Phenolic compounds in Coleostephus myconis (L.) Rchb.f.: characterization by HPLC-DAD-ESI/MS and phenology effects
Artigo de Conferência
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resumo
The Asteraceae family is spread worldwide. In Portugal, there are more than
300 species, standing out as one of the botanical families with largest representation
in the Portuguese flora. Coleostephus myconis (L.) Rchb.f. is a scarcely studied
Asteraceae species, characterized as having ruderal growth and persistence in
abandoned soils (an expanding problem due to the desertification phenomena in rural
areas). In this work, the flowers of C. myconis were collected in three different
flowering stages (i: flower bud; ii: flower in anthesis; iii: senescent flower) from the
Northwestern area of the Portuguese territory. Powdered samples (1 g) were extracted
twice with ethanol:water 50:50 (v/v). After removing solvents, the combined extracts
were re-dissolved, filtered through 0.22-μm disposable LC filter disks and analyzed by
high performance liquid chromatography coupled to a diode array detector and
electrospray ionization-mass spectrometry (HPLC-DAD/ESI-MS). The phenolic
compounds were characterized according to their UV and mass spectra, and retention
times. For the quantitative analysis, calibration curves of standard compounds were
used.
According to the UV spectra (λmax = 314-330 nm) and pseudomolecular ions
([M-H]-) at m/z 353 and 515, all producing an m/z 191 ion, four compounds derived
from quinic acid were detected: 3-O-caffeoylquinic acid (Figure 1A), 5-O-caffeoylquinic
acid (Figure 1B), 3,5-O-dicaffeoylquinic acid (Figure 1C) and 4,5-O-dicaffeoylquinic
acid (Figure 1D), as also supported by the literature [1,2]. A fifth phenolic acid was
identified as protocatechuic acid. The detected flavonoid were quercetin-O-glucuronide, quercetin-3-Oglucoside,
myricetin-O-methyl-hexoside and a second glycosylated myricetin (not
possible to identify completely). Some statistically significant changes were detected
among the different assayed flowering stages; nevertheless, 3,5-O-dicaffeoylquinic
acid was the major compound, independently of the phenologic stage.
According to the previous results, C. myconis might be considered as a
potential natural source of these valuable bioactive compounds, especially
considering the high botanical representativeness of this plant and its
inexpensiveness.
