Aronia melanocarpa (Rosaceae), also called chokeberry, is the small berry native to North America that has a high economic value. The flesh is deep red with a bitter and astringent taste. Chokeberry fruit is a dark blue and round berry. Generally, chokeberries is used for processing into fruit jams, fruit wines, fruit juices, dried fruit, canned-foods and other products.
Plant polyphenols are known for their unique antioxidant and antiproliferative activities. But there is a great difference between the components and the content of polyphenols in different kinds of plants. Due to its rich content of polyphenols, berries can be a good source of natural antioxidants [1
]. In previous reports, it was confirmed that berry polyphenol substances can effectively remove free radicals from the body, reduce blood lipid levels and effectively regulate the body’s immune system, to maintain the normal function of the human body [4
Early results showed that the fruit of Aronia melanocarpa
(chokeberry) was rich in polyphenols. Reaching a total polyphenols content of 7.85 g/100 g (DW) [8
]. The fresh red flesh also shows a large proportion of polyphenols in fruit pomace, but the bitter and astringent taste, it makes it hard for a lot for people to accept, but it can be used as a good source of natural antioxidants, to effectively utilize the rich polyphenol content of Aronia melanocarpa
The study shows that the free radicals produced during the oxidation of the body are strongly oxidizing and can damage tissues and cells in the body, which can lead to chronic diseases and aging effects [11
]. Polyphenols, due to their redox properties, can be used as hydrogen donors, reductants, and singlet oxygen quenchers, thus playing a key anti-oxidation role [12
]. Hwang found that, because it contains a lot of polyphenols, flavonoids and procyanidins, chokeberry extract showed stronger antioxidant activity than blueberry extract, allowing the body to reduce the damage from active oxygen free radicals [13
]. In in vivo experiments, chokeberry extract also exhibited significant antioxidant activity in plasma and liver. Every 100 g of chokeberry fruit (dry weight) showed a DPPH free radical scavenging capacity of 279.38 μM Trolox equivalent. For ABTS free radical the scavenging capacity was 439.49 μM Trolox equivalent [8
]. A thorough comparison of the anthocyanin content of nine kinds of blackberry, three kinds of raspberry, nine kinds of black currant, four kinds of red currant and chokeberry show that anthocyanin content of chokeberry was significantly higher than that of the other berries. The reasons for the high antioxidant activity of the extract were confirmed by comparing the antioxidant capacity of chokeberry fruit in different forms. It was found that the antioxidant capacity of fruit residue was significantly higher than that of fruit and fruit juice, which had a great relationship with the distribution and content of polyphenol in different parts of the fruit [8
The hypolipidemic function of chokeberry has been widely praised in clinical research, and a study found that in rats fed a diet containing high levels of cholesterol, chokeberry juice can significantly hinder the increase of total cholesterol, low density lipoprotein and triglycerides in vivo, thus reducing the incidence of cardiovascular disease [6
]. In addition, Kim et al.’s research demonstrated that the mechanism of the chokeberry extract reduction of cholesterol content is independent of the expression of genes related to cholesterol metabolism in the liver [14
]. Due to the rich flavonoid content of the fruit, it can effectively inhibit pancreatic lipase, α-amylase and α-glucosidase so as to regulate the digestion and absorption of lipids and carbohydrates in the gastrointestinal tract, therefore chokeberry can be used as a raw material for functional foods, and the prevention of hyperglycemia and obesity, and the extract can be used for hyperglycemia and hyperlipemia treatment [15
Macroporous resins are an effective method for the purification of plant polyphenols. They can greatly improve the purity of plant extracts. In this study, the purification of polyphenols by different types of macroporous resin was screened and the optimal static and dynamic adsorption−desorption conditions were obtained by optimizing the parameters of the purification process. On this basis, we also compared the antioxidant and antiproliferative activities of three kinds of berries (chokeberry, blueberries, haskap berries) using ‘in vitro’ assays.
Chokeberry fruit is rich in polyphenols and the antioxidant activity of its extracted compounds is several times higher than for other berry extracts. Wojdylo et al. [8
], found that the total phenolic content of chokeberry fruit reached 7849.21 mg/100 g (dry weight), which is mainly composed of procyanidins, which account for 66% of the total phenol content. The anthocyanin content accounted for 25% of the total phenol content, and consists of four components, namely cyanidin 3-O
-arabinoside and 3-O
-xyloside, of which the 3-O
-galactoside id the main one. The content of chlorogenic and neochlorogenic acid accounts for 7.5% of the total phenol content, and the phenolic acid content in fruit juice is far greater than the phenolic acid content of fruit and fruit residue due to its good water solubility. Compared with the anthocyanins and the proanthocyanins, the flavonoid content is lower, at about 1.3% of the total phenolic content. Wojdylo et al. identified three types: quercetin 3-rutinoside, quercetin 3-galactoside and quercetin 3-glucoside, respectively. In addition, Slimestad et al. [16
] used 1D- and 2D-nuclear magnetic resonance experiments together with electrospray mass spectrometry analysis of chokeberry fruit and identified eriodictyol 7-O
-β-glucuronide, together with the rare flavonols quercetin 3-vicianoside, quercetin 3-robinobioside and other quercetin glycosides and they determined the flavonoids content of fresh chokeberry fruit. It was found that each 100 g of fruit contains > 71 mg of flavonoids. In addition, after comparison, it was found that the polyphenol content of chokeberry fruit pomace was higher than that of fruit and fruit juice.
