Chitosan elicitation of Isatis tinctoria L. hairy root cultures for enhancing flavonoid productivity and gene expression and related antioxidant activity.

Elicitation for phytochemical enhancement via cost-effective elicitors can overcome the limitation of commercial application faced by plant cell and organ culture technology. Chitosan is a natural, low-cost, and nontoxic elicitor that can trigger plant defense responses with the concomitant enhancement in phytochemical biosynthesis. In this work, the elicitation of Isatis tinctoria L. hairy root cultures by chitosan was conducted to enhance the production of pharmacologically active flavonoids. In comparison with control (2.31 ± 0.29 mg/g DW), a 7.08-fold enhancement of total flavonoids (16.35 ± 0.88 mg/g DW) was achieved in 24 day-old I. tinctoria hairy root cultures elicited by 150 mg/L chitosan for 36 h. Interestingly, the multiple hydroxyl-substituted flavonoids (rutin, quercetin, isorhamnetin, and isoliquiritigenin) were noticed to increase significantly in chitosan-elicited I. tinctoria hairy root cultures. Moreover, the transcription of associated genes involved in flavonoid biosynthesis pathway was significantly up-regulated underlying chitosan elicitation, among which chalcone synthase and flavonoid 3'-hydroxylase might play an important role in flavonoid enhancement. Additionally, extracts from chitosan-elicited I. tinctoria hairy root cultures exhibited higher antioxidant activities with lower IC₅₀ values as compared with control. Overall, a cost-effective strategy via the simple chitosan elicitation is provided here to enhance the production of high-added value flavonoids in I. tinctoria hairy root cultures, which paves the way toward the successful commercialization of this in vitro culture system in the future.