Establishment of adventitious root cultures and assessment of secoiridoid production in the Chinese medicinal plant Gentiana scabra

Gentiana scabra is an important medicinal herb that is used to treat inflammation, tuberculosis, rheumatism, cholecystitis, and hepatitis. The primary bioactive components in G. scabra are secoiridoids derived from the roots and rhizomes of the plant. In this study, we sought to establish a means of reliably producing these secoiridoids through G. scabra in vitro adventitious root culture. To that end, we studied the effect of phytohormones, light condition, explant type, and medium composition on adventitious root induction and secoiridoid production. Maximal induction frequency (100%) was ultimately achieved when using leaf explants cultured on Murashige and Skoog (MS) medium containing 3.0 mg L NAA and 0.25 mg L TDZ with a 16/8-h photoperiod, yielding 53.20 ± 3.15 roots per explant. We explored root growth curves over an 8-wk period in MS liquid medium prepared as above, and observed maximal fresh weight (FW) and dry weight (DW) values of 26.94 ± 0.38 g per flask and 1.79 ± 0.032 g per flask, respectively, in 4-wk-old cultures. The accumulation of secoiridoids (gentiopicroside, swertiamarin, and sweroside) in these adventitious root cultures was assessed via high-performance liquid chromatography (HPLC), revealing maximal gentiopicroside (25.59 ± 0.65 mg g DW), swertiamarin (1.61 ± 0.04 mg g DW), and sweroside (4.42 ± 0.11 mg g DW) levels after 4 wk. Together, our results reveal that G. scabra adventitious root cultures represent a viable approach to the in vitro production of secoiridoids. This is the first study to our knowledge to have explored the isolation of secoiridoids following the in vitro growth of G. scabra adventitious roots. These data may represent an important step toward the development of large-scale adventitious root cultures for commercial secoiridoids production.