Rosmarinic acid production of Ehretia asperula Zollinger & Moritzi cell suspension cultures: effects of cell aggregate size, glucose, and chitosan

Abstract

Rosmarinic acid (RA) is an ester of caffeic acid and 3,4-dihydroxy phenyl lactic acid with anti-oxidant, anti-bacterial, anti-viral, and anti-cancer properties. It has been found in some plants of the Boraginaceae and Lamiaceae families. Ehretia asperula Zollinger & Moritzi is a medicinal plant, widely distributed in some countries such as China, Vietnam, Myanmar, and Thailand. Cell suspensions were obtained by transferring 1 g of friable callus into 20 mL of B5 liquid medium supplemented with 0.4 mg/L NAA and 0.1 mg/L BA, on orbital shaker at 90 rpm in the dark. The subculture was carried out after each of 21 days along with removing brown cell aggregates. To investigate the effects of cell aggregation, glucose, and chitosan on cell biomass and RA biosynthesis, the yellow cell suspensions were transferred to a new liquid medium. The results showed that non-sieved cell aggregates produced the highest biomass and RA content of E. asperula Zollinger & Moritzi cell suspension cultures. Glucose concentrations had direct effects on RA production. An addition of 45 mg/L glucose showed a significant (1.198 fold) increase in RA yield compared with control (30 mg/L) and other concentrations. On the other hand, the optimum concentration of chitosan for enhancing RA content was found at 50 mg/L after 48 hours of treatment, with an RA concentration 1.17 times greater than the control. These findings suggested that the using of cell clusters which size more than 0.125 mm, the addition of appropriate concentrations of sugar and chitosan could stimulate RA biosynthesis of E. asperula Zollinger & Moritzi cell suspensions