Distribution of exudate flavonoids in the genus Plectranthus

Thirty-four species of the genus Plectranthus (including species of the former genera Coleus and Solenostemon, fam. Lamiaceae) were surveyed for exudate flavonoids to see whether the distribution of these compounds would support a recent classification of the genus based on molecular and morphological characters. In this classification two major groups had been identified, the Coleus and Plectranthus clades. Only about 40% of the species, predominantly from the Plectranthus clade, were found to produce exudate flavonoids, which were mainly flavones. Flavanones were restricted to five species of the Plectranthus clade, whereas flavonols were only found in two species of the Coleus clade, Plectranthus montanus Benth. (synonyms Plectranthus marrubioides Hochst. ex Benth. and Plectranthus cylindraceus Hochst. ex Benth.) and Plectranthus pseudomarrubioides R.H.Willemse. Four of these flavonols were isolated from P. montanus and identified by NMR spectroscopy as the 3,7-dimethyl ether and 3,7,4′-trimethyl ether of quercetin and the 3,6,7-trimethyl ether and 3,6,7,4′-tetramethyl ether of quercetagetin. The remaining flavonols and flavones were identified by HPLC–UV and LC–MS of crude extracts on the basis of their UV and mass spectra, retention times and comparison with standards. Most flavonols were 3-methyl ethers and many of the flavones and flavonols were oxygenated at the 6-position. The most common flavones, occurring in both clades, were cirsimaritin and salvigenin, which are methoxylated at the 6- and 7-positions. 6-Hydroxylated flavones such as scutellarein and ladanein were restricted to species of the Plectranthus clade.     

New insight into the flavonoid composition of Chenopodium botrys

Due to their beneficial medicinal effects, in recent years there has been an increasing interest in the research of flavonoids in plant sources.In the conducted research the flavonoid composition of Chenopodium botrys was defined by applying an approach which included different extraction procedures and methods of detection. Primary extraction of polyphenols with two different solvents, HPLC-PDA fingerprint profiling and an Orbitrap UHPLC-MS/MS detection were used. The fingerprint profile of polyphenols showed that the major constituents were the methoxylated flavones nepetin, hispidulin and jaceosidin, while the quercetin glycosides represented a minor part. In order to elucidate their structure, the fragmentation of the compounds was examined by means of ESI-MS/MS analysis. A novel explanation of the fragmentation pathways of the methoxylated flavones was introduced. Nepetin, nobiletin, eupatilin, rutin and quercetin-3-O-galactoside were identified in the polyphenol complex of C. botrys for the first time.     

Exudate flavones and flavanones in Origanum species and their interspecific variation

Surface flavonoids in nine species of Origanum, representing taxa from all three of the currently recognised subgeneric groups, were examined both by HPLC coupled to diode-array detection and APCI–MS. Many of the flavonoids present were characterised by O-substituent at C-6 (OH, OMe) and/or C-8 (OMe). In total, 25 flavones and flavanones are described in this study, of which 13 are new to the genus and 5,4′-dihydroxy-6,7,3′-trimethoxyflavanone is reported for the first time. Taxa in subgeneric Group A accumulated flavonoids with methoxyl groups at both C-6 and C-4′; however, taxa in subgeneric Group B did not accumulate 4′-methoxylated compounds, and taxa in Group C did not accumulate 6-methoxylated compounds.     

Phytoestrogens as natural prodrugs in cancer prevention: dietary flavonoids

There are many reasons why vegetables and fruits may protect against cancer. As well as containing vitamins and minerals, which help keep the body healthy and strengthen the immune system, they are also good sources of biologically active compounds, which can help to protect cells in the body from damage that can lead to cancer. Notably, dietary flavonoids and other polyphenols are thought to have an important role as chemopreventive agents. Most studies on the possible mechanism of the chemopreventive action of dietary compounds have assumed that free hydroxyl groups of flavonoids and other polyphenols are necessary for their biological effects. However, in the human body dietary polyphenols are rapidly conjugated by glucuronosyltransferases and sulfotransferases, two enzymes that are abundantly present in the small intestine and liver, through which all of the oral dose must pass. Thus, most polyphenols that have been studied, e.g. quercetin, kaempferol, diosmetin, and resveratrol, would not be expected to reach internal organs beyond sites directly along the gastrointestinal tract. When the hydroxyl groups in polyphenols are methylated, the resulting compounds are much less prone to glucuronidation and sulfation. Thus methoxylated compounds are more metabolically stable, increasing their bioavailablity. The peel of various Citrus species can contain high concentrations of polymethoxyflavones, whereas the juice mainly contains hydroxylated flavones. At present, very little is known about the mechanisms by which methoxylated flavones may affect growth and development of tumour cells. Recently, it was shown that tumour specific enzymes can catalyze the O-demethylation of methoxylated flavones, resulting in the formation of flavones with free hydroxyl groups. We propose that demethylation of methoxylated flavones is another example of bioactivation of naturally occurring prodrugs.     

