Growth, morphology and bioactive phenolic compounds production in Pyrostegia venusta calli

Pyrostegia venusta is a medicinal climbing plant commonly used in traditional Brazilian medicine to treat diarrhea, vitiligo, cough and common infections. In order to evaluate the growth, morphology and bioactive phenolic compounds production in P. venusta calli, cultures were established on MS medium supplemented with 4.52 μM of 2,4-dichlorophenoxyacetic acid and 8.88 μM 6-benzylaminopurine in the absence of light. Morphological analyses were performed with scanning and transmission electron microscopy. Total proteins, amino acids, soluble and reducing sugars, phenols, and flavonoids contents were quantified by spectrophotometric assays, and the phenolic compounds profile was evaluated by high-performance liquid chromatography. The calli growth showed a sigmoidal pattern, with four distinct phases: lag, exponential, linear and decline phases. Ultrastructural analysis showed cells with meristematic characteristics at the start of the culture (lag and exponential phases), cellular organizations in clusters in the linear phase and ruptured cells without visible organelles in the decline phase. The highest levels of primary metabolites (proteins, amino acids, soluble and reducing sugars) and secondary metabolites (phenols and flavonoids) were observed at 10 days of culture (lag phase) and in general decreased with callus growth. Benzoic and p-coumaric acid derivatives and rutin were observed in the initial explant, and caffeic acid derivatives were detected in the callus culture at 60 and 120 days.