Synthesis and antiproliferative activity of epoxy and bromo compounds derived from estrone.

Based on biological properties of epoxyquinols from natural sources, bromo and epoxyquinols derived from estrone were synthesized and screened against Fem-X, HeLa and K(562) cell lines. Evidence was found that the bromine atom and the epoxy moiety significantly increase the antiproliferative activity within the series.

Labelling of breast carcinoma, thyroid carcinoma and melanoma with manno- and galacto-specific lectins from marine invertebrates.

Three marine invertebrate FITC-labelled lectins, CNL, GCL, and GSL, isolated respectively, from the sponges Chondrilla nucula, Geodia cydonium, and the hexacoral Gerardia savaglia, were used as potential diagnostic tools for different breast tumors. The lectins vary in their carbohydrate binding properties: GSL is D-mannose specific, GCL and CNL D-galactose specific. GSL labels most investigated types of malignant tissues distinctively, while the results with CNL and GCL are less consistent. The well known D-mannose specific lectin, concanavalin A, also binds to tumor tissues, but with much lower intensity than GSL.

Inhibition of human immunodeficiency virus-1 infection by human conglutinin-like protein: in vitro studies.

The lectin-like protein analogous to bovine conglutinin was purified from human serum. The carbohydrate-binding ability of conglutinin-like protein was inhibited by D-mannose, N-acetylglucosamine and L-fucose as well as by mannan-containing oligosaccharides. By applying a lectin-based ELISA system it was demonstrated that conglutinin-like protein binds to human immunodeficiency virus-1 (HIV-1) glycoprotein 120 (gp120) via its carbohydrate binding site. In vitro experiments with T-lymphoblastoid CEM cells revealed that conglutinin-like protein abolishes infection by HIV-1; a 50% cytoprotective concentration of 23.9 micrograms/ml was measured. These findings demonstrate that human conglutinin-like protein binds to HIV-gp120 and inhibits, under the described in vitro conditions, CEM cell infection.

Action of the antileukemic and anti-HTLV-III (anti-HIV) agent avarol on the levels of superoxide dismutases and glutathione peroxidase activities in L5178y mouse lymphoma cells.

The antileukemic and anti-HTLV-III (anti-HIV) agent avarol, a sesquiterpenoid hydroquinone, was determined to be converted into its corresponding quinone derivative avarone via the semiquinone free radical. Its g-value was 2.0047; after hyperfine splitting the energy levels revealed 16 isotropic Hfs. The redox reaction products were identified at the pH values 4.0, 7.0 and 12.0 and the overall reaction pathways were formulated. In vivo experiments with L5178y mouse lymphoma cells in the ascites of mice revealed that the cytostatic potencies of avarol and avarone cannot be augmented by lowering the pH value. Incubation studies with L5178y cells in vitro showed that the intracellular levels of superoxide dismutases (SODases) and of glutathione (GSH) peroxidase activities significantly change after avarol administration. While both the Mn-SODase and the Cu/Zn-SODase activities dropped significantly, the GSH peroxidase activity increased inversely. From these experiments we assume that the anti-tumour and the antiviral effects of avarol/avarone may be due to an increase, induced by the drug, of the intracellular concentrations of superoxide radicals.

Avarol-induced DNA strand breakage in vitro and in Friend erythroleukemia cells.

The hydroquinone-containing cytostatic compound avarol inhibits predominantly growth of those cell lines which have a low level of superoxide dismutase. The substrate of this enzyme, the superoxide anion, was found to be formed during the in vitro oxidation reaction of avarol to its semiquinone radical in the presence of oxygen. Under the same incubation conditions plasmid DNA (pBR322) was converted from the fully supercoiled circular form mainly to the nicked circular form, indicating that the compound causes primarily single-strand breaks. Using Friend erythroleukemia cells (FLC) it was found that avarol induces a dose-dependent DNA damage; the maximum number of DNA strand breaks was observed at 5 h after addition of the compound to the cells. Removal of avarol resulted in a rapid DNA rejoining with biphasic repair kinetics [first half-time, 8 min (90% of the breaks) and a second half-time, 40 min (10% of the breaks)]. When the degree of avarol-induced DNA damage in FLC was compared with the drug-caused inhibition of cell growth a close correlation was established. Avarol displayed no effect on dimethyl sulfoxide-induced erythrodifferentiation of FLC as determined by the benzidine reaction and by dot blot hybridization experiments. From incubation studies of FLC with [3H]avarol no hint was obtained for the formation of an adduct between DNA and the compound. The subcellular distribution of [3H]avarol was studied in liver cells after i.v. application of the compound. The predominant amount of the compound was present in the cytosolic fraction; little avarol was associated with plasma membranes, nuclei, and mitochondria. Using (a) oxidative phosphorylation and (b) oxygen uptake as parameters for mitochondria function, no effect of the compound on the activity of this organelle was determined. These results suggest that avarol forms superoxide anions (and in consequence possibly also hydroxyl radicals) especially in those cells which have low levels of superoxide dismutase. Moreover, evidence is provided that the active oxygen species cause DNA damage resulting in the observed cytotoxic effect.

Antibacterial and antifungal activity of Avarone and Avarol.

