Effects of 6-benzylaminopurine and thidiazuron on in vitro regeneration and antioxidant content of Sorbaria pallasii (Rosaceae) microshoots

Findings are presented about an influence of synthetic cytokinins—6-benzylaminopurine and thidiazuron—on the formation of microshoot culture and levels of phenolic compounds (phenolcarboxylic acids, tannins, flavonols, and catechins) in vitro shoots of Sorbaria pallasii (Rosaceae). The cultivation was implemented on the MS and ½ MS medium. The largest number of microshoots per explant (5.79 ± 1.23) was observed on the MS medium containing 6-benzylaminopurine, whereas with thidiazuron, this number was lower (4.45 ± 1.5). The height of microshoots did not differ significantly among all the tested media, and this parameter varied from 9.52 ± 3.3 to 8.81 ± 2.1 mm. The number of leaves per microshoot did not differ significantly among microshoots cultivated on the media containing these plant growth regulators and was 3.37 ± 1.14 to 3.72 ± 1.01. The largest number of leaves per microshoot was observed on the regulator-free MS medium (4.16 ± 0.57) and the ½ MS medium (4.75 ± 0.85). A phytochemical analysis of the profile and levels of phenolic compounds revealed that the antioxidants (such as flavonols, tannins, and catechins) accumulated more actively in S. pallasii microshoots cultivated either on the complete MS medium without the hormones or on the MS medium supplemented with thidiazuron. The higher antioxidant activity of extracts from these microshoots is probably due to high concentrations of mainly catechin (3.03 mg/mL; in the case of cultivation on the MS medium) or of epigallocatechin gallate (0.62 mg/g) and epicatechin (2.08 mg/g) (on thidiazuron-containing MS). These studies provide the basis for the development of a protocol for obtaining S. pallasii biomass with a high content of phenolic antioxidants.