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Four novel stilbenes ( 1 – 4 ) were isolated from the root bark of Ekebergia benguelensis . The structures were established by spectroscopic methods including 2D NMR analysis. The structure of 1 , a new stilbene–coumarin hybrid representing a novel skeleton, was confirmed by single X-ray analysis. Compounds 1 – 4 were evaluated against a panel of human cancer cell lines.

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).

A known aporphine alkaloid, (-)-roemerine [1], isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells. In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive. As indicated by its ability to inhibit ATP-dependent [3H]vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein. In addition to alkaloid 1, three inactive compounds [the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin [2] (a new natural product), and (+)-syringaresinol] were also isolated.

From the leaves of Monotes engleri, five prenylated flavanones were isolated as constituents that displayed cytotoxic activity against several human cancer cell lines. Three of these substances are novel, namely, 6-(1,1-dimethylallyl)naringenin, 6-(1,1-dimethylallyl)eriodictyol and 3′-O-methyl-6-(1,1-dimethylallyl)eriodictyol, with the other two active substances being the known flavanones, 6,8-diprenyleriodictyol and hiravanone. Additionally, two novel, but non-cytotoxic, biogenetically related flavanones were isolated, 6-[(2RS)-hydroxy-3-methyl-3-butenyl]-8-prenyleriodictyol and 5,4′-dihydroxy-4″,4″-dimethyl-5″-methyl-5″H-dihydrofurano[2″,3″:6,7]flavanone. The structures of the new compounds were determined by spectral analysis 1D- and 2D-NMR experiments.

Four novel stilbenes ( 1 – 4 ) were isolated from the root bark of Ekebergia benguelensis . The structures were established by spectroscopic methods including 2D NMR analysis. The structure of 1 , a new stilbene–coumarin hybrid representing a novel skeleton, was confirmed by single X-ray analysis. Compounds 1 – 4 were evaluated against a panel of human cancer cell lines.

A new coumarin, 5-(4-hydroxyphenethenyl)-4,7-dimethoxycoumarin (1) was isolated from the combined ethyl acetate extracts of the root bark, root wood and stem bark of Monotes engleri, and found to be cytotoxic against two cell lines in a human tumor panel. Its structure was determined on the basis of spectroscopic methods.

The rootwood of Aeschynomene mimosifolia Vatke (Leguminosae) has yielded a new neoflavonoid, mimosifoliol (1), and an unusual C16-styrylcycloheptenone derivative, mimosifolenone (2). The structures of these compounds were determined on the basis of spectral analysis. Compound 1 demonstrated weak activity in DNA-strand scission assay, while compound 2 was found to be inactive. Mimosifoliol (1) was inactive toward several human cell lines, while 2 was moderately active against the KB cell line.

Two structurally novel cytotoxic ent-kaurene diterpenoids, 13-methoxy-15-oxozoapatlin and 13-hydroxy-15-oxozoapatlin, were isolated from the root bark of Parinari curatellifolia, together with the known compound, 15-oxozoapatlin, on the basis of bioactivity-guided chromatographic fractionation and found to demonstrate broad-spectrum cytotoxic activity against a panel of cultured human cancer cell lines. The structures of these compounds were determined by analysis of their spectroscopic data. The presence of an alpha, beta-unsaturated carbonyl group in 13-methoxy-15-oxozoapatlin suggested that the cytotoxic potential of this compound could be mediated through reaction with cellular nucleophiles by means of a Michael-type addition. The compound 13-methoxy-15-oxozoapatlin reacted with the nucleophiles L-cysteine and beta-mercaptoethanol. The adduct with beta-mercaptoethanol was isolated, structurally characterized and found to be approximately 5-fold less cytotoxic than 13-methoxy-15-oxozoapatlin itself. The compound 13-methoxy-15-oxozoapatlin did not interact with DNA nor guanosine, and it was not mutagenic for Salmonella typhimurium strain TM677. The effects of 13-methoxy-15-oxozoapatlin on the growth of human cancer cells were analyzed utilizing cultured ZR-75-1 breast cancer cells. Biosynthesis of DNA, RNA and protein was reduced in treated cells, and accumulation at the G2/M phase of the cell cycle was observed. The compound 13-methoxy-15-oxozoapatlin did not mediate antimitotic activity with dibutyryl cAMP-treated cultured astrocytoma cells, suggesting that the cell cycle effect is G2 specific. No antitumor activity was observed when athymic mice carrying KB cells were treated with 13-methoxy-15-oxozoapatlin. These data indicate that the cytotoxic activity of 13-methoxy-15-oxozoapatlin is mediated in part by covalent reaction with a cellular component (such as sulfhydryl-containing protein) by means of a Michael-type addition, and this results in the blockage of cell-cycle progression.

A new polyacetylenic diepoxide compound, gummiferol [1] was isolated from the leaves of Adenia gummifera by KB cytotoxicity-guided fractionation. Compound 1 exhibited significant activity against the KB human cell line and a broad cytotoxic spectrum against other human cancer cell lines. The structure of 1 was established primarily on the basis of its spectral data.

Raman and infrared spectra of neat n‐hexadecane were measured as a function of hydrostatic pressure up to 54 and 83 kbar, respectively. The application of high pressure leads to anomalous frequency shifts and band splittings, and induces drastic changes in the band shapes and in the distribution of intensities within the spectra. The pressure‐induced changes in the vibrational spectra of n‐hexadecane are discussed in terms of phase transitions, molecular distortions, interchain interactions, frequency dispersions, and Fermi resonance interactions. The effect of pressure on the Raman and infrared spectra of n‐hexadecane is used to test conclusions drawn from theoretical Fermi resonance calculations concerning the origin of several features in the Raman spectra of n‐alkanes. Evidence is given to show that some assumptions made in these calculations are incorrect and that the model used is too simple to account for the intensity distribution in the CH stretching region of the Raman spectra of n‐alkanes. It i...

The infrared spectra of tripalmitoyl glyceride confirm the tuning fork configuration previously attributed to trilauroyl glyceride (Small, D. M. 1986. Handbook of Lipid Research. Vol. 4). The acyl chains in solid tripalmitoyl glycerol, either within each molecule or between neighboring molecules, are oriented parallel to each other with the sn-3 acyl chains extended toward the opposite direction of the sn-1 and sn-2 chains. The presence of cholesterol increases the orientational disorder of the tripalmitoyl glyceride molecules in terms of increased reorientational fluctuations and twisting/torsion motions of the acyl chains. In the solid mixture, cholesterol is embedded in the tripalmitoyl glyceride lattice which results in a reorientation of the acyl chains within each molecule from a parallel packing to a nonparallel packing. No evidence was found for hydrogen bond formation between the OH group of cholesterol and any of the three C = O groups of tripalmitoyl glyceride.