Adubação orgânica, micropropagação e validação analítica para doseamento de cardenolídeos totais em Digitalis purpúrea subs. heywoodii

Abstract

Digitalis purpurea subsp. heywoodii (Plantaginaceae) is considered a medicinally important species due to the presence of glycoevatromonoside cardenolide, responsible for its antiviral potential for human herpes. Its field cultivation presents a few obstacles, demanding the use of organic fertilization and in vitro cultivation as alternative for this issue. Thus, the objective was to cultivate the D. purpurea subsp. heywoodii species in pots with different doses of organic fertilization, as well as in vitro under the influence of physical and chemical factors, in order to evaluate its effects over growth and content of total cardenolides. The method for quantifying total cardenolides by UV spectrophotometry was validated, with selection at 494 nm for not presenting significant absorption in reading solution without the addition of coloring reagent, remaining linear in the range from 0.025 to 0.125 mg/mL, R2=0.9994. Interday (DPR = 3.26%) and intra-day (DPR = 3.58%) precision were considered exact from low to intermediate concentrations in the linear interval (98.4% and 98.9%), and robust for the reaction time of 25 min, with small variations in the length of the reading wave. The organic fertilization evaluated was chicken manure. The doses of this manure that better provided number and gain of foliar biomass were of 6 and 9 kg m-2. The absence of fertilizer provided greater root biomass gains, higher R/PA relation and higher average contents of cardenolides. However, cardenolide productivity were superior with the dose of 6 kg m-2. Concerning the chemical factors, different concentrations and combinations of cytokines BAP and TDZ (mg L-1) were used, in a total of thirteen treatments. A higher number of sprouts occurred with the BAP + TDZ combinations of 0.5 + 0.5; 0.25 + 0.75; 1.0 + 0.5 mg L-1. The average accumulation of dry biomass and productivity of total cardenolides was favored with the combination of 0.375 + 0.125 mg L-1. The effect of physical factors, such as intensity, quality and light shock were also evaluated. Intensity and light shock with 139 μmol m-2 s-1 produced greater the aerial part, root and total biomass, as well as higher content and productivity of total cardenolides. Blue LEDs favored both biomass production of the aerial part and productivity of total cardenolides. Therefore, the method was linear, precise, exact, robust, selective and reproducible, with ease of execution. The application of 6 kg m-2 of chicken manure in in vitro cultivation; the combination of 0.375 + 0.125 mg L-1 of BAP + TDZ supplemented to a MS culture medium; intensity and light shock with 139 μmol m-2 s-1; and blue LED in in vitro cultivation provided good conditions for the cultivation of the species, with increments in the production of biomass and productivity of total cardenolides.