The mechanism of adipocere formation 1. Identification and chemical properties of hydroxy fatty acids in adipocere

Lipidomes in Cadaveric Decomposition and Determination of the Postmortem Interval: A Systematic Review

Lipids are a large group of natural compounds, together with proteins and carbohydrates, and are essential for various processes in the body. After death, the organism's tissues undergo a series of reactions that generate changes in some molecules, including lipids. This means that determining the lipid change profile can be beneficial in estimating the postmortem interval (PMI). These changes can also help determine burial sites and advance the localization of graves. The aim was to explore and analyze the decomposition process of corpses, focusing on the transformation of lipids, especially triglycerides (TGs) and fatty acids (FAs), and the possible application of these compounds as markers to estimate PMI and detect burial sites. A systematic review of 24 scientific articles from the last 23 years (2000-2023) was conducted. The results show that membrane glycerophospholipids (such as phosphatidylcholine and phosphatidylglycerol, among others) are the most studied, and the most promising results are obtained, with decreasing patterns as PMI varies. Fatty acids (FAs) are also identified as potential biomarkers owing to the variations in their postmortem concentration. An increase in saturated fatty acids (SFAs), such as stearic acid and palmitic acid, and a decrease in unsaturated fatty acids (UFAs), such as oleic acid and linoleic acid, were observed. The importance of intrinsic and extrinsic factors in decomposition is also observed. Finally, as for the burial sites, the presence of fatty acids and some sterols in burial areas of animal and human remains can be verified. In conclusion, glycerophospholipids and fatty acids are good markers for estimating PMI. It has been observed that there are still no equations for estimating the PMI that can be applied to forensic practice, as intrinsic and extrinsic factors are seen to play a vital role in the decomposition process. As for determining burial sites, the importance of soil and textile samples has been demonstrated, showing a direct relationship between saturated fatty acids, hydroxy fatty acids, and some sterols with decomposing remains.

A practical review of adipocere: Key findings, case studies and operational considerations from crime scene to autopsy

After death, the body begins decomposition, a process that starts with the breakdown of organic matter and typically leads to the complete degradation of a body. Such a process is highly affected by (micro and macro) environmental factors of intrinsic and extrinsic nature. Adipocere is a substance formed from the decomposition of adipose tissue and represents a disruption to the typical decomposition process. Such disruption causes decomposition to slow or arrest completely, placing a body into a state of preservation, and determines complications in the estimation of the time since death (Post-Mortem Interval, PMI). While several studies have been performed on the nature, the formation and the degradation of adipocere, there is still no reliable model to assess the PMI of a body exhibiting it. Case studies are an important source to aid pathologists and investigators during a case. This review presents a summary and an update on the knowledge surrounding the chemistry and the factors affecting adipocere formation and degradation, the timing and the distribution of adipocere throughout a body, and the techniques used to investigate it. Furthermore, a table of the most important case studies involving adipocere since 1950, several images and descriptions of recent cases and operational considerations for the best practice at the crime scene and autopsy are presented to be used as a reference to facilitate forensic professionals in adipocere cases.

Four millennia of dairy surplus and deposition revealed through compound-specific stable isotope analysis and radiocarbon dating of Irish bog butters

Bog butters are large white or yellow waxy deposits regularly discovered within the peat bogs of Ireland and Scotland. They represent an extraordinary survival of prehistoric and later agricultural products, comprising the largest deposits of fat found anywhere in nature. Often found in wooden containers or wrapped in animal bladders, they are considered to have been buried intentionally by past farming communities. While previous analysis has determined that Irish bog butters derive from animal fat, their precise characterisation could not be achieved due to diagenetic compositional alterations during burial. Via compound-specific stable isotope analysis, we provide the first conclusive evidence of a dairy fat origin for the Irish bog butter tradition, which differs from bog butter traditions observed elsewhere. Our research also reveals a remarkably long-lived tradition of deposition and possible curation spanning at least 3500 years, from the Early Bronze Age (c. 1700 BC) to the 17^th century AD. This is conclusively established via an extensive suite of both bulk and compound-specific radiocarbon dates.

Waxing Grave About Adipocere: Soft Tissue Change in an Aquatic Context

When postmortem environmental conditions are "just right," according to the "Goldilocks Phenomenon," soft tissues (and associated fatty acids) are converted into and preserved as adipocere. To better understand this conversion process and the development of adipocere three human cadavers were immersed in outside, water-filled pits for over 3 months to observe adipocere formation in an underwater context simulating actual field conditions. Recordings of environmental conditions showed that temperatures were between 21 degrees C and 45 degrees C, a range sufficient for the growth of Clostridium perfringens. Chemical analysis of liquid and tissue samples revealed an increase in palmitic acid and decrease in oleic acid. This study tracked the remarkable gross morphological changes that can occur in human bodies subjected to an aquatic postmortem environment. The results support the "Goldilocks Phenomenon" and substantiate previous findings that the presence of bacteria and water is crucial for adipocere to form.

