There is ongoing research about the functional (not flavor) use of teas. For instance as found by querying PubMed:
Acta Pharm Sin B. 2016 Mar;6(2):170-81. doi: 10.1016/j.apsb.2015.11.003. Epub 2015 Dec 24.
Investigation of free amino acid, total phenolics, antioxidant activity and purine alkaloids to assess the health properties of non-Camellia tea.
Bi W1,
He C1,
Ma Y1,
Shen J1,
Zhang LH2,
Peng Y1,
Xiao P1.
Author information
Abstract
To find novel functional beverages from folk teas, 33 species of frequently used non-Camellia tea (plants other than Camellia) were collected and compared with Camellia tea (green tea, pu-erh tea and black tea) for the first time. Data are reported here on the quantities of 20 free amino acids (FAAs) and three purine alkaloids (measured by UHPLC), total polyphenols (measured by Folin-Ciocalteu assay), and antioxidant activity (DPPH). The total amounts of FAAs in non-Camellia tea (0.62-18.99 mg/g) are generally less than that of Camellia tea (16.55-24.99 mg/g).
However, for certain FAAs, the quantities were much higher in some non-Camellia teas, such as γ-aminobutyric acid in teas from Ampelopsis grossedentata, Isodon serra and Hibiscus sabdariffa. Interestingly, theanine was detected in tea from Potentilla fruticosa (1.16±0.81 mg/g). Furthermore, the content of polyphenols in teas from A. grossedentata, Acer tataricum subsp. ginnala are significantly higher than those from Camellia tea; teas from I. serra, Pistacia chinensis and A. tataricum subsp. ginnala have remarkable antioxidant activities similar to the activities from green tea (44.23 μg/mL). Purine alkaloids (caffeine, theobromine and theophylline) were not detected in non-Camellia teas. The investigation suggest some non-Camellia teas may be great functional natural products with potential for prevention of chronic diseases and aging, by providing with abundant polyphenols, antioxidants and specific FAAs.
Chamomile has a very mild (not strong) flavor. You may also find these articles about chamomile tea informative:
https://www.sciencedaily.com/releases/2005/01/050104112140.htm
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2995283/
Further:
J Pharm Biomed Anal. 2016 Oct 25;130:326-335. doi: 10.1016/j.jpba.2016.01.042. Epub 2016 Jan 21.
The determination of elements in herbal teas and medicinal plant formulations and their tisanes.
Pohl P1,
Dzimitrowicz A2,
Jedryczko D2,
Szymczycha-Madeja A2,
Welna M2,
Jamroz P2.
Author information
Abstract
Elemental analysis of herbal teas and their tisanes is aimed at assessing their quality and safety in reference to specific food safety regulations and evaluating their nutritional value. This survey is dedicated to atomic spectroscopy and mass spectrometry element detection methods and sample preparation procedures used in elemental analysis of herbal teas and medicinal plant formulations. Referring to original works from the last 15 years, particular attention has been paid to tisane preparation, sample matrix decomposition, calibration and quality assurance of results in elemental analysis of herbal teas by different atomic and mass spectrometry methods. In addition, possible sources of elements in herbal teas and medicinal plant formulations have been discussed.
And with regard to GABA, a free article:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4863311/
Be aware that herbal tea is not all good or bad... Plants take up minerals from the soils where they grow, and some may take up lead...not something you want. Apparently the longer you steep the tea the more lead may leach out into the water, hence this is one reason to follow steeping directions. Cheers!