Food Chemistry 134 (2012) 1069–1073

Contents lists available at SciVerse ScienceDirect

Food Chemistry

journal homepage: www.elsevier .com/locate / foodchem

Nutritional and nutraceutical comparison of Jamaican Psidium cattleianum(strawberry guava) and Psidium guajava (common guava) fruits

Kayanne P. McCook-Russell a, Muraleedharan G. Nair b, Petrea C. Facey a, Camille S. Bowen-Forbes a,⇑a Department of Chemistry, The University of the West Indies, Mona, Kingston 7, Jamaicab Bioactive Natural Products and Phytoceuticals Laboratory, Department of Horticulture, Michigan State University, East Lansing, MI 48824, USA

a r t i c l e i n f o a b s t r a c t

Article history:Received 6 April 2011Received in revised form 27 February 2012Accepted 6 March 2012Available online 16 March 2012

Keywords:Psidium cattleianumPsidium guajavaStrawberry guavaAntioxidantCOX enzymeJamaica

0308-8146/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.foodchem.2012.03.018

⇑ Corresponding author. Tel.: +1 876 927 1910; faxE-mail address: camille.bowen02@uwimona.edu.jm

Psidium cattleianum (strawberry guava) is one of many underutilised edible fruits that grow wild inJamaica, and could potentially be commercially exploited to yield health and economic benefits. In thisstudy, the total phenolics, proximate contents, and antioxidant, anti-inflammatory, and antimicrobialactivities of P. cattleianum and P. guajava (common guava), a well-known species, were compared. Straw-berry guavas were found to be superior to common guavas in antioxidant and antimicrobial activities,total phenolics and vitamin C content. They also possessed relatively high fibre content (24.9%). The hex-ane and ethyl acetate extracts of strawberry guavas showed cyclooxygenase-2 enzyme inhibitory activ-ities of 18.3% and 26.5%, respectively (250 lg/mL), indicating anti-inflammatory activity. The EtOAc andMeOH extracts of P. guajava showed 56.4% (COX-2) and 44.1% (COX-1) inhibitory activity, respectively.Additionally, nine compounds were isolated from strawberry guava fruits, some of which demonstratedanti-inflammatory activity. These results indicate that strawberry guavas are beneficial for health.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

The Myrtaceae family consists of at least 133 genera and morethan 3800 species (Wilson, O’Brien, & Gadek, 2001). Many fruits ofthis family have a history of being used in traditional medicines inethnobotanical practices in the tropical and subtropical regions(Marin et al., 2008). Members of the Myrtaceae family includethe Eugenia, Myrcianthes, Campomanesia and Psidium genera (Marinet al., 2008). The Psidium genus is represented by approximately120–150 species and may be found throughout the tropics andsubtropics of America and Australia (Pino, Bello, Urquiola, Marbot,& Martí, 2004). The constituents of some of the species have beenstudied, with special focus being placed on the flavour componentsof the fruits. Antioxidant activities of some members have alsobeen examined. The most popular Psidium species, guajava, simplycalled guava, has been extensively examined. The round-oval fruitis green-yellow and shows a light yellow, pink (Shreier & Idstein,1985), white or salmon pulp depending on the variety (Merca-dante, Steck, & Pfander, 1999). It grows on a low evergreen treeor shrub and can attain a height between 6 and 33 feet (2–11 m).The trees grow rapidly and fruit within 2–4 years from the seed.World production of guavas is estimated at approximately500,000 metric tonnes, with Brazil, Colombia, Mexico and Venezu-ela producing significant quantities from the South American re-

ll rights reserved.

: +1 876 977 1835.(C.S. Bowen-Forbes).

gions. The industry provides a range of processed products suchas beverages, syrup, ice cream, jams and jellies, to name a few(Jiménez-Escrig, Rincón, Pulido, & Saura-Calixto, 2001). The majorproducers of guava products are South Africa, India, Hawaii,Colombia, Puerto Rico, Jamaica, Brazil and Israel (Mercadanteet al., 1999). In Jamaica, P. guajava is commonly used in the man-ufacture of jams, jellies, ice cream and juices, among otherproducts.

