Inhibition of Mycobacterium tuberculosis growth by saringosterol from Lessonia nigrescens.

Assay-guided fractionation of an antitubercular extract obtained from Lessonia nigrescens yielded the phytosterol saringosterol as its active component. No appreciable toxicity against Vero cells was observed for this compound. Saringosterol was also synthesized by oxidation of fucosterol. The MIC values for antitubercular activity of saringosterol and its 24S and 24R epimers were determined as 0.25, 1, and 0.125 microg/mL.

Triterpenoid saponins from Acacia victoriae (Bentham) decrease tumor cell proliferation and induce apoptosis.

This report describes the isolation and partial purification of novel triterpenoid saponins [Fraction 35 (F035)] and two pure biologically active derivatives (termed avicins D and G) from Acacia victoriae, an Australian desert tree of the Leguminosae family. F035 and the avicins markedly inhibited the growth of several tumor cell lines with minimum growth inhibition in human foreskin fibroblasts, mouse fibroblasts, and immortalized breast epithelial cells at similar concentrations. F035 and the avicins induced cell cycle (G1) arrest of the human MDA-MB-453 breast cancer cell line and apoptosis of the Jurkat (T-cell leukemia) and the MDA-MB-435 breast cancer cell line. The triterpenoid saponins also partially inhibited phosphatidylinositol 3-kinase activity in Jurkat T cells in a time-dependent manner and phosphorylation in the downstream protein Akt, whereas no affect was seen on the Ras/mitogen-activated protein kinase cascade. These observations as well as other work from our laboratory demonstrating mitochondrial perturbation, chemoprevention, and inhibition of nuclear factor kappaB suggest that triterpenoid saponins from A. victoriae have potential as novel anticancer agents. Recent work linking Akt signaling with glucose metabolism, stress resistance, and longevity suggests other potential applications of these compounds.

Antitubercular activity of triterpenoids from Lippia turbinata.

Assay-guided fractionation of the antitubercular MeOH-CH(2)Cl(2) extract obtained from Lippia turbinata led to the isolation of four novel triterpenoids-3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-(3-methylbut-2-en-1-oyloxy)olean-12-ene-28-oic acid (1); 3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-angeloyloxyolean-12-ene-28-oic acid (2); 3beta,25-epoxy-3alpha,21alpha-dihydroxy-22beta-tigloyloxyolean-12-ene-28-oic acid (3); and 3beta,25-epoxy-3alpha-hydroxy-22beta-(2-methylbutan-1-oyloxy)olean-12-ene-28-oic acid (4)-together with the known triterpenoids lantanilic acid (5), camaric acid (6), lantanolic acid (7), and rehmannic acid (8). The MIC values of 1-8 for growth inhibition of Mycobacterium tuberculosis were determined in the radiorespirometric BACTEC system.

Two novel flavanones from Greigia sphacelata.

As part of our continuing phytochemical investigations of plants from arid environments in Chile, the aerial parts of Greigia sphacelata were examined. Two novel flavanones, 5,7,3'-trihydroxy-6, 4',5'-trimethoxyflavanone (1) and 5,3'-dihydroxy-6,7,4', 5'-tetramethoxyflavanone (2), as well as eight known compounds-1, 3-O-di-trans-p-coumaroylglycerol (3), 1-O-trans-p-coumaroylglycerol (4), a mixture of 1-(omega-feruloyldocosanoyl)glycerol (5) and 1-(omega-feruloyltetracosanoyl)glycerol (6), trans-ferulic acid 22-hydroxydocosanoic acid ester (7), arborinone (8), arborinol (9), and isoarborinol (10)-were isolated.

Antibacterial diterpenoid acids from Azorella compacta.

The two novel diterpenoid acids mulin-12,14-dien-11-on-20-oic acid (1) and mulin-12-ene-11,14-dion-20-oic acid (2) have been isolated from Azorella compacta. Their structures have been elucidated by 1D and 2D NMR methods. In contrast to the closely related known mulinolic acid (3) and its dehydration product (4) these new natural products have been shown to exhibit antimicrobial activity.

