Novel acetylated flavonoid glycosides from the leaves of Allium ursinum

Seven flavonoid glycosides, kaempferol 3-O-α-L-rhamnopyranosyl (1→2)-[3-O-acetyl]-β-D-glucopyranoside (1), kaempferol 3-O-α-L-rhamnopyronosyl (1→2)-[6-O-acetyl]-β-D-glucopyranoside (2), kaempferol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (3), kaempferol 3-O-β-D-glucopyranoside (4), kaempferol 3,7-di-O-β-D-glucopyranoside (5), 7-O-β-D-glucopyranosyl kaempferol 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside (6), kaempferol 3-O-α-L-rhamnopyranosyl (1→2)-β-D-glucopyranoside-7-O-[2-O-(trans-p-coumaroyl)]-β-D-glucopyranoside (7) were isolated from the n-butanol fraction of Allium ursinum L. and the structures of these compounds were elucidated on the basis of mass spectrometry, ¹H NMR, ¹³C NMR, HMQC and HMBC data. Among them, 1 and 2 are novel compounds and compounds 4 and 5 were isolated from this plant species for the first time.     

Characterisation of flavonoids in Orostachys japonicus A. Berger using HPLC–MS/MS: Contribution to the overall antioxidant effect

Orostachys japonicus cultivated in the Republic of Korea was analysed for flavonoid content via HPLC coupled to MS/MS. Amongst 16 compounds that were characterised, eight flavonoids and one alkaloid were characterised for the first time: two procyanidin dimer gallate isomers (1 and 2), epigallochatechin-3-gallate (3), two procyanidin dimer digallate isomers (4 and 9), quercetin 3-O-rhamnosyl-7-O-glucoside (6), myricetin 3-O-glucoside (10), kaempferol (16) and N¹,N⁵,N¹⁰-tri-p-(E,E,E)-coumaroylspermidine (15). The identified compounds were quantified by HPLC–UV/DAD. The antioxidant activity of the O. japonicus flavonoids was determined via 2,2-diphenyl-1-picrylhydrazyl radical (DPPH^•), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS^•+) and nitric oxide radical (NO^•) scavenging assays.     

Kaempferol acetylated glycosides from the seed cake of Camellia oleifera

The seed cake is a big by-product after crushing cooking oil from the seeds of Camellia oleifera Abel. Chemical investigation on the seed cake of C. oleifera led to the isolation of two new kaempferol acetylated glycosides (1 and 2). In addition, five kaempferol glycosides (3–7) and their aglycone, kaempferol (8), were also obtained, in addition to gallic acid (9). Their structures were determined by the detailed spectroscopic analysis and acidic hydrolysis. The new compounds were characterised as kaempferol-3-O-[4′′′′-O-acetyl-α-l-rhamnopyranosyl-(1→6)]-[β-d-glucopyranosyl-(1→2)]-β-d-glucopyranoside (1) and kaempferol-3-O-[4′′′′-O-acetyl-α-l-rhamnopyranosyl-(1→6)]-[β-d-xylopyranosyl-(1→2)]-β-d-gluco-pyranoside (2), respectively. The DPPH radical scavenging activity of all the isolated compounds was described.     

Chemical composition, nutritional value, and antioxidant constituents of Kalopanax pictus leaves

This study was carried out to analyze the nutritional composition, mineral content and antioxidant activity of Kalopanax pictus leaves. K. pictus leaves are high in carbohydrates (60.37%) and crude protein content (27.05%) on a dry weight basis with low content of fatty acids (1.45%). Hyperoside (1), 3,5-di-O-caffeoyl quinic acid (2), methyl 3,5-dicaffeoyl quinate (3), and 3-O-feruloylquinic acid (4) were isolated and purified from this plant as well. In all the chemical assays used, compound 3 exerted better 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activity, reducing power ability, and was a potent inhibitor of hydrogen peroxide (H₂O₂)-induced human embryonic kidney 293 (HEK 293) cell death and lipid peroxidation, whereas compound 4 presented as a powerful radical scavenger against superoxide radicals. Our results suggest that the chemical components of K. pictus leaves possess good antioxidant capacities and this species might have potential applications in the food and medical industries.     

