Scholarly article on topic 'Nutraceuticals in prevention of cataract – An evidence based approach'

Nutraceuticals in prevention of cataract – An evidence based approach Academic research paper on "Clinical medicine"

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{Cataract / Nutraceutical / Age / Antioxidant / Diabetes}

Abstract of research paper on Clinical medicine, author of scientific article — Amandeep Kaur, Vikas Gupta, Ajay Francis Christopher, Manzoor Ahmad Malik, Parveen Bansal

Abstract Cataract is a principal cause of blindness in the world and is characterized by clouding of eye’s natural lens. Surgery is the major therapeutic step taken to cure cataract; however, it is having its own limitations and complications such as iris prolapse, raised IOP, infection, cystoid macular edema and posterior capsular opacification (PCO). So world is looking toward more robust and natural ways to prevent cataract. One of the important factors that can play a role in prevention of any and many diseases is diet of the people. The inclusion of certain naturally occurring food and nutraceuticals is coming up as a best alternative for curing cataract because of their presumed safety, potential nutritional and therapeutic effects. Some nutraceuticals can act as an anticataract agent through some or the other molecular mechanism if consumed by normal population deliberately or inadvertently.

Academic research paper on topic "Nutraceuticals in prevention of cataract – An evidence based approach"

SJOPT 453 No. of Pages 8, Model NS

Saudi Journal of Ophthalmology (2016) xxx, xxx-xxx

20 21 22

Review article

Nutraceuticals in prevention of cataract — An evidence based approach

Amandeep Kaura; Vikas Guptaa; Ajay Francis Christophera; Manzoor Ahmad Malik b1; Parveen Bansala* Abstract

Cataract is a principal cause of blindness in the world and is characterized by clouding of eye's natural lens. Surgery is the major therapeutic step taken to cure cataract; however, it is having its own limitations and complications such as iris prolapse, raised IOP, infection, cystoid macular edema and posterior capsular opacification (PCO). So world is looking toward more robust and natural ways to prevent cataract. One of the important factors that can play a role in prevention of any and many diseases is diet of the people. The inclusion of certain naturally occurring food and nutraceuticals is coming up as a best alternative for curing cataract because of their presumed safety, potential nutritional and therapeutic effects. Some nutraceuticals can act as an anticataract agent through some or the other molecular mechanism if consumed by normal population deliberately or inadvertently.

Keywords: Cataract, Nutraceutical, Age, Antioxidant, Diabetes

© 2016 Production and hosting by Elsevier B.V. on behalf of Saudi Ophthalmological Society, King Saud University. This is an open

access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). 23 http://dx.doi.org/10.1016/jj.sjopt.2016.12.001

25 Introduction

26 Cataract is a principal cause of blindness in the world and

27 occurs due to the clouding of the eye's natural lens. The pro-

28 teins in the lens aggregate resulting in clouding of the lens

29 and formation of cataract. As the light cannot pass clearly

30 through the lens, there is some loss of vision. Since new cells

31 cover the outside of lens, the other cells are compacted into

32 the center of the lens resulting in the cataract. Cataract ulti-

33 mately results in the loss of vision in people over the age of

34 40 years. The most recent estimates from World Health

35 Organization (WHO) reveal that 47.8% of global blindness

36 is due to cataract. In India cataract is the principal cause of

37 blindness accounting for 62.6% cases of blindness and

38 77.5% cases of avoidable blindness.1 India is one of the signa-

tories in a program Vision 2020 for elimination of avoidable 39

blindness. It can occur due to aging, infection in newborn 40

babies, injury or poor development prior to birth or during 41

childhood, complications of various diseases and exposure 42

to toxic substances such as UV radiations, corticosteroids 43

and diuretics. 44

In the early stages of the disease, optimal refractive man- 45

agement and advice on glare reduction can lessen the impact 46

of cataract formation. Surgery is undertaken only in case 47

other measures are no longer adequate for the patient's 48

visual needs because of its known limitations. Significant 49

intraoperative complications of phacoemulsification in expe- 50

rienced hands are rare. Early postoperative complications 51

include iris prolapse, raised IOP and infection. Cystoid macu- 52

lar edema (CMO) and posterior capsular opacification (PCO) 53

are the most common late complications. So world is looking 54

Received 13 July 2015; received in revised form 2 November 2016; accepted 6 December 2016; available online xxxx. a University Centre of Excellence in Research, Baba Farid University of Health Sciences, Faridkot, Punjab, India

b Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar, Jammu and Kashmir 190011, India * Corresponding author.

