence of wines as a mean of wine authentication and its fingerprint. The findings, based on polyphenols from fruits and fruit wines, their bioactivity and health properties, offer valuable insights for future endeavours focused on designing healthy food products.

Ultrasound-Assisted Deep Eutectic Solvent Extraction of Phenolic Compounds from Thinned Young Kiwifruits and Their Beneficial Effects

Fruit thinning is a common practice employed to enhance the quality and yield of kiwifruits during the growing period, and about 30-50% of unripe kiwifruits will be thinned and discarded. In fact, these unripe kiwifruits are rich in nutrients and bioactive compounds. Nevertheless, the applications of thinned young kiwifruits and related bioactive compounds in the food and functional food industry are still limited. Therefore, to promote the potential applications of thinned young kiwifruits as value-added health products, the extraction, characterization, and evaluation of beneficial effects of phenolic compounds from thinned young fruits of red-fleshed Actinidia chinensis cv 'HY' were examined in the present study. A green and efficient ultrasound-assisted deep eutectic solvent extraction (UADE) method for extracting phenolic compounds from thinned young kiwifruits was established. A maximum yield (105.37 ± 1.2 mg GAE/g DW) of total phenolics extracted from thinned young kiwifruits by UADE was obtained, which was significantly higher than those of conventional organic solvent extraction (CSE, about 14.51 ± 0.26 mg GAE/g DW) and ultrasound-assisted ethanol extraction (UAEE, about 43.85 ± 1.17 mg GAE/g DW). In addition, 29 compounds, e.g., gallic acid, chlorogenic acid, neochlorogenic acid, catechin, epicatechin, procyanidin B1, procyanidin B2, quercetin-3-rhamnoside, and quercetin-3-O-glucoside, were identified in the kiwifruit extract by UPLC-MS/MS. Furthermore, the contents of major phenolic compounds in different kiwifruit extracts prepared by conventional organic solvent extraction (EE), ultrasound-assisted ethanol extraction (UEE), and ultrasound-assisted deep eutectic solvent extraction (UDE) were compared by HPLC analysis. Results revealed that the content of major phenolics in UDE (about 15.067 mg/g DW) was significantly higher than that in EE (about 2.218 mg/g DW) and UEE (about 6.122 mg/g DW), suggesting that the UADE method was more efficient for extracting polyphenolics from thinned young kiwifruits. In addition, compared with EE and UEE, UDE exhibited much higher antioxidant and anti-inflammatory effects as well as inhibitory effects against α-glucosidase and pancreatic lipase, which were closely associated with its higher content of phenolic compounds. Collectively, the findings suggest that the UADE method can be applied as an efficient technique for the preparation of bioactive polyphenolics from thinned young kiwifruits, and the thinned young fruits of red-fleshed A. chinensis cv 'HY' have good potential to be developed and utilized as functional foods and nutraceuticals.

Changes in the Fruit Quality, Phenolic Compounds, and Antioxidant Potential of Red-Fleshed Kiwifruit during Postharvest Ripening

Kiwifruit is very popular for its unique flavor and nutritional value, and for its potential health benefits, which are closely related to its richness in a variety of natural antioxidant substances, in which polyphenolics play a non-negligible role. This study investigated changes in the fruit quality, phenolic compounds, and antioxidant potential of Chinese red-fleshed kiwifruit “Hongshi No. 2” during postharvest ripening at room temperature (20 ± 1 °C). Results showed that the weight loss rate slowly increased, the firmness rapidly decreased, and the soluble solid concentration gradually increased during the postharvest ripening of red-flesh kiwifruit. In addition, the total phenolic (TPC), total flavonoid (TFC), and total proanthocyanidin (TPAC) contents gradually increased during postharvest ripening. The most abundant phenolic compounds in kiwifruit throughout postharvest ripening were catechin (CC), proanthocyanidin B1 (PB1), and proanthocyanidin B2 (PB2). Furthermore, the methanolic extracts of red-flesh kiwifruit exhibited remarkable antioxidant activities throughout postharvest ripening stages. Indeed, some phenolic compounds showed good correlations with antioxidant activities; for instance, chlorogenic acid (CHL) showed a significantly positive correlation with ferric reducing antioxidant power (FRAP), and isoquercitrin (IS) showed a significantly negative correlation with DPPH free radical scavenging ability. The findings from this study are beneficial to better understanding the quality profile of red-flesh kiwifruit “Hongshi No. 2” during postharvest ripening.