Psidium cattleianum Sabine (strawberry guava) is often de-scribed as being more aromatic than Psidium guajava (commonguava). There are two known cultivars – the red fruit and the yel-low fruit (Luximon-Ramma, Bahorun, & Crozier, 2003). This speciesis a shrub or tree which can grow 3–10 m high and is very commonto Southern Brazil (Marin et al., 2008). Other names synonymouswith strawberry guava include Psidium littorale Raddi or purpleguava. The fruit is widely cultivated in Central and South Americaand has been naturalised in Jamaica in the parishes of Clarendon,Manchester and St. Ann (Adams, 1972). In Hawaii, the plant isactually considered as a forest weed and is able to propagate quiteeasily from the seed. It has not been as extensively studied as theguajava species, however the volatile constituents of the fruit havebeen quantified and characterised (Pino, Marbot, & Vázquez, 2001).Additionally, P. cattleianum, P. guajava and other Mauritia grownfruits have been analysed for their antioxidant capacity, total poly-phenolic and nutritional contents. This research was undertaken tocompare the nutraceutical and nutritional value of the P. cattleia-num to the more well-known P. guajava (Luximon-Ramma et al.,

1070 K.P. McCook-Russell et al. / Food Chemistry 134 (2012) 1069–1073

2003). In the present study, the phytochemistry of P. cattleianumfruits, which has not been previously reported, was investigated.The anti-inflammatory activity of the fruits of this species is nowbeing reported for the first time. An exploration of the naturalproducts, antioxidant, antimicrobial and anti-inflammatory prop-erties of Jamaican strawberry guavas would shed light on thisessentially unknown fruit, which could become a normal part ofpeople’s diets, and positively impact health. Additionally, the fruitcould be potentially exploited to improve the country’s economyvia commercialisation.

OH

H H

HH

COOH

OH

H

H

H

R

COOH

OH

H

H

H

R

O

OO

OH

O

O OH

R1

R

Fig. 1. Compounds 2–6 and 8–9.

2. Materials and methods

2.1. General experimental procedures

The 1H and 13C NMR spectra were recorded in deuterated chlo-roform, acetone or methanol using Bruker Avance 200 and500 MHz NMR spectrometers (Bruker, Karlsruhe, Germany). Silicagel (230–400 mesh) was used for column chromatography. Folin–Ciocalteau phenol reagent, gallic acid, 20,20-azinobis(3-ethylbenzo-thiazoline-6-sulphonic acid) diammonium salt (ABTS) and 6-hy-droxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox)were obtained from Sigma Aldrich Inc., St. Louis, MO, USA. The bac-terial cultures used in the antimicrobial assay were provided bythe University Hospital of the West Indies (UHWI), St. Andrew, Ja-maica. The COX-1 enzyme was prepared from ram seminal vesiclespurchased from Oxford Biomedical Research, Inc. (Oxford, MI,USA). COX-2 enzyme was prepared from Spodoptera frugiperda cellscloned with human PGHS-2 (prostaglandin endoperoxide H syn-thase-2) enzyme. P. cattleianum fruits (orange-red) were harvestedfrom Mason River, Clarendon, while Psidium guajava fruits (palepink) was collected from Papine, St. Andrew, both in Jamaica, inOctober and November, 2009, respectively. A portion of the hexaneextract was separated using an Agilent GC 6890 gas chromato-graph (Agilent Technologies, Palo Alto, CA, USA) equipped withan SLBTM-5MS fused silica capillary column (30 m � 0.25 m �0.25 lm, Supelco, Bellefonte, PA, USA) with the GC oven tempera-ture programme: 60 �C (50) to 300 �C at 10 �C/min. Splitless injec-tion was used at a temperature of 250 �C and He carrier gas at1.3 mL/min flow. The model 5973 mass-selective detector wasoperated at a scanning mass range of 50–600 m/z with 70 eV ion-isation energy, 230 �C EI ion source temperature and the quadru-polar mass detector at 150 �C.

