Isolation and synthesis of flavonols and comparison of their antioxidant activity (original) (raw)

Flavonol glycosides from aerial parts of Astragalus thracicus Griseb

Phytochemistry Letters, 2021

Five flavonol glycosides, including a new glutaryl-conjugated compound, were isolated from methanolic extract of the endemic Balkan species Astragalus thracicus Griseb. Based on NMR and MS spectra, one new compound was identified as kaempferol 3-O-[β-glucopyranosyl-(1→4)-α-rhamnopyranosyl-(1→6)-(2"-3-hydroxy-3-methylgutaroyl)-β-galactopyranoside)] (1). The other compounds, all known, were identified as mauritianin (2), kaempferol-3-O-α-L-rhamnopyranosyl-(1→2)-β-galactopyranoside (3), kaempferol-3-O-β-apiofuranosyl-(1→2)β-galactopyranoside (4), and quercetin-3-O-β-apiofuranosyl-(1→2)-β-galactopyranoside (5). All of them, except 2, were found for the first time in a representative of genus Astragalus.

Flavonoid Glycosides from Endemic Bulgarian Astragalus aitosensis (Ivanisch.)

Molecules, 2019

Astragalus is a very interesting plant genus, well-known for its content of flavonoids, triterpenes and polysaccharides. Its secondary metabolites are described as biologically active compounds showing several activities, e.g., immunomodulating, antibacterial, antiviral and hepatoprotective. This inspired us to analyze the Bulgarian endemic A. aitosensis (Ivanisch.) to obtain deeper information about its phenolic components. We used extensive chromatographic separation of A. aitosensis extract to obtain seven phenolic compounds (1–7), which were identified using combined LC-MS and NMR spectral studies. The 1D and 2D NMR analyses and HR-MS allowed us to resolve the structures of known compounds 5–7 as isorhamnetin-3-O-robinobioside, isorhamnetin-3-O-(2,6-di-O-α-rhamno-pyranosyl-β-galactopyranoside), and alangiflavoside, respectively, and further comparison of these spectral data with available literature helped us with structural analysis of newly described flavonoid glycosides 1–4. ...

FLAVONOIDS FROM ASTRAGALUS GENUS

In this review our main focus is on flavonoid groups which are one of the main active constituents found with other active constituents like saponins and polysaccharides, while poisonous groups are nitro-compounds, indolizidine alkaloids and the seleniferous derivatives in Astragalus genus. It is well established fact that flavonoid possess many biological activity such as antiallergic, anti-inflammatory, antitumor, antiviral, antioxidant anticancer including anticarcinogenic and prodifferentiative activities. Many flavonoids, including those which are phytoalexins, provide plants with a defense against viral infections. The estrogenic action of many isoflavones is well known and mixtures of flavonoids are commonly used commercially to reduce capillary fragility. Astragalus root is a very old and well known drug in traditional Chinese medicine and have been used to improve resistance to infections and to aid in immunological disorders and viral infections, and also used as hepatoprotective, heart tonic, nephritis and diabetes. This review reports all flavonoids isolated till date which is nearly about 131 from 60 species of Astragalus genus; these flavonoid are further characterized and classified into flavones, flavonols, flavanones, flavan-4-ols, isoflavones, isoflavans, petrocarpans and miscellaneous.

New Flavonol Triglycoside and Other Flavonol Glycosides from Astragalus armatus Willd. (Fabaceae)

Record of Natural Products, 2013

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.

A new flavonol triglycoside and other flavonol glycosides from Astragalus armatus Willd. (Fabaceae)

Records of Natural Products

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.

Isolation and synthesis of flavonols and comparison of their antioxidant activity (original) (raw)

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