Significant increases in Donghong kiwifruit yield by a novel umbrella-shaped trellis system and identification of associated molecular mechanisms

China is the largest kiwifruit producer in the world, accounting for more than half of the total. However, in terms of yield per unit area, China is much lower than the global average and lags behind that of other countries. Yield improvement is of critical importance for the current kiwifruit industry in China. In this study, an improved overhead pergolas trellis (OPT) system, namely, the umbrella-shaped trellis (UST) system, was developed for Donghong kiwifruit, which is now the second most popular and widely cultivated red-fleshed kiwifruit in China. Surprisingly, the estimated yield on the UST system was more than two times higher than that with a traditional OPT, while the external fruit quality was maintained and the internal fruit quality was improved. One of the mechanisms contributing to the yield improvement was the significant promotion of the vegetative growth of canes at 6 ~ 10 mm in diameter by the UST system. The upper canopy of the UST treatment served as a natural shading condition for the lower fruiting canopy and thus had positive effects on the accumulation of chlorophylls and total carotenoids in the fruiting canopy. The most productive zones on the fruiting canes (6 ~ 10 mm in diameter) contained significantly higher (P < 0.05) levels of zeatin riboside (ZR) and auxin (IAA) and ratios of ZR/gibberellin (GA), ZR/abscisic acid (ABA), and ABA/GA. A relatively high carbon/nitrogen ratio may promote the flower bud differentiation process of Donghong kiwifruit. The outcomes of this study provide a scientific basis for manifold increase in production of kiwifruit and contribute to the sustainability of the kiwifruit industry.

Genome-Wide Identification of Kiwifruit SGR Family Members and Functional Characterization of SGR2 Protein for Chlorophyll Degradation

The STAY-GREEN (SGR) proteins play an important role in chlorophyll (Chl) degradation and are closely related to plant photosynthesis. However, the availability of inadequate studies on SGR motivated us to conduct a comprehensive study on the identification and functional dissection of SGR superfamily members in kiwifruit. Here, we identified five SGR genes for each of the kiwifruit species [Actinidia chinensis (Ac) and Actinidia eriantha (Ae)]. The phylogenetic analysis showed that the kiwifruit SGR superfamily members were divided into two subfamilies the SGR subfamily and the SGRL subfamily. The results of transcriptome data and RT-qPCR showed that the expression of the kiwifruit SGRs was closely related to light and plant developmental stages (regulated by plant growth regulators), which were further supported by the presence of light and the plant hormone-responsive cis-regulatory element in the promoter region. The subcellular localization analysis of the AcSGR2 protein confirmed its localization in the chloroplast. The Fv/Fm, SPAD value, and Chl contents were decreased in overexpressed AcSGR2, but varied in different cultivars of A. chinensis. The sequence analysis showed significant differences within AcSGR2 proteins. Our findings provide valuable insights into the characteristics and evolutionary patterns of SGR genes in kiwifruit, and shall assist kiwifruit breeders to enhance cultivar development.

Comparative changes of health-promoting phytochemicals and sugar metabolism of two hardy kiwifruit (Actinidia arguta) cultivars during fruit development and maturity

Introduction

Hardy kiwifruit (Actinidia arguta) has an extensive range of nutritional and bioactive compounds and has been valued as a great resource for kiwifruit breeding. A better understanding of the dynamic changes of the composition and accumulation of nutritional compounds during fruit development and ripening is required before genetic or cultural improvements can be targeted.

