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Tumour necrosis factor-alpha (TNF), originally discovered by its antitumor activity, is one of the most pleotropic cytokines acting as a host defence factor in immunologic and inflammatory responses. Although the antitumour activity and mediation of inflammation by TNF could be beneficial to the host, unregulated TNF is now known to be the basis for development of various diseases including septic shock, the wasting disease, cachexia, and various inflammatory and/or autoimmune diseases. With an attempt to find potential therapeutic agents for TNF-mediated diseases, research during the last decade has led in the identification of well over one hundred natural inhibitors of either TNF production/secretion or function. This review summarises the structures, mechanism of action and therapeutic potential of these natural products.

Treatment of human endothelial cells with cytokines such as tumour necrosis factor-alpha (TNF) or E. coli lipopolysaccharide (LPS) induces the expression of several adhesion molecules and enhances leukocyte adhesion to endothelial cell surface. Interfering with this leukocyte adhesion or adhesion molecules upregulation is an important therapeutic target for the treatment of bacterial sepsis and various inflammatory diseases. In the course of screening marketed European anti-inflammatory herbal drugs for TNF antagonistic activity, a crude ethanolic extract of corn silk (stigma of Zea mays) exhibited significant activity. The extract at concentrations of 9-250 micrograms/ml effectively inhibited the TNF- and LPS-induced adhesiveness of EAhy 926 endothelial cells to monocytic U937 cells. Similar concentration ranges of corn silk extract did also block the TNF and LPS but not the phorbol 12-myristate 13-acetate-induced ICAM-1 expression on EAhy 926 endothelial cell surface. The extract did not alter the production of TNF by LPS-activated macrophages and failed to inhibit the cytotoxic activity of TNF. It is concluded that corn silk possesses important therapeutic potential for TNF- and LPS-mediated leukocyte adhesion and trafficking.

Cassia auriculata is a popular Asian beverage and medicinal plant widely used in traditional medicine for treating diabetes and hyperlipidemic conditions. The scientific evidence for the folklore uses of the plant have been provided in recent years but the active principles remains to be isolated and identified. In the present study, an alpha-glucosidase and pancreatic lipase enzyme inhibition studies as in vitro model of diabetes and obesity assays respectively were used. The clinically used drugs including acarbose and orlistat were used to serve as positive controls. It was found that the crude extract of C. auriculata has significant effect in both assay systems. Bioassay-guided fractionation of the crude extract resulted in the identification of kaempferol-3-O-rutinoside along with many related compounds. The activity profile (including synergism), therapeutic potential and structure-activity-relationship of the isolated compounds are discussed

An imbalance between the production of reactive oxygen species (ROS) and antioxidant defences is considered to be an important pathogenic factor for the development of a variety of disease conditions including cancer, neurodegenerative diseases, aging, diabetes and inflammation [1]. While antioxidant compounds offer some benefit in these disease conditions, multifunctional compounds acting at multiple targets of these diseases have tremendous therapeutic potential. In this communication, a case study on one ornamental and edible plant native the USA, Peltiphyllum peltatum, is presented. The leaves [2,3] and rhizomes of this plant are source of various antioxidant flavonoids (aglycones and glycosides) and gallic acid derivatives. The differenzial activity of these isolated compounds in cellular and cell free antioxidant assays together with potential neuroprotection and antidiabetic effects are discussed.

Sigmoidin A (SGN) is a prenylated flavanone derivative of eriodictyol (ERD) with reported moderate antioxidant, antimicrobial and anti-inflammatory activity. Since ERD and other structurally similar antioxidant phenolic compounds have been shown to induce prooxidative macromolecular damage and cytotoxicity in cancer cells, the comparative IN VITRO effects of these structural analogues on cancer cell viability and Cu(II)-dependent DNA damage were studied. In the presence of Cu(II) ions, both SGN and ERD (7.4-236 microM) caused comparable concentration-dependent pBR322 plasmid DNA strand scission. The DNA damage induced by SGN and ERD could be abolished by ROS scavengers, glutathione (GSH) and catalase as well as EDTA and a specific Cu(I) chelator neocuproine. Both ERD and SGN readily reduce Cu(II) to Cu(I) suggesting a prooxidative mechanism of DNA damage. In a cell free system, ERD and SGN did also show comparable radical scavenging activity. SGN was, however, by an order of magnitude more cytotoxic to cancer cells than ERD and this effect was significantly attenuated by GSH suggesting a prooxidative mechanism of cell death. A depletion of intracellular GSH level by SGN in cancer cells is also demonstrated.

Knipholone (KP) and knipholone anthrone (KA) are natural 4-phenylanthraquinone structural analogues with established differential biological effects including in vitro antioxidant [1] and antimicrobial properties [2]. The present study was designed to investigate the comparative in vitro cytotoxic activity and the possible mechanism of action of these two compounds. We demonstrated that KA is by order of magnitude more cytotoxic to mammalian cells than KP. In parallel with the demonstrated cytotoxic effect, KA but not KP induces prooxidative DNA damage in the presence of copper ions. In order to establish the possible involvement of reactive oxygen species in the KA-mediated prooxidative effect, we investigated the protective effect of several metal chelators and reactive oxygen species scavengers. Our data suggest that reactive oxygen species such as hydrogen peroxide are involved and a good correlation between prooxidative action, antioxidant effect and cytotoxicity is established for these two structural analogues. The chemistry, pharmacology and potential medicinal/toxicological potential of these compounds are discussed.

