Identification and characterisation of anthocyanins in the antioxidant activity-containing fraction of Liriope platyphylla fruits

The objective of this study was to investigate antioxidant activities and anthocyanin profiles in the fruits of Liriope platyphylla, where these are considered functional substances in Korea. The acidic methanol extract of this species exhibited potent antioxidant activities, showing 83.9% DPPH scavenging activity and 92.5% ABTS scavenging activity at a concentration of 0.5 mg/ml. Moreover, anthocyanins were identified by reversed-phase C₁₈ column chromatography, NMR spectroscopy, and HPLC-DAD-ESI/MS analysis. Seven anthocyanins were characterised, including delphinidin-3-O-glucoside (1), delphinidin-3-O-rutinoside (2), cyanidin-3-O-glucoside (3), petunidin-3-O-glucoside (4), petunidin-3-O-rutinoside (5), malvidin-3-O-glucoside (6), and malvidin-3-O-rutinoside (7). Among these, petunidin-3-O-rutinoside (5) (7302.2 μg/g) and malvidin-3-O-rutinoside (7) (5776.1 μg/g) were the predominant anthocyanins, whereas the least prevalent anthocyanin was found to be cyanidin-3-O-glucoside (3) (64.9 μg/g). Therefore, our results suggest that strong antioxidant activities of the acidic methanol extract of L. platyphylla fruits are correlated with high anthocyanin contents, particularly the petunidin-3-O-rutinoside (5) and malvidin-3-O-rutinoside (7).     

Characterisation of phenolic phytochemicals and quality changes related to the harvest times from the leaves of Korean purple perilla (Perilla frutescens)

The objective of this study was to investigate the profiles of phenolic phytochemicals in the leaves of Korean purple perilla (cv. Bora, Perilla fructescens) using reversed-phase C₁₈ column chromatography and HPLC with DAD-ESI/MS analysis. Changes in their contents were also the first reported through eight different harvest times during two months. They were characterised as five anthocyanins and three phenolic acids including cyanidin-3,5-di-O-glucoside (1), cyanidin-3-O-glucoside (2), cyanidin-3-O-(6-O-caffeoyl)glucoside-5-O-glucoside (3), cyanidin-3-O-(6-O-coumaroyl)glucoside-5-O-glucoside (4), cyanidin-3-O-(6-O-coumaroyl)glucoside (5), caffeic acid (6), rosmarinic acid (7), and rosmarinic acid methylester (8). Significant differences were observed between individual and total phytochemical contents, especially, cyanidin-3-O-(6-O-coumaroyl)glucoside-5-O-glucoside (4) and rosmarinic acid (7) exhibited the predominant constituents. Among different harvest times, the highest content was found with 82.473 mg/g on 21st September, while the lowest was 39.000 mg/g on 17th August. These results may be useful in determining the optimal harvest time at which phenolic phytochemicals reaches a maximum level in mid-September.     

Anthocyanins in cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata]

The aim of this study was to isolate and identify the anthocyanins in the black seed coated cowpea [Vigna unguiculata (L.) Walp. ssp. unguiculata] using reverse phase C-18 open column chromatography and high performance liquid chromatography (HPLC) with diode array detection and electro spray ionization/mass spectrometry (DAD-ESI/MS) analysis, respectively. Anthocyanins were extracted from the coat of black cowpea with 1% trifluoroacetic acid (TFA) in methanol, isolated by RP-C-18 column chromatography, and their structures elucidated by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. The isolated anthocyanins were characterized as delphinidin-3-O-glucoside (2) and cyanidin-3-O-glucoside (4). Furthermore, 5 minor anthocyanins were detected and identified as delphinidin-3-O-galactoside (1), cyanidin-3-O-galactoside (3), petunidin-3-O-glucoside (5), peonidin-3-O-glucoside (7), and malvidin-3-O-glucoside (8) based on the fragmentation patterns of HPLC-DADESI/MS analysis.     