e-mail addresses: maliksgpgi@gmail.com (M.A. Malik), bansal66@yahoo.com, aman11091991@gmail.com (P. Bansal).

1 Co-corresponding author at: Cancer Diagnostic Centre, Department of Immunology and Molecular Medicine, Sher-I-Kashmir Institute of Medical Sciences, Soura, Srinagar, Jammu and Kashmir 190011, India.

Peer review under responsibility of Saudi Ophthalmological Society, King Saud University

Production and hosting by Elsevier

Access this article online:

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A. Kaur et al.

toward more robust and natural ways to prevent cataract. One of the important factors that can play a role in prevention of any and many diseases is the diet of people.

The inclusion of certain naturally occurring food and nutraceuticals is coming up as a best alternative that reminds words of Hippocrates 2500 years ago ''Let thy food be medicine and medicine be thy food''. A nutraceutical is the opposite of ''junk food and according to the World Health Organization, over 80% of the world's population (4.3 billion people) rely upon such traditional plant-based systems of medicine as phytochemicals, nutritional constituents or as functional food.2 The term ''Nutraceutical'' was coined in 1979 by Stephen De Felice and is defined ''as a food or part of diet with medical or health benefits, including the prevention and treatment of disease''. Nutraceuticals may be isolated nutrients, dietary supplements, genetically engineered ''designer'' food, traditional herbal product and processed products such as cereals, soups, and beverages. Plant derived nutraceuticals/functional foods have received considerable attention because of their presumed safety, potential nutritional and therapeutic effects. This renewed interest in nutraceuticals reflects the fact that consumers are aware about epidemiological studies which indicate the role of a specific diet or component of the diet in association with a lower risk of certain diseases. This review is about the hypothesis behind the mechanism of action of various nutraceuticals in prevention of cataract. Authors have compiled a list of commonly used vegetables, fruits, nuts and grains that have a probable mechanism of action against cataract formation. This compilation is intended to provide information to scientists working in this particular field to create more evidences for the mechanism of action and to disseminate the idea of use of nutraceuticals for prevention of cataract.

the lens epithelium and inhibits membrane lipids as well as transporter proteins such as Na+K+ATPase ultimately leading to epithelial cell death and loss of lens transparency. Although individuals may have a genetic susceptibility to ROS, yet exposure to environmental factors such as smoking and UV exposure, the presence of certain diseases such as diabetes and the intake of systemic drugs are also important variables.

Pathogenesis of diabetic cataract

In diabetes, there is high concentration of glucose in the aqueous humor that is passively transported into the lens. The enzyme Aldose Reductase (AR) catalyzes the conversion of glucose to sorbitol through the polyol pathway and results in intracellular accumulation of sorbitol that further leads to osmotic changes resulting in degeneration of hydropic lens fibers and formation of cataract.6,7 In addition, the intracellular sorbitol cannot be removed through diffusion because of its polar character. The intracellular accumulation of sorbitol leads to a collapse and liquefaction of lens fibers that causes opacities in lens.6,8 Further studies have shown that osmotic stress in the lens caused by sorbitol accumulation9 induces apoptosis in Lens Epithelial Cells (LEC)10 leading to the development of cataract.11 Moreover, increased glucose levels in the aqueous humor may cause glycation of lens proteins, a process resulting in the generation of superoxide radicals (O2) and in the formation of Advanced Glycation End products (AGE).12 As the AGE interacts with cell surface receptors in the epithelium of the lens, there is generation of O2 and H2O2.

