A New Rare Halogenated Depside from Lichen and Study of its Anti-Proliferative Activity

Lichens are a symbiotic association of algae and fungus, belonging to the family Parmeliaceae. Some lichen species are edible and used as an active ingredient for preparation of exotic spices as well as folklore medicine to cure different kinds of ailments. A specimen of lichen was collected from Munner in the Kerala State of South India for chemical profiling. Chemical analyses of the diethyl ether extract of the defatted lichen led to the isolation of six phenols 1-6 with variation of relative abundance. Amongst them, the relative abundance of compound 3 was the greatest (1 % of crude extract) and it was identified as atranorin. The structures of known compounds were confirmed by comparison of their 1H-NMR, 13C NMR, and mass data with published values available in the literature. In vitro bioassay for anti-proliferative activity of these compounds has been conducted against various human cancer cell lines in comparison with paclitaxel as control using SRB assay. Interestingly, a new compound 5 was found along with previously reported compounds from this lichen. This new compound was designated as fluoroatranorin 5 which was reported for the first time herein. The structural characterization of a new depside was determined by spectral methods such as 1H-NMR, 13C NMR, 19F NMR, IR, LC-HRESI-MS, and LC-MS/MS study. Its structure was confirmed by single crystal X-ray diffraction study. This new compound was designated as fluoroatranorin 5 which was reported first time herein. Anti-proliferative activity of all these compounds was evaluated against six different cancer cell lines. The inhibitory activity, IC50 value of compounds 1-3 and 5 exhibited at 99.64, 102.04, 109.20, 53.0 and 2.4 μM on cancer cell lines HT-29 (colon), Hela (cervical), HT-29, HPAC (pancreas) and A2780 (ovarian cancer cell line) respectively in comparison with paclitaxel as control. The new compound 5 exhibited significant activity with IC50 value 2.4 μM on A2780 ovarian cancer cell line.

Strategies for the discovery of potential anticancer agents from plants collected from Southeast Asian tropical rainforests as a case study

Covering up to early 2023The present review summarizes recent accomplishments made as part of a multidisciplinary, multi-institutional anticancer drug discovery project, wherein samples comprising higher plants were collected primarily from Southeast Asia, and also from Central America, and the West Indies. In the introductory paragraphs, a short perspective is provided on the current importance of plants in the discovery of cancer therapeutic agents, and the contributions of other groups working towards this objective are mentioned. For our own investigations, following their collection, tropical plants have been subjected to solvent extraction and biological evaluation for their antitumor potential. Several examples of purified plant lead bioactive compounds were obtained and characterized, and found to exhibit diverse structures, including those of the alkaloid, cardiac glycoside, coumarin, cucurbitacin, cyclobenzofuran (rocaglate), flavonoid, lignan, and terpenoid types. In order to maximize the efficiency of work on drug discovery from tropical plant species, strategies to optimize various research components have been developed, including those for the plant collections and taxonomic identification, in accordance with the requirements of contemporary international treaties and with a focus on species conservation. A major component of this aspect of the work is the development of collaborative research agreements with representatives of the source countries of tropical rainforest plants. The phytochemical aspects have included the preparation of plant extracts for initial screening and the selection of promising extracts for activity-guided fractionation. In an attempt to facilitate this process, a TOCSY-based NMR procedure has been applied for the determination of bioactive rocaglate derivatives in samples of Aglaia species (Meliaceae) collected for the project. Preliminary in vitro and in vivo mechanistic studies carried out by the authors are described for two tropical plant-derived bioactive lead compounds, corchorusoside C and (+)-betulin, including work conducted with a zebrafish (Danio rerio) model. In the concluding remarks, a number of lessons are summarized that our group has learned as a result of working on anticancer drug discovery using tropical plants, which we hope will be of interest to future workers.

Phytochemical Profiles and Biological Studies of Selected Botanical Dietary Supplements Used in the United States

Based on their current wide bioavailability, botanical dietary supplements have become an important component of the United States healthcare system, although most of these products have limited scientific evidence for their use. The most recent American Botanical Council Market Report estimated for 2020 a 17.3% increase in sales of these products when compared to 2019, for a total sales volume of $11,261 billion. The use of botanical dietary supplements products in the United States is guided by the Dietary Supplement Health and Education Act (DSHEA) from 1994, enacted by the U.S. Congress with the aim of providing more information to consumers and to facilitate access to a larger number of botanical dietary supplements available on the market than previously. Botanical dietary supplements may be formulated for and use only using crude plant samples (e.g., plant parts such as the bark, leaves, or roots) that can be processed by grinding into a dried powder. Plant parts can also be extracted with hot water to form an "herbal tea." Other preparations of botanical dietary supplements include capsules, essential oils, gummies, powders, tablets, and tinctures. Overall, botanical dietary supplements contain bioactive secondary metabolites with diverse chemotypes that typically are found at low concentration levels. These bioactive constituents usually occur in combination with inactive molecules that may induce synergy and potentiation of the effects observed when botanical dietary supplements are taken in their different forms. Most of the botanical dietary supplements available on the U.S. market have been used previously as herbal remedies or as part of traditional medicine systems from around the world. Their prior use in these systems also provides a certain level of assurance in regard to lower toxicity levels. This chapter will focus on the importance and diversity of the chemical features of bioactive secondary metabolites found in botanical dietary supplements that are responsible for their applications. Many of the active principles of botanical dietary substances are phenolics and isoprenoids, but glycosides and some alkaloids are also present. Biological studies on the active constituents of selected botanical dietary supplements will be discussed. Thus, the present chapter should be of interest for both members of the natural products scientific community, who may be performing development studies of the products available, as well as for healthcare professionals who are directly involved in the analysis of botanical interactions and evaluation of the suitability of botanical dietary supplements for human consumption.

Effects of Corchorusoside C on NF-κB and PARP-1 Molecular Targets and Toxicity Profile in Zebrafish

The present study aims to continue the study of corchorusoside C (1), a cardenolide isolated from Streptocaulon juventas, as a potential anticancer agent. A mechanistic study was pursued in a zebrafish model and in DU-145 prostate cancer cells to investigate the selectivity of 1 towards NF-κB and PARP-1 pathway elements. Compound 1 was found to inhibit the expression of IKKα and NF-κB p65 in TNF-α induced zebrafish and inhibit the expression of NIK in vitro. The protein expression levels of XRCC-1 were increased and p53 decreased in DU-145 cells. XIAP protein expression was initially decreased after treatment with 1, followed by an increase in expression at doses higher than the IC₅₀ value. The activity of caspase-1 and the protein expression levels of IL-18 were both decreased following treatment of 1. The binding interactions for 1 to NIK, XRCC-1, p53, XIAP, and caspase-1 proteins were explored in molecular docking studies. Additionally, the toxicity profile of 1 in zebrafish was favorable in comparison to its analog digoxin and other anticancer drugs at the same MTD in zebrafish. Overall, 1 targets the noncanconical NF-κB pathway in vivo and in vitro, and is well tolerated in zebrafish supporting its potential in the treatment of prostate cancer.

