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Review Article
 

Evidence-Based Therapeutic Effects of Anthocyanins from Foods



Hock Eng Khoo, See Meng Lim and Azrina Azlan
 
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ABSTRACT

This review covers potential health benefits and efficacies of anthocyanins as well as anthocyanidins, in the prevention of several diseases. Blue, red and purple coloured fruits, vegetables and grains are rich in anthocyanins and have several health benefits, such as prevention of chronic diseases, antimicrobial, antioxidative and anti-inflammatory effects as well as improve vision and memory. Various in vitro and in vivo studies demonstrated the efficacy of anthocyanins in fruits and vegetables for the prevention of diseases and other health benefits. Most of the studies showed positive results towards the improvement of disease conditions. In short, anthocyanins and the anthocyanin-rich extracts are some of the best remedies used in prevention of several diseases, memory enhancement and behavioural improvement.

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  How to cite this article:

Hock Eng Khoo, See Meng Lim and Azrina Azlan, 2019. Evidence-Based Therapeutic Effects of Anthocyanins from Foods. Pakistan Journal of Nutrition, 18: 1-11.

DOI: 10.3923/pjn.2019.1.11

URL: https://scialert.net/abstract/?doi=pjn.2019.1.11
 
Received: June 29, 2018; Accepted: September 08, 2018; Published: December 15, 2018


Copyright: © 2019. This is an open access article distributed under the terms of the creative commons attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.

INTRODUCTION

Anthocyanins are the coloured pigments found in plant. These pigments are belonging to the phenolic group as they share the same basic flavonoid structure with a positively charged oxygen atom at the C-ring of the structure1. The flavylium ion of anthocyanin is stabled at acidic condition, whereas blue quinonoidal species is formed at increasing pH. Anthocyanin appears red while blue hue can be seen in basic solution2. The red hue of a plant comes mainly from the flavylium ion of anthocyanins. Among many types of anthocyanidin found in plants, cyanidin, delphinidin, malvidin, pelargonidin, peonidin and petunidin are the most common types of anthocyanidin detected in flowers, fruits and leaves1.

Anthocyanins play essential roles in plant physiology, in the food industry and human health. Numerous studies have been performed to investigate the health-promoting effects of anthocyanins against some diseases, using in vitro and in vivo models. Most of the studies only focused on certain types of diseases or the selected health benefits. Although, a review article reported the potential health benefits of anthocyanins from plants, the review did not cover antioxidant capacity, anticancer and antimicrobial effects of anthocyanins. Therefore, this review included the health benefits of anthocyanins reported in the literature, which covered the significant findings on antioxidative and antimicrobial effects, improving coronary heart disease, antiobesity and antidiabetes, anticancer activities, improving neurodegenerative disorders and increasing visual acuity. Table 1 summarises some of the recent studies on the protective effects of anthocyanins from natural products using either animal or human model.

ANTIOXIDATIVE EFFECT

Free radicals are highly reactive and the oxygen-containing molecule has one or more unpaired electrons. These free radicals generated in the body chemically interact with the electrons of the cell components such as deoxyribonucleic acid (DNA), protein or lipid in order to be stabilised3. The cumulative oxidative damage that triggered by the free radicals in the body can elicit various diseases including cancer, inflammation, diabetes, rheumatoid arthritis, heart and blood vessel disorders, cataracts and ageing4. In fact, an antioxidant is able to scavenge or reduce the effect of free radicals. It also allows other compounds to perform such functions and thus help to maintain a balance between the effect of free radicals and oxidative stress in the body5.

Anthocyanins are the phenolic compounds that exhibit antioxidative properties. Several studies demonstrated that anthocyanins-rich foods such as berries, blackcurrant and grapes exhibited great antioxidant properties (Table 1). The compounds are able to scavenge free radicals and cease the chain reaction that will cause oxidative damage6. The radical scavenging effect and antioxidative activity of anthocyanin, owing to the presence of hydroxyl group in position 3 of the C-ring of anthocyanin molecules as well as the hydroxyl groups in 3’, 4’ and 5’ positions of the B-ring7. However, the glycosylated form of anthocyanin decreases the ability of anthocyanin radicals to delocalise electrons. Thus the glycosylated anthocyanin reduces the radical scavenging activity in comparison to its aglycone.