Methods

In the present study, the phytochemical analysis of two A. arguta cultivars 'Yilv' and 'Lvmi-1' showed that they comprised different morphology, with a higher fruit diameter while a lower vertical fruit diameter of 'Lvmi-1' compared with 'Yilv'. The antioxidant capacity of both cultivars decreased during the maturity time and showed no significant difference between them. Furthermore, although glucose gradually increased during the maturity time, the predominant sugar composition was speculated to be fructose in 'Lvmi-1' fruit while sucrose in 'Yilv' fruit at the early fruit developmental stages. Moreover, the predominant acids in 'Yilv' and 'Lvmi-1' were citric acid followed by quinic acid, malic acid, and oxalic acid. The expression of sugar- and starch-related genes encoding the crucial enzymes suggested different changes in 'Yilv' and 'Lvmi-1'. Notably, a subsequent correlation analysis showed a significant positive correlation between sucrose phosphate synthase (SPS) expression and glucose in 'Yilv', fructokinase (FK) expression, and starch content in 'Lvmi-1', implying their vital roles in sugar and starch accumulation. By contrast, a significant negative correlation between FK expression and fructose in 'Lvmi-1' fruit was observed.

Results and Discussion

In summary, our results provide supplementary information for the dynamic changes of nutritional compounds and antioxidant capacity during hardy kiwifruit maturity time and give a clue for exploring the mechanism of sugar and starch accumulation in hardy kiwifruit.

The ITS analysis and identification of Actinidia eriantha and its related species

The dried plant material of medically important plant Actinidia eriantha especially when it remains in the form of powder often look morphologically similar to its related species. The lack of efficient methods to distinguish the authentic material from other similar species leads to chances of adulteration. The molecular authentication of herbal plant materials such as the internal transcribed spacer (ITS) sequences is considered as more reliable method compared to morphological traits. In this study, we aim to evaluate the potential of identification for roots of A. eriantha and its related species by ITS sequences. The lengths of ITS regions ranged from 624 to 636 bp with GC content ranging from 50.96% to 59.55%. A total of 194 variation sites and 46 haplotypes were formed in 185 samples. Among them, the roots of A. eriantha possessed specific sites at 85bp (C), 205bp (T), 493bp (C), 542bp (G), 574bp (C), 582bp (T) and 610bp (G), while A. hemsleyana, A. callosa, A. valvata and A. polygama have their own specific sites. The inter-specific genetic distance among 8 Actinidia species in the range 2.28% to 11.00%. The phylogenetic tree constructed with ITS, ITS1 and ITS2 region showed that the ITS sequences have higher potential for identification in 8 Actinidia species. However, as to A. eriantha, A. hemsleyana and A. valvata, these three barcodes have the same identification ability. The ITS regions indicated that different samples from same species can be grouped together, except for A. arguta and A. melanandrah. In conclusion, the ITS sequences can be used as an efficient DNA barcode for the identification of A. eriantha and its related species.

Insoluble and Soluble Dietary Fibers from Kiwifruit (Actinidia deliciosa) Modify Gut Microbiota to Alleviate High-Fat Diet and Streptozotocin-Induced TYPE 2 Diabetes in Rats

This study aims to examine the anti-diabetic properties of insoluble and soluble dietary fibers from kiwifruit (KIDF and KSDF) in rats with type 2 diabetes mellitus (T2DM) resulting from a high-fat diet (HFD) and streptozotocin (STZ). Both KIDF and KSDF treatments for four weeks remarkably decreased body weight and increased satiety. In addition, the blood glucose level and circulatory lipopolysaccharide (LPS) content were decreased, while the insulin resistance, inflammatory status, and lipid profiles improved. These anti-diabetic effects might be related to the regulation of gut microbiota and increased SCFA content. The key microbial communities of KIDF and KSDF were different. Furthermore, the KIDF treatment increased the level of total SCFAs and isobutyric acid, while KSDF increased the levels of total SCFAs and butyric acid. The association between critical species and SCFA and between SCFA and biochemical parameters indicated that the mechanisms of KIDF and KSDF on T2DM might be different.