Spermidine alkaloid and glycosidic constituents of Vietnamese Homalium cochinchinensis

Phytochemical investigation of the aerial parts of Homalium cochinchinensis led to the isolation of secondary metabolites belonging to the spermidine alkaloid, glycoside, depsidone and phenol classes. Of the eleven secondary metabolites isolated in this study, two spermidine alkaloids, dovyalicins H (1) and I (2), which belong to a rare group among this class, and six glycosides (3-8) are previously undescribed. The structures of all new isolates were determined by interpretation of spectroscopic and spectrometric data. In this report, the structural elucidation of these unprecedented secondary metabolites (1-8) is described.

Structurally Modified Cyclopenta[b]benzofuran Analogues Isolated from Aglaia perviridis

Four new cyclopenta[b]benzofuran derivatives based on an unprecedented carbon skeleton (1-4), with a dihydrofuran ring fused to dioxanyl and aryl rings, along with a new structural analogue (5) of 5‴-episilvestrol (episilvestrol, 7), were isolated from an aqueous extract of a large-scale re-collection of the roots of Aglaia perviridis collected in Vietnam. Compound 5 demonstrated mutarotation in solution due to the presence of a hydroxy group at C-2‴, leading to the isolation of a racemic mixture, despite being purified on a chiral-phase HPLC column. Silvestrol (6) and episilvestrol (7) were isolated from the most potently cytotoxic chloroform subfraction of the roots. All new structures were elucidated using 1D and 2D NMR, HRESIMS, IR, UV, and ECD spectroscopic data. Of the five newly isolated compounds, only compound 5 exhibited cytotoxic activity against a human colon cancer (HT-29) and human prostate cancer cell line (PC-3), with IC₅₀ values of 2.3 μM in both cases. The isolated compounds (1-5) double the number of dioxanyl ring-containing rocaglate analogues reported to date from Aglaia species and present additional information on the structural requirements for cancer cell line cytotoxicity within this compound class.

α-Pyrone and Sterol Constituents of Penicillium aurantiacobrunneum, a Fungal Associate of the Lichen Niebla homalea

Four new metabolites, 4-epi-citreoviridin (1), auransterol (3), and two analogues (2 and 4) of paxisterol (6), together with two known metabolites (15R*,20S*)-dihydroxyepisterol (5) and (6), were isolated from cultures of the fungal associate, Penicillium aurantiacobrunneum, of the lichen Niebla homalea, endemic to California and Baja California. The structures of all compounds were determined by comprehensive spectroscopic and spectrometric methods, as well as single-crystal X-ray diffraction for the determination of the absolute configuration of 3. Compound 1 showed selective cytotoxicity toward MCF-7 breast and A2780 ovarian cells with IC₅₀ values of 4.2 and 5.7 μM, respectively.

Caspase-Dependent Apoptosis in Prostate Cancer Cells and Zebrafish by Corchorusoside C from Streptocaulon juventas

Corchorusoside C (1), isolated from Streptocaulon juventas collected in Vietnam, was found to be nontoxic in a zebrafish ( Danio rerio) model and to induce cytotoxicity in several cancer cell lines with notable selective activity against prostate DU-145 cancer cells (IC₅₀ 0.08 μM). Moreover, corchorusoside C induced DU-145 cell shrinkage and cell detachment. In CCD-112CoN colon normal cells, 1 showed significantly reduced cytotoxic activity (IC₅₀ 2.3 μM). A preliminary mechanistic study indicated that 1 inhibits activity and protein expression of NF-κB (p50 and p65), IKK (α and β), and ICAM-1 in DU-145 cells. ROS concentrations increased at 5 h post-treatment, and MTP decreased in a dose-dependent manner. Moreover, decreased protein expression of Bcl-2 and increased expression of PARP-1 was observed. Furthermore, corchorusoside C increased both the activity and protein levels of caspases 3 and 7. Additionally, 1 induced sub-G1 population increase of DU-145 cells and modulated caspases in zebrafish with nondifferential morphological effects. Therefore, corchorusoside C (1) induces apoptosis in DU-145 cells and targets the same pathways both in vitro and in vivo in zebrafish. Thus, the use of zebrafish assays seems worthy of wider application than is currently employed for the evaluation of potential anticancer agents of natural origin.

Potential Anticancer Agents Characterized from Selected Tropical Plants

Higher plants are well known for their value in affording clinically useful anticancer agents, with such compounds acting against cancer cells by a range of mechanisms of action. There remains a strong interest in the discovery and development of plant secondary metabolites as additional cancer chemotherapeutic lead compounds. In the present review, progress on the discovery of plant-derived compounds of the biflavonoid, lignan, sesquiterpene, steroid, and xanthone structural types is presented. Several potential anticancer leads of these types have been characterized from tropical plants collected in three countries as part of our ongoing collaborative multi-institutional project. Preliminary structure-activity relationships and work on in vivo testing and cellular mechanisms of action are also discussed. In addition, the relevant work reported by other groups on the same compound classes is included herein.

Anticancer and antibacterial potential of Rhus punjabensis and CuO nanoparticles

The present study reports ecofriendly synthesis of CuO nanoparticles (NPs) using an extract of Rhus punjabensis as a reducing agent. NPs structural and composition analysis are evaluated by X-rays diffraction (XRD), Fourier transform infrared, Energy dispersive spectroscopy, Scanning electron microscopy, Transmission electron microscopy, and Thermal analysis. The NPs have pure single phase monoclinic geometry with spherical structure and high stability toward heat and with average particle size of about 36.6 and 31.27 nm calculated by XRD and SEM, respectively. NPs are tested for antibacterial, protein kinase (PK) inhibition, SRB cytotoxic, and NF-κB activities. Antibacterial activity is observed against B. subtilis and E. coli. Significant PK and SRB cytotoxic activity is observed with some NF-κB inhibition. NPs IC₅₀ values against HL-60 and PC-3 prostate cancer cells are 1.82 ± 1.22 and 19.25 ± 1.55 μg/mL. The results encourage further studies for antibacterial and anticancer drug development of NPs using animal models.