Prevention of cataract

Pathogenesis of age related cataract

An eye lens consists of crystallins, cytoskeletal and membrane proteins. Crystallins make up to 90% of lens proteins and have high refractive index. It exists in the cytoplasm of lens fibers in the form of complex protein solution. The majority of proteins are in a soluble phase, and this soluble form accounts for transparency. With increase in age a wide range of proteins leave the soluble phase and form high molecular weight aggregates. The primary mechanism that lies behind protein aggregation is posttranslational modification associated disulfide bond formation and non-enzymatic glycation. These changes occur in the nucleus that contains the long-lived proteins.3,4 Reactive oxygen species (ROS) such as peroxide, superoxide and hydroxyl radicals are causes of protein modification. Normally the healthy lens contains antioxidants such as glutathione, ascorbate and catalase that protect lens proteins against ROS. Glutathione is one of the most important antioxidants found in eye lens.5 Reduced glutathione (GSH) reacts with ROS and is converted to its oxidized form (GSSG). GSH is restored through the action of the enzyme glutathione reductase (GR). Hydrogen peroxide (H2O2) has been considered as the major oxidant in the pathogenesis of cataract. Normally, H2O2 is eliminated by GSH, or through the action of the enzymes glutathione peroxidase and catalase. However, with age there is decrease in activity of these protective mechanisms that result into elevation of H2O2 levels in the lens.3 This acts on

Cataract is a major global cause of blindness, and large section of the world's population cannot assess cataract surgery. It has been found that mechanisms related to glucose toxicity, namely oxidative stress, processes of non-enzymatic glycation and enhanced polyol pathway are significantly involved in the development of eye lens opacity. There is an urgent need for inexpensive, non-surgical approaches to prevent cataract. The following types of dietary phytochemicals could be implied to obtain the desired therapeutic action:

1. Antioxidants or ROS scavengers

2. Aldose Reductase inhibitors

3. Antiglycating agents

4. Inhibitors of Lens Epithelial Cell apoptosis. Antioxidants

Various classes of antioxidants that can be used to prevent cataract are flavonoids, carotenoids, ascorbic acid, tocopherol, caffeine, and pyruvate.

Flavonoids: Flavonoids are C6-C3-C6 compounds with fifteen carbon atoms. Flavonoids exert antioxidant effects due to their ability to scavenge free radicals, donate hydrogen as hydrogen donating compounds, and act as singlet oxygen quenchers and metal ion chelators. Examples of few flavonoids acting as antioxidants are myrcetin, quercetin, rham-netin, morin, diosmetin, naringenin, apigenin, catechin,

Nutraceuticals in prevention of cataract

kaempferol and flavones. These flavonoids can be obtained from fruits such as apple, grapes, bananas, cherries, and berries and from green leafy vegetables.

Vitamins: Vitamin C and vitamin E are the main sources of antioxidants. Corn oil and wheat germ oil are major sources of vitamin E, whereas vitamin C i.e. ascorbic acid is mainly found in amla and other citrus fruits.

Carotenoids: Carotenoids are a family of 700 compounds found in fruits, vegetables and green plants. Out of these 700 compounds, about 20 have been detected in human plasma and tissues. Lutein and zeaxanthin are two dietary carotenoids that are in the human eye lens. It has been reported that these two carotenoids can be beneficial in prevention of cataract. These compounds have the potential to filter harmful short wave blue light, to reduce H2O2 mediated damage of lens protein, lipid and DNA,13 to function as antioxidants and to stabilize membrane integrity. These biological functions are believed to play a crucial role in helping to reduce light-induced oxidative damage caused by ROS, which is major contributing factor in the pathogenesis of cataract.14 Table 1 depicts sources of lutein and zeaxanthin.

