Determination of Daidzein in Rat Plasma by LC By:

Daidzein (4′,7-dihydroxylisoflavone), a water-insoluble isoflavone, is mainly present in leguminous plants. This study was aimed at investigating the absorption characteristics of daidzein across the intestinal membranes. Borneol has been used to enhance the intestinal absorption and bioavailability of daidzein. We chose an in vitro diffusion chamber system using isolated rat intestinal membranes as a model. A sensitive, accurate and reliable LC method was developed and validated to determine daidzein in rat plasma. A linear relationship for daidzein was found in the range of 20–800 ng mL. The mean absolute recoveries of daidzein determined over three concentrations were 89.8 ± 4.8, 91.3 ± 2.8 and 95.4 ± 1.7%. The coefficients of variation for inter-day and intra-day assay were found to be less than 6.1%. The plasma concentration of daidzin following oral administration was significantly increased by coadministration of borneol in rats, and a 1.5-fold enhancement of relative bioavailability of daidzein was observed as compared to daidzein administered alone. Article: INTRODUCTION Daidzein (Figure 1) (4′,7-dihydroxylisoflavone), a water-insoluble isoflavone, is mainly present in leguminous plants, especially in soybeans, soy foods and Pueraria lobata Ohwi (Leguminosae) [1, 2]. It has already been demonstrated that diadzein can reduce breast cancer occurrence, and may play a key role in protection against colon cancer [3]. More recently, Wilcox and Blumenthal [4] have hypothesized that isoflavones might reduce the aggregation of platelets at the sites of arterial injury associated with atherosclerotic development [5]. Figure 1: Structure of daidzein Nevertheless, the occurrence of any beneficial effects of bioactive compounds is mainly related to their ability to be absorbed in the intestine. Only limited studies on absorption, metabolism, and distribution of isoflavones are available [6–11]. Studies of Setchell et al. [12, 13] on isoflavone bioavailability in healthy women, showing a curvilinear relationship between dietary intake and plasma levels. We focused our attention on intestinal absorption characteristics of daidzein because data regarding absorption of this isoflavone are very limited. Borneol, has been used in our work to enhance the intestinal absorption and bioavailability of this poorly watersoluble isoflavone. Oral administration is the preferred route by virtue of its convenience and better compliance. However, the development of this delivery system is considered to be a great challenge due to the poor water-solubility, poor permeability and rapid metabolism of some drugs. A variety of formulation strategies has been developed to improve the solubility and bioavailability of such drugs. Several approaches such as absorption enhancers [14, 15], chemical modification [16, 17] and dosage forms [18, 19] have been explored in order to attain peroral delivery of drugs. Of these approaches, the use of absorption enhancers has often been adapted to enhance the intestinal absorption [15, 20]. Some studies have shown that borneol could improve the oral bioavailability of some drugs [21]. In this study, we have investigated the absorption characteristics of daidzein across the intestinal membranes. The influence of borneol as an absorption enhancer on the intestinal absorption and oral bioavailability of daidzein was also investigated in rats.