Cytotoxic and NF-κB and mitochondrial transmembrane potential inhibitory pentacyclic triterpenoids from Syzygium corticosum and their semi-synthetic derivatives

Syzygium is a large genus of flowering plants, with several species, including the clove tree, used as important resources in the food and pharmaceutical industries. In our continuing search for anticancer agents from higher plants, a chloroform extract of the leaves and twigs of Syzygium corticosum collected in Vietnam was found to be active toward the HT-29 human colon cancer cell line. Separation of this extract guided by HT-29 cells and nuclear factor-kappa B (NF-κB) inhibition yielded 19 known natural products, including seven triterpenoids, three ellagic acid derivatives, two methylated flavonoids, a cyclohexanone, four megastigmanes, a small lactone, and an aromatic aldehyde. The full stereochemistry of (+)-fouquierol (2) was defined for the first time. Biological investigations showed that (+)-ursolic acid (1) is the major cytotoxic component of S. corticosum, which exhibited also potent activities in the NF-κB and mitochondrial transmembrane potential (MTP) inhibition assays conducted, with IC50 values of 31 nM and 3.5 µM, respectively. Several analogues of (+)-ursolic acid (1) were synthesized, and a preliminary structure-activity relationship (SAR) study indicated that the C-3 hydroxy and C-28 carboxylic acid groups and 19,20-dimethyl substitution are all essential in the mediation of the bioactivities observed for this triterpenoid.

Isolation of Bioactive Rotenoids and Isoflavonoids from the Fruits of Millettia caerulea

Three new rotenoids (1-3), two new isoflavonoids (4 and 5), and six known analogues (6-11) were isolated from an n-hexane partition of a methanol extract of the fruits of Millettia caerulea, with the structures of the new compounds elucidated by analysis of their spectroscopic data. The relative configurations of the rotenoids were determined by interpretation of their NMR spectroscopic data, and their absolute configurations were established using electronic circular dichroism spectra and specific rotation values. All compounds isolated were evaluated for their cell growth inhibitory activity against the HT-29 human colon cancer cell line, and the known compounds, (-)-3-hydroxyrotenone (6) and (-)-rotenone (7), were found to be potently active. When tested in an NF-κB inhibition assay, compound 6 showed activity. This compound, along with the new compound, (-)-caeruleanone D (1), and the known compound, ichthynone (8), exhibited K-Ras inhibitory potency. Further bioactivity studies showed that the new compounds, (-)-3-deoxycaeruleanone D (2) and (-)-3-hydroxycaeruleanone A (3), and the known compounds 8 and 11 induced quinone reductase in murine Hepa 1c1c7 cells.

New acyclic bis phenylpropanoid and neolignans, from Myristica fragrans Houtt., exhibiting PARP-1 and NF-κB inhibitory effects

The bioassay-guided fractionation of the aril of Myristica fragrans (mace spice) yielded five phenolic compounds, one new acyclic bis phenylpropanoid (1) and four previously known phenolic compounds: compounds (1) (S) 1-(3,4,5-trimethoxyphenyl)-2-(3-methoxy-5-(prop-1-yl) phenyl)-propan-1-ol, (2) benzenemethanol; α-[1-[2,6-dimethoxy-4-(2-propen-1-yl)phenoxy]ethyl]-3,4-dimethoxy-1-acetate, (3) odoratisol A, phenol, 4-[(2S,3S)-2,3-dihydro-7-methoxy-3-methyl-5-(1E)-1-propenyl-2-benzofuranyl]-2,6-dimethoxy, (4) 1,3-benzodioxate-5-methanol,α-[1-[2,6-dimethoxy-4-(2-propenyl)phenoxy]ethyl]-acetate, (5) licarin C; benzofuran,2,3-dihydro-7-methoxy-3-methyl-5-(1E)-1-yl-2-(3,4,5-trimethoxyphenyl). An NMR tube Mosher ester reaction was used in an approach to characterize and determine the assignment of the absolute configuration of the new isolated chiral alcohol (1). The PARP-1 inhibitory activity was evaluated for compound (1) (IC50=3.04μM), compound (2) (IC50=0.001μM), compound (4) (IC50=22.07μM) and compound (5) (IC50=3.11μM). Furthermore, the isolated secondary metabolites were tested for NF-κB and K-Ras inhibitory activities. When tested in the p65 assay, compounds (2) and (4) displayed potent NF-κB inhibition (IC50=1.5 nM and 3.4nM, respectively).

New Bioactive Lupane Triterpene Coumaroyl Esters Isolated from Buxus cochinchinensis

Five new lupane triterpene coumaroyl esters (1-5), together with betulin (6) and a known Buxus alkaloid, N-3-benzoyldihydrocyclomicrophylline F (7), were isolated from a CHCl3-soluble partition of a methanol extract of Buxus cochinchinensis Pierre ex Gagnep. (Buxaceae) collected in Vietnam. Isolation work was monitored using human colon cancer cells (HT-29). The structures of the new compounds (1-5) were determined on the basis of spectroscopic data interpretation. In addition to their cytotoxicity against HT-29 cells and nuclear factor-kappa B (p65) inhibitory activity in an enzyme-linked immunosorbent assay, all isolates as well as two semisynthetic compounds derived from betulin and 5, respectively, were also evaluated for their in vitro antiplasmodial activities against the drug-resistant Dd2 strain of Plasmodium falciparum and antifungal effects on the growth of the pathogenic yeast Candida albicans. The new lupane triterpene coumaroyl esters (1-5), along with a betulin derivative and the known Buxus alkaloid, were found to show significant in vitro antimalarial activities, with IC50 values ranging from 0.26 to 2.07 µM.

Ambiguine I Isonitrile from Fischerella ambigua Induces Caspase-Independent Cell Death in MCF-7 Hormone Dependent Breast Cancer Cells

Ambiguine I isonitrile (AmbI) obtained from the cultured cyanobacterium Fischerella ambigua was identified as a potent NF-κB inhibitor (IC50=30 nM). The cytotoxic effect was evaluated in both HT-29 colon cancer cell line (EC₅₀=4.35 μM) and MCF-7 breast cancer cell line (EC₅₀=1.7 μM) using the SRB assay. In the cells treated with AmbI, an increased population of cells was detected in sub G₁-phase. The apoptotic effect was associated with block in G₁-phase of the cell cycle in treated cells; however, cell death was induced independently of caspase-7. The NF-κB expression of p50 and p65 units were also examined in treated cells and compared with the positive control, rocaglamide (IC₅₀=75 nM). Moreover, the expression of mediators of the NF-κB pathway such as kinase IKKκ was studied at increasing concentrations of AmbI. The down stream effect of NF-κB inhibition and the effect on the expression of TNF-α induced ICAM-1 was evaluated. Thus, the dose-dependent and time-dependent effect of AmbI on MCF-7 cells was examined in an attempt to investigate its potential mechanism of action on inducing apoptosis.

