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.     

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.     

Chemical characterisation of anthocyanins in tamarillo (Solanum betaceum Cav.) and Andes berry (Rubus glaucus Benth.) fruits

The anthocyanin composition of tamarillo (Solanum betaceum Cav., red variety) and Andes berry (Rubus glaucus Benth.) was determined by HPLC–PDA and HPLC–ESIMS. From the anthocyanin-rich extracts (AREs), pure compounds (1–7) were obtained by MLCCC (multilayer countercurrent chromatography) and further preparative HPLC, and their unequivocal structures were obtained by 1D and 2D NMR analyses. The new anthocyanin delphinidin 3-O-α-l-rhamnopyranosyl-(1 → 6)-β-d-glucopyranoside-3′-O-β-d-glucopyranoside, as well as the known cyanidin-3-O-rutinoside, pelargonidin-3-O-rutinoside, and delphinidin-3-O-rutinoside were identified as constituents of tamarillo fruit. Although the anthocyanin composition of Andes berry had been reported before in the literature, the unequivocal structure elucidation of the major compound, cyanidin-3-O-α-l-rhamnopyranosyl-(1 → 6)-O-β-d-xylopyranosyl-(1 → 2)-β-d-glucopyranoside, was achieved for the first time.     

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).     

Terpenoids and hexenes from the leaves of Crataegus pinnatifida

Crataegus pinnatifida have long been used in traditional Chinese medicine and European herbal medicine, and are widely consumed as food, in the form of juice, drink, jam and canned fruit. Four new compounds, a sesquiterpene and its glycoside (1–2), two monoterpene glycosides (3–4), together with eight known compounds (5–12), were isolated from the leaves of C. pinnatifida. Their structures were elucidated as (5Z)-6-[5-(2-hydroxypropan-2-yl)-2-methyltetrahydrofuran-2-yl]-3-methylhexa-1,5-dien-3-ol (1), (5Z)-6-[5-(2-O-β-d-glucopyranosyl-propan-2-yl)-2-methyl tetrahydrofuran-2-yl]-3-methylhexa-1,5-dien-3-ol (2), 5-ethenyl-2-[2-O-β-d-glucopyranosyl-(1″ → 6′)-β-d-glucopyranosyl-propan-2-yl]-5-methyltetrahydrofuran-2-ol (3), 4-[4β-O-β-d-xylopyranosyl-(1″ → 6′)-β-d-glucopyranosyl-2,6,6-trimethyl-1-cyclohexen-1-yl]-butan-2-one (4), (Z)-3-hexenyl O-β-d-glucopyranosyl-(1″ → 6′)-β-d-glucopyranoside (5), (Z)-3-hexenyl O-β-d-xylopyranosyl-(1″ → 6′)-β-d-glucopyranoside (6), (Z)-3-hexenyl O-β-d-rhamnopyranosyl-(1″ → 6′)-β-d-glucopyranoside (7), (3R,5S,6S,7E,9S)-megastiman-7-ene-3,5,6,9-tetrol (8), (3R,5S,6S,7E,9S)-megastigman-7-ene-3,5,6,9-tetrol9-O-β-d-glucopyranoside (9), (6S,7E,9R)-6,9-dihydroxy-4,7-megastigmadien-3-one 9-O-[β-d-xylopyranosyl-(1″ → 6′)-β-d-glucopyranoside] (10), Linarionoside C (11), and (3S,9R)-3,9-dihydroxy-megastigman-5-ene 3-O-primeveroside (12), using a combination of mass spectroscopy, 1D and 2D NMR spectroscopy and chemical analysis. Cytotoxicity of the new compounds was assayed against selected human glioma (U87) cell lines.     

