Yeast extract-mediated elicitation of anti-cancerous compounds licoisoflavone B, licochalcone A, and liquirtigenin in callus cultures of Glycyrrhiza glabra

Licoisoflavone B, licochalcone A, and liquirtigenin are important flavonoids found in the medicinal plant Glycyrrhiza glabra and are known for their preventive and therapeutic potential against cancer. Extraction of these flavonoids in commercially viable quantities is a challenging task. Therefore, an attempt has been made to elicit the production of these flavonoids in tissue cultures of G. glabra. We investigated the effect of the biotic elicitor yeast extract (YE) on the production of three flavonoids in G. glabra callus cultures grown in a previously standardized nutrient medium consisting of Murashige and Skoog’s medium components supplemented with naphthalene acetic acid and benzyl amino purine. The YE elicitor was tested in the concentration range of 25–175 mg/l. At each elicitor concentration, a time-course analysis was also performed to determine the effect of the duration of YE treatment on flavonoid production. The effect of YE on the key enzyme of the phenylpropanoid pathway, phenylalanine ammonia lyase (PAL), antioxidant enzymes, polyphenoloxidase (PPO), and peroxidase (POD) was also observed. The results revealed that 75 mg/l concentration of YE was most suitable for elicitation of biosynthesis of flavonoids in G. glabra cultures and more than a 2-fold increase in the production of all the three flavonoids was obtained. The activities of the enzymes, PAL, PPO, and POD, also increased significantly, suggesting that the stress response was elicited by YE. These results provide evidence of activation of phenylpropanoid metabolism and regulation of its key enzymes by YE, eventually leading to enhanced production of anti-cancerous flavonoids licoisoflavone B, licochalcone A, and liquirtigenin.