Bioactive indole alkaloids isolated from Alstonia angustifolia

Bioassay-guided fractionation was conducted on a CHCl₃-soluble extract of the stem bark of Alstonia angustifolia (Apocynaceae) collected in Vietnam using the HT-29 human colon cancer cell line, and led to the isolation of a new sarpagine-type indole alkaloid (1), together with nine known alkaloids, including four macroline-derived alkaloids (2-5), a sarpagine-type alkaloid (6), and four macroline-pleiocarpamine bisindole alkaloids (7-10). The structure of the new compound (1) was determined on the basis of spectroscopic data interpretation. Compounds 1-10 were evaluated in vitro for their NF-κB (p65) inhibitory activity against the Hela cells in an ELISA assay. The new sarpagine alkaloid, N(4)-methyltalpinine (1), was found to show significant NF-κB inhibitory activity (ED₅₀ = 1.2 µM). Furthermore, all the isolates (1-10) were evaluated in vitro for their antileishmanial activity, and compounds (1-4, 6 and 8-10) exhibited leishmaniacidal activity against promastigotes of Leishmania mexicana.

Investigation of Vietnamese plants for potential anticancer agents

Higher plants continue to afford humankind with many new drugs, for a variety of disease types. In this review, recent phytochemical and biological progress is presented for part of a collaborative multi-institutional project directed towards the discovery of new antitumor agents. The specific focus is on bioactive natural products isolated and characterized structurally from tropical plants collected in Vietnam. The plant collection, identification, and processing steps are described, and the natural products isolated from these species are summarized with their biological activities.

Caeruleanone A, a rotenoid with a new arrangement of the D-ring from the fruits of Millettia caerulea

Caeruleanone A (1), a novel rotenoid with an unprecedented arrangement of the D-ring, was isolated with another two new analogues, caeruleanones B (2) and C (3), together with 11 known rotenoids from the fruits of Millettia caerulea. The structures of the new compounds were determined by spectroscopic data analysis, with that of 1 being confirmed by single-crystal X-ray diffraction. Compounds 2 and 3 displayed potent mitochondrial transmembrane potential inhibitory and quinone reductase induction activities.

Apoptosis induction by 13-acetoxyrolandrolide through the mitochondrial intrinsic pathway

The aim of this study was to evaluate the mechanisms of cytotoxicity of the sesquiterpene lactone 13-acetoxyrolandrolide, a nuclear factor kappa B (NF-κB) inhibitor that was previously isolated from Rolandra fruticosa. The effects associated with the inhibition of the NF-κB pathway included dose-dependent inhibition of the NF-κB subunit p65 (RelA) and inhibition of upstream mediators IKKβ and oncogenic Kirsten rat sarcoma (K-Ras). The inhibitory concentration of 13-acetoxyrolandrolide on K-Ras was 7.7 µM. The downstream effects of the inhibition of NF-κB activation were also investigated in vitro. After 24 h of treatment with 13-acetoxyrolandrolide, the mitochondrial transmembrane potential was depolarized in human colon cancer (HT-29) cells. The mitochondrial oxidative phosphorylation was also negatively affected, and reduced levels of nicotinamine adenine dinucleotide phosphate (NAD(P)H) were detected after 2 h of 13-acetoxyrolandrolide exposure. Furthermore, the expression of the pro-apoptotic protein caspase-3 increased in a concentration-dependent manner. Cell flow cytometry showed that 13-acetoxyrolandrolide induced cell cycle arrest at G1 , indicating that the treated cells had undergone caspase-3-mediated apoptosis, indicating negative effects on cancer cell proliferation. These results suggest that 13-acetoxyrolandrolide inhibits NF-κB and K-Ras and promotes cell death mediated through the mitochondrial apoptotic pathway.

Apoptotic Effect of Wortmannolone on Cancer Cells through Potent ROS Induction

Nuclear factor κappa-B inhibitors isolated from natural sources that induce apoptosis are promising new agents with anticancer properties. Wortmannin and wortmannolone were isolated from endophytic fungus (Penicillum polonicum) and showed NF-κB inhibitory effects with inhibitory concentration (IC₅₀) of 0.47 μM and 2.06 μM for wortmannin and wortmannolone, respectively. The activity was compared with rocaglamide (IC₅₀=0.075 μM). The mechanism through which wortmannin and wortmannolone exhibited an attenuating effect on the NF-κB pathway was further evaluated in this study. Wortmannolone showed significant reactive oxygen species (ROS) inducing effects in HeLa cervical cells. The ROS inducing effect was concentration dependent, and the ROS generating activity was comparable with daunomycin, a potent chemotherapeutic agent. The findings suggested that the elevated formation of ROS was partially involved in the induction of apoptosis in treated cells. Potent cytotoxic and apoptotic effects were also displayed in MDA-MB-231 hormone independent breast cancer cells when treated with wortmannolone (IC₅₀=3.79 nM). Thus, wortmannolone, a furanosteroid from an endophytic fungus, is a promising agent for further drug development.

Sphenostylisins A-K: bioactive modified isoflavonoid constituents of the root bark of Sphenostylis marginata ssp. erecta

Sphenostylisins A-C (1-3), three complex dimeric compounds representing two novel carbon skeletons, along with an additional eight new compounds, sphenostylisins D-K (4-11), were isolated from the active chloroform-soluble extract of the root bark of Sphenostylis marginata ssp. erecta using a bioactivity-guided isolation approach. The structures were elucidated by means of detailed spectroscopic analysis, including NMR and HRESIMS analysis, and tandem MS fragmentation was utilized to further support the structures of 1-3. The absolute configuration of sphenostylisin C (3) was established by electronic circular dichroism analysis. Plausible biogenetic relationships between the modified isoflavonoids 1-11 are proposed, and a cyclization reaction of 9 was conducted to support one of the biogenetic proposals made. All of these pure isolates were evaluated against a panel of in vitro bioassays, and among the results obtained, sphenostylisin A (1) was found to be a very potent NF-κB inhibitor (IC50 = 6 nM).