A study reported that cyanidin-3-galactoside extracted from apple peel was more sensitive to hydrogen peroxide (H2O2), most active free radical and contributes more to H2O2scavenging compared with other phenolic compounds such as caffeic acid, chlorogenic acid, coumaric acid, ferulic acid, gallic acid, syringic acid and other phenolic compounds in the sample8.

Table 1:Antioxidative and cardioprotective effects of anthocyanins in foods
AA: Ascorbic acid, AI: Atherogenic index, ALT: Alanine transaminase, AST: Aspartate transaminase, CK-MB: Creatine kinase-MB, GPx: Glutathione peroxidase, GSH: Glutathione, HDL: High-density lipoprotein, LDH: Lactate dehydrogenase, LDL: Low-density lipoprotein, MDA: Malondialdehyde, SOD: Superoxide dismutase

Another study also demonstrated that anthocyanin-rich extract of red leaves of Elatostema rugosum had higher DPPH radical scavenging activity than the phenolic constituents extracted from green leaves of the plant9. Anthocyanins extracted from the red leaves of E. rugosum comprised of malvidin (44%), peonidin (23%), cyanidin (17%), petunidin (11%) and delphinidin (5%). The study also reported that these compounds were able to significantly increase superoxide dismutase and catalase activity in vitro compared with the phenolic constituents obtained from the green leaves. Therefore, these findings suggested that anthocyanins from plants contributed more to total antioxidant capacity from phenolic compounds.

Based on Trolox equivalent antioxidant capacity (TEAC) assay, the antioxidant capacity of 26 different types of sweet cherry cultivars, contained anthocyanins from 4.80-360.90 μg g–1 fresh weight (FW) ranged from 1.53-2.58 nmol Trolox equivalents (TE) mg–1 FW10. The homemade purple grape juice and concord grape juice were also reported to contain higher antioxidant activity with 4520 mg ascorbic acid (AA) mL1 and 4781 mg AA mL1,respectively, compared with only 2752 mg AA mL1 in red wine11. The processing method of wine compared to grape juice is different which may explain the discrepancy of the antioxidants activities between the red wine and grape juice. Maqui berry, an edible wild berry that grows in south-western Argentina as well as central and southern Chile, contains anthocyanins as the main polyphenolic compounds. The berry extract exhibited 28.18, 18.66, 25.22 g TE kg1 dry weight (DW) and 0.12 g ethylenediaminetetraacetic acid equivalent kg–1 DW,which measured using DPPH radical scavenging assay, ABTS radical cation scavenging activity assay, ferric reducing antioxidant power (FRAP) and ferrous ion-chelating ability assay, respectively12.

Some underutilised plants such as black carrots originate in Turkey and the Middle and the Far East which cultivated for at least 300 years are now getting more attention due to their high anthocyanin content18. Based on a previous study, the total antioxidant activity of black carrot juice was 23 and 48 μmol TE mL1, which assessed using FRAP and cupric ion reducing antioxidant capacity assays19 respectively. Canarium odontophyllum Miq. fruit, also called as dabai by the people of Sarawak, Malaysia, is a highly nutritious underutilised fruit with dark purple/black skin when ripe20. The fruit (skin and flesh), contained about 2.49 mg monomeric anthocyanin pigment g1 DW,was showed to have substantial antioxidant activities that determined by TEAC and FRAP assays21.

