Cardiovascular protective flavonolignans and flavonoids from Calamus quiquesetinervius
Graphical abstract
Tricin-type flavonolignans (1–6), along with six known phenolic compounds (7–12), were isolated from the EtOAc extract of Calamus quiquesetinervius.
Introduction
Calamus quiquesetinervius Burret (Arecaceae), also referred to as Calamus orientalis Chang, is clustered as vines, which include their small spines. It is widely distributed in the mountain district of middle and Northern Taiwan. Traditionally, C. quiquesetinervius has served as an edible vegetable and as a craft material for indigenous Taiwanese peoples (Liao, 2000). The aforementioned plant has also been used as a treatment for several diseases, such as hypertension, stroke and hepatitis in folk herbal medicine (Chiu and Chang, 1991). However, these effects have not either been quantified by any phytochemical or pharmacological studies. In our continuing search for cardiovascular protective agents in Taiwanese plants, we have found that the ethanol extracts of the stem of C. quiquesetinervius have several pharmacological activities, including promoting vasorelaxation in endothelium-intact (+E) Sprague–Dawley rat aortic rings, and scavenging reactive oxygen species (ROS). Therefore, the bioactive constitutes and the biological effects were further investigated.
Herein, we show that bioassay-guided fractionations led to isolation and structural elucidation of six new tricin-type flavonolignan compounds (1–6) from a partitioned EtOAc extract derived from the EtOH extrtact. The novel isolates, 1–3 and 6 were comprised of a dihydrotricin skeleton with either a phenylpropanoid or chromanone moiety, whereas 4 and 5 contained a tricin skeleton with either a phenylpropanoid moiety. In addition, six known phenolic compounds, including five flavonoids (7–9 and, 11–12) and one benzoic derivative (10), were obtained (Fig. 1). Structural elucidation of these new isolated constituents was mainly based on spectroscopic analyses, including 1D and 2D NMR techniques. Most of the isolates were evaluated for the protective effects in the cardiovascular system assayed by the vasorelaxation of Sprague–Dawley rat aortic rings, anti-platelet aggregation induced by AA or PAF, and ROS scavenging activity. Preliminary structure–activity relationships are also discussed.
Section snippets
Structural elucidation of isolated compounds
The dried stem of C. quiquesetinervius (15.4 kg) was extracted with 95% ethanol and dried in a vacuum to yield a syrupy residue (ca. 1 kg), which was partitioned in successive steps using n-hexane, EtOAc, and n-butanol in H2O. Because the EtOAc layer exhibited the most potent scavenging activities (for OH with an IC50 of 1.09 μg/ml and for with an IC50 of 0.45 μg/ml) and was found to induce 100% vasorelaxation with a dose of 120 μg/ml, it was purified by repeated column chromatography (CC) and
Conclusions
Oxidative stress derived from environmental and physiological factors is usually associated with the generation of various reactive oxygen species (ROS). The major ROS generated by extrinsic stimulated materials and endothelial cells, including superoxide (), hydroxyl (OH), peroxyl () radicals, hydrogen peroxide (H2O2) etc., have been proved to play a committed role in the initiation and progression of cardiovascular diseases such as hypertension, diabetes, heart failure and renovascular
General experimental procedures
Chromatographic materials containing Celite 535 (Macherey–Nagel GmbH and Co. KG, Germany), Sephadex™ LH-20 (GE Healthcare Bio-Sciences AB), silica gel 60 (70–230 mesh and 230–400 mesh, Merck, Darmstadt, Germany), silica gel 60 GF254 (Merck, Darmstadt, Germany) were used. Silica gel 60 F254 plates (Merck, Darmstadt, Germany) were used for TLC. The chromatographic substances on TLC plates were visualized by anisaldehyde–H2SO4 as a spray reagent with UV-lamp (254 and 365 nm) visualization. Melting
Acknowledgements
This research was financially supported by the National Science Council of Taiwan, Republic of China (NSC95-2816-B-077-001 and NSC 95-2313-B-077-002-MY2). We are also grateful to Ms. Mei-Ling Chuang and Mr. Feng-Wu Lai for kindly providing help in the collection of C. quiquesetinervius.
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