Activity-guided fractionation of Theobroma grandiflorum ("cupuaçu") seeds resulted in the identification of two new sulfated flavonoid glycosides, theograndins I (1) and II (2). In addition, nine known flavonoid antioxidants, (+)-catechin, (-)-epicatechin, isoscutellarein 8-O-beta-d-glucuronide, hypolaetin 8-O-beta-d-glucuronide, quercetin 3-O-beta-d-glucuronide, quercetin 3-O-beta-d-glucuronide 6' '-methyl ester, quercetin, kaempferol, and isoscutellarein 8-O-beta-d-glucuronide 6' '-methyl ester, were identified. Theograndin II (2) displayed antioxidant activity (IC(50) = 120.2 microM) in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) free-radical assay, as well as weak cytotoxicity in the HCT-116 and SW-480 human colon cancer cell lines with IC(50) values of 143 and 125 microM, respectively. While 1 was less active as an antioxidant than 2, the known compounds were more potent in the DPPH assay (IC(50) range 39.7-89.7 microM).

Six tropane alkaloid esters were isolated from the stems of Erythroxylum rotundifolium. The structures of three new tropane esters, 7beta-hydroxy-6beta-(3,4,5-trimethoxybenzoyloxy)-3alpha-(E)-(3,4,5-trimethoxycinnamoyloxy)tropane (1), 6beta-benzoyloxy-3alpha-(Z)-(3,4,5-trimethoxycinnamoyloxy)tropane (2), and (-)-6beta-benzoyloxy-3alpha-hydroxytropane (3), were established by spectroscopic techniques. When alkaloids 1-6 were evaluated against a panel of human cancer cell lines, the new compound 6beta-benzoyloxy-3alpha-(Z)-(3,4,5-trimethoxycinnamoyloxy)tropane (2) and three known compounds, 6beta-benzoyloxy-3alpha-(3,4,5-trimethoxycinnamoyloxy)tropane (4), 6beta-benzoyloxy-3alpha-(E)-(3,4,5-trimethoxycinnamoyloxy)tropane-7beta-ol (5), and 7beta-acetoxy-6beta-benzoyloxy-3alpha-(E)-(3,4,5-trimethoxycinnamoyloxy)tropane (6), demonstrated greatest activity with multidrug-resistant oral epidermoid carcinoma (KB-V1) cells incubated in the presence of vinblastine. Thus, tropane esters of this type can reverse the multidrug-resistance phenotype, presumably by interacting with P-glycoprotein.

P-Glycoprotein (Pgp)-mediated drug efflux can yield a multidrug-resistance phenotype that is associated with poor response to cancer chemotherapy. Pervilleines B and C (PB and PC), two new tropane alkaloid aromatic esters obtained from a chloroform extract of the roots of Erythroxylum pervillei as the result of bioactivity-guided fractionation, were found to restore the vinblastine (VLB) sensitivity of cultured multidrug-resistant KB-V1 cells, with 50% inhibitory concentration values of 0.17 microM in each case. To explore the potential relevance of this response, KB-V1 cells were placed in hollow fibers and implanted into NCr nu/nu mice. Cell growth was not significantly inhibited when VLB or PB or PC were administered as single agents, but when used in combination with vinblastine inhibition of up to 77.7% was observed. Equimolar doses of verapamil were less effective. These data suggest that PB and PC are effective inhibitors of Pgp and should be further evaluated for clinical utility.

Nine tropane alkaloid aromatic esters (1-9) were isolated from the roots of Erythroxylum pervillei by following their potential to reverse multidrug-re si stance with vinblastine-resistant oral epidermoid carcinoma (KB-V1) cells. All isolates, including seven new structures (3-9), were evaluated against a panel of human cancer cell lines, and it was found that alkaloids 3 and 5-9 showed the greatest activity with KB-V1 cells assessed in the presence of vinblastine, suggesting that these new compounds are potent modulators of P-glycoprotein. Confirmatory results were obtained with human ovarian adenocarcinoma (SKVLB) cells evaluated in the presence of adriamycin and synergistic studies performed with several cell lines from the NCI tumor panel. The structures of the new compounds were determined using spectroscopic techniques. Single-crystal X-ray analysis was performed on the monoester, tropane-3alpha,6beta,7beta-triol 3-phenylacetate (1).

