Pharmacokinetics and Bioavailability of Haplopine in Mice by Ultra‐High‐Performance Liquid Chromatography–Tandem Mass Spectrometry

Haplopine, a furoquinoline alkaloid with documented anti‐inflammatory, antioxidant, and anti‐atopic dermatitis properties, has not yet been characterized with respect to its in vivo disposition. Here, we developed a fast UPLC‐MS/MS assay for quantifying haplopine in mouse blood. Aliquots of 20 μL of blood were subjected to acetonitrile‐based protein precipitation and resolved on a BEH C18 column within a 4‐min run. Quantification was performed in the positive‐ion electrospray multiple reaction monitoring mode, monitoring the transitions m/z 246.2 → 231.3 for haplopine and m/z 326.2 → 291.4 for the internal standard. The method was linear over 1–1000 ng/mL ( r 2 = 0.9998), with intra‐ and inter‐day precision below 13% and 11%, respectively; accuracy ranged from 90.2% to 110.8%, recovery exceeded 87.2%, and matrix effects were 92.8%–99.1%. The validated assay was then applied to study the pharmacokinetics of haplopine in mice following intravenous (2.0 mg/kg) and oral (8 and 16 mg/kg) administration. Absolute oral bioavailability reached 39.1% and 55.0% at 8 and 16 mg/kg, respectively, indicating moderate, dose‐dependent systemic bioavailability. Collectively, these data constitute the first pharmacokinetic description of haplopine and provide a foundation for its continued development.