Diterpenoids from Baccharis pingraea.

From the aerial parts of Baccharis pingraea the known furolabdane, angeloyl-gutierrezianolic acid (1); two novel diterpenoids, furolabda-6,8-dien-17-oic acid (2) and furolabd-7-en-17-oic acid (3); and the known linear diterpenoid, (10E)-centipedic acid (4), were isolated. LC/MS suggested the presence of gutierrezianolic acid (5). The structures of the new compounds were elucidated by 1D and 2D NMR methods.

Antitubercular activity of pentacyclic triterpenoids from plants of Argentina and Chile.

Screening of plants from South America for antitubercular activity and subsequent assay-guided fractionation resulted in the isolation and characterization of several pentacyclic triterpenoids. The MIC values of 22 triterpenoids were determined using the radiorespiratory BACTEC assay and range from 8 microM to above 128 microM. The structure-activity relationships are discussed.

Antibacterial and antifungal flavanones from Eysenhardtia texana.

An activity-guided fractionation of a methanol-dichloromethane extract obtained from the aerial parts of Eysenhardtia texana led to the isolation of two novel antibacterial and antifungal flavanones together with a known flavanone. Their structures were established as 4',5,7-trihydroxy-8-methyl-6-(3-methyl-[2-butenyl])-(2S)-flavanone, 4',5,7-trihydroxy-6-methyl-8-(3-methyl-[2-butenyl])-(2S)-flavanone and 4',5-dihydroxy-7-methoxy-6-(3-methyl-[2-butenyl])-(2S)-flavanone on the basis of their UV, 1D and 2D-NMR spectra.

Flavonoids and terpenoids from Luma gayana (Barn.) Burret.

The flavonoids 5-hydroxy-7-methoxyflavanone, 6,8-dimethyl-5,7-dihydroxyflavanone and 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone, a mixture of alkyl esters of p-coumaric acid, the triterpenoids oleanolic acid and maslinic acid, the monoterpenoid 1 alpha,2 beta,4 beta-trihydroxy-p-menthane, the sesquiterpenoid clovandiol and beta-sitosterol were isolated from the aerial parts of Luma gayana (Barn.) Burret. This is the first report on the chemistry of this species.

A new antitubercular mulinane diterpenoid from Azorella madreporica Clos.

Bioactivity-guided fractionation of the petroleum ether extract of Azorella madreporica Clos has led to the isolation of the novel, antitubercular mulinane diterpenoid 1. The structure has been elucidated on the basis of its 1D and 2D NMR spectra and by comparison with mulinolic acid 2 and a dehydration product 3 obtained from 1. The MIC of 1 for growth inhibition of the H37Rv strain of Mycobacterium tuberculosis was determined as 20 microg/mL. LC-MS and NMR have suggested the presence of this new compound in four other species of Azorella.

Antimycobacterial activity of substituted isosteres of pyridine- and pyrazinecarboxylic acids.

Pyrazines and pyridines substituted with alkylated tetrazoles, esterified vinylogous carboxylic acids, and ketosulfides were synthesized as precursors of antimycobacterial agents which, after penetration of the mycobacterial cell wall, could be biotransformed by esterases or peroxidase-catalases. The expected products are tetrazoles, a vinylogous carboxylic acid, and CH-acidic ketosulfoxides, isosteres of pyrazinoic and nicotinic acids, which should inhibit mycobacterial growth when released inside the bacterial cell. The growth inhibitory activity of the synthesized compounds against the H37Rv strain of Mycobacterium tuberculosis was determined to assess the viability of this concept. It was shown that all of the compounds designed as lipophilic precursors were more active than the unmodified polar isosteres of pyrazinoic and nicotinic acids.

Triterpenoids from Acaena pinnatifida R. et P.

Eight urs-12-ene triterpenoids, beta-sitosterol, (+)-catechin, and apigenin 7-O-glucoside were isolated from the leaves of Acaena pinnatifida R. et P. The triterpenoids were characterized as pomolic acid, pomolic acid-3-acetate, tormentic acid, 2-epi-tormentic acid, euscaphic acid, tormentic acid glucoside, niga-ichigoside F1, and niga-ichigoside F2.

