The flavonoids and phenolic acids of the genus Silphium and their chemosystematic value.

The current review outlines the distribution of flavonoids and phenolic acids in eleven species of Silphium (Asteraceae). The chemosystematic significance of these findings is discussed and compared with DNA and morphological-based assignments for eleven species. Special attention is given to the five flavonol triglycosides that were previously isolated and characterized from Silphium species: isorhamnetin 3-O-alpha-L-rhamnosyl (1""-->6")-O-beta-D-galactopyranoside 7-O-beta-L-apiofuranoside (1), quercetin 3-O-alpha-L-rhamnosyl (1"'-->6")-O-beta-D-galactopyranoside 7-O-beta-L-apiofuranoside (2), quercetin 3-O-beta-L-galactosyl (1"'-->6")-O-beta-D-rhamnopyranoside 7-O-alpha-L-apiofuranoside (3), kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl (1""-6"')-O-beta-D-galactopyranoside (4) and kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl (1""-->6"')-O-beta-D (2"'-O-E-caffeoylgalactopyranoside) (5). In addition, several other known mono and diglycosidic flavonoids, along with 18 phenolic acids, were also identified and the structures of all of the compounds were established by LC/MS and NMR spectral investigations.

A new kaempferol triglycoside from Fagonia taeckholmiana: cytotoxic activity of its extracts.

In addition to apigenin, apigenin 7-O-glucoside, kaempferol 3-O-glucoside, kaempferol 3,7-di-O-rhamnoside, quercetin, and quercetin 3-O-glucoside, the methanolic extract of Fagonia taeckholmiana afforded a new compound identified as kaempferol 3-O-beta-l-arabinopyranosyl-(1-->4)-alpha-l-rhamnopyranoside-7-O-alpha-l-rhamnopyranoside. Identification of the isolated compounds was based on chemical and spectroscopic analyses including UV, FABMS, (1)H, (13)C and 2D NMR, and DEPT. The cytotoxic activities of the compounds against several cancer cell lines were determined.

Triterpene saponins from Silphium radula.

Nine triterpene saponins (1-9) were isolated from leaves and stems of Silphium radula Nutt. (Asteraceae). Their structures were determined by extensive 1D ((13)C, (1)H, DEPT, TOCSY) and 2D NMR (NOESY, HSQC, HMBC) and ESI-MS studies. The compounds were identified as 3beta,6beta,16beta-trihydroxyolean-12-en-23-al-3-O-beta-glucopyranosyl-16-O-beta-glucopyranoside (1), urs-12-ene-3beta,6beta,16beta-triol-3-O-beta-galactopyranosyl-(1-->2)-beta-glucopyranoside (2), 3beta,6beta,16beta-trihydroxyolean-12-en-23-oic acid-3-O-beta-glucopyranosyl-16-O-beta-glucopyranoside (3), urs-12-ene-3beta,6beta,16beta,21beta-tetraol-3-O-beta-glucopyranoside (4), olean-12-ene-3beta,6beta,16beta,21beta-tetraol-3-O-beta-glucopyranoside (5), olean-12-ene-3beta,6beta,16beta,21beta,23-pentaol-3-O-beta-glucopyranosyl-16-O-beta-glucopyranoside (6), olean-12-ene-3beta,6beta,16beta-triol-3-O-beta-glucopyranosyl-16-O-alpha-arabinopyranosyl-(1-->2)-beta-glucopyranoside (7), olean-12-ene-3beta,6beta,16beta,23-tetraol-3-O-beta-glucopyranosyl-16-O-alpha-arabinopyranosyl-(1-->2)-beta-glucopyranoside (8), 3beta,6beta,16beta,21beta-tetrahydroxyolean-12-en-23-al-3-O-beta-glucopyranoside (9). The presence of a 6beta-hydroxyl function was not common in the oleanene or ursene class and the aglycones of these compounds were not found previously in the literature. Moreover, the cytotoxic activities of the isolated compounds were tested against human breast cancer cell line MDA-MB-231. Results showed that compound 2 decreased cell proliferation in a statistically significant manner at 25 microg/ml.

Constituents of Chrysothamnus viscidiflorus.

