Tipo de explante e reguladores de crescimento vegetal na indução de calos, produção de compostos fenólicos e atividade antioxidante em Amburana cearensis

Abstract

Amburana cearensis, a native species of Brazil, is valued for its wood and the medicinal benefits of its metabolites. Direct extraction of these compounds can lead to the species' extinction, making tissue culture an effective alternative for producing metabolites in a controlled environment. The aim of this study was to evaluate the type of explant and plant growth regulators (PGRs) in callus induction, phenolic compound production, and antioxidant activity in A. cearensis. Seeds of A. cearensis were germinated in vitro, and after 30 days, the seedlings were sectioned into four types of explants: leaf, cotyledon, epicotyl, and root. These explants were placed in Murashige-Skoog (MS) medium with combinations of PGRs (Thidiazuron (TDZ) + 1-naphthaleneacetic acid (ANA) and TDZ + 2,4-dichlorophenoxyacetic acid (2,4-D)) for callus formation and growth. After induction, the three treatments with the highest growth were analyzed after 30 days to determine total phenolic content (TPC), total flavonoid content (TFC), and antioxidant activity, using the 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and phosphomolybdenum assays. The PGR combinations were effective in callus induction and growth. However, the combinations 5 mg L-1 TDZ + 1 mg L-1 ANA (5T+1A), 1 mg L-1 TDZ + 1 mg L-1ANA (1T+1A), 1 mg L-1 TDZ + 1 mg L-1

2,4-D (1T+1-2,4D) resulted in the greatest (p ≤ 0.05) mass of callus from all explants, particularly leaves and cotyledons. The epicotyl callus with the combination 1T+1A and 1T+1-2,4D showed higher (p ≤ 0.05) levels of phenolic compounds, while the cotyledon with the combinations 5T+1A and 1T+1A showed higher levels of flavonoids and coumarin, respectively, compared to root and leaf. Antioxidant activity varied significantly according to the explant type and PGR combination. In epicotyl and root calluses, there was no correlation between phenolic compounds and antioxidant activity. In contrast, in leaf and cotyledon calluses, as well as in the parent plant of A. cearensis, there was a correlation with at least one antioxidant method (DPPH, ABTS, and phosphomolybdenum). All calluses, as well as the parent plant, contained phenolic compounds and exhibited antioxidant activity at different concentrations, demonstrating their ability to produce the same compounds as the original plant. In conclusion, although a direct relationship between antioxidant activity and phenolic compounds was not found, the calluses contain phenolic compounds, including coumarins and flavonoids, making them potentially valuable for the pharmaceutical industry.