186 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTSpumpkins, the red color of tomatoes, and the green color of manyvegetables.There are two commonly acceptedclassesof carotenoids:(a) carotens,composed only carbonandhydrogen,and(b) oxycarotenoids, of composedof carbon,hydrogen,andoxygen.All of thesecompounds havean identicalbackbone structureandtheir chemicalandbiochemicalactivitiesarerelatedto their uniquestructure,consistingof an extendedsystemof conjugateddoublebonds.Although the color of fruits and vegetables important,the isprimary role of carotenoids natureis to protectfrom ultraviolet rays the inchlorophyll found in plant leaves. Carotenoidsalso help chlorophyll toabsorblight energy.In fact, they act like excellentantioxidantsby quenchingsinglet oxygen,reactiveoxygenspecies, ndthe free radicalsthat areby-productsof meta- abolic processes vegetableand humancells or environmentalpollutants. inHowever, the hydrophilic propertiesof oxycarotenoids,like lutein andzeaxantin,allow themto reactwith singletoxygengenerated the water inphasemore efficiently than nonpolar.Both carotenoidsandoxycarotenoidsseemcapableof preventingUV-inducedDNA damage, rotectingboththe phumaneyesand skin againstphotoaging.In this chapterwe try to review the distribution and potential protectiveactivity of carotenoidsand oxycarotenoidsin the human body and toexplorenew potentialstrategies explainthe causallink betweenoxidative tostressand skin aging.9.1 The Protective Role of CarotenoidsNutrition playsan importantrole in the treatment f many diseases, an o andappropriate selectionof nutrientscontributesto the preventionof disorderssuch ashyperlipidermia,hypertension, r vitamin deficiency[1,2]. Within othis context,carotenoidsare amongthe compoundsthat have attractedagreatdeal of attention.They are a classof linearall-trans (E) form C40 polyenesfound in plants,algae, and somebacteriaand fungi. The numberof naturally occurringcarotenoidsreportedcontinuesto rise and has now reachedabout 750(Fig. 9.1). Although animals and humans cannot biosynthesizethem
9: ANTIOXIDANT BENEFITS OF ORAL CAROTENOIDS,MORGANTI 187Figure 9.1 Structure of some common carotenoids in the human diet.de novo, carotenoids often present,sometimes high concentrations, are inin animal tissue.Animals obtainthesecompounds from diet or perhaps,n isome cases,from associated micro-organisms, ut they may modify the bstructure of the ingestedcarotenoidsto produce new metabolites.Chemically,typical carotenoidpigmentsare tetraterpenoids, consistingofeight 5-carbonisoprenoidunits.Carotenoids, esponsible the yellow color of corn, the orangecolor r forof pumpkins,and the red color of tomatoes,have the primary role toprotect the chlorophyll found in plant leaves.As is common knowl-edge,chlorophyll is the primary sourceof energygenerationin plants.However,you might not be awareof the fact that chlorophyll is suscep-tible to damagecausedby exposureto excessive amountsof light, par-ticularly ultravioletrays. Carotenoids, articularlylutein and zeaxanthin, pare presentin the chloroplaststo help protectthe chlorophyll from suchdamage.Additionally, carotenoidshelp chlorophyll to collect lightenergy.Moreover, it has been shown that thesepigmentsprotectphotosyntheticorganismsagainstpotentiallylethal photosensitization meansof endo- bygenousphotosyntheticpigments [5,6]. Therefore,carotenoidpigments
188 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTSFigure 9.2 Structure of the xanthophylls lutein and zeaxanthin.may havea protectiverole not only in plantsbut in humansas well. Thereare two known classes carotenoids: of • carotens, omposed only carbonand hydrogen,including, c of a-carotene,~ - c a r o t e n e , and lycopene • xanthophylls,composedof carbon, hydrogen,and oxygen, including lutein, zeaxanthin,and ~ - c r y p t o x a n t h i nBecause hundreds naturalcarotenoids the of containone of severalcentersor axes of chirality, they can also occur in various optical isomers.Suchconfigurationalchangesmay have a significanteffect on the physicalandbiochemicalpropertiesof the molecules.Hydrocarboncarotenoids,as incarotens,are apolarlipophylic moleculesand are not solublein waterbutare readily solublein organicsolventsand, to someextent,in fats and oils.The presence a hydroxy group, as in xanthophylls,gives the molecules ofsomepolarity, but such compoundsare still predominantlyhydrophobic(Fig. 9.2).9.2 BioavailabilityBecause their hydrophobicity,carotenoidsare not solublein the aque- ofous environmentof the gastrointestinal ract. They need to be dissolved! tcarriedin lipid + bile salt systemsto be absorbedat the enterocytebrushborder. It is importantto remember,in fact, that the uptakeof all carote-noids from diet is influencedby many variablessuch as: (a) the stateofthe food (raw, cooked,and/orprocessed); b) the presence ( and efficiencyof digestive enzymesand other endogenousdigestives; and (c) thecompositionof a meal (presenceof fibers, fat, and its physical form).