Content of flavonols in Italian bean (Phaseolus vulgaris L.) ecotypes

Methanol extracts of seeds from 23 accessions of 3 Phaseolus vulgaris ecotypes (“Sarconi”, “Lamon”, “Zolfino del Pratomagno”), grown in different Italian regions (Basilicata, Veneto, Tuscany) were analyzed for their flavonoid content. Flavonoid glycosides were found in the seed coat from ten accessions of the “Zolfino” ecotype and in one accession of the “Sarconi” ecotype. From highest to lowest concentration these compounds were kaempferol 3-O-glucoside (compound 2), kaempferol 3-O-xylosylglucoside (compound 1) and a not completely identified kaempferol monoglucoside (compound 3). Total flavonol content varied from 0.19 to 0.84 g/kg of seed fresh weight. A great variability in the total flavonol content, being between 18% and 50%, and in the relative abundance of different kaempferol derivatives was observed for the same genotypes sampled in the original locations in the 2001–2003 period. Fluctuation in flavonol content suggests that further researches are necessary for an exhaustive comprehension of physiological mechanisms influencing the expression of these phenolic compounds. Obtained results evidenced that some Italian bean ecotypes may be an important source of functional compounds as kaempferol glycosides.     

Antioxidant activity of a new phenolic glycoside from Lagenaria siceraria Stand. fruits

The antioxidant properties of different extracts of Lagenaria siceraria (bottle gourd) fruit were evaluated. In the process, a new phenolic glycoside (E)-4-hydroxymethyl-phenyl-6-O-caffeoyl-β-d-glucopyranoside (1) was isolated and identified together with 1-(2-hydroxy-4-hydroxymethyl)-phenyl-6-O-caffeoyl-β-d-gluco-pyranoside (2), protocatechuic acid (3), gallic acid (4), caffeic acid (5) and 3,4-dimethoxy cinnamic acid (6). Their structures were elucidated by extensive NMR experiments including ¹H-¹H (COSY) and ¹H-¹³C (HMQC and HMBC) spectroscopy and chemical evidences. The antioxidant potential of the compound 1 and 2 was tested in different in vitro assay systems such as free radical scavenging assay, 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, superoxide scavenging activity, reducing power assay and linoleic acid peroxidation assay.     

Identification of phenolic antioxidants from Sword Brake fern (Pteris ensiformis Burm.)

Sword Brake fern (Pteris ensiformis Burm.) is one of the most common ingredients of traditional herbal drinks in Taiwan. In an effort to identify antioxidants from the aqueous extract of Sword Brake fern (SBF), the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity-guided isolation was employed. Three new compounds, kaempferol 3-O-α-l-rhamnopyranoside-7-O-[α-d-apiofuranosyl-(1-2)-β-d-glucopyranoside] (1), 7-O-caffeoylhydroxymaltol 3-O-β-d-glucopyranoside (3) and hispidin 4-O-β-d-glucopyranoside (4), together with five known compounds, kaempferol 3-O-α-l-rhamnopyranosid-7-O-β-d-glucopyranoside (2), caffeic acid (5), 5-O-caffeoylquinic acid (6), 3,5-di-O-caffeoylquinic acid (7) and 4,5-di-O-caffeoylquinic acid (8) were isolated and determined on the basis of spectroscopic analyses. HPLC with UV detector was further employed to analyze the content of each compound in SBF based on the retention time by comparison with isolated pure compounds. It was found that the most abundant phenolic compound was compound 3, followed by compounds 7 and 4. The di-O-caffeoylquinic acids (7 and 8) have the strongest DPPH scavenging potential with IC₅₀ around 10 μM and the highest Trolox equivalent antioxidant capacity (TEAC) about 2 mM. This data indicates that SBF is rich in phenolic antioxidants.     

