Antioxidant activity, phenol and flavonoid contents of plant and callus cultures of Plectranthus barbatus andrews

Abstract

Background and objective Plectranthus barbatus is cultivated in many parts of the world for healing and food tradition. This study describes a protocol for the establishment of callus cultures of P. barbatus and examines their content of active compounds as well as their effects as antioxidants compared with in-vitro plants.Materials and methods For obtaining callus cultures, three different explants were tested on MS medium with different growth regulators. Growth index was calculated for the best explant which gave the highest percentage of callus induction. Two different solvents were used for extraction. 2,2′‐Diphenyl-1‐picrylhydrazyl-scavenging activity, total phenolic and flavonoid contents were determined. Gas chromatography–mass spectroscopy analysis was performed to detect the different components.Results and conclusion Maximum callus induction (100%), fresh weight (3.5 g), and growth index (16.5) were obtained from cotyledon explants cultured on MS medium supplemented with 2.0 mg/l naphthalene acetic acid+2.5 mg/l benzyl adenine. Aqueous methanol extracts exhibited higher 2,2′‐diphenyl-1‐picrylhydrazyl radical scavenging activity than hexane extracts at all tested concentrations. Likewise, methanolic extract of in-vitro plant and callus cultures gave the highest values of total phenolic (1.39 and 1.19 mg/g dry weight, respectively) and total flavonoid contents (4.87 and 1.14 mg/g dry weight, respectively). Thirty-one bioactive ingredients have been identified in the hexane extract of in-vitro plant and callus cultures of P. barbatus by gas chromatography–mass spectroscopy analysis.