comparative analysis of the chemical composition and antioxidant activity of red (psidium...

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Comparative Analysis of the ChemicalComposition and Antioxidant Activity of Red(Psidium cattleianum) and Yellow (Psidiumcattleianum var. lucidum) Strawberry Guava FruitRenata Biegelmeyer, Juliana Maria Mello Andrade, Ana Lucia Aboy, Miriam Anders Apel, Roger Remy Dresch, Rafaela Marin,Maria do Carmo Bassols Raseira, and Amelia Teresinha Henriques

Abstract: Strawberry guava (Psidium cattleianum Sabine) is a native fruit of Brazil widely consumed fresh and used inthe food industry. In this context, the present study deals with the chemical characterization and the antioxidant activityof the red (Psidium cattleianum) and yellow (P. cattleianum var. lucidum Hort.) strawberry guava fruits, cultivars Irapuaand Ya-Cy, respectively. Knowledge of chemical composition is fundamental to human nutrition, contributing to thequality of foods. Phenolic compounds in both fruits were analyzed by HPLC–DAD and the total flavonoid content wasdetermined by the Folin–Ciocalteu assay. The antioxidant activity was evaluated by the total reactive antioxidant (TRAP)method. Psidium cattleianum presented a higher content of polyphenolic compounds than P. cattleianum var. lucidum (501.33and 292.03 mg/100 g, respectively), with hyperoside being one of the major flavonoids identified for both cultivars. Inaddition to flavonoids, P. cattleianum presented an anthocyanin, identified as cyanidin. The antioxidant activity varied in aconcentration-dependent manner for both strawberry guava species. The volatile oils in fruits and fatty acids in seeds werequantified by GC-EM. The analysis of the essential oil of yellow strawberry guava was compared with a previous studyon the red cultivar, revealing β-caryophyllene as the main component in both oils. The fatty acid composition was alsoquite similar and was especially characterized by the presence of unsaturated fatty acids (86.25% and 76%, respectively),among which linoleic acid as the most abundant.

Keywords: essential oils, fatty acids, Psidium cattleianum, polyphenolic compounds, strawberry guava

Practical Application: In this study, the chemical characterization and the antioxidant activity of the red (Psidium cat-tleianum) and yellow (P. cattleianum var. lucidum Hort.) strawberry guava fruits were investigated. This is important forpotential application of strawberry guava as functional food. Moreover, it may be the experimental basis for furtherdevelopment and use in food industry.

IntroductionStrawberry guava (Psidium cattleianum Sabine), Myrtaceae, is a

native fruit of Brazil and can be found in locations from MinasGerais to Rio Grande do Sul and the Northeast region of Uruguay(Mattos 1989). The fruit is small (2 cm diameter) contains numer-ous seeds with either yellow or reddish skin, and its weight canexceed 20 g in some cases. The pulp is translucent, very juicy andhas an excellent strawberry-like flavor, with a spicy touch. It isrich in vitamin C, with a content that is 3 to 4 times that of citrusfruits (Raseira and Raseira 1996). It is a small tree (1 to 4 m tall),which grows in a moist and luminous environment. It bloomsfrom June to December and the fruit ripens between September

MS 20110068 Submitted 1/18/2011, Accepted 6/17/2011. Authors Biegelmeyer,Andrade, Aboy, Apel, Dresch, Marin, and Henriques are with Faculdade de Farmacia,UFRGS, Av. Ipiranga 2752, 90.610.000, Porto Alegre, RS, Brazil. Author Raseirais with EMBRAPA Clima Temperado, Caixa Postal 403, Pelotas, RS, Brazil. Directinquires to author Biegelmeyer (E-mail: [email protected]).

and March. Currently, the plant is cultivated in many countries,where it has easily adapted to a variety of climates. In tropicalclimates, it is often found growing at greater heights, where themean temperature is not too cold. The yellow variety grows atslightly lower elevations.

In Brazil, P. cattleianum is known by various popular names,including “araca, araca-rosa, araca-de-comer, and araca-da-praia”.Correa (1926) cites P. cattleianum as a producer of yellow and redfruits. There is no consensus, however, among specialists aboutthis species, and a recent study showed differences in the structuralorganization of the stems of the plant (Rocha and others 2008).Thus, 2 botanical varieties can be considered according to Popenoe(1920): P. cattleianum (also named as P. cattleianum var. cattleianum),which produces red fruits, and P. cattleianum var. lucidum Hort.,producing yellow fruits.