2.2. Extraction of fruits

Fresh, fully ripe fruits of P. cattleianum (2129 g) and P. guajava(366 g) were lyophilised to yield 443 and 63 g of dried material,respectively. A portion of the former (413 g) was extracted succes-sively with hexane (2 � 3L), ethyl acetate (2 � 3L) and methanol(2 � 3L). Smaller volumes (2 � 600 mL) were used for extractingP. guajava (63 g). The first extraction was done for 3 h and the otherwas carried out for 16 h. An orbital shaker was used to facilitateextraction. The extracted plant material were filtered, pooled asappropriate, and concentrated en vacuo to give 5.9, 2.4 and 220 ghexane, ethyl acetate and methanol extracts, respectively, for P.cattleianum and 0.83, 1.2 and 24 g, respectively, for P. guajava.

2.3. Isolation of natural products from P. cattleianum

Silica gel column chromatography was carried out on a portionof the hexane extract (4.2 g) using increasing concentrations ofEtOAc/hexane. This led to the isolation of compounds 1 and 2(3.25 g and 50.7 mg). Further purification of a mixed fraction fromthis extract produced a mixture of compounds 3 and 4 (17 mg),

which were obtained during elution with 15:85, ethyl acetate/hex-ane. A portion of the hexane extract was analysed by GC/MS.

The same method of purification was applied to the ethyl ace-tate extract (2.2 g). This yielded compound 1 (27 mg), a mixtureof compounds 3 and 4 (10.3 mg), a mixture of compounds 5 and6 (8.3 mg) and compound 7 (107 mg). Compounds 1–6 were iso-lated during elution with the same solvent system as that in thehexane extract while 7 was obtained using a solvent system ofethyl acetate/hexane (60:40, v/v). A portion of the methanolic ex-tract (77 g) was dissolved in water (500 mL) and extracted withethyl acetate (4 x 400 mL). The resultant concentrate was sub-jected to column chromatography using silica gel. Fraction A wasobtained by eluting the column with ethyl acetate/hexane(50:50, v/v), while fraction B contained compounds which wereeluted in EtOAc. Successive column chromatography of fraction Ayielded compounds 1 (14.3 mg) and 2 (15 mg), both isolated usingethyl acetate/hexane (2:98, v/v), while 7 (53.8 mg) and a mixtureof 8 and 9 (92 mg) were isolated from fraction B during elutionwith solvent systems comprising of 60:40 (v/v) and 50:50 (v/v)ethyl acetate/hexane, respectively. Compounds 8 and 9 were pres-ent in an approximate mole ratio of 1:1, based on the intensities ofthe NMR signals of the respective compounds. The structures of thecompounds are shown in Fig. 1.

2.4. Antioxidant assay

The antioxidant activities of the extracts were determined usingTrolox equivalent antioxidant capacity (TEAC) (Seeram et al.,2006). 20,20-Azinobis(3-ethylbenzothiazoline-6-sulphonic acid)diammonium salt radical cations were generated by adding solidmanganese dioxide to a 5 mM aqueous solution of ABTS. Acalibration curve was established using ethanolic solutions ofTrolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid).The methanolic extracts of the fruits were tested at a concentrationof 1 mg/100 lL. For each measurement, ABTS�+ solution (2 mL) wasadded to each sample and standard (20 lL). Samples were assayedin triplicate and the absorbance was read at 734 nm. TEAC valueswere calculated and expressed as Trolox equivalents (lmol/g).