Inhibitory effect of six green tea catechins and caffeine on the growth of four selected human tumor cell lines.

Green tea is an aqueous infusion of dried unfermented leaves of Camellia sinensis (family Theaceae) from which numerous biological activities have been reported including antimutagenic, antibacterial, hypocholesterolemic, antioxidant, antitumor and cancer preventive activities. From the aqueous-alcoholic extract of green tea leaves, six compounds (+)-gallocatechin (GC), (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), (-)-epigallocatechin gallate (EGCG) and caffeine, were isolated and purified. Together with (+)-catechin, these compounds were tested against each of four human tumor cells lines (MCF-7 breast carcinoma, HT-29 colon carcinoma, A-427 lung carcinoma and UACC-375 melanoma). The three most potent green tea components against all four tumor cell lines were EGCG, GC and EGC. EGCG was the most potent of the seven green tea components against three out of the four cell lines (i.e. MCF-7 breast cancer, HT-29 colon cancer and UACC-375 melanoma). On the basis of these extensive in vitro studies, it would be of considerable interest to evaluate all three of these components in comparative preclinical in vivo animal tumor model systems before final decisions are made concerning which of these potential chemopreventive drugs should be taken into broad clinical trials.

Synthesis and evaluation of azole-substituted tetrahydronaphthalenes as inhibitors of P450 arom, P450 17, and P450 TxA2.

In search of potential drugs for the treatment of estrogen- and androgen-dependent cancer as well as the prophylaxis of metastases, tetralones, tetralins, and dihydronaphthalenes bearing a OCH3 substituent at the benzene nucleus and an imidazol-4-yl, imidazol-1-yl, or 1,2,4-triazol-1-yl substituent in 2-position were synthesized with and without C1-spacer between the rings (compounds 2-26). The compounds were tested in vitro for inhibition of the three targets enzymes P450 arom (human placental microsomes), P450 17 (rat testicular microsomes), and P450 TxA2 (citrated human whole blood). To examine selectivity, some compounds were further tested in vitro for inhibition P450 18 (bovine adrenal mitochondria), P450 scc (bovine adrenal mitochondria) and corticoid formation (aldosterone, corticosterone; ACTH stimulated rat adrenal tissue). In vitro, selected compounds were examined in Sprague Dawley rats regarding P450 TxA2 inhibition, reduction of plasma testosterone concentration, antiuterotrophic activity (inhibition of the uterotrophic activity of androstenedione), reduction of plasma estradiol concentration (pregnant mares' serum gonadotropin-primed rats), and mammary tumor inhibiting activity (dimethylbenzanthracene-induced tumor; pre-and postmenopausal model). In the series of imidazol-4-yl compounds, which represent a novelty in the field of azole inhibitors of steroidogenic P450 enzymes, strong inhibitors of P450 arom and/or P450 17 were found; 7-OCH3-2-(imidazol-4-ylmethylene)-1-tetralone (4) and 7-OCH3-2-(imidazol-4-ylmethyl)-tetralin (12) are among the most potent inhibitors of P450 arom in vitro known so far. Compound 4 is a selective inhibitor, whereas 12 shows in addition strong inhibition of P450 17. In contrast to 12, the 6-OCH3 derivative (compound 11) is a selective inhibitor of P450 17, being 50 times more potent than ketoconazole. Some imidazol-1-yl compounds show a marked inhibition of P450 TxA2: 2-(imidazol-1-ylmethyl)-1-tetralone (13) is a selective inhibitor of P450 TxA2, whereas 7-OCH3-2-(imidazol-1-ylmethyl)-tetralin (17) as well 2-(imidazol-1-ylmethyl)-tetralin (16) and 7-OCH3-2-imidazol-1-yl-3, 4-dihydronaphthalene (25) additionally show strong inhibition of P450 arom and P450 17. Regarding the other steroidogenic P450 enzymes as well as corticosterone formation, the compounds show only little inhibitory activity. Aldosterone formation, however, is inhibited at low concentrations. Nevertheless, 4 and 12 are more selective, i.e. inhibit aldosterone synthesis less than the well known inhibitor of P450 arom fadrozole. The compounds show activity in the aforementioned in vivo tests.