Red cabbage and red radish were also found to contain highly conjugated anthocyanins22, which may exhibit high antioxidant activity. Superoxide dismutase (SOD) and catalase are the enzymes that help break down potentially harmful oxygen molecules in cells, whereas the reduced glutathione (GSH) and ascorbic acid (AA) are important antioxidants in human body23. A previous study reported that supplementation of red cabbage extract that contains a high amount of anthocyanins prevented elevation of lipid peroxidation in the treated rats13. The extract had a total anthocyanins content of 50.21±3.45 mg 100 g1 leaf, where cyanidin-3-diglucoside-5-glucoside was the major anthocyanin found in the cabbage leaf24. A decreased in the SOD and catalase activities and the contents of reduced GSH and AA were also observed for the atherogenic-fed treated rats. The study also showed that the anthocyanin-rich extract helped in restoring the antioxidant status of the rats by acting as an antioxidative agent and as a free-radical scavenger. Similar results were also reported by Khoo et al.14 on defatted dabai peel extract which was showed to inhibit lipid peroxidation and to elevate SOD and glutathione peroxidase levels in the treated white rabbits.

CARDIOPROTECTIVE EFFECT

Cardiovascular diseases are complex diseases that thought to be caused by lifestyle factor. It is linked with numerous disorders involving the heart and blood vessels, which including cerebrovascular disease, congenital heart disease, coronary heart disease, deep vein thrombosis, peripheral artery disease, pulmonary embolism and rheumatic heart disease25. The beneficial effects of anthocyanins on cardiovascular disease are believed to be linked with their antioxidative stress ability. Several mechanisms have been proposed for anthocyanin isolates and anthocyanin-rich mixtures in relation to the protection from anti-inflammatory activity, DNA cleavage, enzyme inhibition, estrogenic activity, increased cytokine production, lipid peroxidation as well as decreased capillary permeability and fragility and membrane strengthening.

As shown in Table 1, several studies demonstrated the cardioprotective effect of anthocyanins. Anthocyanin-rich red cabbage extract is reported having hypocholesterolaemia, cardioprotective and hepatoprotective properties on atherogenic diet-induced oxidative stress and tissue injury in rats13. The red cabbage extract also increased the excretion of lipids through faeces in the rats. The supplementation of the defatted pulp of dabai also exhibited a positive hypocholesterolaemia with a significant reduction in totalcholesterol and low-density lipoprotein cholesterol levels as well as inhibited the formation of atheromatous plaque15. The cholesterol-lowering properties of the dabai sample could be due to the action of polyphenol compounds including cyanidin-3-glucoside as the main anthocyanin in the sample, especially in the fruit peel20.

Anthocyanins are not only being shown to exert benefits in animal models but also have similar beneficial effects in humans. A double-blind, randomised, placebo-controlled trial for 12 weeks in 120 dyslipidaemia patients aged 40-65 years has been performed previously. The result showed that the intake of berry-derived anthocyanin improved lipoprotein profile through cholesteryl ester transfer protein inhibition, an increased in high-density lipoprotein (HDL) cholesterol levels and a decreased in low-density lipoprotein (LDL) cholesterol levels16. A few mechanisms on the hypolipidaemic effects of anthocyanins are proposed as the compounds help in improving lipid haemostasis, enhancing energy expenditure, decreasing fat mass, stimulating favourable changes to lipid metabolism associated genes and deferring fat absorption and secretion of chylomicron26.

Consistent consumption of berries also been reported in the literature that has protective effects on cardiovascular disease through improving plasma lipid profile and endothelial function, increasing plasma total antioxidant activity and resistance to LDL oxidation. A study was done to investigate the benefits of eating 500 g of strawberries daily for a month among healthy subjects17. The study showed that strawberry consumption helped to improve the status of plasma antioxidant biomarkers and plasma lipids profile, increases antihaemolytic defences and platelet function in the subjects. A high intake of fruit-based anthocyanins associated with a 14% lower risk of non-fatal myocardial infarction in a prospective cohort study of well-characterised men with 24 years of follow-up27. A similar result obtained in a prospective cohort study of women aged 25-42 years with 18 years of follow-up showing that a higher intake of anthocyanins from foods was associated with a 32% reduction in myocardial infarction risk28.