2.5. Total phenolic content

Samples were analysed spectrophotometrically for total pheno-lic contents using 10% Folin–Ciocalteau reagent, and gallic acid wasused as a reference. Standards of concentration 0.8, 1.6, 2.4, 3.2 and4.0 ppm were prepared from a stock solution of gallic acid with a

K.P. McCook-Russell et al. / Food Chemistry 134 (2012) 1069–1073 1071

concentration of 100 ppm. The samples (1.2 – 1.5 g) were extractedwith boiling water (100 mL) for 4 min, then filtered and made up to100 mL. A portion of this solution (1 mL) was diluted to 25.0 mLand the procedure followed as that for the standards. Absorbanceswere read at 750 nm and values calculated and expressed aslg gallic acid equivalents (GAE)/g fresh weight (Chen & Yen, 2006).

2.6. Antimicrobial assay

Antibacterial assay was carried out using the hexane, ethyl ace-tate and methanolic extracts of P. cattleianum, by employing thedisc diffusion assay (Bauer, Kirby, Sherris, & Turck, 1966; Boyd,1984). The compounds obtained from the ethyl acetate extractwere also analysed. The bacteria used in the assay were Bacillussubtilis, Pseudomonas aureginosa, Escherichia coli and Staphylococcusaureus. For the crude extracts, 500 lg/disc was used while 50 lg/disc was used for individual compounds. The activities of the ex-tracts and compounds were compared to that of the known antibi-otic, gentamicin, at a concentration of 10 lg/disc.

2.7. COX enzyme inhibitory assay

The method used for the COX enzyme inhibitory assay was pre-viously reported (Bowen-Forbes, Mulabagal, & Nair, 2009). Extractsand pure compounds were tested at 250 and 25 mg/L respectively,using dimethyl sulphoxide (DMSO) as the solvent. Due to paucityof COX enzymes, the analyses were done in duplicate.

2.8. Proximate analysis

The fat, protein, ash, calcium and crude fibre contents of thePsidium species were analysed using AOAC (2005) methods. Vita-min C was determined using an iodometric titration (Volpe, Col-lins, Simoni, & Silva, 1999).

3. Results and discussion

3.1. Characterisation of compounds

The identities of all compounds were elucidated by NMR spec-tral methods. The metabolites were identified as triolein (1), b-sitosterol (2) (Nes, Norton, & Benson, 1992), ursolic acid (3) (Mah-ato & Kundu, 1994), oleanolic acid (4) (Mahato & Kundu, 1994), 2a-hydroxyursolic acid (5) (Begum et al., 2002), 2a-hydroxyoleanolicacid (6) (Abou-Mansour et al., 2005), citric acid (7) (Pouchert &Behnke a, 1993), and a mixture of citrate esters, 1,2,3-propanetri-carboxylic acid-2-hydroxy-1-methyl ester (8) (Han et al., 2001)and 1,2,3-propanetricarboxylic acid-2-hydroxy-2-methyl ester (9)(Jayaprakasha et al., 2007). In addition to using NMR spectroscopy,the identities of the compounds triolein, b-sitosterol, ursolic acid,oleanolic acid, and citric acid, were further confirmed based onTLC comparison with authentic samples. Additionally, GC/MS anal-yses confirmed the presence of triolein and revealed that caryo-phyllene and its oxide were also present.

Triolein was the major component of the hexane extract withan abundance of 76%, representing 0.2% of the fruit. b-Sitosterolis a common plant sterol which has been associated with the Psid-ium genus. Ursolic and oleanolic acids, which were isolated fromboth the hexane and ethyl acetate extracts, were obtained as amixture. Both acids have been found in the fruit of P. guajava (Peng,Hsieh, & Chen, 2008) and have been shown to exhibit anti-inflam-matory properties in laboratory animals (Liu, 1995). Citric acid,which was relatively abundant in the fruit, comprised 5% of theethyl acetate extract. This compound is prevalent in citrus fruitsand is associated with the sour taste of limes and lemons.

