Follow up: palmitic acid ester of tetrahydrocannabinol (THC) and palmitic acid diester of 11-hydroxy-THC - unsuccessful search for additional THC metabolites.

ABSTRACT

OBJECTIVES: In a previous investigation we searched for the occurrence of palmitic acid ester compounds of delta9-tetrahydrocannabinol (THC) and its primary metabolite 11-hydroxy-delta9-THC (11-OH-THC) in human body fluids and tissues (THC palmitic acid monoester [THC-Pal] and 11-OH-THC palmitic acid diester [11-OH-THC-DiPal]). As those esters could not be detected in various human body fluids (e.g. blood) or tissues (e.g. adipose tissue) we extended the investigation analyzing adipose tissue samples of mice previously given synthetic THC or a cannabis extract. METHODS: In total, 48 adipose tissue samples previously tested positive for THC by means of a liquid chromatographic triple quadrupole mass spectrometric (LC-QQQ-MS) method were analyzed for the presence of THC-Pal and 11-OH-THC-DiPal by means of LC-QQQ-MS. RESULTS: THC-Pal and 11-OH-THC-DiPal were not detected among the adipose tissue samples analyzed despite the presence of high THC concentrations within the adipose tissue. THC concentrations in adipose tissue were in a range of approximately 7-2,595 ng/g (median 468 ng/g, average 704 ng/g). CONCLUSIONS: A (site-specific) synthesis of 11-OH-THC palmitic acid monoesters (11-hydroxy-delta9-THC-1-palmitate and 11-palmitoyloxy-delta9-THC) still remains to be done. After synthesis of these monoesters, their presence in the body fluids and tissues after THC administration should be investigated.