Absolute oral and subcutaneous bioavailability of ortho-topolin riboside in mice

Among essential phytohormones playing a pivotal role in regulating growth and development, ortho-topolin riboside (oTR) exerts the most substantial anti-tumor potency in various cancer cell lines. This study was designed to establish a quantitative determination method for oTR in mouse plasma using high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC-MS/MS), to validate the analytical method including stability, and to characterise its pharmacokinetic behaviour in mice. After simple protein precipitation with acetonitrile including kinetin riboside (internal standard), oTR was eluted on a reversed-phase column using a mobile phase of water and acetonitrile (3:7 v/v, including 0.1% formic acid). The protonated precursor ion [M+H]⁺ and major fragment ion were confirmed at m/z 374.06 and 241.99 for oTR, and 348.23 and 216.06 for the IS, respectively. oTR was stable under bench and storage conditions. The analytical method met the criteria of FDA-validated bioanalytical methods and was successfully applied to a pharmacokinetic study for the first time following oral, subcutaneous, and intravenous administrations. While oTR was merely absorbed by an oral route, 90% of the absolute subcutaneous bioavailability was observed.