The 1H NMR data for the citrate ester showed two tall singlets at3.68 (9) and 3.77 (8) ppm which are characteristic of protonsbelonging to a methoxy group. There was also a broad singlet at5.10 ppm, indicative of an exchangeable proton belonging to anamine, acid or alcohol. This corresponded to the unmethylated car-boxyl groups and the hydroxyl moiety. The 13C NMR data showedthree methlyene carbons at 43.8 (9), 44.1 (8) and 44.2 ppm (9), allof which were in the region of the chemical shift for the methylenegroups in citric acid. Additionally, there were two signals resonat-ing at 52.3 (8) and 53.2 ppm (9), confirming the presence of meth-oxy groups. A pair of oxygenated quaternary carbon atoms wasalso observed in the 13C NMR spectrum at 72.8 (8) and 73.2 ppm(9). A cluster of peaks in the region of 170–176 ppm indicated thatthere were carboxylic and carboxylate groups in different chemicalenvironments. These NMR data suggested that a mixture of citricacid methyl esters was present. They were determined to be1,2,3-propanetricarboxylic acid-2-hydroxy-1-methyl ester (8) and1,2,3-propanetricarboxylic acid-2-hydroxy-2-methyl ester (9)based on comparison with literature data. Citric acid (7) was a ma-jor natural product found in the P. cattleianum fruits. Consideringthat compounds 8 and 9 were obtained from the methanol extract,the possibility exists that were derived from methylation of citricacid during extraction.

Caryophyllene and its epoxide are well-known volatile constit-uents of Psidium cattleainum. Previous studies on the volatile fla-vour components of the fruit using GC/MS showed aconcentration of 10.25 ppm for b-caryophyllene and 1.16 ppm forits epoxide. Both are believed to contribute a spicy note to the fla-vour of the fruit (Pino et al., 2001).

3.2. Antioxidant assay

The methanolic extracts were analysed for antioxidant activity.The antioxidant components of the fruit are expected to be concen-trated in this extract. The TEAC of strawberry guavas was found tobe three times that of P. guajava (i.e. 11.3 + 0.1 compared to3.8 + 0 lmol Trolox/g fresh weight). In a previous study carriedout on Mauritian fruits, red strawberry guavas were found to pos-sess almost seven times the Trolox equivalence as that of commonguavas (Luximon-Ramma et al., 2003). The levels reported were,however, significantly higher than the ones now being reported.The dissimilarity between the results is likely to be due to differ-ences in extraction protocols as well as environmental factors.None of the metabolites which were isolated from strawberry gua-va showed antioxidant activity at the concentration tested.

3.3. Total phenolic content

The total phenolic contents within the cattleianum and guajavaspecies was 4439 and 1952 lg GAE/g fresh weight, respectively. Inother words, strawberry guavas had more than twice as muchpolyphenols as common guavas. Both red and yellow varieties ofP. cattleianum from Mauritia showed phenolic contents exceeding5000 lg GAE/g fresh weight. The levels reported in pink and whiteMauritian common guavas were comparatively lower with valuesof 1264 + 60 and 2473 + 45 lg GAE/g fresh weight, respectively(Luximon-Ramma et al., 2003).

3.4. Antimicrobial activity

The methanolic extract of P. cattleianum possessed intermediateactivity against B. subtilis and S. aureus. No other extract producedpositive results against the bacteria tested. No activity was demon-strated by the P. guajava fruit extracts. S. aureus is a Gram-positivebacterium responsible for diseases such as pneumonia and menin-gitis while the less harmful B. subtilis is not a human pathogen. The

Table 1Proximate analysis, total phenolics, and antioxidant activity (TEAC) of P. cattleianumand P. guajava fruits.a

P. cattleianum P. guajava

% Fat 1.24 + 0.01 0.97 + 0.04

1072 K.P. McCook-Russell et al. / Food Chemistry 134 (2012) 1069–1073

essential oils of the leaves of strawberry guava showed 55 and 58%inhibition of S. aureus and P. aeruginosa, respectively (Apel et al.,2006), while in folk medicine, extracts of the roots, bark and leavesof P. guajava have been used to treat gastroenteritis, vomiting anddiarrhoea (Peng et al., 2008).