Tetrahydronaphthalenes: influence of heterocyclic substituents on inhibition of steroid enzymes P450 arom and P450 17.

In search of new leads for selective inhibition of estrogen and androgen biosynthesis, respectively, heterocyclic substituted 2-(arylmethylene)-1-tetralones (1-4, 9-17), 2-(aryl-hydroxymethyl)-1-tetralones (5-8), exo-1a,2,3,7b-tetrahydro-1H-cyclopropa[alpha] naphthalenes (18-24), and 3-alkyl substituted 4,5-dihydronaphtho[1,2-c]pyrazoles (25-27) were synthesized and tested for inhibitory activity toward four steroidogenic enzymes (P450 arom, P450 17, P450 18, and P450 scc, as well as another P450 enzyme, thromboxane A(2) (TXA(2)) synthase. The test compounds inhibited human placental P450 arom, showing a wide range of inhibitory potencies. (Z)-4-Imidazolyl compound 17 was the most potent inhibitor, with a relative potency (rp) of 110 [rp of aminoglutethimide (AG) = 1), rp of fadrozole = 359]. A competitive type of inhibition was shown by the (E)-4-imidazolyl compound 16(rp = 71). On the other hand some of these compounds inhibited rat testicular P450 17. Maximum activity was shown by the 3-pyridyl compound 20 (rp = 10, ro of ketoconazole = 1). 20 was the only compound which exhibited a marked inhibition of TXA(2) synthase (IC(50) = 14.5 microM; IC(50) of dazoxiben = 1.1 microM). Regarding selectivity toward the steroidogenic enzymes, compound 16 was relatively selective toward P450 arom, whereas compound 20 was relatively selective toward P450 17. (P450 arom: K(m) testosterone = 42 nM, K(i)16 = 33 nM, K(i)20 = 3 microM. P450 17: K(m)progesterone = 7 microM, K(i)16 = 9 microM, K(i)20 = 80 nM). 17 and 24 were not selective since they showed strong inhibition of P450 arom (K(i)17 = 26 nM, K(i)24 = 0.12 microM) and P450 17 (K(i) 17 = 0.7 microM, K(i)24 = 0.11 microM).

Prevention of photocarcinogenesis by topical administration of pure epigallocatechin gallate isolated from green tea.

Topical application of purified (-)-epigallocatechin-3-gallate (EGCG), a polyphenolic antioxidant isolated from green tea, inhibited photocarcinogenesis in BALB/cAnNHsd mice with no visible toxicity. Mice were treated with 0, 10, or 50 mg of EGCG in 200 microliters of acetone three times weekly for three weeks before ultraviolet (UV) treatments began and throughout the experiment. UV radiation consisted of five 30-minute exposures per week to banks of six FS40 Westinghouse sunlamps for 25 weeks. In the photocarcinogenesis study, mice received a total dose of approximately 2.1 x 10(6) J/m2. Skin cancer incidence in UV-irradiated mice was 96% at 28 weeks after the first UV treatment; EGCG at 10 or 50 mg reduced this incidence to 62% and 29%, respectively. UV-induced immunosuppression, assessed by the inability of UVB-irradiated mice to reject a syngeneic antigenic tumor, was not influenced by topical EGCG. Oral administration of 0, 100, or 500 mg of pure EGCG per liter of drinking water (approximately 0, 0.56, or 2.8 mg/day, respectively) did not decrease UV-induced skin tumor incidence, rate of primary tumor growth, or inability to reject antigenic tumors. Thus induction of skin tumors by UV radiation was significantly reduced by topical, but not by oral, administration of purified EGCG through a mechanism distinct from inhibition of photoimmunosuppression.