The flora of the Yucatan peninsula (Mexico) includes approximately 3000 plant species. Sideroxylon foetidissimum Jacq. subsp. gaumeri (Sapotaceae) is an endemic plant to the Yucatan peninsula; its fruit is edible and local people use the plant for medicinal purposes, although no details on its preparation or application are available [1,2]. A preliminary cytotoxic evaluation of the ethanolic root extract of S. foetidissimum revealed a potent activity against murine macrophage like cell line RAW 264.7 (IC50=39.54±4.11µg/mL). The systematic bioassay-guided fractionation of the extract resulted in the identification of the active saponin-containing fraction (IC50=33.69±6.19µg/mL). Four new triterpenoid saponins and a 1:1 mixture of two saponins were isolated from the active saponin- containing fraction. The evaluation of their cytotoxic activity revealed no activity for the tested pure saponins; however, the 1:1 mixture of saponins showed a potent activity (IC50=11.91±1.49µg/mL). The isolation of the saponins was carried out using semi-preparative HPLC. The structural assignments of the pure saponins were based on 1D (1H and 13C and DEPT-135) and 2D (COSY, HMBC, HSQC and TOCSY) NMR and mass spectrometry analyses. In this presentation, the isolation, identification and cytotoxic activity of the isolated compounds is discussed in more detail.

Epilobium parviflorum Schreb. (Onagraceae) is used for the treatment of benign prostatic hyperplasia (BPH), which is regarded as an endocrine disorder caused by age-related hormone imbalance and increased oxidative damage [1,2,3]. Epilobium can moderate the obstructive and the irritative symptoms of BPH [1] but its biological action is not entirely identified. E. parviflorum is rich in phytosterols, flavonoids (myricetin, quercetin, kaempferol and their glycosides), phenolic acids, catechins, ellagi- and gallotannins [4]. The potential biological effects of Epilobium parviflorum Schreb. have been investigated, in respect to its antioxidant, anti-inflammatory, enzyme-inhibitory and anti-androgenic effect. The whole-plant water extract showed higher antioxidant effect (IC50=1.65±0.05µg/mL) in DPPH assay than Trolox or ascorbic acid and inhibited the lipid peroxidation examined in TBA assay (IC50=2.31±0.18mg/mL). In concentrations 0.20-15.00µg/mL the extract possessed a protective effect comparable to catalase enzyme (2500 IU/mL), against oxidative damage generated on fibroblast cells. The examination of the COX-inhibitory effect showed that E. parviflorum had an anti-inflammatory effect (IC50=1.38±0.08µg/mL). Investigation of steroid receptor binding ability and the aromatase enzyme-inhibition showed negative results in the concentration range examined.

During routine screening of medicinal plants for small molecular weight inhibitors of cell adhesion, the crude ethanolic extract of the anti-rheumatic herbal drug gravel root (rhizome of Eupatorium purpureum), was identified as a potent inhibitor of some beta 1 and beta 2 integrin-mediated cell adhesions. The active principle of gravel root has now been isolated and identified as 5-acetyl-6-hydroxy-2,3-dihydro-cis-2-isopropenyl-3- tiglinoyloxybenzofuran (1). Compound 1 inhibited integrin-dependent cell-cell and cell-protein interactions in vitro with EC50 values between 7-20 micrograms/ml. As with indomethacin, 1 administered orally two hours before induction of inflammation (in rat paw) by carrageenan inhibited oedema formation in a dose (10 and 50 mg/kg)-dependent manner. It appears that 1 has therapeutic potential for diseases where integrin adhesion molecules play a significant role.

A novel diterpene, (5R, 8R, 9S, 10R)-12-oxo-ent-3,13(16)-clerodien-15-oic acid, has been obtained from the leaves of Premna schimperi (Verbenaceae) using an anti-microbial bioassay-guided isolation procedure. The diterpene was identified on the basis of spectroscopic data and is active against the Gram-positive bacteria Staphylococcus aureus and Bacillus subtilis in the concentration range 20-25 micrograms ml-1.

The cytotoxicity and immunosuppressive activities of jaborosalactone-L and three 16 alpha-oxygenated withanolides from the leaves of Discopodium penninervium were studied. Jaborosalactone-L showed cytotoxicity only to the murine macrophage cell line, RAW 264.7, but the 16 alpha-oxygenated withanolides exhibited cytotoxicity to both human (COR-L23 and ECV 304) and murine (L929 and RAW 264.7) carcinoma cell lines with IC50 values ranging from 1.2-150 microM. The non-toxic concentrations of these withanolides were also found to reduce the proliferative response of both inactive and E. coli lipopolysaccharide and concanavalin A activated rat spleen cells in vitro.

A new withanolide, 6alpha,7alpha-epoxy-5alpha,17beta-dihydroxy-1-oxowitha-2,24-dienolide, together with the known compounds withanolide A and withanone have been isolated from the roots of Discopodium penninervium. The identity of the new compound was established from spectroscopic data.

The cytotoxicity of two diterpenes from Premna schimperi and Premna oligotricha (Verbenaceae) was studied using the MTT assay. Their cytotoxic activity against three human (HeLa, SK.N.SH, and ECV 304) and two murine (L929 and RAW 264.7) carcinoma cell lines varied between 1.5 to 35 micrograms/ml and was comparable with azauridine and chlorambucil.