Flavonoids: structural requirements for antiproliferative activity on breast cancer cells

Several classes of flavonoids (flavones, flavanones, 2′-hydroxychalcones and flavan-4-ols) having a variety of substituents on A ring were investigated for their antiproliferative activity against MCF-7 human breast cancer cells. Structure–activity relationships of these compounds were discussed. 2′-hydroxychalcones and methoxylated flavanones were found to be potent inhibitors of MCF-7 cells growth whereas flavones and flavan-4-ols appeared to be weak inhibitory agents except 7,8-dihydroxyflavone.     

Identification of very-long-chain polyunsaturated fatty acids from Amphidinium carterae by atmospheric pressure chemical ionization liquid chromatography-mass spectroscopy

A method is described for the enrichment of very-long-chain polyunsaturated fatty acids (VLCPUFAs) from total fatty acids of Amphidinium carterae and their identification as picolinyl esters by means of microbore liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The combination of argentation TLC and LC-MS/APCI was used to identify unusual VLCPUFAs up to hexatriacontaoctaenoic acid. Two acids, 36:7n-6 and 36:8n-3, were also synthesized to unambiguously confirm their structure. The possibilities of VLCPUFAs biosynthesis are proposed.     

Flavonoid systematics of the genus Perideridia (Umbelliferae)

A survey of flavonoids in sixteen of the seventeen taxa in the genusPerideridia (Umbelliferae) showed the presence of thirteen glycosides of the flavonols kaempferol, quercetin, and isorhamnetin, and seven glycosides of the flavones apigenin, luteolin and chrysoeriol. An anthocyanin and four other flavonoids also occur, but remain unidentified dueto their low concentration. Several species characteristically produce speciesspecific compounds. The majority of species, however, produce flavonoids common to one or more taxa, but each taxon can be distinguished by its own specific complement of these flavonoids. Based on classes of flavonoids the genus can be divided into three groups: (1) those species which produce only flavonols; (2) those which produce mainly flavonols and a few flavones; and (3) those which produce predominantly flavones with flavonols absent or present only in trace amounts. Geographically, the flavonol-producing species are centered in California, extending northeastward to Idaho and eastward into Arizona. The flavonol/flavone producers are concentrated more towards the Pacific Northwest and eastward through the Rocky Mountains to the midwestern United States.     

Flavones and anthocyanins from the leaves and flowers of Japanese Ajuga species (Lamiaceae)

Flavones and anthocyanins were isolated from the leaves and flowers of 14 Ajuga taxa (Lamiaceae), which are all native or naturalized in Japan. Of 13 flavones obtained from the leaves, 11 were characterized as apigenin, luteolin, 6-hydroxyluteolin and acacetin glycosides. Ten flavones were isolated from the flowers. Ten anthocyanins were isolated from the flowers. Six of these anthocyanins were identified as acylated delphinidin glycosides and four were shown to be acylated cyanidin glycosides. Japanese Ajuga taxa were chemotaxonomically discussed by their distribution patterns, especially foliar flavonoids.     

Identification and characterization of major flavonoids and caffeoylquinic acids in three Compositae plants by LC/DAD-APCI/MS