Spirostane and cholestane glycosides from the bulbs of Allium nigrum L

A phytochemical investigation of the fresh bulbs of Allium nigrum L. led to the isolation of new spirostane-type glycosides as two inseparable isomer mixtures, nigrosides A1/A2 (1a/1b) and nigrosides B1/B2 (2a/2b), two new cholestane-type glycosides, nigrosides C and D (3 and 4), together with the known compounds, 25(R,S)-5α-spirostan-2α,3β,6β-trio1-3-O-β-d-glucopyranosyl-(1 → 2)-O-[β-d-xylopyranosyl-(1 → 3)]-O-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (5a/5b) and 25(R,S)-5α-spirostan-2α,3β,6β-trio1 3-O-β-d-glucopyranosyl-(1 → 2)-O-[4-O-(3S)-3-hydroxy-3-methylglutaryl-β-d-xylopyranosyl-(1 → 3)]-O-β-d-glucopyranosyl-(1 → 4)-β-d-galactopyranoside (6a/6b), isolated from this plant for the first time. All structures were elucidated mainly by spectroscopic analysis (1D and 2D NMR experiments, FABMS, HRESIMS) and by comparison with literature data. Cytotoxicity of the isolated compounds was assessed against human colon carcinoma (HT-29 and HCT 116) cell lines. Compounds 5a/5b and 6a/6b were found to be the most active with IC₅₀ values 1.09 and 2.82 μM against HT-29 and 1.59 and 3.45 μM against HCT 116, respectively.     

Flavonoid glycosides from Pouteria obovata (R. Br.) fruit flour

Three unknown dihydroflavanol glycosides: 2R,3R-4′O-methyl dihydrokaempferol 7-O-[3″-O-acetyl]-β-d-glucopyranoside (1), 2R,3R-4′-O-methyl dihydrokaempferol 7-O-β-d-β-l-xylopyranosyl-(1″′ → 6″)-[3″-O-acetyl]-β-d-glucopyranoside (2), 2R,3R-4′-O-methyl dihydrokaempferol 3-O-β-d-β-l-xylopyranosyl-(1″′ → 6″)-[3″-O-acetyl]-β-d-glucopyranoside (3), together with gallic acid (4) were isolated from the n-butanol fraction of Pouteria obovata fruit flour by chromatographic methods and their structures were elucidated on the basis of CD, UV, MS, monodimensional NMR (¹H and ¹³C) and bidimensional NMR (COSY, HSQC and HMBC). The quantitative analysis of flavonoids and phenols were also reported. Total phenolic amount (51.1 ± 14.1 mg GAE/1000 g; p < 0.0006) and flavonoid content (153.2 ± 3.5 mg CE/100 g; p < 0.004) were detected spectrophotometrically.     

Constituents of Sideritis syriaca. ssp. syriaca (Lamiaceae) and their antioxidant activity

The aerial parts of Sideritis syriaca ssp. syriaca (Lamiaceae) were extracted, after defatting, with diethyl ether, ethyl acetate and n-butanol. The antioxidant activities of the extracts were evaluated through in vitro model systems, such as 1,1-diphenyl-2-picryl hydrazyl (DPPH) and Co(II) EDTA-induced luminol chemiluminescence. In both model systems the ethyl acetate extract was the most effective. Phytochemical analysis of ethyl acetate extract showed the presence of two new isomeric compounds (1 and 1′), identified as 1-rhamnosyl, 1-coumaroyl, dihydrocaffeoyl, protocatechuic tetraester of quinic acid, as well as chlorogenic acid (2), apigenin 7-O-glucoside (3), apigenin (4), 4′-O-methylisoscutellarein 7-O-[6′′′-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-d-glucopyranoside] (5), isoscutellarein 7-O-[6′′′-O-acetyl-β-D-allopyranosyl-(1 → 2)-β-d-glucopyranoside] (6), 4′-O-methylisoscutellarein 7-O[β-d-allopyranosyl-(1 → 2)-β-d-glucopyranoside] (7) and 4′-O-methylisoscutellarein 7-O-[β-d-allopyranosyl-(1 → 2)-6′′-O-acetyl-β-d-glucopyranoside] (8). The above compounds were identified by spectroscopic methods.     