Aldose reductase inhibitors

The accumulation of polyol sorbitol in the lens results in the formation of diabetic cataract.19-21 The enzyme aldose reductase within the lens converts glucose to sorbitol and is responsible for the accumulation of sorbitol in eye lens. Hence Aldose Reductase inhibitors can be used as potential therapeutic agents to prevent the onset or progression of diabetic cataract.22-24 A large hydrophobic pocket forms the inhibitor-binding site of Aldose Reductase and acts as a target for pharmacophore.25 Inhibitor binding is therefore a repercussion of polar and non-polar interactions between the inhibitor and the complementary residues that match the enzyme-binding pocket. It has been proposed that the specificity for the inhibitor was mainly due to inhibitorenzyme interactions at the non-polar domain.26 There are some dietary phytochemicals, illustrated in Tables 2-5, that act as ARI (Aldose Reductase Inhibitors).

Antiglycating agents

The process of non-enzymatic glycation is one of the well-known mechanisms involved in diabetic cataract.43-47 With the age, there is accumulation of advanced glycation end products, which may contribute to lens opacity.48 So clinically used antiglycating agents are also reasonable option as anti-cataract agents. Some of these agents are given below:

Polyphenols: Polyphenols are the most abundant dietary antioxidants, which are common constituents of fruits, vegetables, cereals, seeds, nuts, chocolate and beverages such as coffee, tea, and wine. These dietary constituents have shown strong antiglycating activity. Based on their chemical structure, these are further classified as phenolic acids and flavonoids.

Phenolic acids: These are the most important non-vitamin antioxidant phytochemicals naturally present in almost all vegetables and fruits. Caffeic acid is a naturally occurring cin-namic acid (type of phenolic acid), found in various plants such as coffee, pear, basil, oregano and apple.49 Caffeic acid present in Ilex paraguariensis, Chrysanthemum morifolium and Chrysanthemum indicum has the ability to inhibit the formation of AGEs.50'51 Ferulic acid is another naturally occurring cinnamic acid reported in drinks and foods such as rice, wheat, and oats, some fruits and vegetables.52 It has been reported that ferulic acid being an antioxidant prevents AGE formation. It binds to the amino groups and inhibits the sugar autoxidation as well as early Maillard Reaction Products (MRP) degradation.53 However the exact mechanism of anti-glycation by ferulic acid needs to be investigated further. The leaves and stems of Erigeron annuus contain quinic acid derivative: 3,5-di-O-caffeoyl-epi-quinic acid, a potent inhibitor of AGEs formation and thus prevents opacification of eye lenses.54 The potent inhibitory effect of rosmarinic acid isolated from Salvia miltiorrhiza Bge has been reported against the formation of AGEs.55 Protocatechuic acid obtained from Rhus verniciflua extracts has been shown to inhibit aldose reductase and accumulation of AGEs.56 Various phenolic compounds such as gallic acid, p-coumaric acid (a typical cinnamic acid) and epicatechin (flavanol) from Cyperus rotundus, have been reported to show potent inhibitory activity on AGEs formation and protein oxidation.57

Flavonoids: A number of naturally occurring flavonoids show inhibitory effects on advanced glycation end product formation. Cuminum cyminum commonly known as Jeera, contains approximately 51.87% w/w flavonoids and acts as antiglycating agent. Quercetin, eriodictyol, 5,6,4'-trihy droxy-7,8,3'-trimethoxyflavone and cirsilineol isolated from the methanol extract of Thymus vulgaris have been reported to reduce the levels of advanced glycation end products under in vitro conditions.58 Chalcones are also considered as members of the flavonoid family.59 One of the chalcones named butein isolated from R. verniciflua has been reported to inhibit the formation of AGEs. Phloridzin, sieboldin and trilobatin are three dihydrochalcones found in Malus domestica. Out of these three dihydrochalcones, sieboldin is more potent antiglycating agent than others.60 Vaccinium vitis-idaea berry extract flavonoids (luteolin, quercetin, and rutin)

Table 1. Sources of lutein and zeaxanthin.15 18

Vegetables

Baked foods

Grains

Parsley

Spinach

Kale15

Green pepper1 Lettuce15 Carrot15 Red pepper15

Egg yolk1

High lutein bread16 High lutein cookie16 High lutein muffin16 Corn chips17 Corn tortilla17

