Induction and determination of total phenols of callus of barbatimão

Abstract

Barbatimão [Stryphnodendron adstringens (Mart.) Coville], is a tree with predominant occurrence in the Cerrado regions in the Brazilian States. Its bark is rich in tannins which is used in folk medicine due to its astringent function. In recent years, the indiscriminate exploitation of barbatimão tree led to a decrease in bark production of this medicinal plant. The aim of this study was to induce calluses from cotyledon segments and determine the weight of fresh and dry matter and the levels of phenols the induced calluses. For callus induction, cotyledon segments were inoculated in a medium with different combinations of growth regulators: 2,4-D × TDZ (0, 0.5, 1.0 and 2.0 mg L-1) and kinetin × picloran (0; 0.5, 1.0 and 2.0 mg L-1). Cultures were incubated in the dark and at a temperature of 27 ± 2 º C. At 60 days of subculture the fresh and dry weight and the levels of total phenols were evaluated. The best results obtained for the calluses fresh weight with the combination (2,4-D × TDZ) were: 0.5 mg L-1 of 2,4-D associated with 0.5, 1.0 and 2.0 mg L-1 concentrations of TDZ. For dry matter values the best combination was: 0.5 and 2.0 mg L-1 TDZ in the absence of 2,4-D. For the (Kinetin × Picloram) combination, the best results for callus induction were: 2 mg L-1 of kinetin and 0.5 mg L-1 of Picloram, with an average of 0.2 g of fresh weight and 0.02 g of dry weight. The results indicated that higher levels of total phenols were found in calluses induced on a medium supplemented with 1.0 mg L-1 of 2,4-D, 2.0 mg L-1 of kinetin and 1.0 mg L-1 of Picloram. A negative effect for TDZ regarding the total phenol levels when combined with 2,4-D was noted. The tests performed in this study, where different growth regulators were used for barbatimão callus induction in order to increase phenol concentrations, did not present satisfactory results. Although a low concentration of phenolic compounds was obtained, it is important to note that the culture medium may be optimized for large scale in vitro production of this compound.