Preparation of Formulation Containing Standardized Isoflavone Rich Extract of Glycine Max Seeds and its Bioavailability Studies

Background: Formulations containing soy extracts containing genistein, daidzein and glycitein are widely available in market and have been utilized for treatment of hyper lipidemia, postmenopausal problems and cancer. Aim: The present study focuses on preparation of capsule formulation containing soy isoflavone rich extract and determination of bioavailability using validated bioanalytical HPTLC method. Methods: The standardized extract containing 40% w/w total isoflavones (genistein 5.74% w/w) was formulated into capsule formulation containing 20 mg genistein per capsule. The bioanalytical HPTLC method was developed wherein protein precipitation of plasma sample was carried out using methanol followed by liquid liquid extraction using diethyl ether. The HPTLC method involved use of precoated silica gel 60GF254 plates as stationary phase with mobile phase of Ethyl Acetate: Pet ether: Toluene [4:4:2 (v/v)] and detection at 262 nm. The absolute bioavailability of genistein was determined by administering 2 mg/kg i.v. and 10 mg /kg per oral to albino rats. The bioavailability of the formulation was determined at the dose of 20 mg/kg per oral. Results: The HPTLC method yielded maximum recovery of 72.77 % w/w of genistein from plasma, with accuracy of 101.69-115.22 % w/w and linearity range was found to be 20-140 ng/band. The absolute bioavailability of genistein was observed to be 14.78%. The Cmax and tmax for formulation containing genistein rich extract (equivalent to 20 mg/kg bw po) were found to be 1.004 ug/ml and 8 h respectively. Relative bioavailability as calculated by comparing AUCs of pure genistein (10 mg/kg bw po) with the formulation (20 mg/kg bw po genistein) was found to be 77.4%. Conclusion: The validated bioanalytical HPTLC method was found to be selective, accurate, reproducible and cost effective. The method was successfully applied for pharmacokinetic study and confirmed that formulation containing genistein showed better bioavailability as compared to pure genistein.