Effect of auxin and cytokinin on phenolic content of Baccharis myriocephala DC. (Asteraceae) produced in vitro

A protocol for large-scale in vitro production of Baccharis myriocephala was developed. Total phenolic content was analyzed in plants cultured on MS + 1.0 mg.L-1 of indoleacetic acid (IAA), benzyladenine (BA) or kinetin (KIN). Nodal segments obtained from seeds germinated in vitro on Murashige and Skoog basal medium (MS) were subcultured on MS basal medium, hormone-free or with different growth regulators added: IAA, BA or KIN. The total phenolic content was determined using the Folin-Denis spectrophotometric method, and the content of phenolics of extracts was expressed in terms of gallic acid-equivalent (µg GA/mg dry weight). The best growth and development of the plants was induced by MS + 1.0 mg.L-1 IAA, which stimulated the production of 23 new nodal segments from a single phytomer after 60 days of in vitro culture. However, MS + 1.0 mg.L-1 IAA accumulated the lowest phenolic content, and only 18.46 µg/mg dry weight. A significant negative correlation was noted, since the phenolic content increased when the dry weight decreased. This culture system is capable of supplying good-quality raw material in adequate quantity to meet the growing demand for medicinal plants. However, the accumulation of polyphenols is lower in cultures with higher dry weight.   Key words: Carqueja, micropropagation, growth regulators, phenolics accumulation.