% Protein 2.10 + 0.03 4.22 + 0.11% Ash 3.05 + 0.01 3.12 + 0.03% Crude fibre 324.9 + 1.7 30.9 + 2.8Calcium 63.2 + 0.7 29.8 + 2.0Vitamin C 2091 + 42 1200 + 46Total polyphenols/lg GAE 4439 + 159 1952 + 111TEAC/lmol TE 11.3 + 0.1 3.8 + 0.0

TE = Trolox equivalent (lmol Trolox/g fresh weight), GAE = gallic acid equivalents(lg GA/g fresh weight).

a Vitamin C and calcium contents are expressed in lg g�1 fresh weight.

3.5. COX-1 and -2 enzyme inhibitory assay

The cyclooxygenase enzyme catalyses the oxidation of arachi-donic acid to prostaglandins and thromboxanes. The isoforms ofthe enzyme COX-1 and COX-2 can be inhibited by non-steroidalanti-inflammatory agents, resulting in reduction in inflammationand pain relief. Inhibition of the COX-2 isoform is linked to a reduc-tion in malignancy (Bowen-Forbes et al., 2009). When tested at aconcentration of 250 lg/mL, the hexane and ethyl acetate extractsof P. cattleianum showed respective COX-2 activities of 18.3 and26.5%. The mixture of ursolic and oleanolic acids (3 and 4) showed19.4% inhibition of the COX-2 enzyme at 250 lg/mL. The highestoverall activity was exhibited by the mixture of their corresponding2a-hydroxy analogues (5 and 6), which demonstrated 52.9 and43.1% inhibition against the COX-2 and COX-1 enzymes, respec-tively. The ethyl acetate extract of P. guajava showed notable activity(56.4%) against the COX-2 isoform, while the methanolic extractexhibited 44.1% inhibition against the COX-1 enzyme (Fig. 2).

3.6. Proximate analysis

The results in Table 1 indicate that P. cattleianum is higher in fat,calcium and vitamin C than its more common relative, P. guajava.Both species had low fat contents, comparable to that noted byPopenoe, 1948 (1.0%). The average % protein for strawberry guavawas approximately four times greater than the 0.53% calculated forP. littorale Radii var. lucidum (yellow Cattley guava) (Hall, Smoot,Knight & Nagy, 1980). In this case, crude fibre was quantified withcommon guava having the greater fibre content. Previous studieshave shown that the peel and pulp of P. guajava possess high levelsof dietary fibre with associated natural antioxidant components(Jiménez-Escrig et al., 2001). It can therefore be classified as a fruit

b

a

Fig. 2. Cyclooxygenase 2 enzyme inhibitory activities of positive controls, Aspirin, Celebr

compounds tested at 250 and 25 lg/mL, respectively (b). Vertical bars represent ± SD for ea

rich in antioxidant dietary fibre (AODF), and polyphenolic com-pounds (Saura-Calixto, 1998). Crude fibre does not encompassthe total fibre composition of a food and so the possibility existsthat P. cattleianum is also high in dietary fibre and may, by exten-sion, be classified as an AODF. The vitamin C content was muchgreater in Jamaican strawberry guava than that noticed in thered variety found in Mauritia, which had a value of 242 + 15 lg/gfresh weight. The value we obtained for P. guajava (1200 lg/g freshweight) was comparable to that found in the Mauritian white com-mon guavas (1426 fresh weight) (Luximon-Ramma et al., 2003).The Jamaican P. guajava species exhibited higher fat, protein, ashand crude fibre contents (see Table 1) compared to those quotedfor the variety from Venezuela (0.4–0.7, 0.8–1.5, 0.5–1.0, and2.0–7.2%, respectively) (Jiménez-Escrig et al., 2001). The generalcomposition of a fruit depends on its stage of maturity (ChyauChen & Wu, 1992), the season and where it is grown. This may par-tially account for the differences in the parameters tested by differ-ent researchers.