Selective breeding programs involving this species over a numberof years at Embrapa Clima Temperado (Pelotas, Rio Grande doSul, Brazil) have resulted in the propagation of 2 cultivars, named“Ya-Cy” and “Irapua.” The cv. Ya-Cy produces yellow fruitsweighing up to 45 g that start to appear 1 y after planting, while

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Chemical composition and antioxidant activity of strawberry guava fruits . . .

the native plant requires 4 y. The cv. Irapua gives fruits with apurple-red color and of a medium to large size, and a productionthat begins 2 y after planting (Raseira and Raseira 1994, 1996).

Despite the amount of attention being devoted to their pro-duction, few studies have been made concerning the chemicalcomposition of strawberry guava fruits. Galho and others (2007)studied the composition of primary metabolites, such as the lev-els of macronutrients, protein content, carbohydrates, sugars, andlipids. Moreover, 2 other articles describe the chemical compo-sition of the essential oil. One of these studied the species withred skin collected in Cuba (Pino and others 2001) and the otherone worked with both yellow and red-skinned fruit from theReunion Island (Vernin and others 1998). Both studies coincidedin the characterization of β-caryophyllene as one of the majorcompounds.

A sound knowledge of the chemical composition of foods isessential for human nutrition and contributes to the control ofquality of foods (Galho and others 2007). In this context, thepresent study deals with the chemical characterization and theantioxidant activity of the red (Psidium cattleianum) and yellow(P. cattleianum var. lucidum) strawberry guava fruits, cultivars Irapuaand Ya-Cy, respectively. The investigation aimed to quantify thecontent of polyphenolic compounds and determine their qualita-tive profile. In addition, the chemical composition of volatile oilsof fruits and fatty acids from the seeds were analyzed.

Materials and Methods

MaterialsAnthocyanidins, flavonoids, and Trolox were purchased from

Sigma-Aldrich (St. Louis, Mo., U.S.A.); acetonitrile (high-performance liquid chromatography [HPLC] grade) was obtainedfrom Merck (Darmstadt, Germany); trifluoroacetic acid (TFA;Vetec, Rio de Janeiro, Brazil) was of analytical grade. Water was pu-rified using a Milli-Q system (Millipore, Bedford, MA, U.S.A.).

Plant materialStrawberry guava fruits and seeds (Psidium cattleianum and

Psidium cattleianum var. lucidum) were obtained from selectionsof the germplasm bank maintained by the Temperate ClimateResearch Center belonging to Embrapa (Empresa Brasileira dePesquisa Agropecuaria, Ministerio da Agricultura, Pecuaria eAbastecimento), Pelotas, Rio Grande do Sul, Brazil, located at31◦40′47"S latitude, 52◦26′24"SW longitude and an altitude of60 m. The fruits were obtained from populations of productiveyellow- and red-skinned plants collected in the area surroundingPelotas with similar characteristics to Ya-Cy and Irapua, respec-tively. The diameter of cv. Ya-Cy varied between 2.3 and 3.5 cmwith a total solid soluble (TSS) of approximately 10 to 12 ◦ Brix.The cv. Irapoa fruits were a little smaller with a transversal diame-ter between 2 and 3 cm and a TSS close to 10◦ Brix. Fruits wereall picked at the firm ripe stage (commercial harvest point) at theend of February. The material was kept at –18 ◦C until analysis.

Total polyphenolic contentThe content of total polyphenols in the fruits was determined

with the Folin–Ciocalteu reagent and the calculated percentagecontent of polyphenols was expressed as gallic acid equivalents(GAE), in milligram per 100 g of fruit (Brazilian Pharmacopoeia2003; Verza and others 2007). The assay was performed in tripli-cate using fresh fruits.

Total flavonoids contentThe total flavonoids were calculated using the Brazilian Pharma-

copoeia (2003) method. Quantification was based on the standardcurve of quercetin and the results were expressed as milligramquercetin equivalents per 100 g of fresh weight.