Phenolic constituents from the flower buds of Lonicera japonica and their 5-lipoxygenase inhibitory activities

Thirteen phenolic constituents, luteolin (1), protocatechuic acid (2), caffeic acid (3), flavoyadorinin-B (4), 4,5-dicaffeoylquinic acid (5), luteolin 7-O-β-d-glucopyranoside (7), 3,5-dicaffeoylquinic acid methyl ester (8), methyl chlorogenate (9), quercetin 3-O-β-d-glucopyranoside (10), 3,5-dicaffeoylquinic acid (11), rhoifolin (12), chlorogenic acid (13), and a novel phenolic glucoside benzoate, vanillic acid 4-O-β-d-(6-O-benzoylglucopyranoside) (6), were isolated from the flower buds of Lonicera japonica. Flavoyadorinin-B (4) was isolated for the first time from a Caprifoliaceae plant. The structures of 1–13 were determined on the basis of chemical and spectroscopic evidence. These compounds were screened for their 5-lipoxygenase inhibitory activity. Only luteolin (1) showed significant inhibitory activity against 5-LOX-catalysed leukotriene production.     

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.     

Diterpene glycosides from Korean fermented red pepper paste (gochujang) and their origin

Two acyclic diterpene glycosides were isolated from the n-butanol layer (50.84 g) of methanol extracts (1639 g) of gochujang (3 kg, wet wt.), Korean fermented red pepper paste. The chemical structures were elucidated as 6E,10E,14Z-(3S)-17-hydroxygeranyllinalool 17-O-α-l-rhamnopyranosyl(1 →$\to$ 4)-[α-l-rhamnopyranosyl-(1 →$\to$ 6)]-β-d-glucopyranoside (1, capsianoside XVIII, 2.3 mg, a novel compound) and capsianoside F (2, 5.3 mg) based on the spectroscopic data of MS and NMR. Compounds 1 and 2 are reported for the first time from gochujang. In addition, the origin of the compounds was determined to be red pepper (Capsicum annuum), which is one of the representative materials of gochujang.     

Bioassay-guided screening and isolation of α-glucosidase and tyrosinase inhibitors from leaves of Morus alba

In this study, bioassay-guided fractionation of extracts from the leaves of Morus alba L. led to the isolation of 15 bioactive constituents with α-glucosidase and tyrosinase inhibitory activities, among which prenylated stilbenes were proved to be a new group of α-glucosidase inhibitors apart from iminosugars derived from Morus alba. Their structures were identified on the basis of extensive spectroscopic analysis and chemical evidence, as well as comparing with data from the literature. Among them, compounds (2R)/(2S)-Euchrenone a₇ (6a/6b), Chalcomoracin (7), Moracin C (8), Moracin D (9) and Moracin N (10) exhibited a significant degree of α-glucosidase inhibitory activity with IC₅₀ of 6.28, 2.59, 4.04, 2.54 and 2.76 μM, respectively, while (2R)/(2S)-Euchrenone a₇ (6a/6b), Moracin N (10), Quercetin (13), Norartocarpetin (14), the interconvertible epimeric mixture of (2R)/(2S)-7-methoxyl-8-ethyl-2′,4′-dihydroxylflavane-2″-O-β-d-glucopyranoside (1a/1b) and the interconvertible enantiomers of (2R)/(2S)-7-methoxyl-8-hydroxyethyl-2′,4′-dihydroxylflavane (5a/5b) displayed a potent tyrosinase inhibitory effect with IC₅₀ of 0.260, 0.924, 0.523, 0.0824, 0.616 and 0.528 μM, respectively. Especially, (2R)-7-methoxyl-8-ethyl-2′,4′-dihydroxylflavane-2″-O-β-d-glucopyranoside (1a), (2S)-7-methoxyl-8-ethyl-2′,4′-dihydroxylflavane-2″-O-β-d-glucopyranoside (1b), (2S)-8-hydroxyethyl-7,4′-dimethoxylflavane-2′-O-β-d-glucopyranoside (2), (2R)-7-methoxyl-8-hydroxyethyl-2′,4′-dihydroxylflavane (5a) and (2S)-7-methoxyl-8-hydroxyethyl-2′,4′-dihydroxylflavane (5b) were identified as new compounds.     

