A 1 H NMR metabolomic approach for the estimation of the time since death using aqueous humour: an animal model

Introduction: The estimation of the time since death, or post-mortem interval (PMI), still remains a main conundrum in forensic science. Several approaches have been so far proposed from either a qualitative or a quantitative point of view, but they still lack reliability and robustness. Recently, metabolomics has shown to be a potential tool to investigate the time-related post-mortem metabolite modifications in animal models. Objectives: Here we propose, for the first time, the use of a 1 H NMR metabolomic approach for the estimation of PMI from aqueous humour (AH) in an ovine model. Methods: AH samples were collected at different times after death (from 118 to 1429 min). 1 H NMR experiments were performed and spectral data analysed by multivariate statistical tools. Results: A multivariate calibration model was built to estimate PMI on the basis of the metabolite content of the samples. The model was validated with an independent test set, obtaining a prediction error of 59 min for PMI < 500 min, 104 min for PMI from 500 to 1000 min, and 118 min for PMI > 1000 min. Moreover, the metabolomic approach suggested a picture of the mechanisms underlying the post-mortem biological modifications, highlighting the role played by taurine, choline, and succinate. Conclusion: The time-related modifications of the 1 H NMR AH metabolomic profile seem to be encouraging in addressing the issue of a reproducible and robust model to be employed for the estimation of the time since death.