Vitreous Humor Hypoxanthine and Potassium as Markers for Post-mortem Interval Estimation: A UPLC-Based Study

The biochemical analysis of vitreous humor provides a valuable approach to estimating the post-mortem interval (PMI). Following death, the vitreous humor undergoes predictable biochemical changes, making it a reliable substrate for temporal estimation. This study explores the relationship between PMI and the chemical constituents of vitreous humor, with particular emphasis on potassium and hypoxanthine (Hx). The study involved a total of 55 medico legal autopsies. Vitreous humor samples were collected from all subjects and the experiments were conducted using the Ultra-Performance Liquid Chromatography (UPLC) technique and an electrolyte analyzer. Hypoxanthine (Hx) levels increased significantly from 78.68 to 268.97 µmol/L across PMIs determined by police records and from 87.26 to 280.09 µmol/L by physical examination. The linear regression analysis of Hx levels concerning PMI from police records and physical examinations demonstrated a statistically significant correlation, with R2 values of 0.86 and 0.76, respectively. This suggests Hx as a more reliable PMI biomarker compared to potassium. In contrast, potassium levels showed no statistically significant relationship with PMI based on either police records (p=0.688) or physical examination findings (p=0.806). The consistent and significant rise in Hx concentration with increasing PMI (p < 0.001) underscores its potential usefulness for estimating time since death. The study concludes that hypoxanthine concentration in vitreous humor serves as a more dependable indicator for PMI evaluation, whereas potassium contributes minimally to time-of-death estimation. Key words: Hypoxanthine; Post-mortem interval; Potassium; UPLC; Vitreous humor