Flavonoid Metabolome-Based Active Ingredient Mining and Callus Induction in Catalpa bungei C. A. Mey

Abstract

Catalpa bungei C. A. Mey is a unique and precious multi-purpose tree species that possesses great timber-related, ornamental and medicinal values. In this study, MS, N6 and DKW were used as basic media, and different concentrations of 6-BA and NAA were added for callus induction. The induction rate and total flavonoid content of callus tissue showed that the best callus induction medium was DKW + 2.0 mg·L−1 6-BA + 0.5–1.0 mg·L−1 NAA. The leaves of different bark phenotypes of C. bungei C. A. Mey and the callus tissue extracted from young leaves of C. bungei C. A. Mey were used as experimental materials to construct metabolomic profiles of widely targeted flavonoids. Based on the metabolomic databases, the predominant flavonoids were screened from the callus tissues. Eight flavonoid metabolites increased in callus, and diosmetin-7-O-rutinoside (diosmin) was the flavonoid constituent with the shortest retention time, most efficient detection and best medicinal functions among these 8. The optimal medium for callus induction was supplemented with different concentrations of elicitors (salicylic acid SA and yeast extract YE). The optimal elicitor and the amount to be added were determined by analyzing the induction rate of callus, as well as the total contents of flavonoids and diosmin. The addition of SA and YE in appropriate amounts increased the total flavonoid content in the callus, but only the addition of YE promoted the formation of diosmin in the callus. The optimal medium formulation to promote the formation of callus was DKW + 2.0 mg·L−1 6-BA + 1.0 mg·L−1 NAA + 30 g·L−1 sucrose + 6.8 g·L−1 agar + 10 μmol·L−1 SA. The medium formulation to optimally increase the content of geraniol glucoside was DKW + 2.0 mg·L−1 6-BA + 1.0 mg·L−1 NAA + 30 g·L−1 sucrose + 6.8 g·L−1 agar + 200 mg·L−1 YE. The results of the present study will provide a scientific basis for the subsequent increase in the content of the active components of the suspension cells via the addition of elicitors, and for the production of diosmin in factory settings.