Chlorogenic (5-CQA), 1,5-, 3,5-, 4,5-and 3,4-dicaffeoylquinic (DCQA) acids were identified and quantified in the methanol extracts of Inula oculus-christi L., I. bifrons L., I. aschersoniana JANKA var. aschersoniana, I. ensifolia L., I. conyza (GRIESS.) DC. and I. germanica L. by HPLC analysis. The amount of 5-CQA varied from 5.48 to 28.44 mg/g DE and the highest content was detected in I. ensifolia. 1,5-DCQA (4.05-55.25 mg/g DE) was the most abundant dicaffeoyl ester of quinic acid followed by 3,5-DCQA, 4,5-DCQA and 3,4-DCQA. The extract of I. ensifolia showed the highest total phenolic content (119.92 � 0.95 mg GAE/g DE) and exhibited the strongest DPPH radical scavenging activity (69.41 � 0.55 %). I. bifrons extract was found to be the most active sample against ABTS * + (TEAC 0.257 � 0.012 mg/mL) and the best tyrosinase inhibitor. The studied extracts demonstrated a low inhibitory effect towards acetylcholinesterase and possessed low cytotoxicity in concentration range from 10 to 300 μg/mL toward non-cancer (MDCK II) and cancer (A 549) cells. Figure 2. HPLC chromatograms of the studied extracts and standard mixture.[a] Results are presented as mean � SD from three replicates (n = 3). Means in the columns with the same letter are not significantly different from each other (p > 0.05) (t-test).
The flower heads of Inula britannica L. of Bulgarian origin afforded sesquiterpene lactones (gaillardin, britannin, 11,13-dihydroinuchinenolide B, ivalin, pulchellin C), triterpenoids (3-O-palmitates of 16β-hydroxylupeol, 16β-hydroxy-β-amyrin, and faradiol) and flavonoids (quercetin, luteolin, luteolin-7-Oglucoside). All compounds are known and they were identified by spectral methods. The observed differences in the chemical content of the chloroform and methanol extracts were also reflected in their free radical scavenging activity, evaluated by DPPH and ABTS assays. Intraspecific variability of I. britannica is discussed.
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