3.7. Conclusion

For the most part, P. cattleianum was found to be a better sourceof nutrients than P. guajava. It showed greater antioxidant and

exTM and Vioxx�, at 60 lM, 26 and 32 nM, respectively (a) and extracts and isolated

ch data point (n = 2). % Inhibition ¼ 1� initial rate of O2 uptake of COX sample solutioninitial rate of O2 uptake of COX DMSO solution

h i� 100%.

K.P. McCook-Russell et al. / Food Chemistry 134 (2012) 1069–1073 1073

antimicrobial activities, as well as higher vitamin C content. Its to-tal phenolic content was almost twice that of P. guajava, which isadvantageous, as these chemicals aid with free radical scavenging.Psidium guajava however does exhibit greater anti-inflammatoryactivity than P. cattleianum. This research has demonstrated thegreat potential of Jamaican strawberry guavas. Based on the pres-ent findings, the fruit may be made more popular due to its healthbeneficial properties, as well as the potential for commercial pro-duction of value-added products. Commercialisation would befacilitated by large scale cultivation, which would be advantageousto the country’s agricultural sector. More detailed study of otherparts of the plant to further explore its nutraceutical potential willbe undertaken.

Acknowledgements

We gratefully acknowledge funding in the form of a New Initia-tive Grant and a Research Fellowship received from The Universityof the West Indies, Mona Campus, for the undertaking of thisproject.

References

Abou-Mansour, E., Djoukeng, Tabacchi R., Tapondjou, A. L., Bouda, H., Lontsi, D., &Djoukeng, Tabacchi. (2005). Antibacterial triterpenes from Syzygium guineense(Myrtaceae). Journal of Ethnopharmacology, 101, 283–286.

Adams, C.D. (1972). Flowering Plants of Jamaica, (p. 519). Glasgow, Scotland: RobertMacLehose and Company Ltd.

AOAC (2005). Official Methods of Analysis (18th ed.). Gaithersburg, MD: AOACInternational.

Apel, M. A., Lima, M. E. L., Souza, A., Cordeiro, I., Young, M. C. M., Sobral, M. E. G.,et al. (2006). Screening of the biological activity from essential oils of nativespecies from the Atlantic rain forest (São Paulo – Brazil). Pharmacology online, 3,376–383.

Bauer, A. W., Kirby, W. M. M., Sherris, J. C., & Turck, M. (1966). Antibioticsusceptibility testing by a standardized single disk method. American Journal ofClinical Pathology, 45, 493–496.

Begum, S., Sultana, I., Siddiqui, B. S., Shaheen, F., & Gilani, A. H. (2002). Structure andspasmolytic activity of eucalyptanoic acid from Eucalyptus camaldulensis var.obtusa and synthesis of Its active derivative from oleanolic acid. Journal ofNatural Products, 65, 1939–1941.

Bowen-Forbes, C. S., Mulabagal, V., & Nair, M. G. (2009). Ursolic acid analogues:non-phenolic functional food components in Jamaican raspberry fruits. FoodChemistry, 116, 633–637.

Boyd, R. F. (1984). General Microbiology, p. 608. Times Mirror/Mosby College, U.S.A.Chen, H., & Yen, G. (2006). Antioxidant activity and free radical-scavenging capacity

of extracts from guava (Psidium guajava L.) leaves. Food Chemistry, 101,686–694.

Chyau, C., Chen, S., & Wu, C. (1992). Differences of Volatile and NonvolatileConstituents between Mature and Ripe Guava (Psidium guajava Linn) Fruits.Journal of Agricultural and Food Chemistry, 40, 846–849.

Hall, N. T., Smoot, J. M., Knight Jnr, R. J., & Nagy, S. (1980). Protein and amino acidcompositions of ten tropical fruits by gas-liquid chromatography. Journal ofAgricultural and Food Chemistry, 28, 1217–1221.

Han, Y. N., Choo, Y., Lee, Y., Moon, Y., Kim, S., & Choi, J. (2001). Monoamine oxidase Binhibitors from the fruits of Opuntia ficus-indica var. saboten. Archives ofPharmacological Research, 24, 51–54.

