Isolation and synthesis of flavonols and comparison of their antioxidant activity (original) (raw)
A new flavonol triglycoside and other flavonol glycosides from Astragalus armatus Willd. (Fabaceae)
Records of Natural Products
From the aerial parts of Astragalus armatus, a new acylated flavonol triglycoside, isorhamnetin-3-O-(5'''-p-hydroxybenzoyl)-β-apiofuranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-galactopyranoside (1) which we named astrarmatuside, has been isolated and structurally elucidated together with seven known flavonol glycosides: tamarixetin-3-O-α-apiofuranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-galactopyranoside (2) (millettiaspecoside D), isorhamnetin-3-O-β-apiofuranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-galactopyranoside (3), kaempferol-3-O-α-rhamnopyranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-glucopyranoside (4), kaempferol-3-O-α-rhamnopyranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-galactopyranoside (mauritianin) (5), isorhamnetin-3-O-α-rhamnopyranosyl-(1→2)[α-rhamnopyranosyl-(1→6)]-β-galactopyranoside (6), kaempferol-3-O-α-rhamnopyranosyl-(1→6)]-β-glucopyranoside (nikotiflorin) (7) and isorhamnetin-3-O-α-rhamnopyranosyl-(1→6)]-β-glucopyranoside (narcissin) (8). The structures of the isolated compounds were established by means of 2D NMR experiments, HPLC-DADMS, HR-MS and UV spectral analyses. Pivotal role in the structure elucidation and in particular in the determination of sugar sequence, played HSQC-TOCSY and ROESY experiments whereas those of the known compounds (2-8) were established by spectral comparison with those published in the literature.
Flavonol glycosides from Asplenium foreziense and its five related taxa and A. incisum
Biochemical systematics and ecology, 2000
The #avonoids of Asplenium foreziense, A. fontanum subsp. fontanum and subsp. pseudofontanum, A. obovatum subsp. obovatum var. obovatum and var. protobillotii, A. obovatum subsp. lanceolatum, and A. incisum were isolated and identi"ed for chemotaxonomic survey. A major constituent of all taxa was kaempferol 3-O-gentiobioside. As minor compounds, kaempferol 3,7-O-glycoside and/or kaempferol 3-O-glycoside were found in A. fontanum, A. obovatum and A. foreziense, and kaempferol 3-O-gentiobioside-4-O-glucoside, kaempferol 3-O-glucoside and quercetin 3-O-diglucoside in A. incisum. It was suggested that A. foreziense, A. fontanum including subsp. pseudofontanum and A. obovatum including subsp. lanceolatum are not only morphologically but also chemotaxonomically related. The East Asian A. incisum was chemically and geographically di!erent from these taxa.
Flavonoids from the genus Astragalus: Phytochemistry and biological activity
Pharmacognosy Reviews, 2016
Flavonoids, the most common plant polyphenols are widely distributed in every species and possess a broad range of pharmacological activities. The genus Astragalus is the largest in the Fabaceae family with more than 2,500 species spread. They are known to contain different metabolites such as flavonoids, saponins, and polysaccharides. Plants from the genus have been used in the traditional medicine of many countries for centuries. This paper is focused on the large group of flavonoid compounds. Details on structure as well as information about the pharmacological properties of flavonoids, isolated from Astragalus species have been discussed. This review is based on publications until the first half of 2014 and includes also the results from our phytochemical investigations of the genus.
