Table 2.
A summary of the compounds that were found as significant in more than one of the examined research papers in the present review. What is believed to be the biological origin of each compound is described here too.
| Compound | Number of Times | Biological Origin |
|---|---|---|
| Dimethyl-sulphide | 11 | Incomplete metabolism of sulphur-containing amino acids in the transamination pathway—cytochrome C oxidase deficiency |
| Limonene | 7 | Limonene is not produced in the human body—metabolised by the P450 enzymes CYP2C9 and CYP2C19—accumulates in the fat of patients |
| Acetone | 7 | Due to hepatic insulin resistance that leads to an increase in triglycerides, free fatty acids and ketones |
| Ethanol | 7 | Due to increased shunting volumes through portocaval shunts |
| Isoprene | 6 | A by-product of cholesterol biosynthesis—the intestinal microbiota may generate isoprene too |
| Acetaldehyde | 6 | Oxidation product in ethanol metabolism—CYP2E1 is induced |
| 2-Pentanone | 5 | Due to hepatic insulin resistance—inhibition of CYP2E1 |
| Carbon-disulphide | 4 | The oxidative metabolism of carbon disulphide—also due to incomplete metabolism of sulphur-containing essential systems |
| 2-Butanone | 4 | Due to hepatic insulin resistance, formed during lipolysis—inhibition of CYP2E1 |
| Benzene | 4 | Environmental pollutant |
| Pentane | 3 | Lipid peroxidation—a by-product of the cytochrome P450 metabolism |
| Hydrogen-sulphide | 3 | Incomplete metabolism of sulphur-containing amino acids in the transamination pathway—cytochrome C oxidase deficiency (less stable than dimethyl-sulphide) |
| Ethane | 3 | Lipid peroxidation of polyunsaturated fatty acids—a by-product of the cytochrome P450 metabolism |
| Trimethyl-amine (TMA) | 3 | The intestinal microflora degrades dietary phosphatidylcholine to form trimethylamine—trimethylamine is metabolised by the hepatic flavin monooxygenase family of enzymes |
| 2-Nonene | 3 | It is yet to be discovered—it has been linked to oxidative stress |
| 2-Propanol | 2 | It is yet to be discovered—it is speculated to be related to inflammatory processes and/or lipid peroxidation |
| Indole | 2 | Derived from the catabolism tryptophan |
| Dimethyl-selenide | 2 | Excretion product of the essential micronutrient selenium |
| Methanol | 2 | Metabolised mainly by alcohol dehydrogenase—pectin degradation—an imbalance of microflora composition in cirrhotic patients |
| 2-Octanone | 2 | Due to hepatic insulin resistance, formed during lipolysis—inhibition of CYP2E1 |
| Octane | 2 | Metabolised by the cytochrome P450 enzymes |
| Alpha-pinene | 2 | Metabolised by the cytochrome P450 enzymes |
| Tridecane | 2 | It is yet to be discovered—it is speculated that it is related to inflammatory processes and/or lipid peroxidation |
| Styrene | 2 | Exogenous sources such as industrial materials—it is oxidised by cytochrome P450 |