Identification,characterisation, and quantification of phenolic compounds in the antioxidant activity-containing fraction from the seeds of Korean perilla (Perilla frutescens) cultivars

The present research was the first to investigate phenolic compound profiles and antioxidant properties in the seeds of various perilla (Perilla frutescens) cultivars. The 80% methanol extract (50 μg/ml) of this species showed potent antioxidant activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radicals. Phenolic compounds were characterised by nuclear magnetic resonance (NMR) spectroscopy, and ultra performance liquid chromatography with photodiode array detector and electrospray ionisation/mass (UPLC-PDA-ESI/MS) analysis. Nine compounds were elucidated as caffeic acid-3-O-glucoside (1), caffeic acid (2), luteolin-7-O-glucoside (3), apigenin-7-O-glucoside (4), rosmarinic acid-3-O-glucoside (5), rosmarinic acid (6), luteolin (7), apigenin (8), and chrysoeriol (9). The individual and total phenolic contents were remarkably different, especially rosmarinic acid-3-O-glucoside (5) and rosmarinic acid (6) which were the predominant compounds (>95%) in all perilla cultivars. Additionally, Yeupsil cultivar exhibited the highest phenolic content (5029.0 μg/g) and antioxidant activity, whereas the lowest was shown by Dasil (2138.7 μg/g). Therefore, these results suggest that antioxidant effects of perilla seeds are correlated with phenolic contents.     

Chemical composition, mineral content and antioxidant activity of Verbena officinalis L.

Aqueous and hydroalcoholic extracts from Verbena officinalis L. were obtained and characterised. The analysis by HPLC-DAD and LC-MS allowed the detection and identification of three iridoids, fifteen flavonoids and four phenolic acid derivatives. Four flavonoids, scutellarein 7-diglucuronide (9), scutellarein 7-glucuronide (13), pedalitin 6-galactoside (15) and scutellarein 7-glucoside (19) are reported for the first time from this plant. In addition, three new flavonoids have been isolated: scutellarein 7-O-(2-O-feruloyl)-diglucuronide (5), pedalitin 6-O-diglucuronide (6) and pedalitin 6-O-(2-O-feruloyl)-diglucuronide (13). To our knowledge, these flavonoids have not been reported as natural products. Both extracts showed significant antioxidant activity using three in vitro model systems and the results have been correlated with total phenolic and total flavonoid contents. The results have allowed establishing an important relation structure-activity and significant correlations have also been found between the mineral content and the flavonoids present in both extracts.     

Isolation and structure elucidation of phenolic compounds from Cyclopia subternata Vogel (honeybush) intact plant and in vitro cultures

In the presented work, an insight was made into the polyphenolic composition of intact plant material and in vitro cultures of indigenous South African plant Cyclopia subternata Vogel (honeybush). Ethyl acetate fractions of methanol extracts were separated by means of gravity column chromatography and/or semipreparative HPLC on two serially connected monolithic RP-18 columns. The structures of the isolated compounds were determined by means of 1D and 2D NMR techniques and additionally confirmed by LC-DAD-ESI-MS. Apart from the previously described honeybush components, that is mangiferin (1), scolymoside (2), hesperidin (3) and narirutin (4), three additional compounds: iriflophenone 3-C-β-glucoside (benzophenone) (5), phloretin 3′,5′-di-C-β-glucoside (dihydrochalcone) (6), and isorhoifolin (flavone) (7) were identified for the first time in the herb of C. subternata. Additionally, three isoflavone glucosides, namely calycosin 7-O-β-glucoside (8), rothindin (9) and ononin (10), which had not been previously reported in Cyclopia plants, were identified in the callus of the above species. As far as the authors are concerned, this is the first report on the presence of benzophenone and dihydrochalcone derivatives in Cyclopia genus.     

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.     

Kumquat (Fortunella japonica Swingle) juice: Flavonoid distribution and antioxidant properties

The flavonoids composition of kumquat (Fortunella japonica) crude juice, obtained from uripe and ripe fruits, were investigated by reverse-phase LC-DAD-ESI-ITMS analysis. Thirteen compounds (C- and O-glycosyl flavonoids) were identified. Acacetin 3,6-di-C-glucoside (1), vicenin-2 (2), lucenin-2 4′-methyl ether (3) narirutin 4′-O-glucoside (4) and apigenin 8-C-neohesperidoside (5) were identified for the first time in kumquat juice. Furthermore, we report on the remarkable antioxidant properties of crude juice, of selected flavonoids fractions and of the main component, phloretin 3′,5′-di-C-glucoside (6).     