Jayaprakasha, G. K., Mandadi, K. K., Poulose, S. M., Jadegoud, Y., Gowda, G. A., & Patil,B. S. (2007). Inhibition of colon cancer cell growth and antioxidant activity ofbioactive compounds from Poncirus trifoliate (L.) Raf. Bioorganic and MedicinalChemistry, 15, 4923–4932.

Jiménez-Escrig, A., Rincón, M., Pulido, R., & Saura-Calixto, F. (2001). Guava fruit(Psidium guajava L.) as a new source of antioxidant dietary fiber. Journal ofAgricultural and Food Chemistry, 49, 5489–5493.

Liu, J. (1995). Pharmacology of oleanolic and ursolic acids. Journal ofEthnopharmacology, 49, 57–68.

Luximon-Ramma, A., Bahorun, T., & Crozier, A. (2003). Antioxidant actions andphenolic and vitamin C contents of common Mauritian exotic fruits. Journal ofthe Science of Food and Agriculture, 83, 496–502.

Mahato, S. B., & Kundu, A. P. (1994). 13C NMR spectra of pentacyclic triterpenoids – acompilation and some salient features. Phytochemistry, 37, 1517–1575.

Marin, R., Apel, M. A., Limberger, R. P., Raseira, M. C. B., Pereira, J. F. M., Zuanazzi, J. Â.S., et al. (2008). Volatile components and antioxidant activity from someMyrtaceous fruits cultivated in Southern Brazil. Latin American Journal ofPharmacy, 27, 172–177.

Mercadante, A. Z., Steck, A., & Pfander, H. (1999). Carotenoids from Guava (Psidiumguajava L.): Isolation and structure elucidation. Journal of Agricultural and FoodChemistry, 47, 145–151.

Nes, W. D., Norton, R. A., & Benson, M. (1992). Carbon-13 studies on sitosterolbiosynthesized from [13C] mevalonates. Phytochemistry, 31, 805–811.

Peng, R. Y., Hsieh, C., & Chen, K. (2008). Review of the medicinal uses of Psidiumguajava L. Recent Progress in Medicinal Plants, 20, 215–248.

Pino, J. A., Bello, A., Urquiola, A., Marbot, R., & Martí, M. P. (2004). Leaf oils of Psidiumparvifolium Griseb. and Psidium cattleianum Sabine from Cuba. Journal ofEssential Oil Research, 16, 370–371.

Pino, J. A., Marbot, R., & Vázquez, C. (2001). Characterization of volatiles instrawberry guava (Psidium cattleianum Sabine). Journal of Agricultural and FoodChemistry, 49, 5883–5887.

Popenoe, W. (1948). Tropical and sub-tropical fruits. (p. 474). Hafner Press, New York,U.S.A.

Pouchert, C. J., Behnke, J. (a) (1993). The Aldrich Library of 13C and 1H FT NMR Spectra,(1st ed.), (p 814). Aldrich Chemical Company Inc., .

Saura-Calixto, F. (1998). Antioxidant dietary fiber product: A new concept and apotential food ingredient. Journal of Agricultural and Food Chemistry, 46,4303–4306.

Seeram, N. P., Henning, S. M., Niu, Y., Lee, R., Scheuller, H. S., & Heber, D. (2006).Catechin and caffeine content of green tea dietary supplements and correlationwith antioxidant capacity. Journal of Agricultural and Food Chemistry, 54,1599–1603.

Shreier, P., & Idstein, H. (1985). Volatile constituents from Guava (Psidium guajava,L.) fruit. Journal of Agricultural and Food Chemistry, 33, 138–143.

Volpe, P. L. O., Collins, C. H., Simoni, J. A., & Silva, C. R. (1999). Ascorbic acid as astandard for iodometric titrations. Journal of Chemical Education, 76, 1421–1422.

Wilson, P. G., O’Brien, M. M., & Gadek, P. A. (2001). Myrtaceae revisited: areassessment of intrafamilial groups. American Journal of Botany, 88,2013–2025.