Abstract
Phytochemical research of two Tolpis species, T. proustii and T. lagopoda, led to the isolation of three new compounds: 30-chloro-3β-acetoxy-22α-hydroxyl-20(21)-taraxastene (1), 3β,22α-diacetoxy-30-ethoxy-20(21)-taraxastene (2) and 3β,28-dihydroxy-11α-hydroperoxy-12-ursene (3). The structures of the new compounds were elucidated by means of extensive IR, NMR, and MS data and by comparison of data reported in the literature. The in vitro antioxidant activities of the extracts were assessed by the DPPH and ABTS scavenging methods. The cytotoxicity of several known compounds and its derivatives was also assessed against human myeloid leukemia K-562 and K-562/ADR cell lines.
Highlights
IntroductionThe Tolpis genus (Asteraceae: Cichorioideae, Cichoriinae) consists of some 20 species distributed throughout Europe, North Africa, Canary Islands, Cape Verde and Asia, this genus being represented in the Canary Islands by around ten species [1]
Islands force plants to develop defence mechanisms against ultraviolet radiation and excessive production of free radicals through the accumulation of antioxidant metabolites [5]. This prompted us to evaluate the antioxidant activity of the crude extract of T. proustii and T. lagopoda, and that of some of the isolated compounds
The same behaviour as for the DPPH assay was observed, T. lagopoda being less active than T. proustii (4.1 and 18.1 μmol of Fe(III) reduced to Fe(II) per gram of dry plant respectively) (Table 3)
Summary
The Tolpis genus (Asteraceae: Cichorioideae, Cichoriinae) consists of some 20 species distributed throughout Europe, North Africa, Canary Islands, Cape Verde and Asia, this genus being represented in the Canary Islands by around ten species [1]. Pitard in Pitard and Proust and T. lagopoda C.Sm. ex Buch The constituents of these extracts were purified by CC, MPLC and preparative TLC. Islands (opposite the northwest coast of Africa) force plants to develop defence mechanisms against ultraviolet radiation and excessive production of free radicals through the accumulation of antioxidant metabolites [5]. This prompted us to evaluate the antioxidant activity of the crude extract of T. proustii and T. lagopoda, and that of some of the isolated compounds. We have evaluated the effects of natural compounds and derivatives on the growth of the human leukemia K-562 and the P-glycoprotein-overexpressing K-562/ADR cell lines
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