Table 2.

The concentrations of TRP and some KP metabolites in herbs, species, and herb-based diet supplements. 3HKyn, XA, CA, PIC and QA were not included in a target list of the analytical methods utilized for quantitative analysis.

Herbs/ Species	Form	Concentration Range (mg/kg)					Ref.
		TRP	KYN	3HAA	AA	KYNA
Basil	leaves	n.a.	n.a.	n.a.	n.a.	12.75–15.41	[19]
Bay leaf	leaves	n.a.	n.a.	n.a.	n.a.	0.90–0.92
Bean	pericarp and loose herbs	n.a.	n.a.	n.a.	n.a.	0.50–0.64	[99]
Birch	loose herbs	n.a.	n.a.	n.a.	n.a.	2.28–3.08
Black pepper	fruits	n.a.	n.a.	n.a.	n.a.	0.09–0.11	[19]
Cloves	flower buds	n.a.	n.a.	n.a.	n.a.	1.22–1.36
Cocoa	powder	12.9–37.5	<LOD	n.a.	n.a.	4.0–4.5	[18]
Cumin	seeds	n.a.	n.a.	n.a.	n.a.	0.61–0.67	[19]
Curry	powder and mixture of herbs	n.a.	n.a.	n.a.	n.a.	3.13–3.65
Dandelion	root and loose herbs	n.a.	n.a.	n.a.	n.a.	0.04–0.06	[99]
Elder	flower and loose herbs	n.a.	n.a.	n.a.	n.a.	1.54–1.92
Fennel	fruits	n.a.	n.a.	n.a.	n.a.	0.70–0.90	[19]
Glechoma	herbs	n.a.	n.a.	n.a.	n.a.	0.99–1.05
Harpagophytum **	root and capsules	n.a.	n.a.	n.a.	n.a.	0.02–0.04	[99]
Hemp	leaves	n.a.	19.0–23.0 *	n.a.	n.a.	8.1–18.6 *	[100]
	stem	n.a.	12.8–19.6 *	n.a.	n.a.	0.5–1.6
	root	n.a.	6.8–7.4 *	n.a.	n.a.	0.80 *
Herbs de Provence	mixture of herbs	n.a.	n.a.	n.a.	n.a.	3.13–3.27	[19]
Horsetail	loose herbs	n.a.	n.a.	n.a.	n.a.	1.91–2.63	[99]
Marjoram	herbs	n.a.	n.a.	n.a.	n.a.	3.70–3.86	[19]
Mint	leaves	n.a.	n.a.	n.a.	n.a.	2.70–3.34
Nettle	loose herbs	n.a.	n.a.	n.a.	n.a.	2.33–3.09	[99]
Oregano	leaves	n.a.	n.a.	n.a.	n.a.	2.18–2.72	[19]
Parsley	leaves	n.a.	n.a.	n.a.	n.a.	0.67–0.85
Peppermint	loose herbs	n.a.	n.a.	n.a.	n.a.	3.36–4.28	[99]
Reumaflos tea	leaves and sachets	n.a.	n.a.	n.a.	n.a.	1.73–2.43
Rosemary	leaves	n.a.	n.a.	n.a.	n.a.	1.17–1.25	[19]
Reumatfix	sachets	n.a.	n.a.	n.a.	n.a.	1.43–1.89	[99]
Sage	leaves	n.a.	n.a.	n.a.	n.a.	1.24–1.32	[19]
Savory	herbs	n.a.	n.a.	n.a.	n.a.	1.14–1.42
Spirulina		~75.0	~0.015	<LOD	~0.09	~0.10	[101]
Tarragon	leaves	n.a.	n.a.	n.a.	n.a.	1.00–1.08	[19]
Thyme	leaves and branches	n.a.	n.a.	n.a.	n.a.	7.87–9.70
Turmeric	rhizoma	n.a.	n.a.	n.a.	n.a.	1.45–1.51
Willow	bark and loose herbs	n.a.	n.a.	n.a.	n.a.	0.21–0.31	[99]

* depending on the growth stage (analysis conducted after 30, 80, and 90 days of growth); ** Radix Harpagophytum, Devil’s Claw; n.a.—data are not available, the analyte was not included in the target list of the applied analytical methods; <LOD—not detected. AA—anthranilic acid; CA—cinnabarinic acid; 3HAA—3-hydroxyanthranilic acid; 3HKyn—3-hydroxykynurenine; KYN—kynurenine; KYNA—kynurenic acid; PIC—picolinic acid; QA—quinolinic acid; TRP—tryptophan; and XA—xanthurenic acid.