ANTIMICROBIAL EFFECT

Antimicrobial activities of anthocyanin are not well-studied compared to its antioxidative effect. Anthocyanins protect against a wide range of microorganisms including preventing the growth of bacteria and other foodborne pathogens29. As reported in the literature, anthocyanins from berry extracts exhibited antimicrobial activity through different pathways, such as inducing damage to the cell wall, membrane and intercellular matrix30. Although, anthocyanins appear to have an antimicrobial effect, the inhibition activity is mainly due to the interaction of hydroxyl group of anthocyanin with sulfhydryl groups of the cell walls of the bacteria. This interaction might cause inactivation or loss of functioning of the cell wall or membrane of the bacteria.

Several studies reported that anthocyanin-rich berry extracts have antimicrobial effects. Berry extracts including blueberry, raspberry and strawberry as well as blackcurrant exhibited inhibitory activity on Gram-negative bacteria, however, no inhibition effect on Gram-positive bacteria31. Cranberry also had an antibacterial activity which was contributed by its bioactive components such as anthocyanins and flavonols32,33. The study also showed that cranberry extract had antibacterial effects towards Enterococcus faecium resistant to vancomycin, Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli.

On top of berries, pomegranate is also one of the anthocyanin-rich fruit. The juice of pomegranate is red in colour, which has high anthocyanins content. Pomegranate peel extract was also reported as having the highest antibacterial activity against Salmonella strains, followed by its seeds, juice and flower extracts4. Although, pomegranate peel contains anthocyanins, the antimicrobial activity could be due the phenolic compounds detected in the peel. Genskowsky et al.12 reported that maqui berry extracts had antibacterial activity, where the highest activities found for the Gram-negative and Gram-positive bacteria, Aeromonas hydrophila and Listeria innocua, respectively.

On the contrary, anthocyanin-containing dabai pulp extracts were not effective against both tested Gram-positive (Methicillin-susceptible Staphylococcus aureus and Methicillin-Resistant S. aureus) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria but had antifungal effect against Candida glabrata34. Cisowska et al.35 suggested that the antimicrobial activities of berries and other anthocyanin-containing fruits are due to the synergistic effect of a mixture of phytochemicals other than anthocyanin alone. The antimicrobial effects of anthocyanin-rich fruits could also be due to the several pathways and multiple mechanisms involving anthocyanins, weak organic acids and other phenolic compounds. Thus, anthocyanins are one of the contributors to antimicrobial effect and not solely due to anthocyanins in the fruit.

ANTIOBESITY AND ANTIDIABETIC EFFECTS

Obesity is a condition related to an excessive accumulation of fat tissue in the body that may give detrimental effects. It happens mostly due to the disproportion of energy intake and its expenditure. Theincrease in the prevalence of the common form of diabetes, such as type 2 diabetes, is closely linked to obesity, where about 90% of type 2 diabetes is attributable to a high body mass index36.

As shown in Table 2, eight types of berries and drupe (açai, bilberry, blackberry, blackcurrant, crowberry, lingonberry, prune and raspberry) have been determined for their ability to prevent obesity and metabolic abnormalities associated with type 2 diabetes in C57BL/6J mice. The results showed that after 13 weeks of high-fat diet (HFD) supplementation with 20% of bilberries, blackcurrants, lingonberries or raspberries, the rats received either one of the berry extracts gained lesser body weight and had lower fasting insulin levels than the control group37. Furthermore, the extracts of lingonberries, blackcurrants and bilberries reduced the percentage of body fat, decreased the accumulation of hepatic lipid and plasma levels of the inflammatory marker plasminogen activator inhibitor (PAI)-1 of the treated rats as well as improved glucose homeostasis. Similar results were obtained by another study which investigated the effect of black chokeberry on the development of obesity in mice fed a HFD38. The study showed that supplementation of black chokeberry decreased weight gain and increased adiponectin levels in the mice. Circulating adiponectin levels are inversely related to the body fat percentage, where the lower adiponectin level is considered a risk factor for type 2 diabetes39.

