Evolution with age of main bitter compounds in the roots of cultivated Gentiana lutea subsp. aurantiaca

Gentiana lutea L. subsp. aurantiaca is an endemic plant distributed in the northwest part of the Iberian Peninsula which shows clear genetic differences compared to other subspecies of G. lutea [1]. This subspecies has been widely used in traditional medicine, especially due to the high concentration of bitter compounds in its roots, mainly secoiridoid glycosides. The concentration of bitter compounds in this subspecies is similar compared with other subspecies as lutea or vardjanii [2]. Like other G. lutea L. subspecies, aurantiaca subspecies is endangered because of intensive and illegal collection. The cultivation of G. lutea subsp. aurantiaca could allow the protection of this subspecies and produce roots with higher concentration in bitter compounds.

In this study we compared the content in the bitter compounds amarogentin, gentiopicroside, sweroside and swertiamarin in the three, four and five years old roots of cultivated G. lutea subsp. aurantiaca collected in the autumn of 2010, 2011 and 2012 with. The experimental field was located near Leon (Spain). For this purpose, methanolic extracts of complete root systems were analysed by HPLC. The results show that the concentration of amarogentin decreases significantly with plant age. However, the concentration of swertiamarin is significantly higher for older root systems, as is the dry weight, which shows a significant increase between years four and five. Gentiopicroside and sweroside concentrations did not show a homogeneous evolution or significant differences.

The evolution of the bitter compounds regarding the age of the roots is variable, favoring collecting younger roots if the desired bitter compound is amarogentin, due to its high bitter index [3]. Conversely, older plants yield a higher concentration of swertiamarine and root mass.

Tab. 1: Dry weight (g) and bitter compound concentration (mg/g of root dry weight) in 3, 4 and 5 years old roots systems of cultivated G. lutea L. subsp. aurantiaca. Bars with different letters for the dry weight and every bitter compound are significantly different (p ≤0.05) according to according to LSD.

Age (years)	Dry weight (g)	Amarogentin (mg/g)	Gentiopicroside (mg/g)	Sweroside (mg/g)	Swertiamarin (mg/g)
3	4.79 b	0.099 a	6.53 ab	0.297 a	0.309 b
4	9.59 b	0.084 b	7.05 a	0.373 a	0.380 a
5	16.73 a	0.071 b	6.16 b	0.297 a	0.367 a

Acknowledgements: Regional Ministry of Education of the Junta de Castilla y León and the European Social Fund PIRTU grants.Orden EDU/1867/2009. And Regional Ministry of the Enviroment of the Junta de Castilla y León. Project (2008/00134/001).

Keywords: Traditional medicine, medicinal plants, Gentiana.

References:

[1] González-López O, Polanco C, György Z, Pedryc A, Casquero PA.. Genetic variation of the endangered Gentiana lutea L. var. aurantiaca (Gentianaceae) in populations from the northwest Iberian Peninsula. Int J Mol Sci 2014; 10052 – 10066

[2] González-López O, Carro G, Aiello N, Scartezzini F, Casquero PA. Main bitter compounds of Gentiana lutea var. aurantiaca roots wild collected in the Leon Province (Spain). Planta Med 2014; 80: 1489 – 1490

[3] Ando H, Hirai Y, Fujii M, Hori Y, Fukumura M, Niiho Y, Nakajima Y, Shibata T, Toriizuka K, Ida Y. The chemical constituents of fresh Gentian root. J Nat Med 2007; 61: 269 – 279

No conflict of interest has been declared by the author(s).