A Novel Bioanalytical Method for Determination of Inotodiol Isolated from Inonotus Obliquus and Its Application to Pharmacokinetic Study

In this study, we developed a bioanalytical method using liquid chromatography coupled to triple quadrupole tandem mass spectrometry (LC-MS/MS) to apply to a pharmacokinetic study of inotodiol, which is known for its anti-cancer activity. Plasma samples were prepared with alkaline hydrolysis, liquid–liquid extraction, and solid-phase extraction. Inotodiol was detected in positive mode with atmospheric pressure chemical ionization by multiple-reaction monitoring mode using LC-MS/MS. The developed method was validated with linearity, accuracy, and precision. Accuracy ranged from 97.8% to 111.9%, and the coefficient of variation for precision was 1.8% to 4.4%. The developed method was applied for pharmacokinetic study, and the mean pharmacokinetic parameters administration were calculated as follows: λ(z) 0.016 min(−1); T(1/2) 49.35 min; C(max) 2582 ng/mL; Cl 0.004 ng/min; AUC(0–t) 109,500 ng×min/mL; MRT(0–t) 32.30 min; Vd 0.281 mL after intravenous administration at dose of 2 mg/kg and λ(z) 0.005 min(−1); T(1/2) 138.6 min; T(max) 40 min; C(max) 49.56 ng/mL; AUC(0–t) 6176 ng×in/mL; MRT(0–t) 103.7 min after oral administration. The absolute oral bioavailability of inotodiol was 0.45%, similar to nonpolar phytosterols. Collectively, this is the first bioanalytical method and pharmacokinetic study for inotodiol.