Studies On The Oral Absorption Mechanism And The Improvement Of Bioavailability Of Naringenin

Naringenin, 4', 5, 7-trihydroxyflavanone, are flavonoids widely existed in the plant kingdom. Previous reports have shown naringenin has many biological and pharmacological activities in home and aboard. The pharmacokinetics studies of naringenin in our lab generated two problems. One was that there existed double peaks phenomenon in the plasma concentration-time curve. The other was the relative low absolute bioavailability after oral administration. So the aim of the article was to analysis how the double peaks phenomenon appeared and to improve the oral bioavailability of naringenin through pharmaceutical methods and chemical structure modification. Moreover, the application of Caco-2 cell model was to study the absorption mechanism of naringenin and offer some basis and new routes for drug structure modification and dosage form design.We further discussed and analysis the double peaks phenomenon from dosages, enterohepatic circulation and gastroenteric circulation. The final result was that the double peaks were mainly due to enterohepatic circulation, then gastroenteric circulation, and dosages had no effects.Previous studies claimed the low oral bioavailability of naringenin. The absolute bioavailability following oral ingestion in rats was 3.8% and 39.8% calculated by free and total naringenin, respectively. The low bioavailability might result in individual differences and increased the production costs. As a result how to improve bioavailability of naringenin is the key to this paper.Naringenin is poorly soluble in water and oil obtained from the investigation of its physical and chemical properties and this may be one of the reasons leading the low bioavailability. So we decided to improve its property by pharmaceutical methods and structure modification.Firstly, the naringenin phytosome, solid dispersion and inclusion compound was prepared and proved to better the water solubility of naringenin. Especially inclusion compound increased the water solubility from 71.33μg/ml to 793.33μg/ml and phytosome obviously improved the solubility in CHCl₃ to 1.52±0.21mg/ml as well as the solubility in water 3-fold than before. On the base we obtained the optimized formulation through orthogonal design. The ratio of naringenin to phospholipids was 1 to 2, reaction temperature was 40℃and the concentration of naringenin was 10ï¼…(g/ml). In Caco-2 cell experiment phytosome prepared by optimized formulation could better the absorption of naringenin and the P_app was 2.22-fold than before, indicating phytosomes might improve the bioavailability of naringenin.Secondly, two naringenin prodrugsâ… andâ…¡were obtained by structure modification. They improved the solubility in oil and water, respectively. To investigate the absorption of prodrugsâ… andâ…¡with Caco-2 cell model results were that the two naringenin prodrugs could hydrolysis to naringenin during the course of absorption, but the transport of prodrugâ… was slow due to its high lipophilicity. Prodrugâ…¡was well absorbed and well soluble in water with a P_app of 9.22×10^-6 cm·s^-1, so prodrugâ…¡can provide more administration routes and have certain exploitation and development potential.By comparison the properties of the obtained products and the Caco-2 cell experiments, it indicated phytosomes and prodrugâ…¡might improve the bioavailability of naringenin. The bioavailability experiment of naringenin phytosome in rats was carried out and the research demonstrated phytosome was clearly improved the bioavailability of naringenin. The relative bioavailability of naringenin phytosome was 236ï¼…and 184ï¼…calculated by free and total naringenin in plasma, respectively. The result was confirmed to Caco-2 cell model. We discussed the in vivo behavior of prodrugâ…¡in plasma following intravenous administration in rats. Prodrugâ…¡could rapidly hydrolysis to naringenin in plasma. Experiment in vivo and in vitro proved prodrugâ…¡can be changed into naringenin during the absorption course and have development potential..The Caco-2 cell model was firstly established and evaluated by morphology feature, TEER, alkaline phosphatase and the transport of Propranolol. The determined value was corresponding to the references. And the integrality, permeability and the expression of alkaline phosphatase in the cell model were good. The established Caco-2 cell model can be used to study the absorption mechanism of oral administration drug.The experiments conducted by Caco-2 cell model were as follows:â‘ To compare the absorption rate of naringin and naringenin. The P_app of naringenin was 6.80×10^-6 cm·s^-1, which was 3 fold than that of naringin 2.24×10^-6 cm·s^-1. â‘¡The absorption mechanism of naringenin was studied from concentration, pH value, efflux of P-gp and absorb-promoting agents. There were no obvious differences in P_app both of different concentration and pH. The results showed that the absorption of naringnein was mainly through passive diffusion with possibly carrier-mediated efflux. PEG 400 had the ability to enhance naringenin absorb while Tween 80 inhibited it.The paper systematically studied that enterohepatic circulation was the main reason leading to the double peaks. What's more, the transport of naringenin was mainly by passive diffusion with efflux which might result in the double peaks and low bioavailability. The obtained phytosomes obviously improved the oral bioavailability of naringenin. While the prodrugâ…¡investigated by experiments in vivo and in vivo was qualified with good behavior following oral administration and having further research and development potential.