Identification of polyphenolic compounds by HPLC-DADHPLC with photodiode array detection (HPLC-DAD) was em-

ployed to identify the polyphenolic compounds in fruit samples.The fruits were milled mechanically and lyophilized. Samples

were prepared with methanol at a concentration of 100 mg/mL.Solvent was evaporated under vacuum and the samples were thencentrifuged at 2000 r.p.m. for 10 min. Extracts were analyzedby HPLC-DAD, performed on a Waters Alliance 2695 chromato-graph equipped with a Waters 996 detector. Total of 10 μL sampleswere analyzed using a Phenomenex Luna C18 (250 × 4.6 mm,with 5 μm particle size) column and a flow rate of 0.8 mL/min.The methanolic extracts were filtered through a membrane filter(0.45 μm pore size, Millipore) prior to injection.

Gradient elution was employed with a mobile phase consistingof 100 : 0.08 (v/v) Water : TFA (solvent A) and 100 : 0.08 (v/v)Acetonitrile : TFA (solvent B). Anthocyanins were detected at520 nm and the gradient profile was: 0 to 20 min from 10% to18% of B, 20 to 35 min from 18% to 25% of B and an isocraticelution with 100% of phase B was maintained until 45 min hadelapsed. All other flavonoids were separated using a 1-step gradientof 14% to 19% of solvent B in 60 min. Compounds were quantifiedat 356 nm.

The only anthocyanin present in the sample of P. cattleianum redskin was previously collected directly from the HPLC column andthen hydrolyzed with 1.2 M HCl for 1 h and 30 min at 95 ◦C.Solvent was evaporated under vacuum and the sample was dilutedin methanol before being analyzed.

Evaluation of antioxidant activity using the total reactiveantioxidant potential method

The total reactive antioxidant potential (TRAP) is widely usedto estimate the antioxidant capacity of samples in vitro. Thismethod is based on the quenching of luminol-enhanced chemi-luminescence (CL) derived from the thermolysis of 2,20-azo-bis(2-amidinopropane)dihydrochloride (AAPH) as the free radicalsource (Dresch and others 2009). The stock solution was preparedwith AAPH (10 mM) and luminol (8 nM) in a glycine buffer(0.1 M; pH 8.6). After 2 h, 20 μL of each sample, Trolox or sys-tem (glycine buffer) were placed in a 96 cell-plate. The cells werecompleted to 200 μL with the stock solution. The count timewas 10 s, and the CL emission was monitored for 3000 s. Sampleswere prepared in methanol, and diluted with glycine buffer forthe final concentrations, in triplicate. Trolox was prepared withglycine buffer. The results were expressed as the area under curve(AUC) compared with concentration (μg/mL) and Trolox equiv-alent antioxidant capacity (TEAC), micromol trolox per gram offruit. A standard curve was obtained by plotting the concentrationof Trolox and the AUC (between 0.05 and 0.4 μM Trolox). TheTrolox equivalent of the sample was calculated using the standardcurve.

Essential oilsTo obtain the essential oils, fresh fruits were milled mechan-

ically and submitted to hydrodistillation using a Clevenger-typeapparatus for 4 h (Apel and others 2006; Marin and others 2008).

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The essential oils were collected, dried over sodium sulfate, andstored in amber-colored vials (+ 4 ◦C) until analysis.

Fixed oilsThe seeds were dried at room temperature and milled in a knife

mill. Approximately 20 g of seeds were weighed and submitted toextraction with n-hexane. The extracts obtained were filtered anddried at room temperature (Adolfo Lutz Insti. 1985).

FAME transesterificationFatty acid methyl esters (FAMEs) were obtained by alkaline

transesterification, according to the Adolfo Lutz Insti. (1985), withsome modifications. Approximately 80 mg of the oil was placedin a round-bottom tube with a screw-cap and 3 mL of hexanesolvent and 4 mL of 0.5 M NaOH/MeOH solution were added.The tube was then placed in a hot water bath (40 ◦C) for 4 min.After cooling in running water, 5 mL of the esterification solution(NH4Cl/H2SO4/MeOH) were added. The tube was shaken andreturned to the hot water bath for 5 min before cooling in runningwater again. Total of 4 mL of NaCl saturated solution and 3 mL ofhexane were then added and the contents of the tube were mixedusing a vortex mixer. Finally, the hexane phase was injected intoa gas chromatograph (GC).

