Abstract
Astilbin and neoastilbin are two flavonoid stereoisomers. In the present study, their solubility, stability, and bioavailability were compared in a rat. The results revealed that the water solubility of astilbin and neoastilbin was 132.72 μg/mL and 217.16 μg/mL, respectively. The oil–water distribution coefficient (log P) of astilbin and neoastilbin in simulated gastric fluid (SGF) was 1.57 and 1.39, and in simulated intestinal fluid (SIF) was 1.09 and 0.98, respectively. In SIF, about 78.6% astilbin remained after 4 h of incubation at 37 °C, while this value was 88.3% for neoastilbin. Most of the degraded astilbin and neoastilbin were isomerized into their cis-trans-isomer, namely neoisoastilbin and isoastilbin, respectively, and the decomposed parts were rare. For bioavailability comparison in a rat, an HPLC method for trace amounts of astilbin and neoastilbin determination in plasma was developed, and the pretreatment of plasma was optimized. A pharmacokinetic study showed that the absolute bioavailability of astilbin and neoastilbin in a rat showed no significant difference with values of 0.30% and 0.28%, respectively.
Highlights
Astilbin, (2R,3R)-3,30,40,5,7-pentahydroxyflavanon-3-α-l-rhamnopyranoside, is a dihydroflavonol found in many plants and plant-based foods, e.g., Smilax glabra Rhizoma (SGR) [1], Engelhardtia roxburghiana [2], grape, and wine [3]
The solubility of astilbin and neoastilbin was compared in water at 25 ◦ C only
After realizing the isomerization in a subsequent study [12], the solubility of astilbin/neoastilbin was determined by HPLC in the present study, which can separate astilbin from its isomers
Summary
Astilbin, (2R,3R)-3,30 ,40 ,5,7-pentahydroxyflavanon-3-α-l-rhamnopyranoside, is a dihydroflavonol found in many plants and plant-based foods, e.g., Smilax glabra Rhizoma (SGR) [1], Engelhardtia roxburghiana [2], grape, and wine [3]. According to the structure of astilbin, it has two asymmetric carbon atoms at C-2 and C-3 and, has four stereoisomers, namely neoastilbin (2S, 3S), astilbin (2R, 3R), neoisoastilbin (2S, 3R), and isoastilbin (2R, 3S) [4]. These four stereoisomers naturally coexist in plants. Its biological activity has been extensively studied, including antioxidant activity, hypoglycemic effect [7], selective immunosuppressive activity [8], etc. Because of the low content of the other three stereoisomers in plants, there are few relevant studies on them
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