Evidence of adipocere in a burial pit from the foot and mouth epidemic of 1967 using gas chromatography–mass spectrometry

Gas-chromatography-mass spectrometry was used to characterise the fatty acids from soils and associated tissues excavated from a 1967 Foot and Mouth burial pit. Subcutaneous fats were mainly comprised of 55-75% palmitic acid, 17-22% stearic acid and 3-16% oleic acid as well as 5-7% myristic acid. The distribution of fatty acids confirmed that the tissues were decayed to adipocere. The loss of oleic acid to <3% in two of the decayed fats suggested advanced stages of adipocere. However, adipocere formation was limited in a third tissue sample recovered from greater depth. Inductively coupled plasma atomic emission spectrometry of the pore waters revealed a decrease in Ca concentration and concurrent increase in Na concentrations this suggested that insoluble calcium salt had formed through displacement of sodium. The use of fatty acid profiles from soils and soil interstitial pore waters provide complementary evidence of adipocere formation in foot and mouth burial pits.

Exploration of anthropological specimens by GC-MS and chemometrics

Anthropological specimens combine a variety of unfavorable characteristics, rendering their evaluation an analytical challenge. Their remarkable status is primarily based on two characteristics: (i) these very rare samples of human origin are testimonies of human history and are, therefore, available only in minute amounts for analytical purposes, and (ii) the analysis of these samples is extremely limited by the decomposition of molecules, which are easily detected in living organisms, such as nucleic acids and proteins, but are subject to rapid post-mortem decay. In this article, we review the methods and results of archaeometry, emphasizing the role of MS combined with chemometrics. Focusing on experimental results for fatty acid profiles, specimens from mummies from different civilizations were compared. Considering in particular the Tyrolean Iceman, the application of chemometric methods to GC-MS data recovers essential information about the preservation and the storage conditions of mummies.

Characterisation of ‘bog butter’ using a combination of molecular and isotopic techniques

The chemical analyses of "bog butters" recovered from peat bogs of Scotland were performed with the aim of determining their origins. Detailed compositional information was obtained from "bog butter" lipids using high temperature gas chromatography (HTGC) and GC-mass spectrometry (GC-MS). The results indicate the degree to which "bog butters" have undergone diagenetic alterations during burial to form an adipocere like substance, consisting predominantly of hexadecanoic (palmitic) and octadecanoic (stearic) acids. GC-combustion-isotope ratio MS (GC-C-IRMS) was used to determine delta13C values for the dominant fatty acids present, revealing for the first time that "bog butters" were derived from both ruminant dairy fats and adipose fats. The results are compared and contrasted with modern reference fats and adipoceres produced in vitro.

Fatty acid composition and preservation of the Tyrolean Iceman and other mummies

In anthropology, objective parameters to adequately describe storage conditions and the preservation of mummies have yet to be identified. Considering that fatty acids degrade to stable products, we analysed their profile in human mummies and in control samples by gas chromatography coupled to mass spectrometry (GC/MS). Originating from different epochs and civilizations, samples of the Tyrolean Iceman, other glacier corpses, a freeze dried mummy, corpses from a permafrost region, a corpse mummified immersed in water, and a desert mummy were evaluated. Chemometric analysis based on the concentrations of 16 fatty acids revealed the degree of similarity between anthropologic and fresh corpse samples, which was mainly influenced by the content of palmitic acid, oleic acid, and 10-hydroxystearic acid. The presence of 10-hydroxystearic acid was associated with immersion in water, whereas dry mummification was accompanied by high contents of oleic acid. Samples of the Tyrolean Iceman clustered between fresh tissue and those of other glacier corpses indicating the good preservation of this mummy. Thus, environmental post-mortem conditions were associated with characteristic fatty acid patterns suggesting that chemometric analysis of fatty acid contents may add to our knowledge about post-mortem storage conditions and the preservation of human corpses.

The identification of adipocere in grave soils

Soil samples recovered from grave exhumations have been analysed in an attempt to identify and characterise adipocere contained in the samples. The soil samples were collected from different environments, including samples recovered from forensic grave sites. Gas chromatography-mass spectrometry (GC-MS) was employed to identify adipocere and characterise the fatty acid composition. X-ray diffraction was used to characterise the soil environments.

