Phenolic acid profiles and antioxidant potential of Pelargonium sidoides callus cultures

Abstract

Pelargonium sidoides DC., an important medicinal plant widely used in traditional medicine in South Africa and Lesotho, has been successfully developed into popular international phytomedicines. In the current study, proliferating P. sidoides callus cultures were established on Murashige and Skoog (MS) medium containing different concentrations and combinations of picloram and thidiazuron (TDZ), and evaluated for their phenolic composition and antioxidant capacity. The concentrations of phenolic acids were determined using ultra performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS). Antioxidant potential of P. sidoides calli was evaluated using 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity, β-carotene/linoleic acid assay and oxygen radical absorbance capacity (ORAC) activity. Callus induction was significantly higher in cultures supplemented with different combinations and concentrations of picloram and TDZ compared to the control. Except for gallic acid, picloram/TDZ combinations significantly increased the concentrations of hydroxybenzoic acid derivatives, namely protocatechuic acid, p-hydroxybenzoic acid, vanillic acid and salicylic acid. The concentration of hydroxycinnamic acid derivatives in P. sidoides calli was variable with catechin only detected in calli produced on PGR-free MS medium whereas caffeic acid was not detected in such calli. Picloram (2.0μM) and TDZ (2.5; 5.0μM) stimulated the highest concentrations of caffeic acid, p-coumaric acid and ferulic acid. The highest antioxidant activity based on the DPPH and β-carotene/linoleic acid model systems was obtained for PGR-free-produced calli whereas picloram and TDZ combinatory treatments had a significant effect on the ORAC. The study suggests that P. sidoides calli can be manipulated on a large scale for the production of phenolic acids that exhibit potent antioxidant activity.