9: ANTIOXIDANT BENEFITS OF ORAL CAROTENOIDS,MORGANTI 189Moreover,the location and the physicalform of all the carotenoids(inadditionto age,gender,smokingstatus,and alcohol composition)influ-encetheir bioavailability andtheir consequent absorption.T hus,absorp-tion of carotenoids and xanthophyllsis enhanced their transferto the bylipid phaseduring cooking in the presence oil and by disruption of ofthe cellular matrix during mastication[7,8]. Absorbedby the mucusofthe small intestine, they are transportedthrough the enterocyteandhepatocyte, and incorporated into chylomicrons. Finally, they arereleasedinto the systemiccirculation carriedby high- and low-densitylipoproteins. It was recently shown that the bioavailability of purifiedlutein diet supplements nearlydoublethat of lutein takenby vegetable isources[9-1 I].9.3 Biological ActivitiesThe chemicalandbiochemicalactivities of carotenoids arerelatedto theirunique structure,consistingof an extendedsystemof conjugateddoublebonds.A numberof biological effects thereforehave been attributedtocarotenoids,ncluding antioxidantactivity,influenceon theimmunesystem, icontrol of cell growth and differentiation, and stimulatoryeffects on gapjunctional communications. owever,recent attemptsat dietary manipu- Hlation appearto be promising in terms of providing protection againstcertain solar-inducedeffects presentin photoagedskin. Carotenoidsarepowerful singlet-oxygenquenchers andexhibit additional antioxidantpro-perties.In fact, their conjugatedpolyenebackbone hasthe ability to delo-calize a charge or an unpaired electron . These physical chemicalpropertiesconferthe ability to act asan antioxidantand to terminatefreeradical reactionsin vitro with the productionof resonance-stabilized freeradical structures.Termination may be a result of (a) adduct formation,wherethe free radicaljoins onto the polyenechainto producea lessreac-tive free radical; (b) electrontransferfrom the carotenoidto the free radi-cal to producea less reactivechargedcarotenoidradical; or (c) donationof a hydrogenmoleculeto the free radical to producea stablecarotenoidradical . However, oxygen speciesthat are efficiently scavenged bycarotenoidsare 102 and peroxyl radicals,and physical quenchingseemsto be the major pathwayinvolved in the deactivationof 102.Moreover, it has been shown that a combination of carotenoidsplusvitamins E and C are more effective than ~ - c a r o t e n e alone [14-16] andmay increasesuperficial skin lipids (Fig. 9.3), skin hydration (Fig. 9.4),
190 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTSFigure 9.3 Percent increase in superficial skin lipids after dietarysupplementation with carotenoids or carotenoids plus other antioxidants.Figure 9.4 Percent increase in skin hydration after dietarysupplementation with carotenoids or carotenoids plus other antioxidants.
9: ANTIOXIDANT BENEFITS OF ORAL CAROTENOIDS,MORGANTI 191Figure 9.5 Percent increase in skin pigmentation after dietarysupplementation with carotenoids or carotenoids plus otherantioxidants.and skin pigmentationof dryness-prone skin (Fig. 9.5), also decreasingoxidative stressat the level of blood serum (Fig. 9.6). Thesemixtures,infact, are able to inhibit the formation of thiobarbituricacid reactivecom-poundsmoreeffectively than single components when they areusedat thesamemolar level. Such a synergisticantioxidanteffect seemsto be morepronouncedwhen either lycopeneor lutein are presentin the mixture.Thesedata indicatethat doselevels of carotenoids may be importantandmay have differential effects as well. The higher protectionprovided bymixturesmay be relatedto the specific positioningof differentcarotenoidsin the cell membrane (Fig. 9.7).9.4 Carotenoids and Skin AgingSkin aging is a complex biological processthat is influenced by bothintrinsic and extrinsic factors that lead to a progressiveloss of the skinsflexibility and youthful appearance.Natural aging is acceleratedbyenvironmentalfactors and by sun exposurein particular. Macroscopic
192 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTSFigure 9.6 Oxidative stress level in blood serum after dietarysupplementation with carotenoids or carotenoids plus other antioxidants.Figure 9.7 Schematic representation of the positioning of carotenoids inthe cell membrane.changes(skin wrinkling, rough skin texture,and irregular pigmentation)andmicroscopicchanges(degradation extracellularmatrix molecules ofand DNA damage)are the hallmark of photoagingattributed to bothUVB and UVA rays [17,18]. All of theseprocesses involved in the are