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.     

A new phragmalin-type limonoid and anti-inflammatory constituents from the fruits of Swietenia macrophylla

The fruit of Swietenia macrophylla is commercially used in healthcare products for the improvement of blood circulation and skin condition. A new phragmalin-type limonoid, 6-O-acetyl-3′-demethylswietephragmin E (1), has been isolated from the fruit of S. macrophylla, together with 16 known compounds. The structure of this new compound was determined through spectroscopic and MS analyses. 6-O-Acetyl-3′-demethylswietephragmin E (1), 3,6-O,O-diacetylswietenolide (5), 3-O-tigloylswietenolide (6), 3-O-tigloyl-6-O-acetylswietenolide (8), swietemahonin E (9), and 6-O-acetylswietemahonin G (10) exhibited inhibition (IC₅₀ ? 35.7 μM) of superoxide anion generation by human neutrophils in response to formyl-l-methionyl-l-leucyl-l-phenylalanine (fMLP).     

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.     

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.     

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.     

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.     

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.     

HPLC analysis and antioxidant activity of Ulmus davidiana and some flavonoids

In this study, we investigated the antioxidative activities of (−)-catechin (1), (−)-catechin-7-O-β-d-apiofuranoside (2) and (−)-catechin-7-O-β-d-xylopyranoside (3) in terms of their abilities to promote metal chelation, prevent lipid peroxidation, and inhibit DNA cleavage. In addition, high-performance liquid chromatography (HPLC) was used to quantify compounds (1–3) in each of various solvent extracts from Ulmus davidiana.     

Effects of Amelanchier fruit isolates on cyclooxygenase enzymes and lipid peroxidation

Bioassay-directed isolation and purification of the ethyl acetate and methanol extracts of Amelanchier canadensis resulted in 1,3-dilinoleoyl 2-olein (1), 1,3-dioleoyl 2-linolein (2), 5-hydroxymethyl-2-furfural (3), 5-(sorbitoloxymethyl)-furan-2-carboxaldehyde (4), 5-(mannitoloxymethyl)-furan-2-carboxaldehyde (5), and 5-(α-d-glucopyranosyloxymethyl) furan-2-carboxaldehyde (6). Four compounds, oleanolic acid (7), ursolic acid (8), kaempferol-3-O-α-l-rhamnopyranosyl (1 ← 2) rhamnopyranoside (9), and kaempferol-3-O-α-l-rhamnopyranoside (10) were isolated from the ethyl acetate extract of fresh fruits of Amelanchier arborea. The compounds were isolated and purified by various chromatographic techniques and characterized by NMR and GC/MS methods. The isolated compounds inhibited lipid peroxidation (by 85%) at 100 ppm when compared to 89%, 87%, and 98% for the commercial antioxidants butylated hydroxy anisole (BHA), butylated hydroxytoluene (BHT), and tert-butylhydroxyquinone (TBHQ) at 1.67, 2.2, and 1.67 ppm, respectively. Although not selective, some of these compounds inhibited cyclooxygenase (COX)-1 and -2 enzymes. Compounds 3–6 were isolated for the first time from A. canadensis and compounds 7–10 were isolated for the first time from A. arborea fruits.     

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 flavonoid level variation in onion (Allium cepa L.) infected by Fusarium oxysporum using liquid chromatography–tandem mass spectrometry

In order to evaluate the flavonoid level variation in an onion (Allium cepa L.) infected by Fusarium oxysporum, the bulbs of a healthy onion and of an infected one were analysed for flavonoids via high-performance liquid chromatography coupled with tandem mass spectrometry (HPLC–MS/MS). Among eleven flavonoids characterised, isorhamnetin 4′-O-galactoside (8) was identified in an onion for the first time. When the healthy bulb was inoculated with the fungus, the two quercetin derivatives (4 and 7) and the two isorhamnetin derivatives (5 and 9) underwent concentration changes typical for the defense materials against pathogens. The yellow granules that were accumulated on the abaxial epidermal cell layers after 8 days of inoculation were confirmed as quercetin (10) and isorhamnetin (11). It was deduced that they were produced from flavonoids 4, 5, 7 and 9 by hydrolysis enzyme of the fungus.