Factors Influencing Oral Bioavailability of Thai Mango Seed Kernel Extract and Its Key Phenolic Principles

Abstract

Mango seed kernel extract (MSKE) and its key components (gallic acid, GA; methyl gallate, MG; and pentagalloyl glucopyranose, PGG) have generated interest because of their pharmacological activities. To develop the potential use of the key components in MSKE as natural therapeutic agents, their pharmacokinetic data are necessary. Therefore, this study was performed to evaluate the factors affecting their oral bioavailability as pure compounds and as components in MSKE. The in vitro chemical stability, biological stability, and absorption were evaluated in Hanks' Balanced Salt Solution, Caco-2 cell and rat fecal lysates, and the Caco-2 cell model, respectively. The in vivo oral pharmacokinetic behavior was elucidated in Sprague-Dawley rats. The key components were unstable under alkaline conditions and in Caco-2 cell lysates or rat fecal lysates. The absorptive permeability coefficient followed the order MG > GA > PGG. The in vivo results exhibited similar pharmacokinetic trends to the in vitro studies. Additionally, the co-components in MSKE may affect the pharmacokinetic behaviors of the key components in MSKE. In conclusion, chemical degradation under alkaline conditions, biological degradation by intestinal cell and colonic microflora enzymes, and low absorptive permeability could be important factors underlying the oral bioavailability of these polyphenols.

Keywords: Caco-2 cells; Mangifera indica L.; fecal lysate; pentagalloyl glucopyranose; pharmacokinetic.

Figure 1

Chemical stabilities of GA, MG and PGG after incubation with HBSS at pH 5, 6, 7 and 8 as individual compounds (2 µM, A; and 20 µM, B) and as principles in MSKE (0.25 mg/mL, C). Each symbol indicates the mean ± S.D. (n = 3).

Figure 2

The recoveries of GA, MG and PGG after incubation for 24 h with Caco-2 cell lysates as individual compounds (100 µM for each compounds, A) and as principles in 0.75 mg/mL MSKE (B). The stabilities of the three phenolic compounds in MSKE are also displayed as the relative recoveries (C). Each symbol indicates the mean ± S.D. (n = 3).

Figure 3

The biological stabilities of GA, MG and PGG at 10 µM for each compound after individual incubation with rat fecal lysates (A1, B1 and C1, respectively), inactive rat fecal lysates (A2, B2 and C2, respectively) and HBSS at pH 6 (A3, B3 and C3, respectively) for 24 h. Each symbol indicates the mean ± S.D. (n = 3).

Figure 4

The recoveries of GA, MG and PGG in the mixture (10 µM, A) and in MSKE (100 µg/mL, B) after incubation with rat fecal lysates. The stabilities of the three phenolic compounds in MSKE are also displayed as the relative recoveries (C). Each symbol indicates the mean ± S.D. (n = 3).

Figure 5

The cellular uptake of GA, MG and PGG after transport as individual compounds, in the mixture and in MSKE across the Caco-2 monolayer from side A to side B (A) and from side B to side A (B). Each symbol indicates the mean ± S.D. (n = 3). ^# indicates that the amount of analyte could not be determined. * Significant difference (p < 0.05).

Figure 6

Blood concentration–time curves of MG after oral administration of the mixture with PGG at a dose of 20 mg/kg (A) and as principles in MSKE at a dose of 143 mg/kg (B). Each symbol indicates the mean ± S.D. (n = 5).

Figure 7

The representative MRM chromatograms of MG, PGG and their sulfate and glucuronide metabolites in blood sample collected at 30 min (A) and urine samples (B) and fecal samples (C) between 0 and 24 h after oral administration of the mixture of MG and PGG at a dose of 20 mg/kg for each compound.

Figure 8

UPLC chromatograms, and UV spectra of GA, MG, and PGG as the reference standards (A1 and A2) and as principles in MSKE (B1 and B2).