The mechanism of human adipocere formation

In adipocere, some specific fatty acids possessing higher melting points, together with soap, play an important role in the formation and stabilization of adipocere. These fatty acids were shown to be mainly 10-hydroxy stearic and 10-hydroxy palmitic acids. Slight amounts of 10-oxo stearic and 10-oxo palmitic acids, which have higher melting points than those of hydroxy fatty acids (OHFAs), exist in the adipocere as well. The substantial adipocere is formed and stabilized mainly by these specific fatty acids. The OHFA and oxo fatty acid (OXOFA) are biosynthesized by some bacterial enzymes. Various aerobic and anaerobic bacteria are involved in the formation of adipocere. For instance, microbial conversion of various unsaturated fatty acids to 10-OHFA by Micrococcus luteus was investigated. It turned out that 10-OHFA was synthesized only from fatty acids possessing cis-9-unsaturatin. It was also shown that 10-OHFAs were converted to the corresponding 10-OXOFAs but 10-OXO compounds were inactive as substrates. It was further found that the enzyme preparations from Flavobacterium meningosepticum solubilized by sonication catalyzed not only hydration of oleic acid to produce 10-hydroxy stearic acid, but also dehydrogenation of this product in the presence of deuterium. On the other hand, we found out that there was 10-hydroxy-12-octadecenoic acid (10-OHODA) in the linoleic acid in human adipocere and that there were 9-chloro-10-methoxy (9-methoxy-10-chloro) palmitic acid and 9-chloro-10-methoxy (9-methoxy-10-chloro) stearic acid in human neonate adipocere.

Epicoprostanol found in adipocere from five human autopsies

Adipocere formation is well known as a later postmortem change. We collected adipocere from five male victims which had been submerged under the sea or fresh water for 1 mon to 4 yr. Fresh subcutaneous fat of a male victim who died from a cerebral contusion was used as the control. The samples were homogenized, and the lipids were extracted with chloroform and methanol followed by injection into a gas chromatograph and a gas chromatograph-mass spectrometer. We detected hydroxy fatty acids (10-hydroxyoctadecanoic acid and 10-hydroxyhexadecanoic acid) as well as 10-ketooctadecanoic acid in adipocere, but not in the control. In addition, we found for the first time a cholesterol-related peak with a molecular ion of 388 in adipocere and identified it as epicoprostanol, suggesting not only oxidation but also reduction had occurred during the formation of adipocere. In addition, we showed the time-course of epicoprostanol accumulation. The relationship between the time of adipocere formation and the characteristic lipid composition is discussed.

Investigation of the triacylglycerol composition of iceman's mummified tissue by high-temperature gas chromatography

The pattern of intact triacylglycerols of a skin sample from the 5300-year-old Iceman mummy (nicknamed Otzi) was resolved on a diphenyl-dimethylpolysiloxane stationary phase by high-temperature gas chromatography. Adipocere from a 64-year-old glacier mummy as well as recent human subcutaneous fat served as a comparison in this study. Qualitatively, the results for mummy samples were similar with well-preserved saturated, but decomposed unsaturated, triacylglycerols, the latter being predominant in subcutaneous fat. Excellent preservation of triacylglycerols with odd carbon numbers and branched acyl chains was observed. The results presented here shed new light on the process of mummification.

Investigations on the mechanism of adipocere formation and its relation to other biochemical reactions

In the adipocere, which is one of the postmortem changes, some specific fatty acids possessing higher melting points, together with soap, play an important role in the formation of adipocere. These fatty acids were shown to be mainly 10-hydroxystearic and 10-hydroxypalmitic acids. Moreover, slight amounts of 10-oxostearic and 10-oxopalmitic acids, which have higher melting points than those of hydroxy fatty acids, exist in the adipocere as well. The substantial adipocere is formed and stabilized by these specific fatty acids together with the soap. The hydroxy fatty acid (OHFA) and oxo fatty acid (OXOFA) are biosynthesized by some bacterial enzymes. Various aerobic and anaerobic bacteria are involved in the formation of adipocere. For example, microbial conversion of various unsaturated fatty acids to 10-OHFA by Micrococcus luteus was investigated. It turned out that 10-OHFA was synthesized only from fatty acids possessing cis-9-unsaturation. It was also shown that 10-OHFAs were converted to the corresponding 10-OXOFAs but the 10-OXO compounds were inactive as substrates. Furthermore, it was found that the enzyme preparations from Flavobacterium meningosepticum solubilized by sonication catalyzed not only hydration of oleic acid to produce 10-hydroxystearic acid, but also dehydrogenation of this product in the presence of deuterium. On the other hand, we found out that there was 10-hydroxy-12-octadecenoic acid (10-OHODA) from linoleic acid in some kinds of adipocere. Recently, 10-epoxy-12-octadecenoic acid (leukotoxin, LTx), which is one of the lipid peroxides, was found not only in rice plants but in polymorphonuclear leukocytes. Since LTx was found in leukocytes related to inflammatory response, interest has been focused on its involvement, not only in the basic mechanism of biological defense, but also on the mechanism of shock as a vasoactive substance. A postmortem change itself is only remotely associated with a phenomenon in a living body. However, 10-OHODA found in adipocere seemed to exist also in polymorphonuclear leukocytes, suggesting that this compound might be closely related to a biological reaction.