Anthocyanins are the main bioactive compounds in blueberry and mulberry. The major anthocyanins in blueberryare cyanidin-3-galactoside, delphinidin-3-galactoside and petunidin-3-arabinoside; whereas the predominant anthocyanins in mulberry are cyanidin-3-glucoside and cyanidin-3-rutinoside. Supplementation of either blueberry or mulberry juice containing these anthocyanins on C57BL/6 mice fed with a HFD for 12 weeks was studied by Wu et al.40. The study shows that blueberry and mulberry juices prevented body weight gain, decreased serum cholesterol and leptin secretion, reduced insulin resistance and inhibited the accumulation of fat in the adipose tissue. Leptin is a hormone produced by adipocytes and links with the homeostasis in body energy and fat stores43. Leptin helps to reduce triglycerides formation by enhancing oxidation of free fatty acid and reducing its esterification to triglyceride. Thus reduces insulin resistance and β-cell dysfunction that may lead to obesity and diabetes44.

Zhang et al.41 used diabetic male KK-Ay mice to study the antidiabetic effect of anthocyanins rich-bayberry fruit extract (200 mg kg–1). The extract significantly lowered the fasting blood glucose levels and improved glucose tolerance and insulin sensitivity in the mice. Serum lipids, inflammation and liver function markers were also significantly reduced. The mice treated with the bayberry fruit extract also have reduced liver weight and accumulation of liver lipid. The hypoglycaemic effect may be explained by the inhibition of hepatic gluconeogenesis, which manifested by reduced in PPARγ coactivator 1-alpha (PGC-1α) and phosphoenolpyruvate carboxykinase (PEPCK) mRNA expressions in the liver of KK-Ay mice. On the other hand,Guo and Ling45 summarised the potential mechanisms of antidiabetic effect of anthocyanins as: (1) suppressed body weight gain, (2) inhibited free radical production and lipid peroxidation, (3) regulated inflammatory response, (4) Reduced blood glucose and lipids levels and (5) improved insulin resistance.A complex interaction of multiple signalling pathways, transcription factors and enzymes might also involve in the protective effects of anthocyanins.

Table 2:Antiobesity and antidiabetic effects of anthocyanins in foods
HFD: High-fat diet, mRNA: Messenger RNA, PAI: Plasminogen activator inhibitor, PEPCK: Phosphoenolpyruvate carboxykinase, PPARGC1A: Peroxisome proliferator-activated receptor gamma coactivator 1-alpha

ANTICANCER EFFECT

Anthocyanins may exert their anticancer activity through a few different mechanisms. The anticancer effects of anthocyanins in foods are shown in Table 3. A recent review done by He and Giusti summarised the possible mechanisms of the anticancer activity of anthocyanins. The possible mechanisms are antimutagenic activity, inhibition of oxidative DNA damage and carcinogen activation, induction of phase II enzymes for detoxification, cell cycle arrest and inhibition of cyclooxygenase-2 enzymes as well as induction of apoptosis and antiangiogenesis6. Several signalling pathways of anticancer activity of anthocyanins have also been studied such as inhibiting Ras signalling, down-regulating the expressions of cyclin-dependent kinases, stopping ethanol-mediated p130Cas/c-Jun N-terminal kinase (JNK) interaction, increasing the Bax/Bcl-2 ratio and inducing signalling by p38/p53 and c-Jun46.

