Indian J Physiol Pharmacol 2000; 44 (2): 215-219

COMPARATIVE STUDY OF ANTIOXIDANT POTENTIAL OFTEA WITH AND WITHOUT ADDITIVES

SUNITA TEWARI,* VAN I GUPTA ANDSANDEEP BHATTACHARYA

Dep artmen.t of Physiology,K. G. Medical College,Lucknow - 226 003

( Received on August 10, 1999)

Abstract : Oxidative damage is one of the many mechanism leading tochronic diseases. Therefore interest is growing in the protection affordedby antioxidant nutrients against free radical reactions. More recently, theattention 'has shifted to polyphenols. Polyphenols are secondary plantmetabolites occurring widely in plant food. They possess outstandingantioxidant properties, suggesting a possible protective role in man. Tea(Camellia sinensis) is a widely consumed beverage throughout the worldcontaining polyphenols more than 35% of its dry weight.

In the present work we have investigated the effect of tea withoutmilk, tea with milk and lemon tea on the serum lipid peroxidation level(as a parameter of free radical generation). The results show that therewere significant decrease in serum lipid peroxidation (Malonaldehyde) levelhalf hour after ingestion of lemon tea and tea without milk which tendsto normalize with increase in time. This decrease is much significant incase of lemon tea than tea without milk after half hour or 'one hour.

Hence the interpretation is, tea without milk is a good source ofantioxidant and addition of lemon to tea increases its antioxidant potential.

Key words: tealipid peroxidation

INTRODUCTION

Free radicals react with almostevery known biological molecules in theirvicinity and damage protein, causesbreakdown of DNA strands and initiatesperoxidation of various molecules. Thehydroxyl radical is most reactive of all andmay be considered the ultimate damagingspecies whenever superoxide is formed. The

free radicals polyphenolsantioxidant potential

ever growing significance of antioxidantnutrients such as alpha tocopherol,beta carotene and ascorbic acid has come tolight (1).

A vast number of literature documentingthe in vitro antioxidant property ofpolyphenol is available. It acts both asprimary as well as secondary antioxidant,

*Corresponding Author

216 Tewari et al

by sequestration of metallic ion and byscavenging active oxygen species (2).However, the mechanism through whichthese compounds act in vivo are stillincompletely understood more so owing totheir bioavailability and metabolic fate inman. Although t ri vwo appreciableantioxidant action following gastricdigestion of condensed polyphenols havebeen reported (3), yet the possibility forinterference with this activity of polyphenolsby compound which are normal constituentsof human diet cannot be ruled out. Theantioxidant potential of polyphenols areclosely related to number of hydroxyl group,higher the number more potent the chainbreaking action of compound (4).

Tea leaves contain >35% of their dryweight as polyphenols whose nature differsdepending upon manufacturing procedure(5). Three main classes of commercial teahas been found -I a] green tea, a nonfermented type of tea rich in flavanols,flavandiols and simple phenolic acid. [b]black tea where fermentation is carried tooptimum extent and is rich in theaflavinsand thearubigens. [c] Oolong tea, a semifermented type having intermediatecharacteristics (4, 6).

During the process of fermentation thesimple polyphenols undergo enzymaticpolymerization resulting in formation ofcompound of condensation. The red color oftea and its astringent property is due tothese polyphenols-astringency is lessenedwhen we add milk due to formation ofcomplex with casein in milk (7, 8).

Indian J Physial Pharmacal 2000; 44(2)

Consequently the antioxidant potential ofmilk tea is much reduced. The present studyincorporates a complete profile of theantioxidant potential of tea without milk,tea with milk and lemon tea in normalhealthy individual.

METHODS

In the present work we have taken fourgroups of young healthy subjects. Controlgroup (taking 300 ml boiled water), teawithout milk group (taking 300 ml of teawithout milk), tea with milk (taking 300 mlof tea with milk) and lemon tea group(taking 300 ml of lemon tea). Samples wereobtained from different groups afterovernight fast, before intake of tea and 30,60, 90 & 120 minutes after intake of tea.Estimation of serum lipid peroxidation wasdone in terms of "Thiobarbituric acidreactants" using 1, 1, 3, 3, tetramethoxypropane (9). To 0.5 ml of serum was addedan equal volume of isotonic saline and to itwas added 2 ml of 50% Trichloroacetic acidin cold to precipitate the protein thencentrifuged at 500 x g for 10 min at 4°C.To 1ml of supernatant was added 2 ml of0.67% aqueous Thiobarbituric acid andmixture was heated in boiling water for15 minutes. The tubes were thenrapidly cooled by keeping in ice andvolume reconstituted to original of2 ml. Optical density was measured at535 nm.

