A potential new metabolite of gamma-hydroxybutyrate: sulfonated gamma-hydroxybutyric acid.

Detection of gamma-hydroxybutyric acid (GHB) became crucial in many clinical and forensic settings due to its increasing use for recreational purposes and drug-facilitated sexual assault. Its narrow window of detection of about 3-12 h in urine represents a major problem. Analogous to ethyl glucuronide, the recently identified GHB-glucuronide exhibits a longer window of detection than the parent drug. It appeared reasonable that a sulfonated metabolite of GHB (GHB-SUL) will also be formed. Due to the lack of an appropriate standard, GHB was incubated with a human liver cytosolic fraction to produce GHB-SUL. Following development of a liquid chromatography/tandem mass spectrometry (LC-MS/MS) assay to measure GHB and GHB-SUL, authentic urine samples (n = 5) were tested for GHB-SUL. These investigations revealed detectable signals of both GHB and GHB-SUL, strongly indicating that GHB is not only glucuronidated but also sulfonated. Given that sulfonated metabolites generally have longer half-life times than the corresponding free drugs, GHB-SUL may serve as a biomarker of GHB misuse along with its glucuronide.

Pitfall in cannabinoid analysis--detection of a previously unrecognized interfering compound in human serum.

In clinical and forensic toxicology, high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS) is increasingly used since it allows the development of sensitive and fast drug analysis procedures. During development of a LC-MS/MS method for determination of the psychoactive cannabinoid Δ(9)-tetrahydrocannabinol (THC) and of its two metabolites 11-hydroxy-THC (THCOH) and 11-nor-9-carboxy-THC (THCCOOH) in serum, a previously unrecognized interfering compound was detected. Extending the fast gradient elution program by an isocratic phase leads to sufficient separation of the interfering compound, initially co-eluting with THCCOOH and exhibiting the same fragments. For characterization, product ion scans and precursor ion scans were performed. Samples from cannabis users were analyzed to estimate the abundance of the interfering compound. The mass spectrometric experiments showed that the interfering compound exhibited the same molecular mass as THCCOOH and a similar fragmentation pattern except for relative fragment intensities. This compound was exclusively detectable in authentic samples. Concentrations were in the range of 4.5 to 51 % (median 14.6 %, n = 73) of those of THCCOOH. After further optimization of the gradient, the method was sufficiently selective and sensitive and validation parameters were within acceptance limits. A new compound related to cannabis use was detected in human serum, and data suggest an isomeric structure to THCCOOH. Considering the rather high amounts observed, it was surprising that this compound had not been detected previously. Further studies on its structure and origin are necessary.

11-nor-9-carboxy-Δ9-tetrahydrocannabinol glucuronide exhibits acyl-migration isomers.

11-nor-Δ9-Tetrahydrocannabinol-9-carboxylic acid glucuronide (THCCOOH-glucuronide) is an 1-ß-O-acyl glucuronide which degrades not only to 11-nor-9-carboxy-Δ9-THC (THCCOOH) but, additionally, to an isomer with a currently unknown structure. The present study was carried out to examine whether acyl glucuronide isomers are formed by acyl migration and if they are involved in formation of this isomer. THCCOOH-glucuronide was incubated in phosphate buffer (pH 7.4, 37°C, 7days) and a variety of glucuronide cleavage procedures were performed. Samples of the incubation mixture and of different biological specimens from cannabis users were analyzed using liquid chromatography-mass spectrometry (LC-MS/MS). A total of six chromatographically separated isomeric acyl glucuronides were detected during incubation of THCCOOH-glucuronide reference substance. In biological specimens of cannabis users, two additional isomers were found. However, the main glucuronide present in human specimens was different from that of a commercially available reference substance. Both, the commercial and the authentic glucuronide were cleaved by ß-glucuronidases, the other formed isomers by alkaline hydrolysis only. Mass spectrometric investigations (i.e. product ion, precursor ion and neutral loss scans) confirmed identity. The THCCOOH isomer was detected in all authentic samples, but not in those after buffer incubation. By analyzing THCCOOH-glucuronide in authentic samples, it has to be taken into account that the authentic glucuronide is different from that of the commercial reference standard. THCCOOH-glucuronide undergoes acyl migration and some isomers occur to minor extents in biological specimens. Acyl migration does not lead to the formation of the THCCOOH isomer.

Investigation of a recently detected 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol isomer: Studies on the degradation of 11-nor-9-carboxy-Δ(9)-tetrahydrocannabinol glucuronide.

An isomer of the tetrahydrocannabinol (THC) metabolite 11-nor-9-carboxy-Δ(9)-THC (THCCOOH) had been detected in blood of cannabis users. The present study was initiated to elucidate whether the labile metabolite THCCOOH-glucuronide could be the precursor. THCCOOH-glucuronide was incubated in human serum and albumin (HSA) solution at various temperatures (-18, 4.5, 22 and 37°C) and pH values (pH 7.4 and 8.3) for seven days in the presence or absence of the esterase inhibitor sodium fluoride. Analysis of incubation samples was performed using LC-MS/MS. Marked degradation of THCCOOH-glucuronide was observed at 37°C. It was found that not only THCCOOH, but also the isomer is a degradation product of THCCOOH-glucuronide and its in-vivo production is assumed. Degradation to THCCOOH and the isomer occurred at alkaline pH, in the presence of fluoride-sensitive esterases and of HSA alone. To inhibit isomer formation during sample storage, refrigeration and controlling of the pH are recommended. However, THCCOOH and the isomer exhibit similar properties during incubations in serum, but differ in their interaction with HSA. The present study confirmed the nature of the isomer as degradation product of the abundant THC metabolite THCCOOH-glucuronide. Serum albumin and esterases are obviously involved. The isomer is formed not only during storage, but also under physiological conditions, suggesting that it can be considered an in-vivo metabolite. However, the chemical structure of the isomer remains unknown and further research is necessary.

Investigation of a recently detected THCCOOH isomer: Post mortem findings and comparison with Δ(8)-THCCOOH.

BACKGROUND: An isomer of the non-psychoactive cannabinoid Δ(9)-THCCOOH was recently detected in blood from cannabis users. The structure of this compound is currently unknown. Therefore, further investigations were performed to elucidate its nature. METHODS: Further biological specimens were analyzed using the previously published LC-MS/MS method to evaluate the distribution of this compound in the human body. Hypothetically, the unknown compound was isomeric in the position of the double bond, i.e. Δ(8)-THCCOOH. An in-vitro metabolism study on Δ(8)-THC and Δ(9)-THC was performed to compare the resulting metabolites with the unknown compound. RESULTS: The unknown THCCOOH isomer was detected in all analyzed human body compartments (urine, bile, liver, lung and kidney) except for brain indicating that its detectability is not limited to blood. The in-vitro metabolism assay with the human CYP2C9 isoform led to the formation of THCOH and THCCOOH of Δ(8)-THC and Δ(9)-THC. However, the unknown isomer present in blood exhibited a different retention time than each of the metabolites formed. CONCLUSION: The unknown THCCOOH isomer accompanied THCCOOH and was detected in various human body compartments. The present in-vitro metabolism study proved that it is not of Δ(8)-THCCOOH structure nor that it is metabolically formed by the human CYP2C9 isoform.