Extensive studies show that anthocyanins inhibited the development of various types of cancers using animal model. Hui et al.47 investigated the anticancer effect of the anthocyanin-rich extract from black rice on BALB/c nude mice bearing breast cancer cells (MDA-MB-453). The results showed that oral administration of the anthocyanin-rich extract (100 mg kg1day1) was significantly suppressed tumour growth and angiogenesis in the mice by suppressing the expression of angiogenesis factors matrix metalloproteinase (MMP)-2, MMP-9 and urokinase-type plasminogen activator (uPA) in tumour tissue. Moreover, the extract also helped to inhibit the vascular endothelial growth factor (VEGF) activated tumour-associated blood vesselsformation in the mice model. VEGF is a signal protein that produced by certain types of cells to stimulate vasculogenesis and angiogenesis. These cells are including macrophages, platelets and tumour cells. Inhibition of VEGF activity may help to suppress the tumour growth or tumour regression48.

Anthocyanins are the coloured pigments that have an anticancer effect on gastric cancer. The cyanidin-3-glucoside, an anthocyanin extracted from red-coloured Chinese bayberry fruit (Myrica rubra Sieb. et Zucc.) was used to investigate its antitumour effect on BALB/c nude mice tumour xenograft model46. The results showed that cyanidin-3-glucoside inhibited the tumour growth in a dose-dependent manner due to cell cycle inhibition rather than apoptosis induction. The cyanidin-3-glucoside was also up-regulated the Krüppel-like transcription factor (KLF)6 gene expression, a tumour suppressor gene and the downstream effector p21 in a p53-independent manner. Moreover, another study showed that anthocyanin-rich extract from roselle was found to inhibit the progression of N-nitrosomethylurea-induced leukaemia in rats by about 33% compared with the control group49. Other studies have shown that anthocyanins have beneficial effects on colon cancer50, oral cancer51, oesophageal cancer52, pancreatic cancer53, breast cancer54 and gastric cancer55.

IMPROVE COGNITIVE FUNCTION AND NEURODEGENERATIVE DISORDERS

Deterioration of cognitive performance and motor abilities with age maybe contributed by oxidative stress and neuroinflammation in the brain56. Inflammatory molecules such as cytokines, superoxide and nitric oxide can lead to multiple sclerosis and central nervous system degenerative disease57. The evidence of anthocyanins in foods on improving neurodegenerative disorder is shown in Table 4.

Consumption of high antioxidants and anti-inflammatory foods is believed to protect our body from deleterious effects such as oxidative stress and inflammation, thus reduce the risk of developing age-related diseases such as Alzheimer disease and Parkinson’s disease58. Pretreated HAPI rat microglial cells with tart cherry which the cyanidin is the most abundantanthocyanins showed a decrement in the levels of nitric oxide (NO), tumour necrosis factor-alpha (TNF-α) and cyclooxygenase-2 in a dose- and time-dependent manner compared with those without pretreatment56.

Table 3:Anticancer effects of anthocyanins in foods
BW: Body weight, KLF: Kruppel-like transcription factor, MMP: Matrix metalloproteinase, uPA: Urokinase-type plasminogen activator

Table 4:Anthocyanins in foods improve neurodegenerative disorder
ATPase: Adenosine triphosphatase, BW: Body weight, iNOS: Inducible nitric oxide synthase, p-NF-KB: Phospho-nuclear factor kappa-light-chain-enhancer of activated B cells, TNF-α: Tumour necrosis factor-α

The therapeutic efficacy of anthocyanins in cognitive deficits is associated with Alzheimer's disease and induced by scopolamine, which was reported by Gutierres et al.59. The study also found that with the treatment of 200 mg kg–1 anthocyanins was able to regulate cholinergic neurotransmission, to restore Na+, K+-ATPase and Ca2+-ATPase activities and to prevent memory deficits in rats induced by scopolamine. In fact, scopolamine is a potent and non-selective muscarinic receptor. It is able to induce memory deficits and to elevate brain oxidative status in animal models60.

