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an increase in the consumption of fruits and vegetables is associated with a decrease in the incidence of cardiovascular disease and reduced risks of certain cancers .
citrus fruits and derived products have a beneficial effect on humans [ 1 , 2 ] .
oranges are a rich source of flavonoids that are bioactive and may protect against age - related diseases .
the absorption of orange flavanones may be affected by factors such as processing , plant species , and geographic sources . additionally , the bioactivity of the absorbed phytochemicals depends on how they are metabolized during absorption .
several analytical methods have been applied to qualitative and quantitative flavonoid determination , especially hplc in conjunction with diode array detection and mass spectrometry , as in honey , citrus grandis , grapes and teas , scutellaria baclensis , glycyrrhiza uralensis , g. glabra and g. inata , blueberries , cultivars of clementine mandarin , satsuma mandarin , hybrid mandarin , navel orange , common orange , and pigmented orange , citrus species , grape cultivars , and orange and grapefruit juices . in the present paper ,
the flavanone contents ( hesperidin , naringin , naringenin , and poncirin ) of commercial and homemade orange juice originating from different places in brazil were evaluated .
the data were processed using principal component analysis ( pca ) to test homogeneity of the analytical results as well as identify outliers that should be removed from the data set to obtain representative values for flavonoids in brazilian orange juice . in recent years , this technique has been used for the evaluation and characterization of different kinds of food [ 13 , 14 ] .
standards for hesp ( hesperitin-7-o - rutinoside or hesperidin ) , narg ( naringenin ) , nar ( naringenin-7-o - neohesperidoside or naringin ) , and pon ( isosakuranetin-7-o - neohesperidoside or poncirin ) were obtained from sigma ( st . louis ) .
methanol and acetic acid reagents were obtained from j. t. baker ( phillipsburg , nj ) .
all solvents employed were hplc - grade and ultrapure ( milli - q ) water was used .
six samples ( 16 ) of orange juice were hand - squeezed ( domestic processing ) , six samples ( 3136 ) were obtained from a fresh - in - squeeze machine , and 24 industrial samples of orange juice were purchased from markets in the bahia and so paulo states ( brazil ) .
these 36 samples of orange juice were obtained during 2008 - 2009 and all belonged to the sinensis variety , a common orange juice source in brazil .
the juice samples were prepared using the adapted liquid - liquid continuous extraction shown in figure 1 .
aliquots of 400  g of orange juice were mixed with 300  ml of ethyl acetate ( etoac ) .
after extraction , the analyte samples were obtained by evaporation to dryness at 40c under vacuum .
after the residues were filtered through 0.22  m filters , they were dissolved in 10  ml of methanol before hplc detection .
hplc - dad analysis was performed on a shimadzu liquid chromatographic system ( kyoto , japan ) equipped with a rheodyne injection valve with a 1  l fixed loop , an scl-10 avp pump , and an autosampler .
the flow rate was 0.3  ml / min , and a thermostated column oven was used with a reverse - phase c18 purospher star tracer 3  m ( 55  4  mm ) ( merck , germany ) column with sample and column temperatures of 5 and 25c , respectively .
compounds were monitored at 240 and 280  nm using a uv - vis photodiode array detector ( shimadzu model spd - md ) , and uv spectra were recorded from 200 to 400  nm and were controlled by a gpc / lc solution workstation ( version 1.21 sp1 ) . a gradient mobile phase consisting of methanol ( solvent a ) and acid h2o ( 1.0% acetic acid ) ( solvent b ) was used for hplc analysis .
the conditions were as follows : initial conditions of 20% a for 5  min , followed by an increase to 60% a for 10  min , 80% a for 20  min , and 60% a in the following 40  min , and then back to the initial conditions for 10  min .
compounds were identified by comparing their retention times ( rt nar = 9.0  min ; rt hesp = 15.0  min ; rt pon = 17.0  min ; rt narg = 22.0 ) and their uv - vis spectra with corresponding standards .
usa ) was used to treat the data for basic statistical parameters and principal component analysis ( pca ) .
each principal component is an eigenvector of the correlation matrix of the standardized original data and is a linear combination of the original variables .
one - way anova was used to estimate significant differences for the calculated data means .
the analytical curves were constructed using standard solutions in the 60300 , 0.010.09 , 0.050.25 , and 0.050.30  mg 100  g ranges for hesperidin , naringin , naringenin , and poncirin , respectively .
the analytical curves exhibited excellent linear behavior over the concentration range . the limits of detection ( lod ) , calculated as the minimal concentration corresponding to 3.3  ( sd / s ) , with sd being the standard deviation of the blank and s the slope of the standard curve , were 0.0037 , 1.87 , 0.0147 , and 0.0066  mg 100  g for naringin , hesperidin , poncirin , and naringenin , respectively . the limits of quantification ( loq ) , calculated as the minimal concentration corresponding to 10  ( sd / s ) , with sd being the standard deviation of the blank and s the slope of the standard curve , were 0.0089 , 7.84 , 0.0302 , and 0.0200  mg 100  g , respectively , for naringin , hesperidin , poncirin , and naringenin , respectively . the calculated values were confirmed with actual analytical values under the established chromatographic conditions .
