Quantification of Flavonoids, Naphthopyranones and Xanthones in Eriocaulaceae Species by LC-PDA.

The linearity, stability, accuracy and inter-day precisions of the assay method were evaluated in methanolic aerial-part extracts of Paepalanthus giganteus and Syngontnhus nitens from the Eriocaulaceae family. Their small capitulae hinder morphological analysis, and thus complicate taxonomic studies of these species, which present anti-ulcer, antimutagenic and antioxidant activities. Taxonomic studies of these plants revealed that the Paepalanthus genus presents flavonols and naphthopyranones while the Syngontnhus genus has flavone and xanthone as majority compounds. The prepared samples were analyzed quantitatively by High Performance Liquid Chromatography with PDA detection for the presence of quercetin, luteolin, 3,6-dimethoxy-1,5,7-tri-hydroxyxanthone and paepalantine. The substances were recovered from these samples at rates from 98.01 to 99.99%. The coefficient of variation in the quantitative analysis of the sample com- pounds was under 5%. The linearity of the method was determined by linear regression. The analysis of the samples spiked with known amounts of analyte demonstrated that the response was proportional to the concentrations of the sam- ples with re-spective determination coefficients of r2 = 0.9999 (luteolin and 3,6-dimethoxy-1,5,7-tri-hydroxyxanthone) and r2 = 0.9998 (quercetin and paepalantine) for the linear range of the analytical calibration curves of the samples. The detection limits were 0.07 μg?mL–1 for quercetin and luteolin, 0.06 μg?mL–1 for 3,6-dimethoxy-1,5,7-tri-hydroxyxanthone and 0.10 μg?mL–1 for paepalantine. The quantification limits were 0.23 μg?mL–1 for quercetin and luteolin, 0.20 μg?mL–1 for 3,6-dimethoxy-1,5,7-tri-hydroxyxanthone and 0.33 μg?mL–1 for paepalantine by LC. The method was considered sen- sitive for quantification of the quercetin, luteolin, 3,6-dimethoxy-1,5,7-tri-hydroxyxanthone and paepalantine in plant samples.