Bioactive flavaglines and other constituents isolated from Aglaia perviridis

Eight new compounds, including two cyclopenta[b]benzopyran derivatives (1, 2), two cyclopenta[b]benzofuran derivatives (3, 4), three cycloartane triterpenoids (5-7), and an apocarotenoid (8), together with 16 known compounds, were isolated from the chloroform-soluble partitions of separate methanol extracts of a combination of the fruits, leaves, and twigs and of the roots of Aglaia perviridis collected in Vietnam. Isolation work was monitored using human colon cancer cells (HT-29) and facilitated with an LC/MS dereplication procedure. The structures of the new compounds (1-8) were determined on the basis of spectroscopic data interpretation. The Mosher ester method was employed to determine the absolute configurations of 5-7, and the absolute configuration of the 9,10-diol unit of compound 8 was established by a dimolybdenum tetraacetate [Mo2(AcO)4] induced circular dichroism procedure. Seven known rocaglate derivatives (9-15) exhibited significant cytotoxicity against the HT-29 cell line, with rocaglaol (9) being the most potent (ED50 0.0007 μM). The new compounds 2-4 were also active against this cell line, with ED50 values ranging from 0.46 to 4.7 μM. The cytotoxic compounds were evaluated against a normal colon cell line, CCD-112CoN. In addition, the new compound perviridicin B (2), three known rocaglate derivatives (9, 11, 12), and a known sesquiterpene, 2-oxaisodauc-5-en-12-al (17), showed significant NF-κB (p65) inhibitory activity in an ELISA assay.

Use of the hollow fiber assay for the discovery of novel anticancer agents from fungi

The hollow fiber assay (HFA) is a drug discovery tool to aid investigators in the prioritization of lead compounds identified by in vitro testing for further development in animal models of disease. In the HFA, cells are cultured in hollow fibers containing pores of a diameter (500 kDa) large enough for proteins and other macromolecules to enter, but too small for the cells to escape. The fibers are filled with cells, sealed and placed in the peritoneal cavity of immunodeficient mice. The mice undergo a predetermined treatment regimen after which the fibers are retrieved and the cells evaluated for activity of a target relevant to the disease modeled. The HFA combines advantages of both in vitro and in vivo assay systems. It uses the same cell lines used in culture systems, is a rapid assay, and requires fewer animals and less test substance than conventional xenograft systems. Like traditional in vivo assays, the test substance is evaluated in a live animal, which affords an initial assessment of associated toxicity and pharmacokinetic properties of the test substance.

Goyazensolide Induces Apoptosis in Cancer Cells in vitro and in vivo

As part of the screening program for anticancer agents from natural sources, the sesquiterpene lactone goyazensolide (GZL) was identified as a potent NF-κB inhibitor. The hollow-fiber assay was used to evaluate the anti-tumor efficacy of GZL in vivo. The mechanistic effects of GZL were evaluated in the HT-29 colonic cell line to reveal the pathway through which GZL exerts its effects. NF-κB subunits p65 and p50 were inhibited, and the upstream mediator IκB kinase (IKKβ) was downregulated in a dose-dependent manner. Apoptosis was mediated by caspase-3, and cell cycle arrest was detected in G1-phase. Consequently, 96% of the cell population was in sub G1-phase after treatment with GZL (10 μM).The antitumor effect of GZL was observed at a dose of 12.5 mg/kg. Cell adhesion was affected as a result of NF-κB inhibition. GZL appears to selectively target the transcription factor NF-κB. In summary, GZL sensitizes HT-29 colon cancer cells to apoptosis and cell death in a dose-dependent manner both in vivo and in vitro, through NF-κB inhibition (IC50 = 3.8 μM). Thus, it is a new potent lead compound for further development into a new effective chemotherapeutic agent.

Peptaibols from two unidentified fungi of the order Hypocreales with cytotoxic, antibiotic, and anthelmintic activities

As part of an ongoing investigation of filamentous fungi for anticancer leads, an active culture was identified from the Mycosynthetix library (MSX 70741, of the order Hypocreales, Ascomycota). The fungal extract exhibited cytotoxic activity against the H460 (human nonsmall cell lung carcinoma) cell line, and bioactivity-directed fractionation yielded peptaibols 1-12 and harzianums A (13) and B (14). Structure elucidation of 1-12 was facilitated by high-resolution MS/MS using higher-energy collisional dissociation and by high field NMR (950 MHz). The absolute configuration was determined by Marfey's analysis of the individual amino acids; the time required for such analysis was decreased via the development of a 10-min ultra performance liquid chromatography method. The isolated peptaibols (1-12), along with three other peptaibols isolated and elucidated from a different fungus (MSX 57715) of the same order (15-17), were examined for activity in a suite of biological assays, including those for cytotoxic, antibacterial, and anthelmintic activities.

Effects of (5Z)-7-oxozeaenol on the oxidative pathway of cancer cells

AIM

As part of an on going investigation of novel anticancer agents from natural origin, the biological and cellular effects of (5Z)-7-oxozeaenol on cancer cells were investigated.

MATERIALS AND METHODS

The expression of nuclear factor kappa B (NF-κB), IκB kinase (IKKα), IKKβ and caspase-3 were analyzed by western blot. Reactive oxygen species (ROS) fluorescence and caspase luminescent assays were used to assess the intracellular effects in HeLa cervical and HT-29 colon cancer cell lines. The mitochondrial transmembrane potential (MTP) was analyzed by fluorescence-activated cell sorting (FACS).

RESULTS

Cells treated with (5Z)-7-oxozeaenol exhibited down-regulation of NF-κB in a dose-dependent manner. Treatment with (5Z)-7-oxozeaenol significantly enhanced the levels of ROS in HeLa and HT-29 cells. MTP was reduced in HT-29 cells. The expression of caspase-3 and -7 was induced in (5Z)-7-oxozeaenol treated HeLa cells, in comparison with those treated with paclitaxel.

CONCLUSION

Our findings suggest that (5Z)-7-oxozeaenol is a potent inhibitor of the NF-κB pathway and potentiates the production of ROS, as well as induces caspase-3 and -7 in HeLa and HT-29 cancer cells. Thus, (5Z)-7-oxozeaenol represents a new lead compound for drug development, particularly as a new cancer chemotherapeutic agent, since programmed cell death might be mediated through the activation of a caspase-arbitrated pathway.