the accuracy of the method was verified in recovery tests using flavanone samples spiked with 60  mg 100  g of hesperidin and 0.30  mg 100  g of flavanone standards ( naringin , naringenin , and poncirin ) .
the mean recoveries were 101 , 107 , 103 , and 98% , for naringin , hesperidin , poncirin , and naringenin , respectively .
the linearity of the hplc method was checked in the 60300  mg 100  g range for hesperidin and the 0.010.09 , 0.050.25 , and 0.050.30  mg 100  g ranges for naringin , naringenin , and poncirin , respectively .
calibrations were performed by injection of the standard working solution in triplicate at five different concentrations for each flavanone based on the expected flavanone content ranges in the samples .
all standard curves passed through the origin were linear in the concentration ranges expected for the samples and had coefficients of determination ranging from 0.9986 ( for naringin ) to 0.9999 ( for naringenin ) .
the flavonoids present in the brazilian orange juices were separated by hplc and the uv spectra of the different peaks were recorded .
the chromatographic conditions allowed for good separation of most of the peaks in the chromatogram . a characteristic hplc - dad chromatogram of the etoac extract of orange juices recorded at 240  nm is presented in figure 2 .
diode array detection ( uv spectra recorded from 200 to 400  nm ) allowed characterization of the phenolics , which were mainly flavonoids .
definitive identification of some of the flavanones was performed by spiking experiments with authentic compounds .
the results of the determinations of hesperidin , poncirin , naringin , and naringenin in the 36 orange juice samples are summarized in table 1 . among these four analytes ,
the average content was 69.85  mg 100  g , and the concentration range found was from 18.80 to 139.00  mg 100  g. it is worth noting that the industrial orange juices showed high contents of hesperidin ( samples 7 to 31 ) .
the presence of this compound is important for juice quality , as hesperidin is known to have antioxidant , anti - inflammatory , antiallergic , and immunomodulatory activities , while naringenin is involved in some pharmaceutical metabolism ( e.g. , dihydropyridines ) and decreases the half - life of medicines that are dependent on cytochrome p450 [ 1517 ] and lower blood lipid and cholesterol [ 1820 ] .
naringin , naringenin , and poncirin showed lower concentration levels in the orange juices ; the average contents and concentration ranges found were 0.019 and 0.010.30 , 0.12 and 0.10.17 , and 0.13 and 0.010.36  mg 100  g , respectively .
the results of the flavanone determinations for the 36 juice samples were analyzed using the multivariate principal component analysis ( pca ) technique .
this statistical tool was employed to evaluate the extraction tendencies and the quantification of the flavonoids .
a data matrix was constructed using the flavanone concentrations as columns and the orange juice samples as rows .
the results of the pca revealed that the first two principal components explained 79.34% of the total variance .
pc1 accounted for 47.72% of the variability in the data , mainly related to the poncirin , naringenin , and naringin concentrations . the score plot
( figure 3 ) did not show well - defined data clustering of the samples with scores on pc1 ( 1 , 2 , and 3 , all circled in figure 4 ) .
finally , the second principal component ( pc2 , describing 31.62% of the total variance ) was primarily associated with variations in the hesperidin and naringin concentrations .
thus , the samples corresponding to points located at the top of the score graph in figure 3 had high contents of these flavanones . according to gattuso et al .
the distribution of the samples throughout pc2 was relatively uniform , showing that the concentrations of theses flavanones have continuous distributions throughout the juice samples .
this paper reports determination of the flavanone composition ( hesperidin , naringin , naringenin , and poncirin ) in orange juice .
the pca technique showed that poncirin , naringenin , and naringin were the principal elements that contributed to the variability in the samples .
these results suggest that flavonoid contents are more expressive in industrial samples maybe due to the mechanical process of obtaining the juices .
flavanones ( hesperidin , naringenin , naringin , and poncirin ) in industrial , hand - squeezed orange juices and from fresh - in - squeeze machines orange juices were determined by hplc / dad analysis using a previously described liquid - liquid extraction method . 
 method validation including the accuracy was performed by using recovery tests . 
 samples ( 36 ) collected from different brazilian locations and brands were analyzed . 
 concentrations were determined using an external standard curve . 
 the limits of detection ( lod ) and the limits of quantification ( loq ) calculated were 0.0037 , 1.87 , 0.0147 , and 0.0066  mg 100  g1 and 0.0089 , 7.84 , 0.0302 , and 0.0200  mg 100  g1 for naringin , hesperidin , poncirin , and naringenin , respectively . 
 the results demonstrated that hesperidin was present at the highest concentration levels , especially in the industrial orange juices . 
 its average content and concentration range were 69.85 and 18.80139.00  mg 100  g1 . 
 the other flavanones showed the lowest concentration levels . 
 the average contents and concentration ranges found were 0.019 , 0.010.30 , and 0.12 and 0.10.17 , 0.13 , and 0.010.36  mg 100  g1 , respectively . 
 the results were also evaluated using the principal component analysis ( pca ) multivariate analysis technique which showed that poncirin , naringenin , and naringin were the principal elements that contributed to the variability in the sample concentrations .