Identification of antioxidants from rhizome of Davallia solida

Davallia solida rhizome has long been used as an herb tonic to treat osteoporosis, arthralgia, and arthritis. The aqueous extract of D. solida rhizome contains a high content of phenolic compounds [210.8 ± 4.6 mg catechin equivalents (CE)/g dry weight] and shows a strong 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity (IC₅₀ = 15.93 ± 1.21 μg dry weight/ml). Further solvent partition of the aqueous extract yielded chloroform, n-butanol, and water layers. Among them, n-butanol layer has the highest phenol content (806.3 ± 12.3 mg CE/g dry weight) and DPPH scavenging potential (IC₅₀ = 3.93 ± 0.31 μg dry weight/ml). Isolation and purification from the n-butanol layer identified 12 compounds. They included four new compounds: 3′-O-p-hydroxybenzoylmangiferin (1), 4′-O-p-hydroxybenzoylmangiferin (2), 6′-O-p-hydroxybenzoylmangiferin (3), and 3-O-p-hydroxybenzoylmangiferin (4); as well as eight known compounds: mangiferin (5), 2-C-β-d-xylopyranosyl-1,3,6,7-tetrahydroxyxanthone (6), 4β-carboxymethyl-(−)-epicatechin (7), 4β-carboxymethyl-(−)-epicatechin methyl ester (8), eriodictyol (9), eriodictyol-8-C-β-d-glucopyranoside (10), icariside E₅ (11), and icariside E₃ (12). DPPH scavenging and Trolox equivalent antioxidant capacity (TEAC) analyses revealed that the most potent antioxidants are 1, 2, and 3, which exerted more than triple activity as compared with the positive controls, α-tocopherol and Trolox.     

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.     

C-dideoxyhexosyl flavones from the stems and leaves of Passiflora edulis Sims

The stems and leaves of Passiflora edulis Sims, are used as a folk medicine for treating both anxiety and nervousness in American countries. Phytochemical investigation of the n-butanol (n-BuOH) fraction of this plant led to the isolation of four new 2,6-dideoxyhexose-C-glycosyl flavones, including luteolin-8-C-β-digitoxopyranosyl-4′-O-β-d-glucopyranoside (1), apigenin-8-C-β-digitoxopyranoside (2), apigenin-8-C-β-boivinopyranoside (3) and luteolin-8-C-β-boivinopyranoside (4), together with five known compounds (5–9). The structures of these compounds were elucidated by extensive spectroscopic methods. All compounds were evaluated for their neurite outgrowth enhancing activities and the results indicated that luteolin (7) enhanced NGF-induced neurite outgrowth in PC12 cells at 50.0 μM.     

Identification,quantification and antioxidant activity of acylated flavonol glycosides from sea buckthorn (Hippophae rhamnoides ssp. sinensis)

A novel acylated flavonol glycoside: isorhamnetin (3-O-[(6-O-E-sinapoyl)-β-d-glucopyranosyl-(1 → 2)]-β-d-glucopyranosyl-7-O-α-l-rhamnopyranoside) (1), together with two known acylated flavonol glycosides: quercetin (3-O-[(6-O-E-sinapoyl)-β-d-glucopyranosyl-(1 → 2)]-β-d-glucopyranosyl-7-O-α-l-rhamnopyranoside) (2) and kaempferol (3-O-[(6-O-E-sinapoyl)-β-d-glucopyranosyl-(1 → 2)]-β-d-glucopyranosyl-7-O-α-l-rhamnopyranoside) (3) were isolated from the n-butanol fraction of sea buckthorn (Hippophae rhamnoides ssp. sinensis) berries for the first time by chromatographic methods, and their structures were elucidated using UV, MS, ¹H and ¹³C NMR, and 2D NMR. Compounds 1–3 showed good scavenging activities, with respective IC₅₀ values of 8.91, 4.26 and 30.90 μM toward the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) radical; respective Trolox equivalent antioxidant capacities of 2.89, 4.04 and 2.44 μM μM⁻¹ toward 2,2′-azino-bis-3-ethyl-benzothiazoline-6-sulphonate (ABTS) radical. The quantitative analysis of the isolated acylated flavonol glycosides was performed by HPLC–DAD method. The contents of compounds 1–3 were in the range of 12.2–31.4, 4.0–25.3, 7.5–59.7 mg/100 g dried berries and 9.1–34.5, 75.1–182.1, 29.2–113.4 mg/100 g dried leaves, respectively.     