Analysis by GC and GC-MS

Essential oils analysisQuantitative and qualitative analyses of the oils were performed

by capillary GC and GC/mass spectrometry (GC/MS), respec-tively. GC analysis of the essential oils was carried out on achromatograph (Shimadzu GC-17A) equipped with fused silicacapillary columns (30 m, 0.25 mm, 0.25 μm) of different polari-ties, 1 coated with DB-5, and another with Carbowax 20 M. Thetemperature was programmed from 60 to 300 ◦C at 3 ◦C/minfor DB-5 and 60 to 250 ◦C at 3 ◦C/min for Carbowax 20 M.Injector and detector temperatures were set at 220 and 250 ◦C,respectively. The GC apparatus was equipped with a flame ioniza-tion detector, while the GC/MS analysis involved a quadrupoleMS system (QP 5000), operating at 70 eV and over a mass rangeof 40 to 400 a.m.u. The relative composition of the oils was ob-tained by electronic integration, without taking relative responsefactors into account. The components of the oils were identifiedby comparison of retention indixes (determined relative to theretention times of n-alkanes homologous series) and mass spectrawith those of authentic samples, data from the Nist GC–MS libraryand reports in the literature (Adams 2001; Apel and others 2002).

FAMEs analysisThe esters were separated on a VS-23 capillary column (30 m ×

0.25 mm). The oven temperature was kept at 50 ◦C for 5 min,

Table 1–Total polyphenols and flavonoids in strawberry guavafruits (mean ± standard deviation; n = 3).

Total Polyphenols Total FlavonoidsFruit (mg/100 g ± SD)A (mg/100 g ± SD)B

Red strawberry guava 501.33 ± 0.0168a 100.20 ± 0.0716a

Yellow strawberry guava 292.03 ± 0.0300b 35.12 ± 0.1270b

APolyphenol concentrations, based upon gallic acid as standard, were expressed per100 g of fresh weight.BFlavonoid concentrations, based upon quercetin as standard, were expressed per 100 gof fresh weight.Different superscripts on the same column are significantly different (P < 0.05; Student’st-test).

followed by a 3 ◦C/min ramp to 240 ◦C, and then held for anadditional 5 min period. Helium was used as the carrier gas at aflow rate of 1 mL/min. The injector and detector temperatureswere maintained at 260 ◦C. FAMEs were identified by comparisonof their retention times with those of pure reference standards(FAME mix: 18919–1, Supelco, Bellefonte, PA, U.S.A.).

Statistical analysisEach sample was analyzed in triplicate. Data are expressed as

mean ± SEM. Student’s t-test was used for comparison between2 means and a one-way analysis of variance (ANOVA) followed byTukey’s test was used for comparison of more than 2 means A dif-ference was considered statistically significant when P < 0.05.Data analyses were performed using the GraphPad Prism5.0 software.

Results and DiscussionThe contents of total polyphenolic and flavonoid compounds

in the samples are presented in Table 1. Red strawberry guavaexhibited a higher polyphenolic (501.33 ± 0.02 mg/100 g) andflavonoid (100.20 ± 0.07 mg/100 g) content than yellow straw-berry guava (292.03 ± 0.03 mg/100 g, 35.12 ± 0.13 mg/100 g,respectively). Previous research had determined a total phenoliccontents of 100 to 820 mg/100 g on a fresh weight basis forsmall fruits, blackberry, blueberry, and strawberry (Zheng and

Figure 1–TRAP from red strawberry guava, F8,18 = 953 (a) and yellowstrawberry guava, F8,18 = 266 (b). A free radical source (AAPH) gener-ates peroxyl radical, and the effect of different concentrations of guavaon free radical induce chemiluminescence was measured as AUC. Trolox(0.05 μg/mL) was used as standard antioxidant. Bars represent mean ±SEM. ∗P < 0.05 (1-way ANOVA followed by Tukey’s test).

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Table 2–Percentage composition of the essential oils obtained from strawberry guava fruits.