New Flavonol Tetraglycosides from Astragalus caprinus
Chemical and Pharmaceutical Bulletin, 2002
Astragalus caprinus MAIRE (Fabaceae) is an endemic of North Africa, the leaves of which are used as an antihaemorrhoidal in Tunisian folk medicine. Our previous paper describing the structure of a new 3-O-tetraglycoside of kaempferol from this plant was the first phytochemical report on this species. 1) Here we report the isolation and structural elucidation of five new flavonol glycosides. Results and Discussion The methanolic extract of dried leaves from A. caprinus, once prepurified, was fractionated by repeated column and preparative thin-layer chromatography to give 1-5. Analysis of the 1 Hand 13 C-NMR spectra of compound 1 (Table 1; all assignments based on heteronuclear single quantum coherence-total correlation spectroscopy (HSQC-TOCSY) and heteronuclear multiple bond correlation (HMBC) experiments) showed the presence of one aromatic system and four sugar moieties. The 1 H-NMR resonances of two metacoupled doublets at d 6.19 and 6.38 ppm (1H, Jϭ1.9 Hz), correlated with the carbons at 99.8 and 94.7 ppm, respectively, in the HSQC spectrum, characterized the 6-and 8-protons of a flavonoid 5,7 dihydroxy A-ring. 2) Ring B was assigned as a 1,4-substituted benzene ring (d H 8.07, d, 2H, Jϭ8.8 Hz; 6.89, d, 2H, Jϭ8.8 Hz) from a HMBC experiment. Thus, the aglycone of 1 was identified as 3,5,7,4Ј-tetrahydroxyflavone (kaempferol), as suggested by its UV spectral properties. A HSQC-TOCSY experiment was performed to identify the spin systems of sugar units, starting from anomeric protons at d 5.57 (d, Jϭ7.8 Hz), 5.22 (s), 4.52 (s) and 4.32 (d, Jϭ7.4 Hz); on the basis of the chemical shifts, multiplicity of the signals and values of the coupling constants, the sugars were identified as b-galactopyranosyl (Gal), a-rhamnopyranosyls (Rha a and Rha b) and b-xylopyranosyl (Xyl). 3) The common D-configuration for Gal and Xyl, and the L-configuration for Rha were assumed according to those most often encountered among the plant glycosides. HMBC experiments showed long-range correlations between Gal H-1 (d 5.57) and Kaempferol C-3 (d 134.5), Rha a H-1/C-1 (d 5.22/102.6) and Gal C-2/H-2 (d 77.5/3.93), Rha b H-1/C-1 (d 4.52/101.8) and Gal C-6/H-6 (d 67.5/3.68), Xyl H-1/C-1 (d 4.32/106.4) and Rha b C-3/H-3 (d 82.3/3.55). Thus, compound 1 was identified as kaempferol-3-O-{[b-Dxylopyranosyl(1→3)-a-L-rhamnopyranosyl(1→6)][a-Lrhamnopyranosyl(1→2)]}-b-D-galactopyranoside. This identification was corroborated by electrospray ionization mass July 2002 Notes Chem. Pharm. Bull. 50(7) 981-984 (2002) 981
Flavonoid constituents and biological screening of Astragalus bombycinus Boiss
Natural Product Research, 2013
Two new flavonoid compounds were isolated from Astragalus bombycinus Boiss. and identified as quercetin-3,7-di-O-�-glucopyranoside 4 0 -O-�-rhamnopyranoside and 5,2 0 ,4 0 -trihydroxy-flavone-8-C-�-arabinopyranoside-7-O-�-glucopyranoside. In addition, apigenin, apigenin-7-O-�-glucopyranoside, apigenin 7-O-gentobioside, luteolin, luteolin-7-O-�-glucopyranoside, quercetin-3,7-di-O-�-glucopyranoside, quercetin-3-O-�-glucopyranoside-7-O-�-rhamnopyranoside and daidzein were also isolated and identified. The structure elucidation of the isolated compounds was performed by chromatographic, chemical and spectroscopic methods. Antioxidant and cytotoxic activities were also determined for the four consecutive extracts of the plant.
Flavone and flavonol glycosides from Astragalus eremophilus and Astragalus vogelii
Natural product communications, 2009
Two new rhamnocitrin glycosides (1 and 2) were isolated from the aerial parts of Astragalus vogelii, along with one known rhamnocitrin glycoside (3). Two known flavonol glycosides (4 and 5) and four known flavone derivatives (6-9) were isolated from the aerial parts of Astragalus eremophilus. Their structures were elucidated by extensive spectroscopic methods including 1D- (1H, 13C and TOCSY) and 2D-NMR (DQF-COSY, HSQC, HMBC) experiments, as well as ESIMS analysis.
