Flores de Centaurea cyanus L. e Clitoria ternatea L.: caracterização química, estabilidade das antocianinas e propriedades funcionais in vitro.

Abstract

The blue flowers of the C. cyanus L. and the C. ternatea L. are used in traditional medicine because of their therapeutic properties. Most studies of bioactive compounds use methyl alcohol and ethyl alcohol acidified with HCl or H2SO4 as extraction solvents and are considered harmful to the human organism if consumed. The extracts of these plants are consumed in the form of tea, extracted with hot water. Therefore, the objective of the present study was to evaluate the influence of temperature and time in the extraction of bioactive compounds with nontoxic solvent and in the in vitro functional properties of extracts of the C. cyanus and the C. ternatea petals. The central rotational composite design 22 was used to evaluate the effect of temperature and time factors in the extraction of bioactive compounds. The results were analysed using multiple linear regression and principal component analysis. In the aqueous extract of the C. cyanus petals, only temperature influenced the content of total phenolic compounds, non-anthocyanic flavonoids, and in vitro antioxidant activity by capturing the DPPH radical. Temperature of 68.3 °C and time of 51.12 minutes was the best condition to maximize bioactive compound content and in vitro functional properties. Chlorogenic, caffeic, ferulic and p-coumaric acids, isoquercitrin, coumarin, cyanidin 3-O-(6-O-succinylglucoside)-5-O-glucoside, and apigenin 7-O-glucuronide-4′-O-(6-O-malonylglucoside) were identified in the optimised aqueous extract of C. cyanus petals. The in vitro functional properties were inhibition of lipid peroxidation, antihemolytic and antihypertensive activity, low cytotoxicity (> 900 μg/mL) for HepG-2, Caco-2 and A549 cell lines, and pro-oxidant action on HepG-2 cell (10-100 μg/mL) without causing cell damage and death. The anthocyanins present in the optimised extract presented a reversible equilibrium and antioxidant activity with pH variation. In the aqueous extract of the C. ternatea petals, optimization indicated that bioactive compound contents, in vitro antioxidant activity, and colour parameters were similar between temperatures from 11.7 to 68.3 °C from 8.47 to 51.12 minutes. Principal component analysis revealed temperature of 40 °C for 30 minutes to maximize the extraction of total phenolic compounds. The crude lyophilised extract of the C. ternatea petals (CLECTP) presetend in vitro functional properties, antihemolytic activities, inhibitors of angiotensin converting enzyme I (ACE-I), α-amylase and α-glycosidase enzymes, and lipid peroxidation in biological system. The partially purified extract of C. ternatea petals (PPECTP) showed higher oxygen radical absorption capacity, inhibition of DNA scission by peroxyl radicals, and inhibition of copper-induced LDL cholesterol oxidation. Both CLECTP and PPECTP extracts presented low cytotoxicity against cell lines A549, HCT8, and IMR90 (> 900 μg/mL) and showed intracellular antioxidant activity against reactive oxygen species (> 100 μg/mL). Twelve compounds were tentatively identified by UHPLC-Q-TOF-MS/MS in CLECTP and PPECTP extracts. In direct/reverse spectrophotometric titration, anthocyanins showed structural changes with variating colour with pH variation, and structural reversibility with preservation of in vitro antioxidant activity. Anthocyanins at both pH values, 3.6 and 5.4, in the presence and absence of fructooligosaccharides showed high activation energy. The extracts exposed to light showed high half-life time in the presence and absence of fructooligosaccharides. The obtained results allow an expansion of the study with the of new functional properties in vitro and in vivo for potential technological application.