Abstract
Glycyrrhizae radix et rhizoma has been used as a traditional Chinese medicine for the treatment of various diseases. Triterpenoids and flavonoids from the plant have many beneficial effects and their chemical structures are modified in the gastrointestinal tract after oral administration. However, absorption of these triterpenoids and flavonoids still needs to be defined. Here, the uptake and transepithelial transport of the selected major triterpenoids, glycyrrhizin (1), glycyrrhetic acid-3-O-mono-β-d-glucuronide (2), and glycyrrhetinic acid (3); and the selected major flavonoids, licochalcone A (4), licochalcone B (5), licochalcone C (6), echinatin (7), isoliquiritin apioside (8), liquiritigenin (9), liquiritin apioside (10) isolated from Glycyrrhizae radix et rhizoma, were investigated in the human intestinal epithelium-like Caco-2 cell monolayer model. Compounds 3, 5–7, and 9 were designated as well-absorbed compounds, 2 and 4 were designated as moderately absorbed ones, and 1, 8, and 10 were assigned for the poorly absorbed ones. The absorption mechanism of well and moderately absorbed compound was mainly passive diffusion to pass through the human intestinal Caco-2 cell monolayer. These findings provided useful information for predicting their oral bioavailability and the clinical application.
Highlights
The genus Glycyrrhiza consists of about 30 species with a nearly global distribution, of which about18 species are found in China
The transport rates of the six selected compounds 3, 5–7, and 9, lipophilic aglycones including major triterpenoid, chalcone, and flavonone compounds in licorice, increased linearly with the concentration and saturation was not observed at the concentrations tested, indicating that the permeation mechanism for these compounds was passive diffusion
The magnitude of the bidirectional flux of these compounds was comparable to propranolol (Papp = (2.51 ± 0.21) × 10−5 cm/s). These data suggest that the compounds 3, 5–7, and 9 were well-absorbed compounds and were transported mainly through passive diffusion by the transcellular pathway
Summary
The genus Glycyrrhiza consists of about 30 species with a nearly global distribution, of which about18 species are found in China. Triterpenoids and flavonoids were the two major active substances, exerting a variety of pharmacological activities including antiviral [6,7,8], anti-inflammatory [9,10,11,12], antioxidative [13,14], hepatoprotective [15,16], antimicrobial [17,18,19,20,21,22], antitumor [23,24,25], antiallergic [26,27,28], and potent cytochrome P450 enzyme inhibitory [29] properties To what extent these components are effective in the human body depends on their bioavailability and metabolism in vivo. The focus of this study was to investigate the critical step towards understanding their potential bioactivity. The focus of this study was to transport and cellular uptake of three major triterpenoids; glycyrrhizin (1), glycyrrhetic investigate the transport and cellular uptake of three major triterpenoids; glycyrrhizin (1), glycyrrhetic acid-3-O-mono-β-D-glucuronide (2) and glycyrrhetinic acid (3), and seven flavonoids; licochalcone acid-3-O-mono-β-D-glucuronide (2) and glycyrrhetinic acid (3), and seven flavonoids; licochalcone A
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