ABSTRACT: Background: Diosgenin, charantin, and hydroxychalcone are utilized for standardization of popular antidiabetic herbal drugs Trigonella foenum-graecum L. belonging to family Fabaceae, Momordica charantia L. belonging to family Cucurbitaceae, and Cinnamomum verum J. Presl belonging to family Lauraceae. However, no reports on the bioavailability of these markers were available. The present study was undertaken to determine the bioavailability and pharmacokinetic profile of the markers and formulations containing the herbs. Methods: The pharmacokinetic profile and absolute bioavailability of the pure active markers were determined in male Wistar rats by administrating individually the doses of 1.5 mg/kg i.v. and 15 mg/kg p.o., followed by estimation of serum levels of the markers at 0, 10, 30, 60, 120, and 240 mins till 24 h time points by a validated bioanalytical HPTLC method. Two standardized antidiabetic capsule formulations containing spray dried hydroalcoholic extracts of seeds of Trigonella foenum-graecum L. (42.8 mg equivalent to 0.95%w/w of diosgenin), fresh fruits of Momordica charantia L. (21.4 mg equivalent to 0.4% w/w of charantin), and bark of Cinnamomum verum J. Presl (10.71 mg equivalent to 0.079 %w/w hydroxychalcone) were prepared. In one formulation, piperine 1.5 mg was added along with the other herbal extracts mentioned. Bioavailability and pharmacokinetic profile of these two formulations were determined in male Wistar rats through estimating serum levels of active markers diosgenin, charantin, and hydroxychalcone at 0, 10, 30, 60, 120, and 240 mins till 24 h later oral administration of the formulations (Formulation without piperine F1 and formulation with Piperine F2). Results: Plasma concentrations were found to decline mono-exponentially following intravenous administration, and the mean elimination half-life (t1/2) was observed to be 7.93, 8.21, and 4.66 h, respectively. The absolute oral bioavailability of pure markers was observed to be 9.0 ± 0.2%, 8.18 ± 0.36%, and 10.54 ± 0.52% by the dose normalization method. The oral bioavailabilities of the formulations with respect to diosgenin, charantin, and hydroxychalcone were found to be 9.78, 10.743, and 8.07%, respectively. The formulation containing piperine indicated a significant (p < 0.01) increase in the bioavailabilities of all the marker compounds. Conclusion: In conclusion, diosgenin and charantin have low bioavailabilities as compared to hydroxychalcone. The bioavailabilities of all the three marker compounds can be increased exponentially with the addition of piperine.