The extraction process of chokeberry extract used in this study was the result of previous research at the authors’ laboratory. This extraction process can effectively extract polyphenols of chokeberry and an extract yield of 19.549 mg/g. In a study on antioxidant active substance extraction by Grunovaite et al. [9
], using different extraction solvents (acetone, ethanol, ethane, water and supercritical fluid extraction-CO2
), it was found that chokeberry fruit residue was a good source of antioxidants. The results show that the antioxidant components of chokeberry in more easily soluble in ethanol solution, which helps to extract antioxidant substances of chokeberry more thoroughly.
The purification process parameters of polyphenols from chokeberry in this study have been validated and put into production in the factory of Shenyang Huangguan Blueberry Biotechnology Co., Ltd. (Shenyang, China). At present, the purification of polyphenols from plants is mainly through macroporous resins. The types of macroporous resin mainly selected for purification of polyphenols are AB-8, D141, XAD-7 and X-5. Sun et al. [17
], selected X-5 resin by comparing eight kinds of macroporous resin and successfully purified polyphenols from apple using this resin. The concentration of polyphenols increased from 35.17% to 74.64%. Previous studies have found that the XAD-7 resin has a better effect on anthocyanins in purple potatoes and jamun [18
The hypolipidemic function of chokeberry has been widely highlighted in clinical research. Worsztynowicz et al., through determination of the activity of porcine pancreatic lipase and amylase experiments further found that chokeberry polyphenols can effectively inhibit the activity of pancreatic lipase and α-amylase [20
] but the different polyphenol components have very different degrees of inhibition of the various digestive enzymes. The main inhibition effect on pancreatic lipase and α-amylase, respectively, is due to the phenolic acids and anthocyanins in the chokeberry polyphenol composition. Through further experiments, it was found that cyanidin 3-O
-glucoside was the most effective inhibitor of pancreatic lipase (IC50
= 1.74 ± 0.04 mg/mL) and α-amylase was inhibited the strongest by chlorogenic acid (IC50
= 0.57 ± 0.16 mg/mL). In addition, cyanidin 3-O
-glucoside can also greatly inhibit the reactions catalyzed by pancreatic lipase (IC50
= 1.17 ± 0.05 mg/mL).
Using mice to test chokeberry polyphenolic compounds in vivo, it was found that chokeberry polyphenols have potential immunoregulatory and anti-inflammatory functions [21
]. The complement system is an important component of the innate immune system, and it includes a set of serum proteins and membrane receptors mainly involved in the dissolution of foreign cells, inflammation and phagocytosis process, and thus play a role in resistance to infection. It is found that the procyanidins C1, B5 and B2 and various aglycones of cyanidin have strong complement-fixing activities and the activity of the cyanidin 3-glucoside was stronger than that of the other anthocyanins. The excessive production of nitric oxide (NO) by macrophages could promote the development of rheumatoid arthritis, septic shock and other autoimmune disorders, so the inhibition of NO has potential therapeutic value for inflammatory diseases. Giang et al.’s research work found that the procyanidins C1, B5 and B2 and proanthocyanidin-rich fractions could show inhibitory activities on nitric oxide (NO) production in LPS-stimulated RAW 264.7 mouse macrophages.
Regarding the anti-inflammatory function, Martin found that chokeberry polyphenols could inhibit the spleen cells C57/BL6 of mice to produce IL-6 by LPS induction [22
]. IL-6 is associated with autoimmune diseases, such as multiple sclerosis, arthritis and enteritis. This further proves the positive anti-inflammatory role of chokeberry components.
Fibrinogen, also called coagulation factor I, accounts for 4% of the total human plasma protein. It mainly involved in the last stage of the blood coagulation cascade. However, the fibrinogen is especially sensitive to compounds like peroxynitrite with strong oxidative and nitrative ability [23
]. Reactions between fibrinogen and peroxynitrite will cause both structural modifications and changes of the biological properties of plasma glycoprotein [24
]. The study found that chokeberry extract (hydroxycinnamic acids, anthocyanins and flavanols ((+)-catechin, (−)-epicatechin and procyanidins) could obviously inhibit the nitration of fibrinogen and high molecular weight protein aggregates induced by the peroxynitrite. That black chokeberry extracts can effectively protect the plasma fibrinogen to avoid peroxynitrite-induced nitrative damage, and play a protective role in peroxynitrite-related cardiovascular diseases [25
In this study, the adsorption and desorption properties of six kinds of macroporous resins for chokeberry polyphenols were determined, and the purification processing parameters were optimised. XAD-7 macroporous resin was selected as the best purification material. The best purification parameters of static adsorption and desorption were pH of 4 for the sample solution for 4 h of adsorption, and desorption solvent was 95% ethanol (pH = 7.0) with 2 h of desorption; the best purification parameters of dynamic adsorption and desorption were 9.3 BV of sample loading amount at a feed flow rate of 2 BV/h, and washing the column with 5.8 BV of water, followed by subsequent elution with an eluent volume of 5.0 BV at flow rate for elution of 2 BV/h. Under the purification conditions, the purity of chokeberry polyphenols increased from 11.62% to 64.37%.
On the basis of the above, contrasting antioxidant and antiproliferative activities of three kinds of berry (chokeberry, blueberries, haskap berries) polyphenols by HepG2 human liver cancer cells, the results show that chokeberry polyphenols have a stronger antiproliferative activity than the other kinds of berry polyphenols. In vitro antioxidant analysis of chokeberry polyphenols on HepG2 cells showed high antioxidant activity, and the CAA value is 334.48 umol Q/100 ug, only slightly lower than that of blueberry polyphenols. Chokeberry fruit can therefore be considered a good source of natural antioxidants because of its polyphenol content.