Preparation, Shelf, and Eating Quality of Ready-to-Eat “Guichang” Kiwifruit: Regulation by Ethylene and 1-MCP

The acceptance of kiwifruit by consumers is significantly affected by its slow ripening and susceptibility to deterioration. Ready-to-eat “Guichang” kiwifruit and its preparation technology were studied by the regulation of ethylene and 1-MCP. Harvested kiwifruits were treated with 100–2000 μl L⁻¹ethylene for 36 h (20°C) and then treatment with 0–0.5 μl L⁻¹ 1-MCP. The results showed that the preservation effect of 0.5 μl L⁻¹ 1-MCP is inefficient when the soluble solid content of kiwifruit exceeded 15%. The ethylene-treated fruits reached an “edible window” after 24 h, but a higher concentration of ethylene would not further improve ripening efficiency, while the optimal ethylene concentration was 250 μl L⁻¹. Moreover, after 250 μl L⁻¹ ethylene treatment, 0.5 μl L⁻¹ 1-MCP would effectively prolong the “edible window” of fruits by approximately 19 days. The volatile component variety and ester content of 0.5 μl L⁻¹ 1-MCP-treated fruits were not different from those of the CK group. Principal component analysis and hierarchical cluster analysis indicated that the eating quality of fruits treated with 0.5 μl L⁻¹ 1-MCP was similar to that of fruits treated with ethylene. Consequently, ready-to-eat “Guichang” kiwifruit preparation includes ripening with 250 μl L⁻¹ (20°C, 36 h) ethylene without exceeding the 1-MCP threshold and then treated with 0.5 μl L⁻¹ 1-MCP (20°C, 24 h). This study highlights the first development of a facile and low-cost preparation technology for ready-to-eat “Guichang” kiwifruit, which could reduce the time for harvested kiwifruit to reach the “edible window” and prolong the “edible window” of edible kiwifruit.

Bioavailability of Macro- and Microelements in Rats Fed Hypercholesterolemic Diets Containing Actinidia arguta Fruits

The aim of this study was to estimate the influence of different cultivars of Actinidia arguta (kiwiberry) on the bioavailability of mineral elements and to examine the mineral profile of rats fed atherogenic diets enriched with kiwiberries. The following cultivars of Actinidia arguta were used: Bingo, M1, Anna, Weiki, Jumbo, and Geneva. Kiwiberry has recently become popular in the market. It is a precious source of biologically active components, vitamins, and minerals. The livers, spleens, and kidneys were examined for mineral contents using the flame atomic absorption spectroscopy method. The bioavailability of Ca, Mg, Fe, Mn, Zn, and Cu was evaluated. The addition of kiwiberries in atherogenic diets increased the contents of Fe in the rat liver. The bioavailability of Mn, Zn, and Cu, calculated on the basis of the contents in the livers, was significantly decreased in rats fed diets with 5% additional kiwiberries. We supposed that the effect of kiwiberry on the bioavailability of the studied minerals may be related to the diet components of bioactive substances present in fruits (polyphenols, vitamins, dietary fiber, and tannins).

Combination of calcium lactate impregnation with UV-C irradiation maintains quality and improves antioxidant capacity of fresh-cut kiwifruit slices

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Calcium lactate and shortwave ultraviolet combined treatment (abbr. CA-L + UV-C) has a synergistic effect on fresh-cut kiwifruits preservation.

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CA-L + UV-C reduced microbial growth.

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CA-L + UV-C increased phenolics accumulation by activating related enzyme activities.

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CA-L + UV-C improved antioxidant capacity by increasing antioxidant enzyme activity and promoting phenolics accumulation.

