Evaluation of the intravenous and topical routes for ocular delivery of hesperidin and hesperetin

Abstract

Purpose: The objective of this study was to determine the ocular bioavailability of hesperidin and hesperetin, especially with respect to their distribution into the posterior segment of the eye, following systemic and topical administration in rabbits.

Methods: Hesperidin and hesperetin were administered either intravenously or topically to male New Zealand white (NZW) rabbits. Vitreous humor and plasma samples were collected after intravenous administration and analyzed to estimate the concentrations of the parent compounds and their metabolites. Ocular tissue concentrations, obtained on topical administration of hesperidin and hesperetin, were also determined.

Results: In the systemic circulation, hesperidin and hesperetin were rapidly metabolized into their glucuronides, which are extremely hydrophilic in nature. Vitreal samples did not demonstrate any detectable levels of hesperidin/hesperetin following intravenous administration. Topical administration produced significant concentrations of hesperidin/hesperetin in all the ocular tissues tested at the 1 and 3 hours time points postdosing, with hesperetin showing higher levels compared to hesperidin. However, only low levels were generated in the vitreous humor. Inclusion of a penetration enhancer, benzalkonium chloride (BAK), improved the back-of-the-eye hesperetin levels.

Conclusions: Ocular delivery of hesperidin/hesperetin via the systemic route does not seem to be feasible considering the rapid generation of the hydrophilic metabolites. Topical application appears to be more promising and needs to be further developed/refined.

FIG. 1.

Selected ion chromatogram and mass spectra of standard compounds (1 μg/mL).

FIG. 2.

Mean plasma concentration–time profile of hesperidin and hesperetin-glucuronide (estimated as hesperetin after the treatment of the plasma samples with beta-glucuronidase to convert hesperetin-glucuronide to hesperetin), generated in vivo, in the rabbits following intravenous administration of hesperidin at 20 mg/kg body weight (n=4).

FIG. 3.

Mean plasma concentration–time profile of hesperetin (from direct analysis) and hesperetin-glucuronide (estimated as hesperetin after the treatment of the plasma samples with beta-glucuronidase to convert hesperetin-glucuronide to hesperetin) following intravenous administration of hesperetin at a dose of 20 mg/kg in rabbits (n=4).

FIG. 4.

Levels of hesperidin observed in the rabbit ocular tissues at 1 and 3 h following topical administration of hesperidin [100 μL of 1% w/v solution containing HP-β-CD (10% w/v), HPMC (0.1% w/v), 1 N NaOH (0.05% v/v), and 1 N HCl (0.05% w/v), IPBS pH 7.4 (q.s.)]. Values represent mean±SD (n=4). HP-β-CD, hydroxylpropyl beta-cyclodextrin; HPMC, hydroxypropyl methylcellulose; IPBS, isotonic phosphate-buffered saline; SD, standard deviation.

FIG. 5.

Levels of hesperetin observed in the rabbit ocular tissues at 1 and 3 h following topical administration of hesperetin [100 μL of 1% w/v solution containing HP-β-CD (10% w/v), HPMC (0.1% w/v), 1 N NaOH (0.05% v/v), and 1 N HCl (0.05% w/v), IPBS pH 7.4]. Values represent mean±SD (n=4).