Pistachio15

Corn18

Durum wheat18 Khorasan wheat1 Einkorn wheat18

A. Kaur et al.

Table 2. Dietary aldose reductase inhibitors from fruits.27'

S. no. Source Active constituent

1. Belamcanda Tectoridin, tectorigenin

chinensis (blackberry)

2. Myrciaria dubia Ellagic acid

(Rumberry)

3. Syzygium cumin Ellagic acid

(jamun)

4. Litchi chinensis Delphinidin 3-O-b-galactopyranoside-

(lychee) 3'-O-P-glucopyranoside

5. Citrus limon (lemon) Rutin

6. Citrus aurantium Rutin

(orange)

7. Psidium guajava Quercetin derivatives

(guava)

8. Malus pumila (apple) Quercetin, epicatechin, procyanidin

9. Vitis vinifera (grapes) Citronellol

Table 3. Dietray aldose reductase inhibitors from spices.32"

S. no. Source Active constituent

1. Curcuma longa (turmeric) Curcumin

2. Zingiber officinalis 2-(4-hydroxy-3-methoxyphenyl)

(Ginger) ethanol

3. Glycyrrhiza glabra Semilicoisoflavone B

(liquorice)

4. Ocimum sanctum (tulsi) Ursolic acid

5. Cinnamomum cassia Trans-cinnamaldehyde

(cinnamon)

6. Cuminum cyminum Cuminaldehyde

(cumin)

7. Foeniculum vulgare Trans-anethole

(fennel)

8. Piper nigrum (Black Piperine

pepper)

9. Allium sativum (garlic) Allicin

10 Coriandrum sativum Linalool, alpha-pinene

(coriander)

Table 4. Dietary Aldose reductase inhibitors from vegetables.30,38

S. no. Source Active constituent

1. Ganoderma lucidum (polypore Ganoderic acid

mushroom)

2. Spinaceae oleracea (spinach) Apigenin-7-

glucoside

3. Trigonella foenumgraceum 4-hydroxyleucine

(fenugreek)

4. Momordica charantia (bitter gourd) Momordin,

charantin

5. Murraya koenigii (Curry leaves) Mahanine, koenine

6. Allium sepa (onion) Alliin

266 have been shown as potent antiglycating agents.61,62 Both

267 the fluorescent and non-fluorescent AGEs formation is inhib-

268 ited by rutin and its metabolites.63 Besides this, the flavo-

269 noids such as engeletin and astilbin from extract of the

270 leaves of Stelechocarpus cauliflorus are potentially useful

271 for therapeutic prevention of diabetic complications resulting

272 from AGEs accumulation.64 It has been studied that compo-

Table 5. Dietary aldose reductase inhibitors from other sources.39"

S. no. Source Active constituent

1. Camellia sinensis (Tea Catechol

leaves)

2. Nelumbo nucifera Rutin, Quercetin

(lotus)

3. Oryza sativa (rice) Cyanidin-3-O-ß-glucoside, Peonidin-

3-O-ß-glucoside

4. Eleusine coracana Quercetin derivatives

(finger millet)

