Optimization of Phytochemical Content and DPPH Scavenging Activity from Pokeweed (Phytolacca americana L.) Callus using Response Surface Models

Abstract

Pokeweed belongs to the Phytolaccaceae family and has been traditionally cultivated as an ornamental plant. However, field-cultivated pokeweed in non-native regions can negatively affect the environment. Therefore, this study aimed to develop pokeweed callus induction protocols and optimize some phytochemicals in calli. Pokeweed leaf explants were cultured on Murashige and Skoog (MS) medium fortified with 6-benzylaminopurine (BAP) and two auxins: 1-Naphthaleneacetic acid (NAA) and Indole-3-butyric acid (IBA). After culture for four weeks, calli were extracted to determine the total phenolic and flavonoid contents (TPC and TFC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant activity. TPC in treatments of 1mg/L BAP with 0.5mg/L IBA, and 3mg/L BAP with 1mg/L IBA were significantly highest, while TFC and DPPH scavenging activity from the BAP treatment without auxins provided the highest contents (P<0.05). Pearson’s correlation coefficients confirmed the relationship between TFC and DPPH, which demonstrated the antioxidant activity of the flavonoid compounds. The surface plots showed that the application of NAA or IBA at higher concentrations reduced flavonoid content and DPPH activity, while the optimal responses were obtained when individual BAP was applied. For the response of TFC, the flavonoid contents increased with BAP concentration, and the optimal content (3.16-3.19µg QE/g DW) was obtained at 3mg/L BAP. The optimal DPPH response (3.43-3.45µg Trolox/mg DW) was observed at 1.98-2.07mg/L BAP. The findings of this study can be applied to produce pokeweed calli and predict plant growth regulator (PGR) concentrations for high flavonoid content and antioxidant activity, which could be further studied on the bioactive properties of pokeweed callus extracts.