Antioxidative properties and flavonoid composition of Chenopodium quinoa seeds cultivated in Japan

To evaluate the nutritional advantages of quinoa seeds (Chenopodium quinoa Willd.) cultivated in Japan, antioxidative properties and flavonoid composition were determined and compared to corresponding data for conventionally-used cereals and pseudo-cereals, including quinoa seeds from South America. The antioxidant activities of these grains against DPPH radicals were strongly associated with the total phenolic content of the tested samples. The crude extracts of quinoa seeds cultivated in Japan exhibited higher antioxidative effects than those from South America and other cereals, excluding buckwheat. Four flavonol glycosides were isolated and identified from the Japanese quinoa seeds, and the chemical composition of the flavonoids – quercetin and kaempferol 3-O-(2″,6″-di-O-α-rhamnopyranosyl)-β-galactopyranosides (1 and 4), quercetin 3-O-(2″,6″-di-O-α-rhamnopyranosyl)-β-glucopyranoside (2), and quercetin 3-O-(2″-O-β-apiofuranosyl-6″-O-α-rhamnopyranosyl)-β-galactopyranoside (3) – was evaluated through quantitative determination. Trioside 2 was isolated for the first time from quinoa seeds. These glycosides were not detected in extracts from any of the tested grains except quinoa. The aglycone quercetin content of the Japanese quinoa seeds is higher than in the seeds from South America and buckwheat. The amounts of quercetin and kaempferol formed via acidic hydrolysis in quinoa are much higher than those of conventionally-used edible plants. The quinoa seeds cultivated in Japan are the most effective functional foodstuff – in terms of being a source of antioxidative and bioactive flavonoids – among cereals and pseudo-cereals.     

Pentadecyl ferulate,a potent antioxidant and antiproliferative agent from the halophyte Salicornia herbacea

An investigation of the chemical constituents of Salicornia herbacea has led to the isolation of one new natural product, pentadecyl ferulate (6), together with 11 known compounds, including phytol (1), stearolic acid (2), γ-linolenic acid (3), (3Z,6Z,9Z)-tricosa-3,6,9-triene (4), linoleic acid (5), stigmasterol (7), ergosterol (8), dioctyl phthalate (9), dibutyl phthalate (10), vanillic aldehyde (11), and scopoletin (12). The chemical structures of these materials were elucidated mainly by spectroscopic analysis. This work represents the first recorded example of the isolation of compounds 1, 2, 3, 4, 9, 10, and 11 from S. herbacea. The antioxidant experiments revealed that compound 6 possessed strong hydroxy radical and superoxide anion scavenging activities and was the principle antioxidant ingredient in the ethyl acetate extract. The antiproliferative results exhibited that compound 1 selectively inhibited HepG2 cells, whereas compounds 3 and 6 showed potent antiproliferative activities against HepG2 and A549 cells.     

Jasmonoid glucosides,sesquiterpenes and coumarins from the fruit of Clausena lansium

The fruit of Clausena lansium (wampee) is popular in southern China and warm areas of the world. Our chemical study on the fruit yielded three jasmonoid glucosides, 12-β-d-glucopyranosyloxy-6-epi-7-isocucurbic acid-1,6-lactone (1), 12-β-d-glucopyranosyloxyjasmonic acid (2) and 12-hydroxyjasmonic acid (3), two sesquiterpenes, (+)-curcumen-12-oic acid (4) and (+)-(E)-α-santalen-12-oic acid (5), two coumarins, xanthotoxol (6) and indicolactone (7), in addition to 3,4-dihydroxybenzoic acid (8), 5-hydroxymethylfuraldehyde (9), isopropyl β-d-glucopyranoside (10) and stigmasterol (11). Their structures were determined by spectroscopic methods. Compound 1 was a new metabolite and the others excluding 6 were reported from the species for the first time. Compounds 1–7 were evaluated for antioxidant and antibacterial activities. Among them, compound 6 showed antioxidant activity in ferric reducing antioxidant power (FRAP) and DPPH radical scavenging assays as well as antibacterial activity against Staphyloccocus aureus and Shigella dysenteriae, while compound 5 was active against Bacillus cereus.     