In this study, a liquid chromatography/diode array detector-atmospheric pressure chemical ionization/mass spectrometry (LC/DAD-APCI/MS) was successfully developed to identify and characterize the main flavonoids and caffeoylquinic acids (CQAs) of three common Compositae plants (Chrysanthemum morifolium Raman, Artemisia annua, and Chrysanthemum coronarium) which have been used as herbal medicine. Identifications were performed by comparing the retention time, UV and mass spectra of samples with standards or/and earlier publications. The crude methanolic extracts of these plants were assayed directly using LC/MS without any further pretreatment. The proposed method is rapid and reproducible and is useful for characterization and evaluation of different plant flavonoids and CQAs. A total of 41 different flavonoids and 6 CQAs were identified and confirmed by APCI-MS. The main components of three Compositae plants were also compared. Although there exist some similarities in the flavonoidic content of the leaf and flower of C. morifolium, significant variations in their varieties and concentrations were observed. Artemisia annua processes substantial amount of alkylated derivatives of flavones and Chrysanthemum coronarium contains only CQAs. These findings suggest that although all the plants studied are from the same Compositae family, their flavonoids and phenolic compositions are markedly different. The proposed method is useful for further chromatographic fingerprinting of plant flavonoids.     

Interactions of flavonoids with iron and copper ions: a mechanism for their antioxidant activity

The metal chelating properties of flavonoids suggest that they may play a role in metal-overload diseases and in all oxidative stress conditions involving a transition metal ion. A detailed study has been made of the ability of flavonoids to chelate iron (including Fe 3+ ) and copper ions and its dependence of structure and pH. The acid medium may be important in some pathological conditions. In addition, the ability of flavonoids to reduce iron and copper ions and their activity-structure relationships were also investigated. To fulfil these objectives, flavones (apigenin, luteolin, kaempferol, quercetin, myricetin and rutin), isoflavones (daidzein and genistein), flavanones (taxifolin, naringenin and naringin) and a flavanol (catechin) were investigated. All flavonoids studied show higher reducing capacity for copper ions than for iron ions. The flavonoids with better Fe 3+ reducing activity are those with a 2,3-double bond and possessing both the catechol group in the B-ring and the 3-hydroxyl group. The copper reducing activity seems to depend largely on the number of hydroxyl groups. The chelation studies were carried out by means of ultraviolet spectroscopy and electrospray ionisation mass spectrometry. Only flavones and the flavanol catechin interact with metal ions. At pH 7.4 and pH 5.5 all flavones studied appear to chelate Cu 2+ at the same site, probably between the 5-hydroxyl and the 4-oxo groups. Myricetin and quercetin, however, at pH 7.4, appear to chelate Cu 2+ additionally at the ortho -catechol group, the chelating site for catechin with Cu 2+ at pH 7.4. Chelation studies of Fe 3+ to flavonoids were investigated only at pH 5.5. Only myricetin and quercetin interact strongly with Fe 3+ , complexation probably occurring again between the 5-hydroxyl and the 4-oxo groups. Their behaviour can be explained by their ability to reduce Fe 3+ at pH 5.5, suggesting that flavonoids reduce Fe 3+ to Fe 2+ before association.     

Interactions of Flavonoids with Iron and Copper Ions: A Mechanism for their Antioxidant Activity

The metal chelating properties of flavonoids suggest that they may play a role in metal-overload diseases and in all oxidative stress conditions involving a transition metal ion. A detailed study has been made of the ability of flavonoids to chelate iron (including Fe 3+ ) and copper ions and its dependence of structure and pH. The acid medium may be important in some pathological conditions. In addition, the ability of flavonoids to reduce iron and copper ions and their activity-structure relationships were also investigated. To fulfil these objectives, flavones (apigenin, luteolin, kaempferol, quercetin, myricetin and rutin), isoflavones (daidzein and genistein), flavanones (taxifolin, naringenin and naringin) and a flavanol (catechin) were investigated. All flavonoids studied show higher reducing capacity for copper ions than for iron ions. The flavonoids with better Fe 3+ reducing activity are those with a 2,3-double bond and possessing both the catechol group in the B-ring and the 3-hydroxyl group. The copper reducing activity seems to depend largely on the number of hydroxyl groups. The chelation studies were carried out by means of ultraviolet spectroscopy and electrospray ionisation mass spectrometry. Only flavones and the flavanol catechin interact with metal ions. At pH 7.4 and pH 5.5 all flavones studied appear to chelate Cu 2+ at the same site, probably between the 5-hydroxyl and the 4-oxo groups. Myricetin and quercetin, however, at pH 7.4, appear to chelate Cu 2+ additionally at the ortho -catechol group, the chelating site for catechin with Cu 2+ at pH 7.4. Chelation studies of Fe 3+ to flavonoids were investigated only at pH 5.5. Only myricetin and quercetin interact strongly with Fe 3+ , complexation probably occurring again between the 5-hydroxyl and the 4-oxo groups. Their behaviour can be explained by their ability to reduce Fe 3+ at pH 5.5, suggesting that flavonoids reduce Fe 3+ to Fe 2+ before association.     

