Elsevier

Fitoterapia

Volume 71, Issue 2, 1 April 2000, Pages 154-161
Fitoterapia

Variance of common flavonoids by brand of grapefruit juice

https://doi.org/10.1016/S0367-326X(99)00131-8Get rights and content

Abstract

Nine commercial brands of grapefruit juice were analyzed for their flavonoid content by HPLC to determine if significant brand-to-brand variance in grapefruit juice flavonoid content exists. Flavonoid glycosides narirutin, naringin, hesperidin, neohesperidin, didymin, and poncirin have been identified in all the grapefruit juices examined. The aglycone quercetin was detected in only two brands. All the juices were free from methoxylated flavonoid aglycones. There was a significant difference in the amounts of total flavonoids and individual flavonoids in the nine brands. The concentration of total flavonoids ranged between 19.44 and 84.28 mg/100 ml juice. Naringin was found to be the major flavonoid followed by narirutin and hesperidin. Their concentrations ranged from 14.56 to 63.8; 2.25 to 12.20; and 0.24 to 3.12 mg/100 ml juice, respectively.

Introduction

This study was designed to characterize the differences in flavonoid concentration of several commercially available brands of grapefruit [Citrus paradisi Macf. (Rutaceae)] juice (GFJ). GFJ has been demonstrated to inhibit the metabolism of several cytochrome P450 (cP450) metabolized drugs [1], [2], [3], [4], [5], [6], [7], [8]. After our analyses were completed newly published research demonstrated that 6′,7′-dihydroxybergamottin, a furanocoumarin, is probably the major cP450 inhibitory substance in grapefruit products [9]. Even so, flavonoids have been demonstrated to exhibit a significant degree of cP450 inhibition and for this reason our data are significant. Furthermore, future plans include expanding the current database to determine if high flavonoid concentration in commercial grapefruit products correlates with high 6′,7′-dihydroxybergamottin concentration, thus demonstrating that both may play a role in cP450 inhibition. Recently, GFJ and orange juice have been demonstrated to significantly lower LDL-cholesterol in animals [10]. Flavonoids in Citrus juices might also play a significant role in lowering cholesterol in humans.

Section snippets

Investigated material

Nine commercial grapefruit juice products detailed in Table 1.

Flavonoid Standards

Rutin trihydrate (quercetin 3-rutinoside), quercetin dihydrate (3,5,7,3′,4′-pentahydroxyflavone), hesperidin (hesperitin 7-rutinoside), naringin (naringenin 7-rutinoside), kaempferol (3,5,7,4′-tetrahydroxyflavone), kaempferide (3,5,7,-trihydroxy-4′-methoxyflavone), and apigenin (5,7,4′-trihydroxyflavone) were obtained from Fluka Chemical Corp. (Ronkonkoma, NY 11779, USA). Poncirin (isosakuranetin 7-neohesperidoside), didymin

Results

High performance liquid chromatography (HPLC) using normal or reversed-phase columns has been utilized by many investigators to quantify flavonoids in Citrus juices [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16]. In our study a similar HPLC method was used to quantify all the major flavonoids present in GFJ. Nine commercial brands of grapefruit juice (Table 1) were analyzed for their flavonoid content. The identification of the flavonoids in the different

Discussion

The small intestine, especially the duodenum, is the site of high concentration cP450 enzymes [21]. When drugs metabolized by these enzymes are administered orally, significant pre-systemic metabolism and thus, reduced bioavailability occurs. Pre-systemic metabolism of several agents by cP450 has been confirmed [1], [2], [4], [5], [6], [7], [22]. These studies describe a variety of drugs having a propensity for increased systemic bioavailability when administered orally and simultaneously with

Acknowledgements

We are grateful to Charles D. Hufford, H. Joseph Byrd, John D. Cleary, and W.W. Widmer for their invaluable assistance.

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