nents of green tea epigallocatechin (EGC), epicatechin (EC), 273

epigallocatechin-3-gallate (EGCG) and epicatechin-3-gallate 274

(ECG) decrease the accumulation of AGEs.65 275

Terpenes, carotenoids and polyunsaturated fatty acids: 276

A terpene 8 (17), 12-Labdadiene-15,16-dial (labdadiene) 277

and 5,6-dehydrokawain (DK) isolated from the rhizome of 278

Alpinia zerumbet, have the potential to inhibit glycation- 279

induced protein oxidation. Number of antioxidants such as 280

carotenoids, polyunsaturated fatty acids and polysaccharides 281

can be produced in microalgae.66 Strong antiglycating 282

capacities of lutein (carotenoid) present in Chlorella and lino- 283

leic acid, arachidonic acid, and eicosapentaenoic acid (unsat- 284

urated fatty acids) in Nitzschia laevis have also been 285

revealed.67 The green microalgae Chlorella zofingiensis con- 286

tains primary carotenoids such as lutein and p-carotene and 287

protects the cells from oxidative damage.68 The green 288

microalgae C. zofingiensis is considered as a natural source 289

of astaxanthin (a red ketocarotenoid) which is a potent 290

antioxidant and is the major carotenoid having role against 291

excessive oxidative damage.68 Astaxanthin has stronger 292

antioxidant activity than other carotenoids such as zeaxan- 293

thin, lutein, canthaxanthin and p-carotene and hundred times 294

stronger antioxidant than that of a-tocopherol.69 295

Polysaccharides: Longan pericarp fruit (Dimocarpus lon- 296

gan) contains polysaccharide that acts as free radical scav- 297

enger and competes with glucose for binding to free amino 298

group in proteins, and thus reduces the concentration of gly- 299

cation targets in proteins.70 Similarly, Ganoderma lucidum 300

polysaccharides have the ability to decrease lipid peroxida- 301

tion and blood glucose levels in diabetes.71 Polysaccharides 302

from pumpkin (Cucurbita moschata) have also shown antigly- 303

cating activity. 304

Other antiglycating agents 305

Citrate a natural dietary constituent found in citrus fruits73 306

when administered orally has the potential to delay the 307

development of cataracts and inhibit the accumulation of 308

AGEs in lens proteins. Fermentation by-products are also 309

capable to inhibit glycation.74 Recycled distilled residues of 310

rice and barley spirit along with their vinegars have shown 311

inhibitory effect on one of the major AGEs such as car- 312

boxymethyl lysine. Pyridoxamine as well as a-lipoic acid has 313

also shown inhibitory effect on formation of glycation end 314

products.75,76 315

Inhibitors of lens epithelial cell apoptosis: Apoptosis is a 316

physiological process of cell death that provides an impor- 317

tant molecular basis for both the initiation and progression 318

of cataracts.77,78 Depending upon the different apoptotic 319

stimuli, there are several mechanisms involved in apoptosis 320

Nutraceuticals in prevention of cataract

321 classified as intrinsic pathway and extrinsic pathway.

322 Mitochondria-dependent pathway is associated with lens

323 opacification. Certain stimuli such as radiations, drugs, toxins

324 and free radicals cause mitochondrial damage and dysfunc-

325 tion. All this results in the release of pro-apoptotic proteins

326 (including cytochrome c and SMAC) from the inner mitochon-

327 drial surface into cytosol,79 which contributes to pro-

328 grammed cell death. Oxidative stress has been recognized

329 as an important mediator of apoptosis in lens epithelial cells

330 and plays an important role in the pathogenesis of cataracts.