Abstract 2837: Assay development for the discovery of semaphorin 3B-inducing agents from natural product sources

The family of semaphorins has been found to regulate cell adhesion and cell motility, the immune response, angiogenesis, and tumor progression. The semaphorins are emerging as regulators of key processes of tumor progression. Semaphorin 3B, in particular, has been found to inhibit proliferation and promote apoptosis. Since there is yet no screening assay available to be used in drug discovery for this crucial target, the present study focuses on the development of a new absorbance-based bioassay to search for new semaphorin 3B inducers from natural sources. Among the parameters considered include the type of cancer cell line, the time of incubation, the type of lysis buffer, secondary effects that affect absorbance levels, and ways to minimize false positives. Vitamin D and actinomycin are being used as controls in this assay. Vitamin D acts as a positive control since it is a semaphorin 3B inducer. Comparison of the levels of induction of the active substances to that of the positive control provides an indication about the level of potential a hit will have if being developed as a drug. Actinomycin inhibits transcription by binding to DNA at the transcription initiation level. When using actinomycin in this assay, its effect is considered to be proportional to that of semaphorin 3B inhibitors. Hence, actinomycin serves as a negative control to discriminate inducers from inhibitors of semaphorin 3B. The use of both controls, therefore, offers the opportunity to discover selective and highly potent semaphorin 3B inducers of natural origin. The assay has been standardized in a 96-well plate format to optimize sensitivity, selectivity, accuracy, robustness, and cost effectiveness. A library of natural product compounds isolated from higher plants, filamentous fungi, and cyanobacteria is currently being screened using this new bioassay. A total of 50 samples have been tested already with two samples exhibiting low induction levels. The most active substances will be further tested using a series of immunoblot secondary assays to validate the potential hits. Additionally, the screening assay presented could be modified to discover new small molecules or drug-like scaffolds as inhibitors or inducers of other semaphorins. Thus, an assay to identify compounds that selectively and potently affect this pathway may lead to new ways of understanding the cell signaling mechanism of these agents, which could be beneficial for the discovery of new natural product leads for cancer treatment. Program project grant P01-CA125066-S1 funded by the National Cancer Institute, NIH.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2837. doi:1538-7445.AM2012-2837

Cytotoxic and NF-κB inhibitory sesquiterpene lactones from Piptocoma rufescens

Six new (1-6) and eight known germacranolide-type sesquiterpene lactones, along with several known phenylpropanol coumarates and methylated flavonoids, were isolated from the leaves of Piptocoma rufescens, collected in the Dominican Republic. The new compounds were identified by analysis of their spectroscopic data, with the molecular structure of 3 being established by single-crystal X-ray diffraction. The absolute configurations of the sesquiterpene lactones isolated were determined from their CD and NOESY NMR spectra, together with the analysis of Mosher ester reactions. Bioassay screening results showed the majority of the sesquiterpene lactones isolated (1-13) to be highly cytotoxic toward the HT-29 human colon cancer cell line, with the most potent compound being 15-deoxygoyazensolide (10, IC(50), 0.26 µM). In addition, several of the sesquiterpene lactones exhibited NF-κB (p65) inhibitory activity.

Isolation, structure elucidation, and biological evaluation of 16,23-epoxycucurbitacin constituents from Eleaocarpus chinensis

Eight new 16,23-epoxycucurbitacin derivatives, designated as elaeocarpucins A-H (1-8), and five known cucurbitacins (9-13) were isolated from the chloroform-soluble partitions of separate methanol extracts of the fruits and stem bark of Elaeocarpus chinensis collected in Vietnam. Isolation work was facilitated using a LC/MS dereplication procedure, and bioassay-guided fractionation was monitored using HT-29 human cancer cells. The structures of compounds 1-8 were determined on the basis of spectroscopic data interpretation, with the absolute configurations of isomers 1 and 2 established by the Mosher ester method. Compounds 1-13 were evaluated in vitro against the HT-29 cell line and using a mitochondrial transmembrane potential assay. Elaeocarpucin C (3), produced by partial synthesis from 16α,23α-epoxy-3β,20β-dihydroxy-10αH,23βH-cucurbit-5,24-dien-11-one (13), was found to be inactive when evaluated in an in vivo hollow fiber assay using three different cancer cell types (dose range 0.5-10 mg/kg/day, i.p.).

Bioassay-guided isolation of constituents of Piper sarmentosum using a mitochondrial transmembrane potential assay

Bioassay-guided fractionation was conducted on a chloroform-soluble extract of the aerial parts of Piper sarmentosum collected in Vietnam, monitored by a mitochondrial transmembrane potential assay using HT-29 human colon cancer cells. This led to the isolation of four new C-benzylated dihydroflavones, sarmentosumins A-D (1-4), as well as 14 known compounds. The structures of the new compounds were elucidated on the basis of spectroscopic data interpretation. Among these compounds, 1-4 as well as five known C-benzylated dihydroflavones (5-9) and a piperamide, pipercallosine (11), were found to induce apoptosis in HT-29 cells by moderately reducing the mitochondrial transmembrane potential (ΔΨm), with ED50 values ranging from 1.6 to 13.6 μM. Furthermore, 7-methoxydichamanetin (8) and pinocembrin (10) exhibited proteasome inhibitory activities in a human 20S proteasome bioassay with IC50 values of 3.45±0.18 and 2.87±0.26 μM, respectively. This is the first time that C-benzylated dihydroflavones have been reported to demonstrate an apoptotic effect associated with disruption of the mitochondrial transmembrane potential.

Cytotoxic and NF-κB inhibitory constituents of the stems of Cratoxylum cochinchinense and their semisynthetic analogues

A new caged xanthone (1), a new prenylxanthone (2), seven known xanthones, and a known sterol glucoside were isolated from the stems of Cratoxylum cochinchinense, collected in Vietnam. Compounds 1 and 2 were determined structurally by analysis of their spectroscopic data. In addition, five new (10 and 16-19) and eight known prenylated xanthone derivatives were synthesized from the known compounds α-mangostin (3) and cochinchinone A (6). Several of these substances were found to be cytotoxic toward HT-29 human colon cancer cells, with the most potent being 3,6-di-O-acetyl-α-mangostin (8, ED50, 1.0 μM), which was tested further in an in vivo hollow fiber assay, but found to be inactive at the highest dose used (20 mg/kg; ip). Of the substances evaluated in a NF-κB p65 inhibition assay, 1,3,7-trihydroxy-2,4-diisoprenylxanthone (5) exhibited the most potent activity (IC50, 2.9 μM). In a mitochondrial transmembrane potential assay, two new compounds, 1 (IC50, 3.3 μM) and 10 (IC50, 1.4 μM), and two known compounds, 3 (α-mangostin, IC50, 0.2 μM) and 11 (3,6-di-O-methyl-α-mangostin, IC50, 0.9 μM), were active. A preliminary analogue development study showed that 3,6-diacetylation and 6-benzoylation both slightly increased the cytotoxicity of α-mangostin (3), whereas methylation reduced such activity. In contrast, neither acetylation, benzoylation, nor methylation enhanced the cytotoxicity of cochinchinone A (6).