Fruits Fruits

Red strawberry Yellow strawberry Red strawberry Yellow strawberryCompounds RI∗ guava guava Compounds RI∗ guava guava

Monoterpenehydrocarbons

0.0 6.6 α-Muurolene 1489 – 0.4

Tricyclene 915 – 0.4 β-Bisaboleno 1493 – 0.2Myrcene 991 – 0.6 Trans-β-guaiene 1494 1.3 –o-Cymene 1014 – 0.1 γ -Cadinene 1500 – 0.6Limonene 1027 – 0.7 δ-Cadinene 1511 4.2a 1.1b

(Z)-β-Ocimene 1034 – 1.5 α-Cadinene 1524 – 0.4(E)-β-Ocimene 1044 – 0.4 Selina-3,7(11)-diene 1533 – 1.6γ -Tepinene 1054 – 0.3 Oxygenated

sesquiterpenes31.1a 25.1b

Iso-terpinolene 1079 – 1.4 (E)-Nerolidol 1551 1.4a 0.9b

Linalool 1093 – 1.2 Trans-nerolidol 1556 – 0.9Oxygenated

monoterpenes0.0 12.7 Caryophyllene alcohol 1461 – 0.9

Terpinen-4-ol 1163 – 0.3 Caryophyllene oxide 1566 1.7a 4.5b

α-Terpineol 1177 – 0.7 Humulene oxide I 1590 0.4a 0.6a

Ethyl octanoate 1187 – 0.1 Epoxide humulene II 1591 – 0.5Neral 1230 – 1.1 1-Epi-cubenol 1617 3.8 –Geraniol 1248 – 8.0 t-Cadinol 1627 2.1a 2.8b

Geranial 1262 – 2.1 Cubenol 1639 6.6a 1.3b

α-Terpenyl acetate 1336 – 0.4 δ-Cadinol 1640 – 0.6Sesquiterpene

hydrocarbons61.8a 44.1b t-Muurolol 1642 – 0.8

α-Ylangene 1358 – 0.2 Neo-intermedeol 1647 14.0 –α-Copaene 1372 1.7a 0.9b α-Muurolol 1648 – 1.0Geranyl acetate 1374 – 0.3 α-Cadinol 1658 – 3.2β-Caryophyllene 1414 22.5a 28.7b α-Eudesmol 1653 1.1a 1.3a

β-Ylangene 1419 – 0.1 14-Hydroxy-9-epi-(E)-caryophyllene

1671 – 0.4

α-Humulene 1444 7.5a 5.4b Eudesm-7(11)-en-4-ol

1698 – 3.4

β-Chamigrene 1459 4.9 – (2Z,6Z)-Farnesol 1711 – 0.2γ -Muurolene 1462 – 1.3 (E)-Nerolidol acetate 1718 – 1.5γ -Himachalene 1463 0.6 – (2E,6Z)-Farnesol 1737 – 0.3α-Amorphene 1466 – 0.2 Others 0.0 1.6β-Selinene 1474 10.1a 1.4b (E,E)-Farnesyl acetate 1831 – 0.3Viridiflorene 1480 – 1.1 Hexadecanoic acid 1892 – 0.3α-Selinene 1484 9.0 – (Z)-9-Octadecenoic

acid2152 – 1.0

Germacrene A 1488 – 0.2 Total 92.9 90.1∗retention indices on DB-5 column.Different superscripts on the same volatile are significantly different (P < 0.05; Student’s t-test).

others 2007; Jacques and others 2009). In general, these smallfruits also present a large variation in their flavonoid contents,ranging from 14 to 290 mg/100 g (Lugasi and Hovari 2002;Lin and Tang 2007). When our results are compared with thesevalues, it seems that the obtained polyphenol and flavonoid con-

Table 3–Fatty acid composition (% of total fatty acids) of seedsfrom strawberry guava (mean ± standard deviation; n = 3).