RESULTS

Table I shows serum malonaldehydelevel in different groups before and after

Indian J Physiol Pharmacol 2000; 44(2) Comparative Study of Antioxidant Potential of Tea 217

TABLE I: Shows serum malonaldehyde level in different groups with timebefore and after intake of tea.

o min 30 min 60 min 90 min 120 min

Control group n=30 0.4580±0.0624 0.4650±0.0424 0.4156±0.0532 0.4156±0.0584 0.4248±0.0382(Group 1)

Tea with lemon n=30 0.4432±0.0612 0.2724±0.0058 0.0724±0.0038 0.1320±0.0458 0.4340±0.0328(Group II)

Tea without milk n=30 0.4352±0.0528 0.1520±0.0382 0.2988±O.0324 0.4156±0.0426 0.4212±0.0388(Group III)

Tea with milk n=30 0.4380±0.0386 0.4280±0.0428 0.4032±0.0512 0.3968±0.0823 0.3884±0.0462(Group IV)

TABLE II: Shows comparison .of serum malonaldehyde level with time.

Groups o min/30 min o min/60 min o min/90 min o min / 120 min

>0.1 >0.1 >0.1 >0.1NS NS NS NS

218 Tewari et al

mechanism and might therefore play animportant role in health protection.

In the present study, we have evaluatedthe in vivo anti oxidative potential of teaby measuring the plasma malonyl aldehyde(end product of lipid peroxidation) afteringestion of tea. We have found that afterhalf hour of ingestion of tea without milk,there was a significant decrease in plasmalipid peroxidation, which tends towardsoriginal value after one and half hour.After ingestion of lemon tea, there wasa much more decrease in plasma lipidperoxidatin after 30, 60 and 90 minuteswhich tends towards original value after twohours, but there was no significant changein lipid peroxidation level of plasma in casesin ingestion of tea with milk after half andone hour.

The mechanism and site of absorptionof polyphenols in human being and theirbiovailability in general have not beenevaluated. We can therefore only speculatethat modifications must have taken pl aceafter ingestion, in the molecular structureof black tea polyphenols. Green teapolyphenols have been known to influence.the formation of DNA strand breaks andlipid peroxidation products in culturedhuman lung cells. The promptness of theantioxidant response (30-60 minutes)suggest that these modifications and thesubsequent absorption of the modifiedpolyphenols must occur in the higher tractof the gastro intestinal system probablystarting from the stomach. The' condensedpolyphenol of black tea (theafl avins andthearubignes) are rapidly broken down inthe stomach by acid gastr-ic secretion similarto what happens when lemon" juice is added

Indian J Physiol Pharmacol 2000; 44(2)

into a cup of black tea. The simplerpolyphenols released by the gastrichydrolysis of the theaflavins andthearubigens would thus become availablefor absorption and for exerting theirantioxidant properties.

In vitro, milk protein combine withpolyphenols to form complex which retaintheir antioxidant potential. This complexwhen ingested becomes resistant to gastrichydrolysis. Thus it becomes unavailable forabsorption in-upper gastro intestinal tract.So in effect there is very little availableantioxidant property from this complex.

Another poss'ibl e interpretation is theinterference with the absorption in thestomach of simple phenolics due to thechange in gastric pH following theintroduction of milk. Simple phenolics areweak acid compounds and as such easilyabsorbable in their non ionized form (10).Even a small rise in gastric pH, such asthat induced by the milk added to tea, wouldincrease the phenols ionization, therebyreducing their passage through the gastricmucosa.

The interpretation of the present workis that polyphenols are bioactive dietarycompounds capable of raising plasma

'antioxidant defenses in men, black teawhich contains condensed polyphenols(theaflavins and thearubigens) have a goodantioxidant potential in vivo. Furthermoreaddition of lemon to tea increases its. .antioxidant potential by breaking condensedpolyphenols to simpler ones and byincreasing its absorption. Addition of milkto tea forms polyphenols milk protein

Indian J Physiol Pharmacol 2000; 44(2)

complex which increases ionization ofpolyphenols and thus lowers its absorptionthrough gastric mucosa.

To conclude, black tea without milk andlemon tea have good antioxidant potentialin vivo than tea with milk. Ingestionof black tea and lemon tea might tosome extent help in prevention of manychronic degenerative disease by increasing

Comparative Study of Antioxidant Potential of Tea 219

the antioxidant defence of body, so theingestion of black tea without milk andlemon tea are much more beneficial thantea with milk.

ACKNOWLEDGEMENT

We are thankful to Dr. S.M. Natu,Department of Chemical Pathology for hisassistance in biochemical analysis.

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