331 Epigallo catechin gallate (EGCG), the most abundant

332 component in green tea (Camellia sinensis), has potent

333 antioxidant activity. It has been shown that EGCG reduces

334 the H2O2-induced generation of reactive oxygen species

335 (ROS), and prevents the loss of mitochondrial membrane

336 potential (DWm), and the release of cytochrome c from the

337 mitochondria into the cytosol. Epigallocatechin gallate inhi-

338 bits the activities of caspase-9 and caspase-3 and thus pre-

Table 6. Dietary sources of resveratrol.87

S. no. Common name Scientific name

1. Grapes Vitis vinifera

2. White hellobore Veratrum grandiflorum

3. Peanut Arachis hypogea

4. Blueberry Vaccinium myritillus

5. Ko-jo-kon Polygonum cuspidatum

6. Mulberry Morus rubra

Table 7. Sources of coenzyme Q10 from various foods.98

Vegetables Fruits Oils Nuts

Spinach Apple Soya bean Peanuts

Chinese cabbag e Strawberry Olive Walnuts

Cauliflower Grapes Sunflower Almonds

Parsley Avocado Hazelnuts

Broccoli Orange Sea same seeds

vents intrinsic apoptosis.80 There are many other 339

polyphenols such as flavonoids, phenolic acids, phenolic alco- 340

hols, stilbenes and lignans which act as dietary antioxidants 341

and are thus effective in apoptosis inhibition. Polyphenols 342

are major constituents of fruits, vegetables, grains, roots, 343

chocolate, coffee, tea, and wine.81,82 344

Grape seed extract (GSE) is a dietary supplement that 345

acts as potent antioxidant and free radical scavenger by influ- 346

encing various signaling pathways and therefore beneficial in 347

preventing cataracts. GSE contains 70-95% standardized 348

proanthocyanidins (class of phenolic compounds). The seeds 349

of the grape are particularly rich source of proanthocyanidins. 350

NF-kB is transcription factor that regulates various genes 351

including apoptosis, cell adhesion, proliferation, inflamma- 352

tion, and cellular-stress response. In un-stimulated or normal 353

cells, NF-kB remains in the cytoplasm as an inactive complex 354

with inhibitor kappa B. Pathogenic stimuli like free radicals 355

activate NF-kB and causes its phosphorylation. After phos- 356

phorylation there is subsequent release of inhibitor kappa 357

B, resulting in translocation of NF-kB to the nucleus followed 358

by binding to DNA control elements that influence the tran- 359

scription of certain specific genes.83,84 ultimately resulting in 360

cell apoptosis. However, it has been shown that grape seed 361

extract reduces the generation of ROS induced by H2O2 as 362

well as translocation of NF-kB in lens epithelial cells ultimately 363

inhibiting apoptosis.85 364

Resveratrol (RES) is a naturally occurring polyphenol that 365

decreases production of ROS and increases protection 366

against oxidative stress. RES has been shown to suppress 367

apoptosis of lens epithelial cells and hence prevents cataract 368

formation.86 Table 6 cites some dietary sources of 369

resveratrol. 370

Coenzyme Q10 (ubiquinone) is a vitamin-like benzo- 371

quinone compound that acts as free radical scavenger.94 It 372

prevents light induced apoptosis in human lens epithelial 373

cells.95-97 Sources of coenzyme Q10 are mentioned in 374

Table 7. Common nutraceuticals used in market and their 375

common mechanism of actions are listed in Table 8 and Fig. 1 376

Table 8. Common nutraceuticals and their common mechanism of actions.

S. no. Dietary source Antioxidants Aldose reductase inhibitors Antiglycating agents Inhibitors

1. Lemon U U

2. Orange U U U U

3. Guava U U U

4. Grapes U ^U U U

5. Apple U U U U

6. Turmeric U U U

7. Ginger U U U

8. Liquorice U U U

9. Tulsi U U U

10. Fennel U U

11. Black pepper U U U

12. Garlic U U U

13. Coriander U U U

14. Onion U U U

15. Rice U U U

16. Wheat U U U

17. Green tea U U U U

18. Pumpkin U U

19. Oats U U

20. Black berries U U U

21. Mango U U U

22. Pomegranate U U

A. Kaur et al.

Figure 1. A diagrammatic representation of mechanism of action.

377 Conclusion

378 In the era of evidence-based medicine, it is pertinent to

379 find alternative ways of treating common ocular morbidities

380 such as cataract. This manuscript is about the scientific evi-

381 dences in favor of some nutraceuticals consumed by normal

382 population knowingly or inadvertently that act as anticataract

383 agent through some or the other molecular mechanism.

384 From meta-analysis of data in the literature, it can be con-

385 cluded that there is a plethora of commonly used nutraceuti-

386 cals that if consumed daily can prevent or revert changes

387 responsible for cataract pathogenesis. These nutraceuticals

388 play their role by adopting one or more of mechanisms singly

389 or simultaneously and work against development of cataract.

390 Most common mechanism followed by nutraceuticals seems

391 to be antioxidant activity and antiglycating activity.

Conflict of interest 392

The authors declared that there is no conflict of interest. 393

Acknowledgment 394

The authors fully acknowledge the support by university 395

authorities for preparation of this manuscript. 396

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Nutraceuticals in prevention of cataract

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