Two types of O-methyltransferase are involved in biosynthesis of anticancer methoxylated 4′-deoxyflavones in Scutellaria baicalensis Georgi

The medicinal plant Scutellaria baicalensis Georgi is rich in specialized 4′-deoxyflavones, which are reported to have many health-promoting properties. We assayed Scutellaria flavones with different methoxyl groups on human cancer cell lines and found that polymethoxylated 4′-deoxyflavones, like skullcapflavone I and tenaxin I have stronger ability to induce apoptosis compared to unmethylated baicalein, showing that methoxylation enhances bioactivity as well as the physical properties of specialized flavones, while having no side-effects on healthy cells. We investigated the formation of methoxylated flavones and found that two O-methyltransferase (OMT) families are active in the roots of S. baicalensis. The Type II OMTs, SbPFOMT2 and SbPFOMT5, decorate one of two adjacent hydroxyl groups on flavones and are responsible for methylation on the C6, 8 and 3′-hydroxyl positions, to form oroxylin A, tenaxin II and chrysoeriol respectively. The Type I OMTs, SbFOMT3, SbFOMT5 and SbFOMT6 account mainly for C7-methoxylation of flavones, but SbFOMT5 can also methylate baicalein on its C5 and C6-hydroxyl positions. The dimethoxylated flavone, skullcapflavone I (found naturally in roots of S. baicalensis) can be produced in yeast by co-expressing SbPFOMT5 plus SbFOMT6 when the appropriately hydroxylated 4′-deoxyflavone substrates are supplied in the medium. Co-expression of SbPFOMT5 plus SbFOMT5 in yeast produced tenaxin I, also found in Scutellaria roots. This work showed that both type I and type II OMT enzymes are involved in biosynthesis of methoxylated flavones in S. baicalensis.     

Chemical constituents of Cardiospermum corindum L. and their distribution in Sapindaceae

Phytochemical investigation on the aerial parts of Cardiospermum corindum L. led to the isolation of two triterpenes [friedelin (1) and friedelinol (2)], two coumarins, [umbelliferone (4) and scopoletin (5)], three methoxylated flavones [umuhengerin (3), luteolin 3’,4’-dimethyl ether (6) and chrysoeriol (7)], one non-cyanogenic glucoside [epidermin (8)] and one cyclitol [(L)-quebrachitol (9)]. To our knowledge, 2, 3, 6 and 8 were isolated for the first time within Sapindaceae. Of these classes of metabolites, the distribution of methoxylated flavonoids in Cardiospermum is reviewed, including the new records, indicating that polymethoxylated flavonoid (3) may be value as chemotaxonomic markers for this genus.     

Odd-numbered very-long-chain polyunsaturated fatty acids from the dinoflagellate Amphidinium carterae identified by atmospheric pressure chemical ionization liquid chromatography-mass spectrometry

A method is described for the enrichment of odd very-long-chain polyunsaturated fatty acids (VLCPUFAs) by means of RP-HPLC and argentation TLC from total fatty acids of the dinoflagellate A. carterae and their identification as picolinyl esters by means of microbore liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The combination of argentation TLC and LC-MS/APCI was used to identify rare and unusual odd VLCPUFAs up to nonacosahexaenoic acid. Two acids, (allZ)-nonacosa-11,14,17,20,23-pentaenoic acid (29:5n-6) and (allZ)-nonacosa-11,14,17,20,23,26-hexaenoic acid (29:6n-3), were synthesized for the first time to unambiguously confirm their structure. Possible biosynthetic pathways for odd VLCPUFAs are also proposed.     

Differentiation des dihydroxy-5, 7 methoxy-6 ou 8 flavones flavonols et methyl-3 flavonols par spectrometrie de masse

5,7-Dihydroxy flavones and flavonols variously methoxylated in the 3-, 6- and/or 8-positions give characteristic fragmentation peaks. The relative abundance of M, M-1 and M-15 peaks and the presence of M-18 peak makes it possible to differentiate the 6-methoxy from the 8-methoxy isomers and three types of 6-methoxyflavones from each other.     