Resorcylic acid lactones with cytotoxic and NF-κB inhibitory activities and their structure-activity relationships

As part of our ongoing investigation of filamentous fungi for anticancer leads, an active fungal extract was identified from the Mycosynthetix library (MSX 63935; related to Phoma sp.). The initial extract exhibited cytotoxic activity against the H460 (human non-small cell lung carcinoma) and SF268 (human astrocytoma) cell lines and was selected for further study. Bioactivity-directed fractionation yielded resorcylic acid lactones (RALs) 1 (a new natural product) and 3 (a new compound) and the known RALs zeaenol (2), (5E)-7-oxozeaenol (4), (5Z)-7-oxozeaenol (5), and LL-Z1640-1 (6). Reduction of (5E)-7-oxozeaenol (4) with sodium borohydride produced 3, which allowed assignment of the absolute configuration of 3. Other known resorcylic acid lactones (7-12) were purchased and assayed in parallel for cytotoxicity with isolated 1-6 to investigate structure-activity relationships in the series. Moreover, the isolated compounds (1-6) were examined for activity in a suite of biological assays, including antibacterial, mitochondria transmembrane potential, and NF-κB. In the latter assay, compounds 1 and 5 displayed sub-micromolar activities that were on par with the positive control, and as such, these compounds may serve as a lead scaffold for future medicinal chemistry studies.

Abstract 4040: Goyazensolide, a sesquiterpene lactone from Piptocoma rufescens inhibits tumor development in hollow fiber

Goyazensolide (C19H20O7) is a rare sesquiterpene lactone isolated from Piptocoma rufescens Cass. (Asteraceae). Goyazensolide significantly inhibits NF-κB transcription factor and decreased the cell growth of HT-29 colon cancer cells in a dose-dependent manner. In the present study, we investigated the effects of goyazensolide in a hollow fiber assay using in vivo setting. We also examined the involvement of ROS-signaling components (ROS levels, NF-κB transcription factor, mitochondrial membrane potential) and demonstrated that the antiproliferative effect of cancer cells is partially mediated by induction of oxidative stress. It is our aim to further investigate the molecular mechanism through which goyazensolide exerts its cytotoxic effect in vitro and its antitumor effect in vivo. Our data therefore supports goyazensolide as an active anti-proliferative agent with great potential for further development.

Acknowledgment

This research was supported by Program Project Grant P01-CA125066 funded by the National Cancer Institute, NIH.We also wish to acknowledge the plant taxonomists who collected the plant material used in this investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4040. doi:10.1158/1538-7445.AM2011-4040

Abstract 4229: Dichamanetin, a C-benzylated flavonoid from Piper sarmentosum inhibits cell growth and induces G1 cell cycle arrest in cancer cells through mitochondrial-mediated apoptosis

Dichamanetin (C29H24O6) is a rare C-benzylated flavanoid isolated as a major metabolite from Piper sarmentosum Roxb. (Piperaceae). Dichamanetin significantly decreased the cell viability of various types of cancer cells in a dose- and time-dependent manner, characterized by G1 arrest of the cell cycle. In the present study, we investigated the molecular mechanism whereby dichamanetin exerts its cytotoxic effect on human cancer cells in vitro. We examined the involvement of ROS-signaling components (ROS levels, NF-kB transcription factor, mitochondrial membrane potential, DNA damage, and proteasome inhibition) and demonstrated that the antiproliferative effect of cancer cells is partially mediated by induction of oxidative stress. Dichamanetin treatment did not significantly inhibited proteasome, but inhibited moderately PARP-1 enzyme activity. Additionally, FACS analysis with JC-1 fluorescent dye established significant deviation of mitochondrial membrane potential by dichamanetin in treated cells. The present data therefore supports dichamanetin as an active anti-proliferative metabolite that acts in part through mitochondrial-mediated apoptosis.

Acknowledgment

This research was supported by Program Project Grant P01-CA125066 funded by the National Cancer Institute, NIH.

We also wish to acknowledge the plant taxonomists who collected the plant material used in this investigation.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4229. doi:10.1158/1538-7445.AM2011-4229

Isolation and characterization of minor analogues of silvestrol and other constituents from a large-scale re-collection of Aglaia foveolata

Two new minor silvestrol analogues [2'''-episilvestrol (1) and 2''',5'''-diepisilvestrol (2)], together with a new 21-norbaccharane-type triterpene (3), two new 3,4-secodammarane triterpenes (4 and 5), and a new eudesmane sesquiterpene (6), as well as nine known compounds, were isolated from a large-scale re-collection of the CHCl(3)-soluble extract of the stem bark of Aglaia foveolata obtained in Kalimantan, Indonesia. The structures of the new compounds were established by interpretation of their spectroscopic data. All of the isolates were tested for cytotoxicity against HT-29 cells. The new silvestrol analogues, 1 and 2, were considerably less active as cytotoxic agents than silvestrol (7) and episilvestrol (5'''-episilvestrol) (8) against this cell line, showing the importance of the configuration at C-2''' in mediating such activity within this compound class. Several of the compounds isolated were also evaluated in a NF-κB (p65) inhibition assay.

NF-kappaB inhibitors from Brucea javanica exhibiting intracellular effects on reactive oxygen species

AIM

Brucea javanica was studied to identify nuclear factor kappaB (NF-κB) inhibitors exhibiting reactive oxygen species (ROS) intracellular amplification.

MATERIAL AND METHODS

Eight compounds were evaluated for selective cytotoxicity using HT-29, HeLa, and HL-60 cells, and in a NF-κB assay. Active compounds were then tested using ROS and mitochondria transmembrane potential (MTP) assays. NF-κB and nuclear factor activated T-cell (NFAT) translocation were also assessed using their respective whole cell assays.

RESULTS

Bruceajavanone B, bruceantin, bruceine A, (-)-hydnocarpin, and chrysoeriol exhibited cytotoxic potential and NF-κB p65 inhibition. Chrysoeriol exhibited selective cytotoxicity against leukemia cells with greater potency and also showed an ability to up-regulate NFAT transcriptional pathways through the amplification of intracellular ROS, in the presence of H2O2, to a greater degree than bruceantin and bruceine.

CONCLUSION

Chrysoeriol selectively kills leukemic cells and potentiates the amplification of ROS levels. Therefore, chrysoeriol could serve as a potential chemotherapeutic modifier for leukemia chemotherapy since leukemia cells have a higher susceptibility to elevated ROS levels.

Proteasome-inhibitory and cytotoxic constituents of Garcinia lateriflora: absolute configuration of caged xanthones

A new biflavonoid (1), a new xanthone enantiomer (2), five new caged xanthones (3-7), and several known compounds were isolated from the stem bark of Garcinia lateriflora, collected in Indonesia. The structures of the new compounds were determined by analysis of spectroscopic data, and the absolute configuration of the caged xanthones was shown for the first time at carbons 5, 7, 8, 8a, 10a, and 27, by analysis of COSY and NOESY NMR and ECD spectra. The biflavonoids exhibited proteasome inhibitory activity, and the known compound, morelloflavone (8) was found to have the greatest potency (IC(50) = 1.3 muM). The caged xanthones were cytotoxic towards HT-29 cells, with the known compound, morellic acid (10) being the most active (ED(50) = 0.36 muM). However, when tested in an in vivo hollow fiber assay, it was inactive at the highest dose tested (20 mg/kg).

