Quantitative estimation of squalene levels in acute respiratory distress syndrome (ARDS) and treated lung tissues by gas chromatography-mass spectrometry

Squalene (SQ), a naturally occurring triterpenoid, is a key precursor in steroid biosynthesis, particularly cholesterol. Its role in lung surfactant contributes to the enhancement of pulmonary function. This study aimed to quantify squalene levels in lung tissues affected by acute respiratory distress syndrome (ARDS) and in hydroalcoholic pre-treated extract <i>Gymnema sylvestre</i> (HAEGS). A highly selective and validated gas chromatography-mass spectrometry (GC-MS) method was developed, utilizing solvent extraction and squalane as the internal standard. The method demonstrated excellent sensitivity, with a limit of detection (LOD) of 0.05 μg mL^-1 and a limit of quantification (LOQ) of 0.5 μg mL^-1. In this study, selective ion monitoring (SIM) mode was employed to monitor ions at <i>m</i>/<i>z</i> 69 for squalene and <i>m</i>/<i>z</i> 71 for squalane (internal standard). In ARDS-affected rat lungs, squalene levels were reduced by 50% compared to healthy controls. Pre-treatment with HAEGS significantly restored squalene levels, showing a 1.8-fold increase at a high dose (250 mg kg^-1) and a 1.2-fold increase at a low dose (125 mg kg^-1) relative to untreated ARDS lungs.