Present work aims to determine the chemical profile and some biological activity of three endemic Astragalus species from Anatolia. The chemical contents of Astragalus leporinus var. hirsutus, Astragalus distinctissimus and Astragalus schizopterus were characterised by LC-MS/MS and GC-MS. In terms of biological activity; the antioxidant, anticholinesterase, antimicrobial and cytotoxic activities were determined. Additionally, the antioxidant properties of the major components were also determined and compared to the antioxidant capacities of these extracts. The most abundant flavonoids in these Astragalus species were determined as rutin (1028.276-13351.76 µg/g extract) and hesperidin (1604.348-9695.435 µg/g extract). A high amount of quinic acid (111302.774 µg/g extract) was detected in A. schizopterus methanol extract. Palmitic acid (C16:0) was found to be the major compound in A. leporinus var. hirsutus (32.9%), A. distinctissimus (32.5%), and A.schizopterus (23.4%). A. schizopterus methanol extract exhibited the highest antioxidant effect in lipid peroxidation (19.62±0.29), DPPH free (54.61±0.38) and ABTS cation radicals scavenging activity (22.01±0.07), and CUPRAC assays. Among all of the extracts, only A. leporinus var. hirsutus petroleum ether extract showed moderate inhibitory activity against acetyl-and butyryl-cholinesterase enzymes. The methanol extracts of the plants exhibited moderate activity against C. albicans. A. leporinus var. hirsutus methanol extract indicated the most viability against L929 fibroblast cells, and the highest cytotoxic effect against A549 cells. In consideration of our findings , these Astragalus species used as animal feed could be a source of naturally, biologically active agents that can be used in food and pharmaceutical industry.
HPLC-DAD analysis of flavonoids and hydroxycinnamic acids in Aster novi-belgii L
Aster novi-belgii is a perennial ornamental herb native to eastern Canada and the United States of America, cultivated in Ukraine. This species should be considered a possible source of phenolic compounds, principally hydroxycinnamic acids and flavonoids. Therefore, in this study, the aim was to determine these compounds in Aster novi-belgii by HPLC-DAD analysis, and validation of this chromatographic method and lay a scientific and technical basis for the utilization and development of the plant resources of the cultivated plants of the genus Aster. The HPLC-DAD method determined the flavonoids and hydroxycinnamic acids composition and content in the herb of Aster novi-belgii L. The HPLC-DAD method allowed the detection of 13 phenolic compounds, namely 6 hydroxycinnamic acids (chlorogenic, sinapic, caffeic, syringic, trans-cinnamic, trans-ferulic acids), and 7 flavonoids (kaempferol 3-O-beta-D-glucoside, naringin, quercetin, luteolin, rutin, kaempferol, rhamnetin). The quantitative detection showed that the main hydroxycinnamic acids were chlorogenic acids (15069.21 ± 0.34 µg/g) and sinapic acids (949.95 ±0.22 µg/g). Concerning flavonoids, the largest amounts were kaempferol 3-O-beta-D-glucoside (8989.79 ±0.31 µg/g) and naringin (2092.02 ± 0.26 µg/g). HPLC-DAD method was evaluated in terms of linearity, precision, accuracy, limits of quantification, and limits of detection. The calibration curves of reference substances were linear (R 2 ≥ 0.997), the LODs were in the range of 0.21-1.71 µg/mL, and the LOQs-of 0.48-5.19 µg/mL, respectively. Our phytochemical research confirms that the study material is a rich source of hydroxycinnamic acids and flavonoids. Findings mean that Aster novi-belgii is a promising plant because of the important role of these phenolic compounds in many biological processes.