Influence of plant growth regulators on the shoot culture of Phyllanthus glaucus and accumulation of indolizidine alkaloids with evaluation of antimicrobial activity

Abstract

In the presented studies, plant growth regulators (PGRs) were evaluated for their influence on the shoot development and the content of biologically active indolizidine alkaloids, securinine, and allosecurinine in Phyllanthus glaucus (Euphorbiaceae) in vitro shoot cultures. The experiments included five cytokinins [kinetin, 6-benzylaminopurine (BAP), 2-isopentenyladenine, and thidiazuron] and two auxins [indole-3-acetic acid and indole-3-butyric acid (IBA)] used in a different concentrations. The results were tested for statistical differences. The highest number of shoot per explant (11.5) was achieved on Murashige and Skoog’s (MS) medium supplemented with IBA 0.5 mg/L and BAP 1.0 mg/L, and the optimal rooting response (87.50%) was obtained on MS medium-containing IBA 1.0 mg/L. The rooted plantlets were transferred into the soil and the survival rate was 70.0%. The differences in accumulation of particular alkaloids were revealed depending on PGRs present in harvesting medium. The highest total concentration of alkaloids was determined in the shoot culture grown in the presence of BAP 0.5 mg/L [5.82 mg/g dry weight (DW)]. In routine propagation, MS medium supplemented with IBA 0.5 mg/L and BAP 0.5 mg/L was used as a compromise between the relatively high proliferation rate (~ 8 shoots/explant) and the total content of alkaloids (4.73 mg/g DW). The antimicrobial activity of the biomass and isolated securinine was evaluated towards 12 strains of bacteria and one fungal strain. The differences in bacterial susceptibility against P. glaucus extract and securinine were showed. The MBC values range from 0.01 to 5 mg/mL and from 0.063 to 0.250 mg/mL, respectively, for extract and securinine.