Profiling phenolic compounds in species of the genus Chuquiraga (Barnadesioideae, Asteraceae) by HPLC-DAD: species classification using chemometric models.

Of the 22 species currently recognized for the genus Chuquiraga, at least 10 of them are used in the traditional medicine of several South American countries. Some species of this genus are widely commercialized, especially in markets of Ecuador and Peru. Event thought, little is known about the phytochemical composition of the genus Chuquiraga. This study aimed to profile phenolic compounds in commercial samples of three Chuquiraga species (C. jussieui, C. weberbaueri and C. spinosa) using HPLC-DAD and employ chemometric models (HCA and OPLS-DA) for species classification. A total of 127 samples were submitted to chromatographic analyses (50% MeOH extracts) on a Zorbax SB-Phenyl column (5 µm, 4.6 × 250 mm) using a linear gradient of H₂O (A) and MeCN (B), both with 1% acetic acid (1.2 mL/min; 4% B→30% B in 50 min, 100% B, in 75 min). The profiles acquired at 270nm were selected and organized prior to baseline correction and alignment using the parametric time warping algorithm. HCA and OPLS-DA statistical analysis were then performed to evaluate similarities and classify the species. A set of 24 previously known pure phenolic compounds was used for peak identification (Fig. 1). The comparison of R _t, UV spectra and co-injections enabled the identification of caffeic acid ester derivatives. On the HCA, three main clusters were observed: 1) samples of C. jussieui, from northern Peru and Ecuador, 2) samples of C. spinosa and C. weberbaueri, and 3) samples of C. jussieui, from southern Peru. Based on the OPLS-DA analysis, the three species were classified and two population of C. jussieui were discriminated. The occurrence of caffeic acid ester derivatives in the genus Chuquiraga is described for the first time.

Fig. 1 Set of phenolic compounds used for peak identification.

1 Galic acid 2 Protocatecuic acid 3 3-O-Caffeoylquinic acid 4 4-O-Caffeoylquinic acid 5 5-O-Caffeoylquinic acid 6 Caffeic acid 7 Caffeic acid ester derivative 8 5-O-Feruloylquinic acid

9 p-Coumaric acid 10 Ferulic acid 11 Rutin 12 Hyperoside 13 Quercetin-3-O-glucoronide 14 Caffeic acid ester derivative 15 3,4-O-dicaffeoylquinic acid 16 1,5-O-dicaffeoylquinic acid

17 3,5-O-dicaffeoylquinic acid 18 Caffeic acid ester derivative 19 4,5-O-dicaffeoylquinic acid 20 Methyl 3,5-O-dicaffeoylquinate 21 Methyl 3,4-O-dicaffeoylquinate 22 Quercetin 23 3-O-Methylquercetin i.s. Chrysin

FAPESP (Grants# 2014/16850 – 6 and 2014/26866 – 7) for funding.

 

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