A phytochemical investigation of the aerial parts of Chrysothamnus viscidiflorus var. viscidiflorus afforded three new [chrysothol (1), 2 and 4] and seven known compounds, including five sesquiterpenes, two cinnamic acid derivatives, two ketoalcohol derivatives and one coumarin glucoside. The structures of two previously reported compounds, 1b and 1c, were revised on the basis of chemical reaction. Structures of the compounds were determined by extensive NMR studies, including DEPT, COSY, NOE, HMQC, HMBC and X-ray analysis. The unpublished X-ray data of the known compounds 6 and 7 are reported. Compounds chrysothol (1), and 8-10 showed anti-cancer activity against human breast cancer cells.

Sylviside, a diterpene glucoside derivative from Gnaphalium sylvaticum.

A new diterpene glucoside (1), named sylviside, was isolated from the aerial parts of Gnaphalium sylvaticum. Its structure was elucidated as 2beta,15alpha,20alpha-trihydroxy-19,20-dicarboxy-ent-kaur-16-ene 2beta-O-(2'-angelate)-beta-D-glucopyranoside, on the basis of spectroscopic analysis ((1)H NMR, (13)C NMR, HMQC, HMBC, NOESY), and was confirmed by X-ray crystallographic analysis. Sylviside (1) displayed weak cytotoxicity against HeLa WT (human epitheloid cervical carcinoma) cells and was also evaluated for its effects on reversing multidrug resistance in HeLa cells overexpressing MDR1.

New prenylflavans from Cyperus conglomeratus.

In addition to luteolin and its 7-methyl ether, the CH2Cl2-MeOH (1:1) extract of Cyperus conglomeratus afforded two new prenylflavans identified as 7,3'-dihydroxy-5,5'-dimethoxy-8-prenylflavan and 5,7,3'-trihydroxy-5'-methoxy-8-prenylflavan. The structures were established by CIMS, 1H-NMR, 13C-NMR, H-H COSY, HMQC, HMBC and DEPT analysis.

Nor-ent-kaurane diterpenes and hydroxylactones from Antennaria geyeri and Anaphalis margaritacea.

In a study of Pacific Northwest plants of the Asteraceae family, a nor-ent-kaurane diterpene and a known diterpene, both displaying antibacterial activities, were isolated together with scopoletin and sitosterol-3-O-beta-glucopyranoside from the aerial parts of Antennaria geyeri. Anaphalis margaritacea afforded two hydroxylactones. The structures were established by one and two dimensional NMR techniques, IR and CIMS.

Flavonoid effects relevant to cancer.

Flavonoids, such as daidzein and genistein, present in dietary plants like soybean, have unique chemical properties with biological activity relevant to cancer. Many flavonoids and polyphenols, including resveratrol in red wine and epigallocatechin gallate in green tea, are known antioxidants. Some of these compounds have estrogenic (and antiestrogenic) activity and are commonly referred to as phytoestrogens. A yeast-based estrogen receptor (ER) reporter assay has been used to measure the ability of flavonoids to bind to ER and activate estrogen responsive genes. Recently, estrogenic compounds were also shown to trigger rapid, nongenomic effects. The molecular mechanisms, however, have not been completely detailed and little information exists regarding their relevance to cancer progression. As a preliminary step toward elucidating rapid phytoestrogen action on breast cancer cells, we investigated the effect of 17-beta estradiol (E2), genistein, daidzein and resveratrol on the activation status of signaling proteins that regulate cell survival and invasion, the cell properties underlying breast cancer progression. The effect of these estrogenic compounds on the activation, via phosphorylation, of Akt/protein kinase B (Akt) and focal adhesion kinase (FAK) were analyzed in ER-positive and -negative human breast cancer cell lines. E2, genistein and daidzein increased whereas resveratrol decreased both Akt and FAK phosphorylation in nonmetastatic ER-positive T47D cells. In metastatic ER-negative MDA-MB-231 cells, all estrogenic compounds tested increased Akt and FAK phosphorylation. The inhibitory action of resveratrol on cell survival and proliferation is ER dependent. Therefore, all estrogenic compounds tested, including resveratrol, may exert supplementary ER-independent nongenomic effects on cell survival and migration in breast cancer cells.

The cycad neurotoxic amino acid, beta-N-methylamino-L-alanine (BMAA), elevates intracellular calcium levels in dissociated rat brain cells.