Red strawberry Yellow strawberryFatty acids guava guava

Palmitic acid (C16:0) 9.12 ± 2.1213a 19.92 ± 0.2616b

Stearic acid (C18:0) 4.63 ± 0.3960a 3.57 ± 0.6223b

Oleic acid (C18:1) 10.83 ± 0.9899a 14.99 ± 0.8839b

Linoleic acid (C18:2n-6) 75.42 ± 3.5002a 61.01 ± 2.5102b

Cis-11-eicosenoic acid (C20:1) - tr∑SFA 13.75 ± 1.2587 23.49 ± 0.4420∑MUFA 10.83 ± 0.9899 14.99 ± 0.8839∑PUFA 75.42 ± 3.5002 61.01 ± 2.5102∑TUFA 86.25 ± 2.2451 76.0 ± 1.6971

tr = trace (< 0.1).Different superscripts on the same fatty acid are significantly different (P < 0.05; Student’st-test).

tents are in good agreement with published values for other smallfruits.

The total polyphenolic content for red strawberry guava as re-ported by Luximon-Ramma and others (2003) was similar to thatdemonstrated in this study. The total flavonoid content, how-ever, was 71 mg/100 g of fruit, below the value found here(100.2 mg/100 g). On the other hand, in the case of yellowstrawberry guava, the content of polyphenolic compounds was563 mg/100 g of fruit, clearly above the value found in thepresent study (292.03 mg/100 g), while the flavonoids content wassimilar. According to Luximon-Ramma and others (2003) bothstrawberry guava fruits contain anthocyanins and other flavonoids.These observed differences may be due to variations in the ma-turity with which fruits are harvested and the site of collection.Furthermore, it is important to consider that in this study the culti-vars of strawberry guava, which were used, had a higher transversaldiameter (up to 3.5 cm) as compared to that of the native fruit(2 cm). Other researchers have noted that red strawberry fruitsharvested at a mature stage showed a marked decrease in quality,characterized by lower soluble solids content (Drehmer and DoAmarante 2008). Casagrande Junior and others (1999) reported


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that a lack of sunlight can influence phenol levels in strawberryguava. In the present study, it was not possible to confirm the pres-ence of anthocyanins by analyzing the chromatographic profile ofyellow strawberry guava at 520 nm.

Strawberry guava is a fruit with a high viscosity due to pres-ence of soluble sugars, pectic substances, and other soluble solidsin the pulp (Haminiuk and others 2006), as a result of whichaqueous extracts are also highly viscous. Therefore, it was nec-essary to precipitate these constituents with methanol; for exam-ple, to avoid any possible interference in the analysis (Vriesmannand others 2009). Extracts for HPLC analysis were prepared withmethanol.

The identification of flavonoids was based on retention time andUV spectra by comparison of the samples with pure commercialstandards. Fruits of both cultivars presented quercetin glycosidessuch as hyperoside and isoquercetrin. Hyperoside constituted oneof the main compounds of the extracts. Anthocyanins were presentonly in the red skin cultivar extract, and in this extract only 1 an-thocyanin was detected. For identification, the peak was collecteddirectly from the HPLC column and immediately hydrolyzed; itwas subsequently identified as cyanidin by comparison with a purecommercial standard by HPLC-DAD. Interestingly, hydrolysis ofthe extract did not allow the identification anthocyanins, probablydue to the interference of other components of the extract thatcould interfere in the reaction (Galho and others 2007).

Both groups of compounds, flavonoids and anthocyanins, aresecondary plant metabolites that exhibit beneficial effects on hu-man health. Hyperoside has been shown to possess various bi-ological functions as a reactive oxygen species scavenger (ROS),such as preventing the free radical-induced oxidation of vitamin Ein human low-density lipoprotein (Zesheng and others 2001).Other effects include increasing superoxide dismutase activity,an antidepressant-like activity through inhibition of nitric oxidesynthase in rat blood and cerebral homogenate (Luoand others2004), and the partial uncoupling of oxidative phosphorylation incardiac mitochondria (Trumbeckaite and others 2006). For cyani-din, reported activities include cytoprotective effects against DNAdamage that could be also correlated with the antioxidant activity(Choi and others 2007).

These biological activities are correlated with the antioxidativepotential these secondary metabolites. In this study, we provedthat the antioxidant activity of red and yellow strawberry guavavaried in a dose-dependent manner (Figure 1). At low concen-

trations (1μg/mL), its activity was comparable to that of Troloxand only red strawberry guava displayed a significant differencewith Trolox. A strong antioxidant effect was verified at concen-trations of 5 and 10 μg/mL. The values of TEAC obtained were156 and 177 μM/g for red and yellow strawberry guava, respec-tively. Goncalves (2008) reported the TEAC of several Braziliannative fruits, including strawberry guava fruit, ranging from 82 to790 μM/g. Our findings are within this range and also are similarto the strawberry guava (159 μM/g).

