ABSTRACTChlorogenic and caffeic acids are bioactive phenolic compounds present in Cecropia glaziovii Snethl., Urticaceae, products that have been used as analytical markers. This paper reports a chemometric study aimed at improving chromatographic performance for quantification of these markers by RP-HPLC. The organic to aqueous content ratio, the acid content of the mobile phase, and the elution method were analyzed using a Response Surface Methodology IV-Optimal design. The resolution between peaks, retention time, tailing and retention factors, number of theoretical plates and peak widths were evaluated. The optimized conditions were mathematically determined as (A) trifluoroacetic acid 0.05% (v/v), (B) 12% (v/v) acetonitrile and (C) increasing gradient. The method was considered specific, fast, precise, reliable and linear in the ranges of 1.0–200.0 and 2.5–100.0 µg/ml for the chlorogenic and caffeic acids, respectively. The adequate conditions to separate and quantify both phenolic acids in C. glaziovii products were demonstrated. Satisfactory resolution was achieved when compared to a previously published chromatographic method which is unable to separate the chlorogenic acid and an interfering compound presented under certain extractive conditions, demonstrating the importance of systematic studies, specifically when analyzing complex plant matrices.

Two new synthetic melanin-like oligomers inspired by the synthesis of pheomelanin (cys-DOPA) were prepared using L-DOPA as a precursor and the amino acids serine (ser-DOPA) and threonine (thr-DOPA) for modifications. The products obtained exhibited appreciable antioxidant activity. The compounds were characterized by liquid chromatography-mass spectrometry (LC-MS), elemental analysis and infrared spectroscopy. The pKa values of the groups present in each melanin suspension were determined in aqueous solution by potentiometric and spectrophotometric titration. Cytotoxicity assays showed an IC50 > 500 mg L-1 resulting in non-toxic compounds for living cells. Finally, cys-DOPA, ser-DOPA and thr-DOPA exhibited antioxidant activity determined by the DPPH scavenging assay, with EC50 = 7.69, 1.02 and 27.60 mg L-1, respectively.

The objective of this study was to show a comparison of the antioxidant properties of aqueous and ethanolic extracts obtained from Baccharis articulata (Lam.) Pers., Baccharis trimera (Less.) DC., Baccharis spicata (Lam.) Baill. and Baccharis usterii Heering, Asteraceae, by several techniques covering a range of oxidant species and of biotargets. We have investigated the ability of the plant extracts to scavenge DPPH (1,1-diphenyl-2-picryl-hydrazyl) free radical, action against lipid peroxidation of membranes including rat liver microsomes and soy bean phosphatidylcholine liposomes by ascorbyl radical and peroxynitrite. Hydroxyl radical scavenger activity was measured monitoring the deoxyribose oxidation. The hypochlorous acid scavenger activity was also evaluated by the prevention of protein carbonylation and finally the myeloperoxidase (MPO) activity inhibition. The results obtained suggest that the Baccharis extracts studied present a significant antioxidant activity scavenging free radicals and protecting biomolecules from the oxidation. We can suggest that the supposed therapeutic efficacy of this plant could be due, in part, to these properties.