Modeling Postmortem Ethanol Production/Insights into the Origin of Higher Alcohols

Abstract

The forensic toxicologist is challenged to provide scientific evidence to distinguish the source of ethanol (antemortem ingestion or microbial production) determined in the postmortem blood and to properly interpret the relevant blood alcohol concentration (BAC) results, in regard to ethanol levels at death and subsequent behavioral impairment of the person at the time of death. Higher alcohols (1-propanol, 1-butanol, isobutanol, 2-methyl-1-butanol (isoamyl-alcohol), and 3-methyl-2-butanol (amyl-alcohol)) are among the volatile compounds that are often detected in postmortem specimens and have been correlated with putrefaction and microbial activity. This brief review investigates the role of the higher alcohols as biomarkers of postmortem, microbial ethanol production, notably, regarding the modeling of postmortem ethanol production. Main conclusions of this contribution are, firstly, that the higher alcohols are qualitative and quantitative indicators of microbial ethanol production, and, secondly that the respective models of microbial ethanol production are tools offering additional data to interpret properly the origin of the ethanol concentrations measured in postmortem cases. More studies are needed to clarify current uncertainties about the origin of higher alcohols in postmortem specimens.

Ethanol and Higher Alcohols’ Production in Fungal and Bacterial Laboratory Cultures and Significance for Forensic Samples

“…Interestingly, the non-production of 1-propanol and 1-butanol in certain microbial culture sets highlights the variability and selective nature of microbial congener alcohol synthesis, corroborating reports of their absence in postmortem cases where ethanol production was detected [18,26,[37][38][39]. This variability reinforces the argument for considering the five higher alcohols (isobutanol, 2-methyl-1-butanol / amyl alcohol and 3-methyl-1-butanol / isoamyl alcohol, 1-butanol and 1-propanol) as critical biomarkers for microbial ethanol synthesis [26], advising against their use as internal standards in forensic laboratories during ethanol analysis due to potential postmortem microbial production.…”

“…Regarding autopsy bloods, the EC models showed the best applicability among the bacterial and yeast models, and especially in cases with BAC ranging from 0.5 to 1.0 g/L (57-64% of samples for EC5-6 and almost 40% of samples for EC1-4) and in cases with putrefaction (20-50% of putrefactive cases) (Figure 1). These findings in autopsy bloods, when compared with the previous results on the applicability of the clostridial models that were reported to apply successfully in up to 95% of autopsy cases with obvious signs of putrefaction and up to 85% of cases with BAC < 0.7 g/L [26,28], showed that the EC models followed the clostridial ones in applicability. The fungal models were by far the least applicable of all; possibly, they can be applicable in specific cases with elevated glucose levels.…”

“…Furthermore, the detection of low-molecular-weight volatiles in postmortem specimens was related to the microbial ethanol neo-formation [ 18 , 19 , 20 , 21 , 22 , 23 ]. Specifically, the volatile compounds known as higher, or congener, alcohols—referring mainly to 1-propanol (or n-propanol), isobutanol (or methyl-1-propanol), 2- methyl-1-butanol (or isoamyl-alcohol), 3-methyl-2-butanol (or amyl-alcohol), and 1-butanol (or n-butanol)—are often detected in postmortem specimens [ 24 , 25 , 26 ], and their presence is considered indicative of putrefaction and microbial activity [ 18 , 27 ]. Moreover, relatively recently, we reported the process characterized as “modelling postmortem ethanol production” [ 28 , 29 , 30 , 31 ] that introduced the models constructed by performing experimental studies with the bacteria E. coli [ 28 , 29 ], K. pneumoniae [ 30 ], S. aureus [ 30 ], E. faecalis [ 30 ], the clostridia C. perfringens [ 28 ], and C. sporogenes [ 28 ], and the fungus C. albicans [ 31 ].…”

Forensic Aspects of a Fatal Intoxication Involving Acetaminophen, Citalopram and Trazodone: A Case Report

“…Several authors correlate an increase in the alcohol concentration with post-mortem production due to the action of different species of bacteria. In most of the cases in which the production of post-mortem ethanol was observed, the concentration was not higher than 0.3 g/L [29][30][31][32]. In Table 2, the analyte concentrations found in peripheral blood and urine are reported.…”

Post‐mortem redistribution of drugs and other factors affecting interpretation: A review

“…When putrefaction occurs, higher alcohols are also often produced, such as the propanols, butanols, and amyl alcohols (Boumba, 2022). These may be detected in a gas chromatographic analysis for ethanol, although their presence will be dependent on the organisms present and the degree of putrefaction providing the method is capable of detecting these higher alcohols.…”