The hydrodistillation of yellow strawberry guava yielded 0.1% ofoil, which was analyzed and compared with the essential oil fromred-skinned fruits studied by our group previously (Marin andothers 2008). The chemical compositions of the oils are summa-rized in Table 2. The oil of red strawberry guava comprised onlysesquiterpenes while the oil of the yellow-skinned fruit, was foundto also contain monoterpenes (19.3%). The sesquiterpene hydro-carbon, β-caryophyllene was found to be the main compound inboth red and yellow oils (22.5% and 28.7%, respectively).

The results reported by Pino and others (2001), from a specieswith red skin collected in Cuba, and by Vernin and others (1998)with both yellow and red-skinned varieties from La ReunionIsland, revealed both qualitative and quantitative differences fromthe oils of our cultivars. In spite of these differences, however, therewas 1 coincidence: β-caryophyllene was the major characterizedcomponent in the oil of all analyzed samples. The observed varia-tion can be explained by the different isolation methods employed,the site of collection and cultivars.

According to Pino and others (2001), the unique flavorof the strawberry guava fruit is due to the combination ofcompounds present and not attributable to one or a few indi-vidual components. The presence of essential oil is fundamentalfor the organoleptic properties of fruits; therefore, these com-pounds are widely used in the food industry. Furthermore, theycan be used in various branches of other industries such as in per-fumery. Because of their pharmacological properties, the oils andtheir isolated compounds are used in the pharmaceutical industry(Henriques and others 2009). Previous studies reported various bi-ological activities for the constituents identified in the strawberryguava essential oil. For the major component, β-caryophyllene,antiinflammatory (Bakır and others 2008), and local anestheticactivities have been observed (Ghelardini and others 2001). Thevolatile oils, however, can also present a synergistic activity due tothe interaction among the constituents.

Figure 2–FAMEs from red strawberry guava (a)and yellow strawberry guava (b) by GC-FID.

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Oils extracted from red and yellow strawberry guava seedsshowed high levels of polyunsaturated fatty acids (PUFAs) andtheir chemical composition is presented in Table 3 and Figure 2.Fatty acids content and composition were very similar for bothstrawberry guava cultivars. The main fatty acid in both seedswas linoleic acid (61.01% ± 2.51%, 75.42% ± 3.50%, respec-tively). There was, however, a quantitative difference in thecontent of the 2nd major component, palmitic acid. For yel-low strawberry guava the level of this acid (19.92% ± 0.26%)was more than double that of red strawberry guava (9.12% ±2.12%).

Fatty acids are necessary for normal physiological health, andvegetable oils have a high content of unsaturated fatty acids, whichare heart-healthy. The nutritional value of PUFAs in the humandiet is well recognized, and increased consumption of these fattyacids has been recommended (Department of Health, 1994). Di-ets that are high in monounsaturated fatty acids (MUFAs) andPUFAs are associated with reduced risk of cardiovascular diseaseand atherogenesis. Therefore, the evaluation of the lipid profile offruit has become an important requirement.

ConclusionsCurrently, there is a growing concern about health mainte-

nance and an increasing awareness of the contribution of naturalalternatives, such as fruits and vegetables to a healthy condition.In this context, a good knowledge of food chemistry has becomefundamental. The analysis of the composition of strawberry guavadeserves special attention, since this fruit can be consumed bothfresh and used in the food industry. Strawberry guava is rich inphenolic compounds and the seeds contain considerable amountsof fatty acids.The presence of these plant metabolites, which arerecognized for biological activities, such as antioxidants as demon-strated here, justify the inclusion of these fruits among functionalfoods. Thus, the consumption of strawberry guava should beencouraged as a means to increase the intake of these compoundsand thereby contribute to maintain a healthy condition. More-over, these antioxidant data are valuable as a support for dietaryguidelines.

AcknowledgmentsThe research was supported by FAPERGS and CNPq, Brazil.

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comparative analysis of the chemical composition and antioxidant activity of red (psidium...

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