Impact of elicitors and precursor on quassinoids and canthin-6-ones production in adventitious root culture of Eurycoma harmandiana Pierre and improvement of their anti-inflammatory activity

The processes of elicitation and precursor are used to increase the production of secondary metabolites in plant tissue cultures. The roots of Eurycoma harmandiana Pierre, a herbal plant used in traditional Thai medicine, are highly sought after to treat fever and erectile dysfunction. Hence, alternative sources from in vitro plant tissue of interest are needed. This study investigated the growth kinetics of adventitious root culture of E. harmandiana and the effect of various elicitors, including yeast extract (YE), chitosan (CH), 2-hydroxypropyl-beta-cyclodextrin (HPCD), and precursor tryptophan (T), to enhance the contents of quassinoids and canthin-6-ones in root biomass and culture media. Elicitors and precursor were added at the 10th week after subculturing, and the root biomass and culture media were harvested on days 7 and 14 after treatment. Canthin-6-ones accumulation on day 14 was up to 2-fold higher than that in the control when the root culture was treated with 200 mu M T, and quassinoid accumulation was 3.6-fold higher when elicited with 2 mg/mL YE. 9-Hydroxy-canthin-6-one was the most abundant in the root biomass after addition of CH (200 ppm), while only eurycomanone and 9-hydroxycanthin-6-one were found in the culture media. Additionally, on day 14, 9-methoxy-canthin-6-one was found in the media culture of the elicited root with HPCD, whereas it was not found after treatment with the other elicitors. Meanwhile, the morphology of adventitious roots changed after elicitation. The enhancement of quassinoids and canthin-6-ones compounds in the root biomass after elicitation led to stronger anti-inflammatory activity than in the non-treated roots owing to significantly inflammatory gene suppression. This study demonstrates the effective elicitation and precursor feeding of adventitious root cultures of E. harmandiana, which enhanced bioactive components and improved anti-inflammatory effects.