New flavonol glycosides from Barbeya oleoides Schweinfurth

Three new flavonol glycosides, 3′,5′ dimethoxymyricetin-4″-O-α-l-rhamnopyranosyl (1–4) β-d-glucopyranoside (1), 3′-methoxyquercetin-4″-O-α-l-rhamnopyranosyl (1–4) β-d-glucopyranoside (2) and 3′-methoxyqurecetin-6″-O-α-l-rhamnopyranosyl (1–6) β-d-glucopyranoside (3), have been isolated from the aerial part of Barbeya oleoides Schweinf., along with twelve known compounds, uvaol (4), ursolic acid (5), corosolic acid (6), arjunolic acid (7), β-sitosterol-3-O-β-d-glucoside (8), (+)–catechin (9), (-)-epicatechin (10), isorhamnetin-4′-O-glucoside (11), arjunglucoside I (12), d-(-)-bornesitol (13), gallocatechin (14) and epigallocatechin (15). Compounds 4–15 were isolated for the first time from Barbeyaceae. Structure elucidation of compounds 1–3 was based on MS and NMR data. The ethyl acetate extract of the stems as well as compounds 5, 6, 14 and 15 showed significant antimicrobial activity, while the ethanol extracts of leaves, stems and compounds 4, 7, 8, 13–15 have dose-dependent spasmolytic action.     

TLC bioautography-guided isolation of antioxidants from fruit of Perilla frutescens var. acuta

Guided isolation through bioautography on TLC using 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH) as a detection reagent led to the isolation of four antioxidant compounds from fruit of Perilla frutescens var. acuta. These compounds were identified as rosmarinic acid (1), luteolin (2), apigenin (3), and chrysoeriol (4), by means of UV, NMR, and ESI MS. All the compounds were isolated for the first time from the fruit of the plant. Compounds 1 and 2 showed significant DPPH scavenging capacities, with IC₅₀ values of 8.61 and 7.50 μM, respectively. Further quantitative HPLC analysis confirmed that compounds 1-4 are the predominant contributors to the free radical scavenging activity of the extract of P. frutescens var. acuta.     

Characterization of the components present in the active fractions of health gingers (Curcuma xanthorrhiza and Zingiber zerumbet) by HPLC–DAD–ESIMS

Curcuma xanthorrhiza and Zingiber zerumbet are two of the most commonly used ingredients in Indo-Malaysian traditional medicines, health supplements and tonics. Recently, a number of products derived from the aqueous extracts of these species have appeared in the market in the form of spray-dried powder packed in sachet or bottle. On-line high performance liquid chromatography, coupled with diode array detection and electrospray ion trap tandem mass spectroscopy (HPLC–DAD–ESI–MSⁿ), was used to analyze the components in the antioxidant-active fractions from the rhizomes of these species. Three components were identified from C. xanthorrhiza, including bisdemethoxycurcumin (1), demethoxycurcumin (2) and curcumin (3). The active fraction from Z. zerumbet consisted of five components, including kaempferol 3-O-rhamnoside (4), compound 5 [kaempferol 3-O-(2″-O-acetyl)rhamnoside (5a) or kaempferol 3-O-(3″-O-acetyl)rhamnoside (5b)], kaempferol 3-O-(4″-O-acetyl)rhamnoside (6), kaempferol 3-O-(3″,4″-O-diacetyl)rhamnoside (7) and kaempferol 3-O-(2″,4″-O-diacetyl)rhamnoside (8). To confirm their identities, the components from Z. zerumbet were isolated conventionally and were analyzed by spectroscopic techniques as well as by comparison with literature data.     

