High-performance liquid chromatography with diode-array detection for the determination of phenolic compounds in peel and pulp from different apple varieties

https://doi.org/10.1016/S0021-9673(98)00294-5Get rights and content

Abstract

Quantitative analysis of phenolic compounds from four apple varieties (Golden and Red Delicious, Granny Smith and Green Reineta) using high-performance liquid chromatography with diode-array detection was carried out. For each variety, both peel and pulp were analysed. The identification of phenolic compounds was made by comparing their retention times and UV spectra with those of standards. The results revealed differences between pulp and peel in all cases studied. The highest levels of phenolic compounds were found in the peel. High levels of catechins and flavonol glycosides, especially rutin, were found in apple peels. Chlorogenic acid was the major peak in the pulp for all apple varieties studied except for Granny Smith. Significant quantitative differences between the apple varieties were also found, the Golden Delicious variety showing the lowest content of phenolic compounds and Green Reineta variety the highest. The recovery of phenolic compounds from both peel and pulp was measured in all apple varieties. The values ranged between 95 and 105%, indicating close to quantitative recovery for the method used.

Introduction

Phenolic compounds are found in plants and thus are part of the human diet [1]. Dietary phenolic compounds, and especially the flavonoids, consist mainly of anthocyanidins, flavonols and catechins [2]. They are absorbed from the gastrointestinal tracts of humans and are excreted in faeces and urine. Accurate data on population-wide intakes of flavonoids are not available but a recent review [1]points out that the most important dietary sources are vegetables, fruits and beverages. It is estimated that tea, onions and apples are the main dietary sources of flavonoids [3]. However, current estimates of daily consumption of flavonoids differ considerably [4]and, consequently, more quantitative data are necessary [1].

The phenolic composition of fruits has been studied by HPLC–diode array detection (DAD) in pulps and juices with regard to their contribution to the color and flavor [5], their qualitative and quantitative differences appearing as a function of the species, degree of ripening and storage 6, 7as well as of their presence in commercial juices and jams 8, 9.

However, few studies of extracts from fresh peel matrices have been reported 10, 11, and comparative studies between peel and pulp are especially limited 12, 13. This comparison is important since apples are consumed both peeled and unpeeled. Taking into account all these considerations, more quantitative data of phenolic compounds from apples (peel and pulp) are needed.

The aim of this work was to carry out a comparative systematic study on the quantitative composition of phenolic compounds in fresh pulp and peel from the apple varieties, Golden Delicious, Red Delicious, Granny Smith and Reineta Green (Spanish apple). These varieties are usually consumed as fresh fruits in the Mediterranean diet [14].

Section snippets

Reagents and standards

The standards (+)-catechin and (−)-epicatechin as well as gallic, caffeic and chlorogenic acids, phlorizdin and rutin were acquired from Sigma (St. Louis, MO, USA). Methanol of HPLC grade was acquired from Sharlau and all other chemicals of analytical-reagent grade were purchased from Merck. In all cases, the water used was of HPLC quality, purified in a Milli-Q system (Millipore, Bedford, MA, USA). All the samples (solutions and extracts) were filtered through 0.45-μm membranes (Millipore) and

Separation and identification

Fig. 1 shows the chromatograms of the extracts from peel and pulp. Table 1 lists the retention times including standard deviation (S.D.) for six replicates of each variety studied, the selectivity factor (α), as well as UV absortion maxima of each peak obtained by DAD.

The gradient elution method used allowed a good separation of the phenolic compounds present with values of α above 1.00 in all cases. This method enabled the identification of the phenolic compounds in all samples studied.

Conclusion

The methodology developed in this work enabled the quantitative determination of the phenolic compounds present in peel and pulp from different varieties of apple. Significant quantitatively differences were observed between the varieties studied. Golden Delicious was the variety with the lowest phenolic content whereas Reineta was the variety with the highest levels of phenolic compounds. In all cases, apple peels showed higher phenolic content than pulp extracts. These quantitatives

References (19)

  • N.C Cook et al.

    J. Nutr. Biochem.

    (1996)
  • E Delage et al.

    J. Chromatogr.

    (1991)
  • B Bartolomé et al.

    J. Chromatogr.

    (1996)
  • K Robards et al.

    Analyst

    (1997)
  • K Herrmann

    Z. Lebensm-Unters. Forsch.

    (1988)
  • W.E Bronner et al.

    J. Chromatogr.

    (1995)
  • K Herrmann

    Chem. Mikrobiol. Technol. Lebensm.

    (1990)
  • G.A Spanos et al.

    J. Agric. Food Chem.

    (1990)
  • B Fernández de Simón et al.

    Z. Lebensm. Unters. Forsch

    (1992)
There are more references available in the full text version of this article.

Cited by (327)

  • Potential health benefits of selected fruits: apples, blueberries, grapes, guavas, mangos, pomegranates, and tomatoes

    2021, Functional Foods and Nutraceuticals in Metabolic and Non-communicable Diseases
View all citing articles on Scopus
View full text