Seeds of the Guam cycad Cycas micronesica K.D. Hill (Cycadaceae), which contain ss-methylamino-L-alanine (BMAA), have been implicated in the etiology of the devastating neurodisease ALS-PDC that is found among the native Chamorros on Guam. The disease also occurs in the native populations on Irian Jaya and the Kii Peninsula of Japan, and in all three areas the cycad seeds are used either dietarily or medically. ALS-PDC is a complex of amyotrophic lateral sclerosis and parkinsonism dementia complex with additional symptoms of Alzheimer's. It is well known that Ca(2+) elevations in brain cells can lead to cell death and neurodiseases. Therefore, we evaluated the ability of the cycad toxin BMAA to elevate the intracellular calcium concentration ([Ca(2+)](i)) in dissociated newborn rat brain cells loaded with fura-2 dye. BMAA produced an increase in intracellular calcium levels in a concentration-dependent manner. The increases were dependent not only on extracellular calcium concentrations, but also significantly on the presence of bicarbonate ion. Increasing concentrations of sodium bicarbonate resulted in a potentiation of the BMAA-induced [Ca(2+)](i) elevation. The bicarbonate dependence did not result from the increased sodium concentration or alkalinization of the buffer. Our results support the hypothesis that the neurotoxicity of BMAA is due to an excitotoxic mechanism, involving elevated intracellular calcium levels and bicarbonate. Furthermore, since BMAA alone produced no increase in Ca(2+) levels, these results suggest the involvement of a product of BMAA and CO(2), namely a beta-carbamate, which has a structure similar to other excitatory amino acids (EAA) such as glutamate; thus, the causative agent for ALS-PDC on Guam and elsewhere may be the beta-carbamate of BMAA. These findings support the theory that some forms of other neurodiseases may also involve environmental toxins.

Kaempferol triosides from Silphium perfoliatum.

Two apiose-containing kaempferol triosides, together with nine known flavonoids were isolated from the leaves of Silphium perfoliatum L. Their structures were elucidated by acid hydrolysis and spectroscopic methods including UV, LSI MS, FAB MS, CI MS, (1)H, (13)C and 2D-NMR, DEPT, HMQC and HMBC experiments. The two new compounds were identified as kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl-(1""-->6"')-O-beta-D-galactopyranoside and kaempferol 3-O-beta-D-apiofuranoside 7-O-alpha-L-rhamnosyl-(1''''--> 6"')-O-beta-D (2"'-O-E-caffeoylgalactopyranoside).

A benzoquinone and flavonoids from Cyperus alopecuroides.

A benzoquinone, named alopecuquinone, was isolated from the ethanol extract of the inflorescences of Cyperus alopecuroides. Its structure was primarily elucidated by spectroscopic analysis including 1H, 13C NMR, APT, HMQC, 1H-1H COSY and CIMS. The known flavonoids, vicenin 2, orientin, diosmetin, quercetin 3,3'-dimethyl ether and its 3,4'-dimethyl ether, were also isolated and characterized. The ethanol extract of the plant material showed moderate estrogenic activity using a strain of Saccharomyces cerevisiae.

Two highly oxygenated eudesmanes and 10 lignans from Achillea holosericea.

Two new highly oxygenated eudesmanes and 10 known lignans were isolated from the aerial parts of Achillea holosericea. Their structures were elucidated by extensive application of one- and two-dimensional 1H and 13C NMR spectroscopy.

Sesquiterpene lactones of Vernonia - influence of glaucolide-A on the growth rate and survival of Lepidopterous larvae.

Sesquiterpene lactone glaucolide-A from Vernonia, incorporated in the rearing diets of five species of Lepidoptera, significantly reduced the rate of growth of larvae of the southern armyworm, Spodoptera eridania; fall armyworm, S. frugiperda; and yellowstriped armyworm, S. ornithogalli. Quantitative feeding tests demonstrated that decreased feeding levels and reduced growth resulted from ingestion of a sesquiterpene lactone. Ingestion of glaucolide-A increased the number of days to pupation in four of the species. In the southern armyworm, it significantly reduced pupal weight. Glaucolide-A decidedly reduced percentage of survival of southern and fall armyworms. Yellow woollybear, Diacrisia virginica, and cabbage looper, Trichoplusia ni, larvae were essentially uneffected by the ingestion of the sesquiterpene lactone. Sesquiterpene lactones adversely affect growth rate and survival of certain insects that feed upon plants containing them. They apparently function as defensive products, screening out a portion of the potential herbivores.