The sesquiterpenoid hydroquinone and quinone, Avarol and Avarone, were previously found to be potent antitumor agents (Müller et al., 1984). In the present study it is reported that in aqueous solution (pH 7.2), in the presence of dimethylsulfoxide, Avarol is converted to Avarone. Avarone and to a smaller extent also Avarol were active against a variety of grampositive bacterial species. The highest activity was determined for Streptococcus pneumoniae and Erysipelothrix rhusiopathiae (MIC 0.781 mg/l). The antibacterial activity can be augmented 2 to 4-fold by lowering the pH in the culture medium from 7.0 to 6.0. The efficiency of Avarone and Avarol was abolished in the presence of serum. No antibacterial activity was determined in gramnegative bacterial species. In addition, Avarol and to a smaller extent also Avarone displayed an antifungal activity on Trichophyton species and Microsporum canis (MIC: 15.6-62.5 mg/l), while Avarone and not Avarol was active on Aspergillus niger, no activity was found against Candida species. These data indicate that the antitumor agents Avarol/Avarone display also antibacterial- and antifungal activities against a limited range of microorganisms.

Potent antileukemic activity of the novel cytostatic agent avarone and its analogues in vitro and in vivo.

Avarone and avarol are novel cytostatic agents which have potent antileukemic activity both in vitro and in vivo (mice). Cell culture experiments revealed that the cytostatic activity of these two compounds on L5178Y mouse lymphoma cells was 13- to 14-fold higher than that determined for HeLa cells and 40- to 43-fold higher than that for human melanoma cells. Nontumor cells (human fibroblasts and human gingival cells) were highly resistant against the two compounds. The inhibitory potency of avarone on L5178Y cells (50% inhibitory concentration, 0.62 microM) was significantly higher than the avarol activity (50% inhibitory concentration, 0.93 microM). Modification of the molecule at the quinone ring or the double bond in the terpenoid skeleton resulted in a significant loss of activity. In vivo studies with L5178Y cells in the ascites of mice confirmed the strong antileukemic effect determined in vitro. At doses of 10 mg/kg given i.p. once daily for 5 days to mice bearing approximately 10(8) leukemia cells, avarone was found to be curative in about 70% of the mice (20% for avarol). The optimal daily i.p. dose of avarone increased life span over controls by 146% when treatment was begun 1 day after tumor implantation and by 87% when treatment was delayed until day 8. Avarol, although active, was less effective. Based on the determined log10 kill values, avarone can be classified as a highly active and avarol as a markedly active cytostatic agent. The efficacy of the two compounds is also emphasized by the therapeutic index of 11.7 for avarone and of 4.5 for avarol. The two agents were determined not to be either direct mutagens or premutagens in the Ames test.

Antimutagenic activity of the novel antileukemic agents, avarone and avarol.

The two antileukemic agents, avarone and avarol, were determined to be neither direct nor indirect mutagenic agents in the Ames microsomal test. Moreover, the two sesquiterpenoid compounds drastically reduced the mutagenic effect of benzo[a]pyrene in the same system. Subsequent enzymic studies demonstrated that avarone and avarol are powerful inhibitors of benzo[a]pyrene monooxygenase.

Avarol, a cytostatically active compound from the marine sponge Dysidea avara.

A main metabolic product of the sponge Dysidea avara was isolated and purified and subsequently identified as avarol by applying a series of analytical techniques, e.g. [13C]NMR, [1H]NMR and i.r. spectroscopy. This sesquiterpenoid hydroquinone was found to possess strong cytostatic activity. Using the L5178y mouse lymphoma cell system in vitro (roller tube assays) avarol reduced cell growth to 50% at a concentration of 0.9 microM. Avarol treated cells did not show "unbalanced growth". Avarol interfered with mitotic processes, preventing telophase formation. Incorporation studies with precursors for DNA, RNA, protein and glycoprotein syntheses revealed increased incorporation rates in response to avarol treatment. From these results and further autoradiographical experiments it is suggested that inhibition of cell growth is due to changes of the intracellular pools and/or alterations of the permeability properties of the cell membrane for the precursors. Avarol diacetate caused the same cytostatic effect as avarol.

Inhibition of mitosis by avarol, a natural product isolated from the sponge Dysidea avara.

Avarol, a sesquiterpenoid hydroquinone, is a cytostatic agent, isolated from the sponge Dysidea avara. Autoradiographic studies show that in vivo (L5178y mouse lymphoma cells) avarol changes the labelling index in favour of the fraction of unlabelled cells (from 1.24 to 1.04). At concentrations below the 50% inhibition dose, the mitotic index increases from 6.5 +/- 0.5 to 10.4 +/- 0.8; at higher concentrations the formation of mitotic figures is almost completely suppressed. In vitro studies applying the methods of viscosimetry and electron microscopy demonstrate that avarol inhibits assembly of brain microtubule protein at an at least stoichiometric concentration ratio. Moreover, evidence is presented that the new antimitotic agent avarol inhibits protofilament elongation rather than lateral association of tubulin during protofilament formation. The results suggest that avarol interferes with polymerization of tubulin both in interphase and during mitosis.