9: ANTIOXIDANT BENEFITSOFORAL CAROTENOIDS,MORGANTI 193initiation andprogression skin cancers. hereis alsoevidenceindicating of TthatprolongedUV exposure depletesthe serumandskin of both carotenoidsand xanthophy [19-21]. lisThe protectiveeffectsare thoughtto be relatedto the antioxidantproper-ties of carotenoids. uring ultraviolet (UV) irradiation,skin is exposedto Dphoto-oxidativedamageinducedby the formation of reactiveoxygenandnitrogen species(ROS and RNS). This damageaffects cellular lipids,proteins,and DNA, and is considered be involved in the formation of toerythema,prematureaging of the skin, photodermatoses, skin cancer. andCarotenoids efficient scavengers f ROS and RNS . are oWhatis importantto underlineis the necessity control the baselinecaro- totenoidconcentration healthysubjectsparticipatingin a diet supplement instudy. In fact, carotenoiddepletionstudiesmay provide a clearpicture ofwhetherand when they are importantantioxidants.This is because almostall the conflicting information on the antioxidantactivity of carotenoidshas been obtainedby administeringcarotenoidsupplementsto alreadywell-fed individuals. Our double-blindplacebo-controlled trial involvingthe useof lutein/zeaxanthin takenorally and at the sametime appliedtopi-cally hasyieldedinterestingresultson differentcontrolledparameters such as skin hydration (Fig. 9.8), superficial skin lipids (Fig. 9.9), skinelasticity (Fig. 9.10), and lipid peroxidation(Fig. 9.11). Test subjectsfol-lowed a 6-day rotationalbalancedMediterranean diet containingno morethan0.5 mg. of ~ - c a r o t e n e / d a y . As a consequence, 15daysbeforestarting,the level of ~ - c a r o t e n e in the bloodserumwasmedially0.35 ± 0.6IlmoIlL,whereas during the supplementationperiod plasma levels increasedmedially to 2.3 ± 1.7 umol/L.What were the unexpectedresults?Xanthophylls and carotensseem tohave not only an interesting moisturizing activity but also a combinedmetabolicroute, and the two influenceeachother.Thus, playing a specificrole asa photoprotective agentthanksto its ability to screenout damagingblue and UV light from the sun, lutein/zeaxanthinhas four primaryfunctions: I. to quenchthe triplet stateof photosensitizer oleculesand m the singletstateof molecularoxygen 2. to act asan antioxidantagainstoxygenand nitrogenreactive species
194 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTSFigure 9.8 Percent increase in skin hydration after treatment with topicallutein, oral lutein, or oral + topical lutein.Figure 9.9 Percent increase in superficial skin lipids after treatment withtopical lutein, oral lutein, or oral + topical lutein.
9: ANTIOXIDANT BENEFITS OF ORAL CAROTENOIDS, MORGANTI 195Figure 9.10 Change in skin elasticity (relative elastic retraction) aftertreatment with topical lutein, oral lutein, or oral + topical lutein.Figure 9.11 Change in skin lipid peroxidation after treatment with topicallutein, oral lutein, or oral + topical lutein.
196 PROTECTYOUR SKIN WITH NATURAL ANTIOXIDANTS 3. to absorbblue wavelengthlight, which is currentlyconsidered muchmore detrimentalthan UV rays 4. to maintainthe moistureactivity at the level of the human horny layerslipid lamellaeIt thereforeappearsthat thesexanthophyllsplayaspecific role as photo-protectiveagentscapableof reducinginflammatoryROS-mediates, modu-lating skin hydration,decreasing skin aging, and, therefore,improving thequality of our life.9.5 Concluding RemarksThe large group of plant carotenoidspresentin the Mediterraneandietattracts major interest becauseof their potential antiaging and otherbeneficialproperties,presumablybasedon their function as natural anti-oxidants. Carotenoidsare compoundsof particular interest becauseoftheir extensiveuse in dietary supplements. heir regular, long-termcon- Tsumptionmay improveantioxidantdefencein vivo and thus help to lowerrisks associatedwith diseases caused oxidativedamage. byHowever, more information on the photoagingactivity of these naturalcompoundsis neededin order to understand how they act on the varioustarget tissues. Systematic pharmacokineticand dose-response studiesare required to determinethe different bioavailability of the individualcarotenoidsand xanthophills, and to estimatethe amountsin diet thatare likely to induce biological effects. Finally, more long-term carote-noid depletion chemical trials with well-characterized diet supplementsare necessaryin order to confirm their beneficial antiaging effects inhumans.References 1. HaslerClvl. (1998) Functionalfood: their role in disease preventionand healthpromotion.FoodTechnoI52(11):63-70. 2. Boelsma HendriksHF,RozaL. (2001)Nutritionalskincare:healtheffects E, of micronutrientsandfatty acids.Am J Clin Nutr 73(5): 853-864. 3. HeinrichV, WielnschM, TronnierH. (1998)Photoprotection from ingested carotenoids. osmetToilet 113:61-70. C 4. BrittonG, Liacen-Jensen ,Pfander (eds.)(2004)CarotenoidsHandbook. S H Birkhauser erlag, Basel. V
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