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CA-L + UV-C maintained quality by improving antioxidant capacity.

This study investigated the combined effects of calcium lactate (CA-L, 3 g L⁻¹) and shortwave ultraviolet (UV-C, 4.0 kJ m⁻²) irradiation on quality attributes and antioxidant defense capacity of fresh-cut kiwifruits at refrigerated storage for 7 d. The results indicated that CA-L and UV-C joint treatment, compared to either treatment alone, alleviated microbial load, showed higher quality on ascorbic acid (AsA), green color, total chlorophyll, flesh hardness, total sugar, total acid and malonaldehyde (MDA) content. Besides, it inhibited O2·- and •OH generation, induced H₂O₂ production, improved the activity of antioxidant enzymes (SOD, CAT and APX), activated critical enzymes (PAL, C4H and 4CL) in phenylpropanoid metabolism pathway and further enhanced total phenolic and proanthocyanidin content. Above results demonstrated that UV-C together with CA-L treatment could synergistically maintain overall quality and improve antioxidant capacity of kiwifruit slices. Therefore, the combination of CA-L and UV-C treatment showed a potential practical application in fresh-cut kiwifruits.

Characterizing Tetraploid Populations of Actinidia chinensis for Kiwifruit Genetic Improvement

Understanding genetic diversity and structure in natural populations and their suitable habitat response to environmental changes is critical for the protection and utilization of germplasm resources. We evaluated the genetic diversity and structure of 24 A. chinensis populations using simple sequence repeat (SSR) molecular markers. The potential suitable distribution of tetraploid A. chinensis estimated under the current climate and predicted for the future climate was generated with ecological niche modeling (ENM). The results indicated that the polyploid populations of A.chinensis have high levels of genetic diversity and that there are distinct eastern and western genetic clusters. The population structure of A. chinensis can be explained by an isolation-by-distance model. The results also revealed that potentially suitable areas of tetraploids will likely be gradually lost and the habitat will likely be increasingly fragmented in the future. This study provides an extensive overview of tetraploid A. chinensis across its distribution range, contributing to a better understanding of its germplasm resources. These results can also provide the scientific basis for the protection and sustainable utilization of kiwifruit wild resources.

Ultrasound-Assisted Extraction, Identification, and Quantification of Antioxidants from 'Jinfeng' Kiwifruit

Kiwifruit (Actinidia chinensis) is a nutrient-dense fruit abundant in vitamin C and phenolic compounds, and it exhibits strong antioxidant capacity. However, the antioxidants in 'Jinfeng' kiwifruit have seldom been extracted and analyzed, and the conditions for the extraction of kiwifruit antioxidants by ultrasound-assisted extraction (UAE) have seldom been investigated. In this study, response surface methodology (RSM) was used to optimize UAE conditions to extract antioxidants from 'Jinfeng' kiwifruit. In addition, the antioxidant capacity, contents of total phenolics and total flavonoids, ascorbic acid, and the profiles of antioxidants were also analyzed. The results showed that the optimal UAE conditions included 68% ethanol, liquid/solid ratio at 20 mL/g, extraction time at 30 min, extraction temperature at 42 °C, and ultrasonic power at 420 W. Under these conditions, the ABTS value of kiwifruit was 70.38 ± 1.38 μM TE/g DW, which was 18.5% higher than that of the extract obtained by conventional solvent extraction. The total phenolic and flavonoid contents were 15.50 ± 0.08 mg GAE/g DW and 5.10 ± 0.09 mg CE/g DW, respectively. Moreover, 20 compounds were tentatively identified by UPLC-MS/MS, and the content of main compounds, such as procyanidin B2, neochlorogenic acid, and epicatechin, were determined by HPLC-DAD. This research revealed the profiles of antioxidant phytochemicals in 'Jinfeng' kiwifruit, which can be a good dietary source of natural antioxidants with potential health functions.