Spirostane,furostane and cholestane saponins from Persian leek with antifungal activity

A phytochemical investigation of the seeds of Persian leek afforded the isolation of two new spirostane glycosides, persicosides A (1) and B (2), four new furostane glycosides, isolated as a couple of inseparable mixture, persicosides C1/C2 (3a/3b) and D1/D2 (4a/4b), one cholestane glycoside, persicoside E (5), together with the furostane glycosides ceposides A1/A2 and C1/C2 (6a/6b and 7a/7b), tropeosides A1/A2 and B1/B2 (8a/8b and 9a/9b), and ascalonicoside A1/A2 (10a/10b), already described in white onion, red Tropea onion, and shallot, respectively. Structure elucidation of the compounds was carried out by comprehensive spectroscopic analyses, including 2D NMR spectroscopy and MS spectrometry, and by chemical evidences. The chemical structure of new compounds were identified as (25S)-spirostan-2α,3β,6β-triol 3-O-[β-d-glucopyranosyl-(1 → 3)] [β-d-xylopyranosyl-(1 → 2)]-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (1), (25S)-spirostan-2α,3β,6β-triol 3-O-[β-d-xylopyranosyl-(1 → 3)] [α-l-rhamnopyranosyl-(1 → 2)]-β-d-glucopyranosyl-(1 → 4)-O-β-d-galactopyranoside (2), furosta-1β,3β,22ξ,26-tetraol 5-en 1-O-β-d-glucopyranosyl (1 → 3)-β-d-glucopyranosyl (1 → 2)-β-d-galactopyranosyl 26-O-α-l-rhamnopyranosyl (1 → 2)-β-d-galactopyranoside (3a,3b), furosta-2α,3β,22ξ,26-tetraol 3-O-β-d-glucopyranosyl (1 → 3)-β-d-glucopyranosyl (1 → 2)-β-d-galactopyranosyl 26-O-β-d-glucopyranoside (4a,4b), (22S)-cholesta-1β,3β,16β,22β-tetraol 5-en 1-O-α-l-rhamnopyranosyl 16-O-α-l-rhamnopyranosyl (1 → 2)-β-d-galactopyranoside (5).     

Dicaffeoylquinic acid derivatives and flavonoid glucosides from glasswort (Salicornia herbacea L.) and their antioxidative activity

Two novel antioxidant compounds, isoquercitrin 6″-O-methyloxalate (6) and methyl 4-caffeoyl-3-dihydrocaffeoyl quinate (salicornate, 7), were isolated from Salicornia herbacea L.. Six known compounds were also identified as 3,5-dicaffeoylquinic acid (1), quercetin 3-O-β-d-glucopyranoside (2), 3-caffeoyl-4-dihydrocaffeoylquinic acid (3), methyl 3,5-dicaffeoyl quinate (4), 3,4-dicaffeoylquinic acid (5), and isorhamnetin 3-O-β-d-glucopyranoside (8). Their chemical structures were determined by spectroscopic data from ESI–MS and NMR. The isolated dicaffeoylquinic acid derivatives (1, 3, 4, 5, and 7) showed similar activities for scavenging 1,1-diphenyl-2-picrylhydrazyl radicals and inhibiting formation of cholesteryl ester hydroperoxide during copper ion-induced rat blood plasma oxidation. The two flavonol glucosides (2 and 6), which have no substitutions in the B ring of their aglycones, also had similar activity. However, compound 8, which has the same structure as 2 except for the presence of a methoxyl group in the C-3′ position of the B ring, showed predominantly lower antioxidant activity than the other isolated compounds.     

Phenolic antioxidants from Chinese toon (fresh young leaves and shoots of Toona sinensis)

Chinese toon (the fresh young leaves and shoots of Toona sinensis), known as a tree vegetable, belongs to the family of Meliaceae. It is one of the most popular vegetables in China. The 80% acetone extract of Chinese toon exhibited considerable antioxidant activity in the 1,1-diphenyl-2-picryldydrazyl (DPPH) radical-scavenging assay. Bioassay-guided purification of the extract led to the isolation of 12 phenolic compounds (1–12), whose structures were determined by detailed spectroscopic analyses, including UV, IR, MS, 1D and 2D NMR techniques. Of them, compounds 3–8 and 11 were isolated from T. sinensis for the first time. All of the isolated compounds were examined for their antioxidant activities by the DPPH method, and the results showed that gallic acid and its derivatives, gallotannins and flavonoids were the main constituents contributing to the antioxidant activity of Chinese toon. From the health point of view, Chinese toon is an ideal dietary vegetable with natural antioxidants.