Capillary gas chromatography mass spectrometry and identification of substituted carboxylic acids in lipids extracted from a 4000-year-old Nubian burial

Polar carboxylic acid fractions of lipids extracted from samples from a 4000-year-old Nubian mummy were investigated by capillary gas chromatography mass spectrometry. They contain series of alpha,omega-dicarboxy, monohydroxy, dihydroxy and keto fatty acids, some of which were found for the first time outside the synthetic laboratory. Their chromatographic and mass spectrometric characteristic properties are reported.

The mechanism of experimental adipocere formation: hydration and dehydrogenation in microbial synthesis of hydroxy and oxo fatty acids

The enzyme preparations from Flavobacterium meningosepticum solubilized by sonication catalyzed not only hydration of oleic acid to produce 10-hydroxystearic acid but dehydrogenation of this product. The mechanism of the hydration and dehydrogenation was proved by gas chromatography-mass spectrometry of 10-hydroxy and 10-oxostearic acids produced in the presence of D2O or H2(18)O. The activity of these enzymes was increased by preincubating Flavobacterium meningosepticum with oleic acid.

The mechanism of experimental adipocere formation: substrate specificity on microbial production of hydroxy and oxo fatty acids

Studies are reported on microbial conversion of various unsaturated fatty acids to 10-hydroxy and/or 10-oxo fatty acids by Micrococcus luteus. Four fatty acids possessing cis-9-unsaturation produced 10-hydroxy and 10-oxo fatty acid products, but three enoic acids possessing trans-9-unsaturation or double bond(s) in other than the 9-carbon position were inactive as substrates. 10-Hydroxy palmitic and stearic acids were converted to the corresponding 10-oxo fatty acids, but the 10-oxo compounds were inactive as substrates. This indicates that the metabolic sequence of cis-9-enoic fatty acid by the microbial enzyme(s) is first converted to 10-hydroxy fatty acid and then to its 10-oxo compound.

Microbial production of hydroxy and oxo fatty acids by several microorganisms as a model of adipocere formation

Some varieties of aerobic or anaerobic microorganisms from the human stool and adipocere were separated and identified. These separated microorganisms together with other authentic ones produced 10-hydroxystearic acid from oleic acid. Some bacteria could convert oleic acid to 10-oxostearic acid as well as 10-hydroxystearic acid. These findings indicate that the microbial enzyme(s) catalyzes the hydration of oleic acid and probably the oxidation of this hydrated product. Aerobic bacteria as well as anaerobic microorganisms were found to be involved in the formation of adipocere.

Identification of 10-hydroxy-12-octadecenoic acid in adipocere

Studies are reported on separation and identification of 10-hydroxy-12-octadecenoic acid in human adipocere. The chemical structure was determined by thin-layer chromatography (TLC), gas-liquid chromatography (GLC) and gas chromatography-mass spectrometry (GC-MS).

Separation and identification of 9-chloro-10-methoxy (9-methoxy-10-chloro)hexadecanoic and octadecanoic acids in adipocere

Two homologs of 9-chloro-10-methoxy(9-methoxy-10-chloro) fatty acids were found in adipocere from the human neonate, and identified as 9-chloro-10-methoxy(9-methoxy-10-chloro)hexadecanoic acid and 9-chloro-10-methoxy(9-methoxy-10-chloro)-octadecanoic acid. The chemical structures of these compounds were confirmed by thin-layer chromatography, gas-liquid chromatography, gas chromatography--mass spectrometry, nuclear magnetic resonance spectrometry and elemental analysis. The adipocere contained approximately 7.2% 9-chloro-10-methoxy(9-methoxy-10-chloro) fatty acids in the total fatty acids.

The mechanism of adipocere formation. II. Separation and identification of oxo fatty acids in adipocere

Two kinds of oxo fatty acids were found to be present in the adipocere. One of them was identified as 10-oxohexadecanoic acid and the other was as 10-oxo-octadecanoic acid. The chemical identity of these compounds was confirmed by thin-layer chromatography (TLC), gas-liquid chromatography (GLC) and gas chromatography-mass spectrometry (GC-MS). The adipocere contained about 1.3 to 1.6% oxo fatty acid of total fatty acids.