Valorization of Kiwi Peels: Fractionation, Bioactives Analyses and Hypotheses on Complete Peels Recycle

Kiwi fruit samples (Actinidia deliciosa Planch, cv. Hayward) represent a suitable and good source for fibers obtainment as well as for polyphenolic and carotenoid extraction. With this aim, in this study they were submitted to a double phase extraction to separate insoluble fibers by an organic phase containing lipophilic substances and an hydroalcoholic phase containing polyphenols and soluble fibers. Insoluble fibers could be separated by filtration and sent to be micronized and reused. Hydroalcoholic fractions were then furtherly fractionated by solid-phase extraction. Data coming from the color CIEL*a*b* and the HPLC-DAD analyses of the extracts were compared and correlate with those coming from the SPME-GC/MS analysis of either the finely shredded peels or of the extracts. The obtained extracts were also submitted to anti-radical activity evaluation and anti-Candida activity. Results show that all of the obtained residues are value added products. Hypotheses were also made about the nature and the possible recycle of the obtained purified solid residue.

Sesquiterpenoids and Xanthones from the Kiwifruit-Associated Fungus Bipolaris sp. and Their Anti-Pathogenic Microorganism Activity

Nine previously undescribed sesquiterpenoids, bipolarisorokins A-I (1-9); two new xanthones, bipolarithones A and B (10 and 11); two novel sativene-xanthone adducts, bipolarithones C and D (12 and 13); as well as five known compounds (14-18) were characterized from the kiwifruit-associated fungus Bipolaris sp. Their structures were elucidated by extensive spectroscopic methods, electronic circular dichroism (ECD), 13C NMR calculations, DP4+ probability analyses, and single crystal X-ray diffractions. Many compounds exhibited anti-pathogenic microorganism activity against the bacterium Pseudomonas syringae pv. actinidiae and four pathogenic microorganisms.

Antifungal Activity and Biocontrol Mechanism of Fusicolla violacea J-1 against Soft Rot in Kiwifruit Caused by Alternaria alternata

Alternaria alternata is the main pathogenic species of various crops, including kiwifruit (Actinidia cinensis). In this study, an antagonistic fungus, J-1, with high antifungal activity against A. alternata was isolated from A. cinensis “Hongyang.” The strain J-1 was identified as Fusicolla violacea via morphological identification and DNA sequencing. This study aimed to evaluate the antifungal activity and potential mechanism of the strain J-1 against A. alternata. The strain J-1 exhibited antifungal activity against A. alternata, with an inhibition rate of 66.1% in vitro. Aseptic filtrate (AF) produced by the strain J-1 could suppress the mycelial growth and conidia germination of A. alternata at the inhibition rates of 66.8% and 80%, respectively, as well as suppress the spread of Alternaria rot in fresh kiwifruit. We observed that many clusters of spherical protrusions appeared at the mycelial tips of A. alternata after treatment with 200 mL L⁻¹ AF of J-1. Scanning electron microscopy analysis results showed that the mycelial structures were bent and/or malformed and the surfaces were rough and protuberant. Variations in temperature, pH, and storage time had little effect on the antifungal activity of the AF. Moreover, the AF could damage the integrity of cell membranes and cause intracellular content leakage. Meanwhile, the chitinase and β-1,3-glucanase enzyme activities increased significantly, indicating that the function of A. alternata cell wall was seriously injured. Eleven antimicrobial metabolites were identified by gas chromatography–mass spectrometry (GC–MS). The strain J-I and its AF exhibited well broad-spectrum antifungal activity against Diaporthe eres, Epicoccum sorghinum, Fusarium graminearum, Phomopsis sp., and Botryosphaeria dothidea, with inhibition rates ranging from 34.4% to 75.1% and 42.7% to 75.2%, respectively. Fusicolla violacea J-1 is a potential biocontrol agent against A. alternata and other fungal phytopathogens.