A total of five 1H-cyclopenta[b]benzofuran lignans (1–5) isolated from the stems of Aglaiaelliptica Bl. (Meliaceae) inhibited the growth of human cancer cells in culture. Of particular note, the IC50 values observed with 1 (methyl rocaglate), 2 (4′-demethoxy-3′,4′-methylenedioxy-methyl rocaglate) and 5 (1-O-formyl-4′-demethoxy-3′,4′-methylenedioxy-methyl rocaglate) were in the 1–30 ng/ml range. Prompted by the high potency of these responses, additional studies were performed with 2, a structurally representative isolate that was available in sufficient quantity as a result of the isolation process. Utilizing cultured Lu1 (human lung carcinoma) cells as a model, compound 2 induced accumulation in the G1/G0 phase of the cell cycle after 24 or 32 h of incubation; normal cell-cycle dynamics were observed at subsequent time periods. Cell proliferation was inhibited in a dose-dependent manner, but during the course of wash-out experiments, colony formation was not reduced. In addition, as judged by [3H]leucine incorporation, the test compound strongly inhibited protein biosynthesis (IC50=25 ng/ml). In analogous studies, nucleic acid biosynthesis was not reduced, even when cells were treated with concentrations as high as 1 μg/ml. These data suggest inhibition of protein synthesis is a key mode of action, and the compound functions by a cytostatic mechanism. Utilizing a human breast cancer cell line (BC1) sensitive to compound 2 in culture (IC50=0.9 ng/ml), an initial assessment of antitumor potential was performed. In accord with the in vitro results, the growth of BC1 in athymic mice was delayed by treatment with compound 2 (10 mg/kg body weight, three times per week, i.p.). Body weight was unaffected and no signs of overt toxicity were observed. However, growth paralleled that of the control group at later time points. Thus, novel 1H-cyclopenta[b]benzofuran lignans are potent cytostatic inhibitors of protein biosynthesis and are capable of delaying tumor growth in an in vivo model. Their full clinical or basic utility requires further investigation.

The dereplication of natural products is gaining greater importance in optimizing the process of natural product drug discovery as the pace of evaluating natural product extracts for their biological potential has increased. Over the years, as new technologies are introduced into analytical chemistry, they have been applied to detect known compounds before isolation and structure elucidation is initiated. Initially, chromogenic reagents were used to obtain information on the chemical classes of compounds found in natural product extracts. Though not very powerful in predictive nature as to the identity of compounds present, chemical class information was used in order to prioritize natural product extracts for subsequent isolation. The power of partially separating extracts with paper and thin-layer chromatographic techniques before subsequently spraying with chromogenic reagents, increased the ability of researchers to distinguish different classes of compounds from one another. TLC techniques were of major importance to many natural product drug discovery groups and are still widely used today. One of the most critical technologies to become available in the past decade and to advance the prioritization process is that of the computer. With the advent of small and powerful computers, information that is widely distributed and difficult to search, is now readily searchable by using any desired parameter such chemical, taxonomic, or pharmacological.

Study on the constituents of Astragali Semen, the seeds of Astragalus complanatus R. BR. (Leguminosae), led to the identification of nine known flavonoids (1, 4, 6-12) and characterization of three new flavonol glycosides (2, 3, 5)as rhamnocitrin 3-O-β-D-apiofuranosyl(1→2)-β-D-glucopyranoside, 3-O-β-D-apiofuranosyl(1→2)-β-D-glucopyranosyl rhamonocitrin 4'-O-β-D-glucopyranoside and 3-O-β-D-apiofuranosyl(1→2)-β-D-glucopyranosyl kaempferol 4'-O-β-D-glucopyranoside, respectively. The occurrence of methyl dihydrophaseate (13), roseoside (14), blumenol C glucoside(15), (±)-3-oxo-α-ionyl glucoside (16a, 16b), tuberonic acid glucoside (17), benzylalcohol-O-α-L-arabiopyranosyl(1→6)-β-D-glucopyranoside (18), piceid (19) and deoxyrhaponticin (20) were also disclosed.

From the bark of Robinia pseudo-acacia L., five new triterpene glycosides, robiniosides A-D (3, 5-7) and compound III (4), were isolated and their structures were elucidated as 3-O-α-L-rhammopyranosyl(1→2)-β-D-glucopyranosyl(1→2)-β-D-glucuronopyranosyl 3β, 22β-dihydroxyolean-12-en-29-oic acid (3), 3-O-α-L-rhamnopyranosyl(1→2)-β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl 3β, 22β, 24-trihydroxyolean-12-en-29-oic acid (4), whose sapogenol was unambiguously characterized and designated as oxytrogenin, 3-O-α-L-rhamnopyranosyl(1→2)-β-D-gluco-pyranosyl(1→2)-β-D-glucuronopyranosyl oxytrogenin (5), 3-O-α-L-rhamnopyranosyl(1→2)-β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl oxytrogenin 22-O-α-L-rhamnopyranoside (6), 3-O-α-L-rhamnopyranosyl(1→2)-β-D-gluco-pyranosyl(1→2)-β-D-glucuronopyranosyl oxytrogenin 22-O-α-L-rhamnopyranoside (7), respectively, together with two known triterpene glycosides, kaikasaponin III (1) and 3-O-α-L-rhamnopyranosyl(1→2)-β-D-galactopyranosyl(1→2)-β-D-glucuronopyranosyl 3β, 22β-dihydroxyolean-12-en-29-oic acid (2).