Cytotoxic Alkaloids from Leaves of Pilea aff. martinii

Two new phenanthroquinolizidine alkaloids (1: and 2: ) and a new piperidine derivative (3: ) were isolated from the leaves of Pilea aff. martinii together with 3 known alkaloids: julandine (4: ), cryptopleurine (5: ), and 1,3,6,6-tetramethyl-5,6,7,8-tetrahydro-isoquinolin-8-one (6: ). Their structures were determined by spectral data analyses including mass spectrometry and 2-dimensional nuclear magnetic resonance data. The absolute configurations of 1: -3: were established by comparison of their experimental circular dichroism data with the calculated electronic circular dichroism spectra. The isolated compounds were evaluated for their cytotoxicity against 4 cancer cell lines: KB (mouth epidermal carcinoma cells), HepG-2 (human liver hepatocellular carcinoma cells), LU-1 (human lung adenocarcinoma cells), and MCF-7 (human breast cancer cells). The new phenanthroquinolizidine pileamartine D (2: ) showed strong and selective proliferation inhibition toward KB and HepG-2 cells with IC₅₀ values of 25 and 27 nM, respectively. Pileamartine C (1: ), julandine (4: ), and cryptopleurine (5: ) exhibited cytotoxicity against 4 tested cancer cell lines with IC₅₀ values less than 1 µM.

Cytotoxic aryltetralin lignans from fruits of Cleistanthus indochinensis

Eight new aryltetralin lignans, cleisindosides A-F (1-6), picroburseranin (7), and 7-hydroxypicropolygamain (8), were isolated from the fruits of Cleistanthus indochinensis (Euphorbiaceae). The structures of the isolates were established on the basis of their one- and two-dimensional NMR spectral data, as well as their mass spectrometric data. Compound 7 was found to have potent cytotoxicity against oral epidermoid carcinoma cells with an IC50 value of 0.062 µM, whereas glycosylation to 3 (IC50 7.5 µM) and stereochemical changes to 8 (IC50 10.8 µM) led to marked decreases in biological activity. Thus, it was determined that the C-7 and C-8' positions are critical for the biological activity of the lignans from this plant.

Acetylcholinesterase inhibitors from the leaves of Macaranga kurzii

Bioassay-guided fractionation of an extract of leaves of Macaranga kurzii yielded four new compounds, a stilbene (furanokurzin, 1) and three flavonoids (macakurzin A-C, 2-4). Nine known compounds were also isolated (5-13). Their structures were determined by spectroscopic analyses including MS and 2D NMR. The isolates were all evaluated for acetylcholinesterase inhibitory activity. Compound 6 (trans-3,5-dimethoxystilbene) exhibited the greatest activity (IC50 9 μM). Cytotoxic evaluation against KB cells showed that compound 7 had an IC50 of 4 μM, followed by 11 (IC50 10 μM) and 3 (IC50 13 μM).

Cytotoxic lignans from fruits of Cleistanthus indochinensis: synthesis of cleistantoxin derivatives

Two new aryl-tetralin lignans, 1 and 2, were isolated from the fruits of Cleistanthus indochinensis by bioassay-guided purification. Their structures were determined by spectroscopic analysis including MS and 2D NMR. The absolute configurations of 1 and 2 were established from examination of their CD spectra. Compound 1 was cytotoxic against KB cells with an IC(50) value of 0.022 μM, while compound 2 had weaker cytotoxicity, with an IC(50) value of 1.4 μM. When tested against other cancer cell lines (MCF-7, MCF-7R, and HT29), 1 showed an IC(50) of 0.014 against MCF-7R cells and an IC(50) of 0.036 μM against MCF-7 cells. A series of amide derivatives of a new lactone, homoderivatives of 1, were prepared. Of these derivatives, only compound 3 had weak cytotoxicity against KB cells.