Comparative Metabolomics Analysis between Red- and White-Flowered Common Buckwheat Cultivars

Common buckwheat (Fagopyrum esculentum), a specialty crop in southwest China, is not only used as a supplement to primary grain crops but also to produce beverages, such as tea and wine. To fully exploit the products made from common buckwheat flower, ultra-performance liquid chromatography–electrospray ionization– tandem mass spectrometry (UPLC–ESI–MS/MS) was conducted to analyze the metabolites in red- (‘Guihong 2’) and white-flowered (‘Fengtian 1’) buckwheat cultivars. A total of 784 metabolites were identified of which flavonoids were the largest group with 191 components, followed by organic acids and derivatives (126), and amino acids and derivatives (95). Besides, dozens of phenylpropanoids, nucleotides and derivates, lipids, alkaloids as well as several kinds of indole derivatives and sterides were detected. Among these rich varieties of metabolites, 24 metabolites were only detected in the red flower that mainly included 8 anthocyanins and 6 flavones, while 22 metabolites were only detected in the white flower, which mainly contained 5 lipids, 5 flavonoids, and 5 organic acids and derivatives. Our results enrich the metabolites’ information of buckwheat and may be helpful for the exploitation of products from common buckwheat flowers.     

Distribution of flavonoids and their systematic significance in Clematis subsection Viornae

Fifteen flavonoids were identified in the eight taxa of Clematis subsection Viornae. Flavonols, flavones, and C-glycosyl flavones were present. The compounds were based primarily on luteolin, apigenin, quercetin, and kaempferol. The systematic significance of the distribution of these compounds among the taxa is discussed.     

Chemical constituents from Elytropappus rhinocerotis (L.f.) Less.

Phytochemical investigation of the ethyl acetate extract of the aerial parts of Elytropappus rhinocerotis (L.f.) Less. led to the isolation of a coumarin (1), four flavonoids (2–5), and four labdane diterpenes (6–9). The structural characterization of the isolated compounds was based on spectroscopic data. All compounds are reported for the first time from this species and from the genus Elytropappus Cass. The isolation of labdane diterpenes and methoxylated flavones is of taxonomical significance.     

Identification of astaxanthin diglucoside diesters from snow alga Chlamydomonas nivalis by liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

A method is described for the identification of astaxanthin glucoside esters from snow alga Chlamydomonas nivalis by means of liquid chromatography-mass spectrometry with atmospheric pressure chemical ionization (LC-MS/APCI). The method is based on the use of preparative HPLC and subsequent identification of astaxanthin diglucoside diesters by microbore LC-MS/APCI. The combination of these two techniques was used to identify more than 100 molecular species. The astaxanthin diglucoside diester, i.e. (all-E)-[di-(6-O-oleoyl-beta-D-glucopyranosyloxy)]-astaxanthin, was also synthesized to unambiguously confirm its structure.     

Structural requirements of flavonoids for inhibition of antigen-Induced degranulation,TNF-alpha and IL-4 production from RBL-2H3 cells

To clarify the structure-activity relationships of flavonoids for antiallergic activity, the inhibitory effects of various flavonoids on the release of beta-hexosaminidase, as a marker of degranulation of RBL-2H3 cells, were examined. Among them, luteolin (IC(50)=3.0 microM), diosmetin (2.1 microM), and fisetin (3.0 microM) were found to show potent inhibitory activity, and the results suggested the following structural requirements of flavonoids: (1) the 2-3 double bond of flavones and flavonols is essential for the activity; (2) the 3- or 7-glycoside moiety reduced the activity; (3) as the hydroxyl groups at the 3'-, 4'-, 5-, 6-, and 7-positions increased in number, the inhibitory activities become stronger; (4) the flavonols with a pyrogallol type moiety (the 3',4',5'-trihydroxyl groups) at the B ring exhibited less activity than those with a phenol type moiety (the 4'-hydroxyl group) or catechol type moiety (the 3',4'-dihydroxyl groups) at the B ring; (5) the activities of flavones were stronger than those of flavonols; and (6) methylation of flavonols at the 3-position reduced the activity. However, (7) several flavones and flavonols with the 4'- and/or 7-methoxyl groups did not obey rules (3), (4), and (5). In addition, several flavonoids, that is apigenin, luteolin, diosmetin, fisetin, and quercetin, inhibited the antigen-IgE-mediated TNF-alpha and IL-4 production from RBL-2H3 cells, both of which participate in the late phase of type I allergic reactions.