Ultra-Performance Liquid Chromatography–Tandem Mass Spectrometry Method for Quantification of 3,14,19-Triacetyl Andrographolide in Rat Plasma: Application to Preclinical Pharmacokinetic Studies

3,14,19-triacetyl andrographolide (ADA), a derivative of andrographolide, has emerged as a promising anti-inflammatory compound. In the present study, we established a rapid and sensitive ultra-performance liquid chromatography–tandem mass spectrometry method for the quantification of ADA in rat plasma. ADA and celecoxib (internal standard, IS) were separated using an ACQUITY UPLC BEH C18 chromatographic columns with a gradient mobile phase of acetonitrile (containing 0.1% formic acid)/water (containing 0.1% formic acid) at a flow rate of 0.3 mL/min. Quantification was performed using the multiple reaction monitoring transitions to m/z 499.1 → 439.1 for ADA, m/z 381.9 → 361.9 for celecoxib, with plasma samples undergoing liquid–liquid extraction. The method effectively detected ADA in plasma and exhibited excellent linearity (R 2 > 0.9921) over concentrations ranging from 5 to 2000 ng/mL. Both within-run and between-run precision (%RSD) were less than 6.88%, and accuracy ranged from 94.86% to 107.61%. Matrix effects were 87.53% and 112.78%, with recoveries ranging from 98.60% to 104.39%. ADA was proven to be stable under different storage conditions (4°C and −70°C) in plasma. The validated method was successfully applied to determine ADA concentrations in rat plasma. The results demonstrated that ADA exhibited a noticeable improvement in bioavailability compared with andrographolide.