Tetrahydro-beta-carboline-3-carboxylic acid compounds in fish and meat: possible precursors of co-mutagenic beta-carbolines norharman and harman in cooked foods

Abstract

The presence of tetrahydro-beta-carbolines and beta-carbolines was studied in raw, cooked and smoked fish and meat. 1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid (THCA) usually was the major beta-carboline found, whereas 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCA) appeared in smoked and 'well done' cooked samples. THCA was detected in raw fish (nd-2.52 micrograms/g), cooked fish (nd-6.43 micrograms/g), cooked meats (nd-0.036 microgram/g), smoked fish (0.19-0.67 microgram/g) and smoked meats (0.02-1.1 micrograms/g). Smoked and cooked samples contained higher amounts of THCA and MTCA than raw products. Deep cooking of fish and meat increased both THCA and MTCA, and this was accompanied by the formation of more beta-carbolines, norharman and harman. The tetrahydro-beta-carbolines THCA and MTCA were chemical precursors of the co-mutagens norharman and harman during cooking. These and previous results confirm that foods are an important source of beta-carbolines in humans.

Exposure to β-carbolines norharman and harman

“…From these studies, it was concluded that high-temperature preparation procedures resulted in the highest levels of HCA including norharman and harman. This was also confirmed in other studies with different food items such as beef or fish [26]. Irrespective of the meat type grilling on an open flame resulted in extremely high levels of norharman and harman [65] (Table 1).…”

“…In addition to intake of norharman and harman, ingestion of precursors may further result in elevated plasma levels of ␤-carbolines, this has been shown for l-tryptophan [78]. It may be hypothesised that dihydro-and tetrahydro-derivatives of ␤-carbolines, ingested with fried food at ppm levels [26] may be transformed in vivo into norharman and harman.…”

“…Finally, when high complex matrices such as meat extract are analysed a further ion-exchange purification using TSK gel columns may be necessary. Other methods include liquid extraction with lipophilic solvent at alkaline pH [2,8,33] or solid-phase extraction using one ion-exchange column [26] or extraction with phthalocyanin-based blue cotton, blue rayon or blue chitin [27,28]. The artefactual formation of ␤-carbolines from precursors such as tryptamine during acidic work-up procedures may be inhibited by fluorescamine [29].…”

“…Most recently it was shown that aromatic ␤-carbolines are formed from the 1,2,3,4-tetrahydro-and 3,4-dihydro derivatives under nitrosating (and oxidising) conditions [69]. Levels of 1,2,3,4-tetrahydro-␤-carboline-3-carboxylic acid and its 1-methyl derivative of up to 1 ppm have been detected in fried fish [26] paralleling levels of norharman and harman, respectively. It was proposed that these tetrahydro-acid derivatives are precursors of the fully aromatic ␤-carbolines and spiking of a swordfish sample with 10 ppm of these tetrahydro-␤-carboline-3-acids resulted in a four-to five-fold increase of norharman and harman following heat preparation.…”

Increased Level of Tetrahydro-β-Carboline Derivatives in Short-Term Fermented Garlic

“…Besides the fermented foodstuffs, β-carbolin derivatives are also present in raw, cooked and smoked fish and meat, and they are possible chemical precursors of the co-mutagens norharman and harman [20]. Therefore, toxicological aspects of fermented garlic will be further studied.…”