Short communications: Exploring temporal fluorescent changes in the composition of human semen stains

Area of Science:

• Forensic Science
• Biochemistry
• Analytical Chemistry

Background:

• Semen traces are crucial forensic evidence, particularly in sexual offense cases.
• Accurate aging of semen stains is vital for forensic investigations.
• The chemical compounds responsible for the fluorescence of aging semen remain unidentified.

Purpose of the Study:

• To identify the specific biofluorophores contributing to the fluorescent behavior of aging semen traces.
• To elucidate the chemical basis of fluorescence in aged semen stains.

Main Methods:

• Semen stains and known biofluorophores were aged for up to 21 days.
• Thin-layer chromatography (TLC) was used for separation.
• Ultra-performance liquid chromatography (UPLC) coupled with mass spectrometry (MS) was employed for identification.

Main Results:

• Several compounds contributing to semen autofluorescence were identified.
• Key identified biofluorophores include tryptophan, kynurenine, kynurenic acid, and norharman.
• These compounds were detected in semen stains aged over time.

Conclusions:

• Tryptophan, kynurenine, kynurenic acid, and norharman are significant contributors to the autofluorescence of aging semen stains.
• Understanding these compounds enhances the forensic analysis of semen traces.
• This research provides a chemical basis for fluorescence-based semen aging techniques.