Ultraviolet Spectrophotometric Analysis of Postmortem Vitreous Humor : Determination of the Component and Estimation of the Hour after Death

Ultraviolet spectrophotometric studies were made on postmortem vitreous humor (VH) of the human to identify the composition of VH and to estimate the hour after death. 1) The absorption spectra of the VH showed maximal absorption at 265 nm (275 samples of VH were investigated). 2) The UV-absorption substances that were separated by using Bio-Gel P-2 column were found to be ascorbic acid, hypoxanthine, uric acid, protein, xanthine and tyrosine. The absorbance peak of ascorbic acid was extremely higher than that of the other substances. 3) After treating the VH with ascorbate oxidase, we classified the UV-spectra into three groups: one appearing as a node or shoulder at around 250nm, another one flat at around 270 nm, and the last showing a peak at around 275-290 nm. 4) The UV-spectrum of each of these three groups was in close agreement with the UV-spectrum of the mixture solution containing various concentrations of hypoxanthine, uric acid and protein. 5) From the findings on 1)-4) above, it was suggested that the characteristic UV-spectra of VH were chiefly derived from ascorbic acid and that the UV-spectra after the treatment of VH with ascorbate oxidase were chiefly derived from hypoxanthine, uric acid and protein. 6) The absorbance of VH after treatment with ascorbate oxidase was measured at 277 nm and 252 nm, and the absorbance difference ⊿A(HX) was determined by a dual wavelength spectrophotometer. 7) A correlation was observed between the ⊿A(HX) value and the hour after death. 8) ⊿A(HX) was high in the cases in which death had occurred in hospital, whereas the ⊿A(HX) was low for the cadaver that had been exposed to cold circumstances. Abnormal values found in the absorbance difference may have been due to prolonged tissue hypoxia and environmental temperature. 9) From the findings on 6)-8) above, the dual wavelength method seems applicable to the estimation of the hour after death, but ⊿A(HX) values should be interpreted in consideration of the tissue hypoxia period before death and the environment of the cadaver.