A recent study reported the neuroprotective effect of anthocyanins extracted from Korean black soybean based on an artificial ageing model. The researchers used D-galactose to induce oxidative stress and inflammatory response which resulted in memory and synaptic dysfunction61. The study found that the anthocyanins treated rats had improved behavioural performance using Morris water maze and Y-maze tests. The study proved that anthocyanin neuroprotection against D-galactose-induced oxidative stress is one of the potential neuroprotective effects. Anthocyanins from the Korean black soybean also inhibited the activated astrocytes and neuroinflammation via suppression of various inflammatory markers including p-NF-KB, inducible nitric oxide synthase (iNOS) and TNF-α in the hippocampus and cortex regions of treated rats brain.

A 12-week randomised controlled trial was performed to investigate whether daily consumption of anthocyanin-rich cherry juice (200 mL) could change cognitive function in older adults with dementia42. The results showed that verbal fluency, short-term and long-term memories improved in the cherry juice groups. A reduction in blood pressure was also exhibited in the intervention group. It has been hypothesised that flavonoids help to improve cognitive function by increasing the number and strength of neuronal signals through the increased brain blood flow as well as the ability to initiate neurogenesis in areas of the brain associated with learning and memory62.

VISUAL ACUITY

The role of anthocyanins to vision is one of the first health benefits recognised to them63. The link between anthocyanins and vision improvements started in part from a body of research published between the 1960s and 1980s on the effects of bilberry on various vision parameters in the in vitro, in vivo and clinical interventions64. Some possible mechanisms of action of anthocyanins on the visual apparatus are the acceleration of re-synthesis of rhodopsin, improvement in microcirculation and modulation of retinal enzyme activity65.

Previous studies reported that anthocyanins in berries improved vision (Table 5). A rat retinal degeneration model, which induced by N-methyl-N-nitrosourea, was used to investigate the effect of cyanidin-3-glucoside from mulberry at 50 mg kg1. The study found that cyanidin-3-glucoside treatment helped to reduce photoreceptor damage and to improve scotopic visual functions in the rats66. Besides these findings, the maqui berry extract also suppressed ROS formation from lacrimal gland tissue and preserved tear secretion using the rat blink-suppressed dry eye model67. Thus, it suggested that maqui berry extract is a nutraceutical for dry eye by regulating tear secretion capacity in the lacrimal gland.

A prospective, randomised, double-blind, placebo-controlled study has been performed to investigate the effect of bilberry extract (480 mg day1) on eye fatigue induced by acute video display terminal (VDT) loads68. The study found that eight weeks of supplementation of bilberry extractalleviated the VDT load-induced reduction in critical flicker fusion. The treatment also helped in mitigating eye heaviness, ocular fatigue sensation, ocular pain, foreign body sensation and uncomfortable sensation in the subjects studied.

Table 5:Anthocyanins in foods improve vision
ROS: Reactive oxygen species

CONCLUSION

Anthocyanins are coloured pigments found in plants. These coloured pigments have therapeutic effects against inflammation, antimicrobial, several chronic diseases, visual and memory functions. Many studies have proven the efficacies of anthocyanins in the prevention of these diseases and improve general health. Although, most studies did not specify the type of anthocyanin used, these studies reported the efficacy of anthocyanin-rich extracts from fruits and vegetables. However, the efficacy of anthocyanins is not mainly due to the compounds themselves. The synergetic effect of anthocyanins and other phenolic compounds is essential for prevention of diseases as well as their antioxidative activities. In a nutshell, anthocyanins are the coloured pigments isolated from plants with therapeutic effects in the prevention of several diseases and health complications.

SIGNIFICANCE STATEMENT

This review reported on the potential health benefits of anthocyanins in the prevention of several diseases. These purple pigments from plants have antioxidative, cardioprotective, antimicrobial, anticancer and several metabolic diseases including antiobesity and antidiabetes potential. Anthocyanins also improve cognitive function and neurodegenerative disorder as well as visual acuity. These evidence-based reports are useful for the scientific community to further research on anthocyanin pigments and for the general public to fully utilise anthocyanins in the prevention of diseases.

ACKNOWLEDGMENT

All authors are very grateful to all those who helped in searching for information.

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