New Insights into the Metabolism of the Flavanones Eriocitrin and Hesperidin: A Comparative Human Pharmacokinetic Study

Abstract

The intake of hesperidin-rich sources, mostly found in orange juice, can decrease cardiometabolic risk, potentially linked to the gut microbial phase-II hesperetin derivatives. However, the low hesperidin solubility hampers its bioavailability and microbial metabolism, yielding a high inter-individual variability (high vs. low-producers) that prevents consistent health-related evidence. Contrarily, the human metabolism of (lemon) eriocitrin is hardly known. We hypothesize that the higher solubility of (lemon) eriocitrin vs. (orange) hesperidin might yield more bioavailable metabolites than hesperidin. A randomized-crossover human pharmacokinetic study (n = 16) compared the bioavailability and metabolism of flavanones from lemon and orange extracts and postprandial changes in oxidative, inflammatory, and metabolic markers after a high-fat-high-sugars meal. A total of 17 phase-II flavanone-derived metabolites were identified. No significant biomarker changes were observed. Plasma and urinary concentrations of all metabolites, including hesperetin metabolites, were higher after lemon extract intake. Total plasma metabolites showed significantly mean lower T_max (6.0 ± 0.4 vs. 8.0 ± 0.5 h) and higher C_max and AUC values after lemon extract intake. We provide new insights on hesperetin-eriodictyol interconversion and naringenin formation from hesperidin in humans. Our results suggest that regular consumption of a soluble and eco-friendly eriocitrin-rich lemon extract could provide a circulating concentration metabolites threshold to exert health benefits, even in the so-called low-producers.

Keywords: citrus; eriocitrin; eriodictyol metabolites; flavanones; gut microbiota; hesperetin metabolites; hesperidin; lemon; orange; pharmacokinetics.

Figure 1

Study design. OE, orange extract; LE, lemon extract.

Figure 2

Representative extracted ion chromatograms (EICs) of urine and plasma metabolites after consuming (A,C) lemon or (B,D) orange extract. Numbers designate the metabolites according to Table 3.

Figure 3

Plasma pharmacokinetic profiles of different metabolites after consuming lemon (blue) or orange (brown) extracts. (A) M8 (hesperetin 3′-O-glucuronide); (B) M7 (hesperetin 7-O-glucuronide); (C) M14 (hesperetin 3′-O-sulfate); (D) M2 (eriodictyol glucuronide isomer-2); (E) M6 (homoeriodictyol glucuronide); and (F) M13 (eriodictyol sulfate). Results are expressed as mean ± SD.

Figure 4

Main metabolic transformations of hesperidin and eriocitrin to their corresponding phase-II conjugates. The identification and quantification of metabolites (M) can be found in Table 3 and Table 4, respectively. The pharmacokinetic values can be found in Table 5. Black lines, microbial metabolism; blue lines, phase-II metabolism; red lines, phase-I or microbial metabolism; dashed lines, proposed new metabolic steps in the human metabolism of hesperidin and eriocitrin. The thickness of the lines represents the most favored pathways. LE, lemon extract; OE, orange extract (hesperidin); glur, glucuronic acid; sulf, sulfonic acid. The formation of eriodictyol (M12) from hesperetin mainly occurs via 4′-demethylation of hesperetin (M17) and the formation of naringenin (M15), after 4′-demethylation plus 3′-dehydroxylation. Besides, M12 could also be formed after CYP-catalyzed 3′-hydroxylation of M15 (Figure 4). These steps were supported by the detection of eriodictyol and naringenin conjugates after hesperidin intake in plasma and urine. However, no homoeriodictyol or derived metabolites (M16, M6, M10) were observed after hesperidin intake, which indicates that 4′-methylation to yield back hesperetin was favored instead of the subsequent 3′-methylation of eriodictyol to yield homoeriodictyol after consuming hesperidin (Figure 4).