Phenolic-rich extract from the Costa Rican guava (Psidium friedrichsthalianum) pulp with antioxidant and anti-inflammatory activity. Potential for COPD therapy

The potential therapeutic effects of Costa Rican guava (Psidium friedrichsthalianum) extracts for chronic obstructive pulmonary disease were examined. The ethyl acetate fraction displayed the highest antioxidant activity, as compared to the hexane, chloroform, and n-butanol fractions, as well as the crude extract. This fraction was evaluated for its anti-inflammatory activity response relationship against interleukin-8 (IL-8) and inhibition of matrix metalloproteinase-1 (MMP-1) expression before and after treatment with cigarette smoke. The ethyl acetate fraction exhibited inhibitory activity against IL-8 production and MMP-1 expression, showing the most potent inhibitory activities in both assays at 100 μg/mL, and nine compounds (1–9) were found. Phenolic compounds 1-O-trans-cinnamoyl-β-d-glucopyranose (2), ellagic acid (3), myricetin (4), quercitrin (7), and quercetin (9) were identified using standard compounds or literature reports from related species. Compounds 1, 5, 6, and 8 were tentatively identified as 1,5-dimethyl citrate (1), sinapic aldehyde 4-O-β-d-glucopyranose (5), 3,3′,4-tri-O-methylellagic acid-4′-O-d-glucopyranoside (6), and 1,3-O-diferuloylglycerol (8), All nine compounds are reported for the first time in Costa Rican guava.     

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.     

Anti-melanogenesis properties of quercetin- and its derivative-rich extract from Allium cepa

In an effort to find a new whitening agent, we have found that the methanol extract of the dried skin of Allium cepa showed inhibition of melanin formation. Bioassay-guided fractionation led to the isolation of quercetin (1) and quercetin 4’-O-β-glucoside (3) from A. cepa as the inhibitors of melanin formation in B16 melanoma cells with IC₅₀ values of 26.5 and 131 μM, respectively. In addition, we evaluated the effect of some quercetin derivatives, such as isoquercitrin (2), quercetin 3,4’-O-diglucoside (4), rutin (5) and hyperin (6) on B16 melanoma cells. These quercetin derivatives did not show any inhibition of melanin formation. Furthermore, the ORAC values of compounds 1–6 were 7.64, 8.65, 4.82, 4.32, 8.17 and 9.34 μmol trolox equivalents/μmol, respectively. Dried skin of red onion showed inhibitory activity against melanin formation in B16 melanoma cells, as well as antioxidant properties.     

Determination of chemical variability of phenolic and monoterpene glycosides in the seeds of Paeonia species using HPLC and profiling analysis

A rapid, sensitive, and accurate HPLC-DAD method was developed and validated for simultaneous determination of one phenolic glycoside and seven monoterpene glycosides, including 1-O-β-d-(4-hydroxybenzoyl)glucose (1), pyridylpaeoniflorin (2), (8R)-piperitone-4-en-9-O-β-d-glucopyranoside (3), oxypaeoniflorin (4), 6′-O-β-glucopyranosylalbiflorin (5), albiflorin (6), β-gentiobiosylpaeoniflorin (7), and paeoniflorin (8), in 44 batches of peony seeds from nine Paeonia species collected from different areas. Using the optimised method, separations were conducted with a YMC-pack ODS-A column with water/formic acid and methanol as the mobile phase. All eight analytes demonstrated good linearity (r² > 0.9993). The recoveries, measured at three concentration levels, varied from 98.20% to 103.81%. Six compounds including 1 and 4–8 occur ubiquitously in all the seeds of nine Paeonia species, and compounds 2 and 3 showed undetectable levels or very low content in several samples. The seed samples were classified into several groups, which coincide with the taxonomy of Paeonia at the section level. Peony seed might be a useful resource in developing new herbal or food products.