Analysis of 5-Methyltryptamine, l-Tryptophan, 5-Hydroxy-l-Tryptophan, and Melatonin in the Bulbs of Garlic by Thin-Layer Chromatographic Method Coupled with Densitometric Detection

Thin-layer chromatography (TLC) methods coupled with densitometric detection were employed in analyses for the presence of non-hallucinogenic indole compounds in methanol extracts from the garlic (Allium sativum L.) bulbs originating from China, Georgia, Spain, Mexico, and Poland, and from granulated garlic in the form of seasoning (commercial product). Four indole compounds for which the garlic bulbs were analyzed, were detected: 5-methyltryptamine, L-tryptophan, 5-hydroxy-L-tryptophan, and melatonin, the amounts of which ranged from 4.2 to 199.6 mg kg−1 dry weight. In contrast, only 3 indole compounds were found in the garlic bulbs from Spain: 5-methyltryptamine, L-tryptophan and melatonin (85.7, 120.1, and 9.6 mg kg−1 dry weight, respectively). The total amount of indole compounds in the extracts from the garlic bulbs from China was the highest (415.4 mg kg−1 dry weight), while the amounts in the others (from Georgia, Spain, Mexico, Poland) were similar and ranged from 215.4 to 283 mg kg−1 dry weight. The granular, freeze-dried garlic contained the lowest content of indole compounds, and their total amount was only 207 mg kg−1 dry weight.