Cytotoxic and NF-kappaB inhibitory constituents of Artocarpus rigida

Four new prenylated flavonoids (1-4), a new stilbenoid (5), and nine known compounds were isolated from the twigs of Artocarpus rigida, collected in Indonesia. The structures of the new compounds were determined by analysis of their spectroscopic data, and the absolute configuration at C-12 of 1 and 2 and the known compounds artonin O (6), artobiloxanthone (7), and cycloartobiloxanthone (8) was determined from their CD and NMR spectroscopic data. Several of the compounds obtained were cytotoxic toward HT-29 human colon cancer cells, with the most potent being compound 2 and the known compounds 6 and 8. Of the substances obtained, compounds 1 and 7 were the most active in the NF-kappaB p50 and p65 assay, respectively.

Bioactivity-guided isolation of cytotoxic sesquiterpenes of Rolandra fruticosa

Cytotoxicity-guided fractionation of a methanol extract of the leaves and twigs of Rolandra fruticosa using the HT-29 human colon cancer cell line led to the isolation of seven sesquiterpene lactones, including the hitherto unknown isorolandrolide, 13-methoxyisorolandrolide (1), and bourbonenolide, 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-isobutyroyloxybourbonen-12,6alpha-olide (2), as well as five known compounds, 13-acetoxyrolandrolide (3), 8-desacyl-13-acetoxyrolandrolide-8-O-tiglate (4), 2-epi-glaucolide E (5), 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-methacryloyloxybourbonen-12,6alpha-olide (6), and 2alpha,13-diacetoxy-4alpha-hydroxy-8alpha-tigloyloxybourbonen-12,6alpha-olide (7). The structures of the two sesquiterpenes were elucidated on the basis of spectroscopic methods. All isolates were evaluated for their cytotoxicity using the HT-29 cell line, and only 13-acetoxyrolandrolide (3) was found to possess a potent inhibitory effect against this cell line. Compounds 3, 5 and 6 were also tested in a NF-kappaB (p65) inhibition assay, and 3 was assessed in an in vivo hollow fiber assay.

Cytotoxic xanthone constituents of the stem bark of Garcinia mangostana (mangosteen)

Bioassay-guided fractionation of a chloroform-soluble extract of Garcinia mangostana stem bark, using the HT-29 human colon cancer cell line and an enzyme-based ELISA NF-kappaB assay, led to the isolation of a new xanthone, 11-hydroxy-3-O-methyl-1-isomangostin (1). The structure of 1 was elucidated by spectroscopic data analysis. In addition, 10 other known compounds, 11-hydroxy-1-isomangostin (2), 11alpha-mangostanin (3), 3-isomangostin (4), alpha-mangostin (5), beta-mangostin (6), garcinone D (7), 9-hydroxycalabaxanthone (8), 8-deoxygartanin (9), gartanin (10), and cratoxyxanthone (11), were isolated. Compounds 4-8 exhibited cytotoxicity against the HT-29 cell line with ED50 values of 4.9, 1.7, 1.7, 2.3, and 9.1 microM, respectively. In an ELISA NF-kappaB assay, compounds 5-7, 9, and 10 inhibited p65 activation with IC50 values of 15.9, 12.1, 3.2, 11.3, and 19.0 microM, respectively, and 6 showed p50 inhibitory activity with an IC50 value of 7.5 microM. Alpha-mangostin (5) was further tested in an in vivo hollow fiber assay, using HT-29, LNCaP, and MCF-7 cells, but it was found to be inactive at the highest dose tested (20 mg/kg).

Bioactive 5,6-dihydro-alpha-pyrone derivatives from Hyptis brevipes

Six new 5,6-dihydro-alpha-pyrone derivatives (1-6), namely, brevipolides A-F, together with seven known compounds, including a 5,6-dihydro-alpha-pyrone derivative (7), three flavonoids, a steroid glycoside, and two triterpenoids, were isolated from the entire plant of Hyptis brevipes. Compounds 1-7 were assigned with the absolute configuration 5R, 6S, 7S, and 9S, as elucidated by analysis of data obtained from their CD spectra and by Mosher ester reactions. Compounds 2, 6, and 7 exhibited ED(50) values of 6.1, 6.7, and 3.6 microM against MCF-7 cells, and compounds 1, 2, 6, and 8 (the known 5,6,3'-trihydroxy-3,7,4'-trimethoxyflavone) gave ED(50) values of 5.8, 6.1, 7.5, and 3.6 microM against HT-29 cells, respectively. However, no significant cytotoxicity was found against Lu1 cells for any of the compounds isolated. When these compounds were subjected to evaluation in a panel of mechanism-based in vitro assays, compound 7 was found to be active in an enzyme-based ELISA NF-kappaB assay, with an ED(50) value of 15.3 microM. In a mitochondrial transmembrane potential assay, compounds 3, 7, and 8 showed ED(50) values of 8.5, 75, and 310 nM, respectively. No potent activity was found in a proteasome inhibition assay for any of the isolated compounds.

Discovery of anticancer agents of diverse natural origin

A collaborative multidisciplinary research project is described in which new natural product anticancer drug leads are obtained from a diverse group of organisms, constituted by tropical plants, aquatic cyanobacteria, and filamentous fungi. Information is provided on how these organisms are collected and processed. The types of bioassays are indicated in which crude extracts of these acquisitions are tested. Progress made in the isolation of lead bioactive secondary metabolites from three tropical plants is discussed.

Investigation of antimicrobial and protease-inhibitory activity from cultured cyanobacteria

A culture collection of cyanobacteria has been established at the University of Illinois at Chicago. This collection includes marine, terrestrial, and freshwater strains and contains representatives of the five orders of cyanobacteria: Chroococcales, Pleurocapsales, Oscillatoriales, Nostocales, and Stigonematales. In this study, extracts from a subset of 61 strains, 16 marine and 45 freshwater/terrestrial, were evaluated against three current protease targets, i.e. 20S proteasome and two SARS viral proteases, two important bacterial targets, i.e. Mycobacterium tuberculosis and Bacillus anthracis, and in the Artemia salina toxicity assay. In total, extracts of 12 strains possessed significant levels of activity in one or more targets. The overwhelming majority of active extracts (11 of 12) were from either freshwater or terrestrial forms of cyanobacteria, with the greater part of these (9 of 12) being heterocyst-forming strains. These results further support the use of cultured cyanobacteria as a source of biologically active natural products.