A weakly antimalarial biflavanone from Rhus retinorrhoea

The biflavanone (2S,2"S)-7,7"-di-O-methyltetrahydroamentoflavone and five known flavonoids, 7-O-methylnaringenin, 7,3'-O-dimethylquercetin, 7-O-methylapigenin, 7-O-methylluteolin, and eriodictyol were isolated from the leaves of Rhus retinorrhoea Steud, Ex Olive. The biflavanone exhibited moderate antimalarial activity with IC50 0.98 microg/ml against Plasmodium falciparum (W2 Clone) and weak activity against P. falciparum (D6 Clone) with IC50 2.8 microg/ml. Nevertheless, it did not display any cytotoxicity. 7-O-Methylnaringenin showed weak antimicrobial activity against Candida albicans, C. krusei, Staphylococcus aureus, Mycobacterium smegmatis, M. intracellulare, and M. xenopi with MIC approximately 100 microg/ml. Characterization of each compound was based on spectral analysis and comparison with reported data.

Separation and quantification of the major daucane esters of Ferula hermonis by HPLC

A simple HPLC method was developed to quantify the major daucane sesquiterpene esters present in herb and roots of Ferula hermonis Boiss. The method utilized a C(18) reversed phase analytical column with isocratic elution for 30 minutes and UV detection at 240 nm. Extracts from two crude plant samples and two commercial products were fingerprinted and quantitatively analyzed.

Microbial transformation of pyrethrosin

Microbial transformation of the germacranolide pyrethrosin (1) using Rhizopus nigricans NRRL 1477 has resulted in the isolation of 6 alpha-acetoxy-1 beta,4 alpha-dihydroxy-5,7 alpha H,8 beta H-eudesm-11 beta,13-dihydro-8,12-olide (5), a new eudesmanolide-type metabolite, in addition to the previously reported eudesmanolides: 2, 3, 4, and 6. The structure elucidation of these metabolites was based primarily on 1D and 2D NMR analyses. The isolated metabolites exhibited cytotoxic, antifungal, and antiprotozoal activities.

Voltammetric determination of parthenolide in spiked human plasma and urine

The voltammetric behaviour of parthenolide, a biologically active sesquiterpene lactone, was studied using direct current (DCt), alternating current and differential-pulse polarography (DPP). Parthenolide developed well-defined cathodic waves over the whole pH range in Britton-Robinson buffers. At pH 10 the diffusion current constant was 3.54 +/- 0.08 (+/- standard deviation; n = 8). The current vs concentration plots were rectilinear over the range 4-36 and 1-28 micrograms/mL in the DCt and DPP modes, respectively, with a minimum detectability of 0.06 microgram/mL (about 1 x 10(-7) M) using the latter technique. The waves were characterised as being diffusion controlled, although adsorption phenomenon played a limited role in the electrode process. The described analytical method was applied to the determination of parthenolide in spiked human urine and plasma; the percentage recoveries were 95.72 +/- 0.22 and 94.0 +/- 0.13 (+/- standard deviation; n = 9), respectively.

Microbial Hydroxylation and Reduction of the Diterpene Psiadin

Microbial bioconversion studies conducted on the diterpene psiadin have revealed that it was metabolized by Aspergillus niger (NRRL 2295) to give 2α-hydroxydeoxopsiadin, Cunninghamella blakesleeana (ATCC 8688a) to give 11β-hydroxypsiadin, and Cylindrocephalum aureum (ATCC 12720), Gongronella butleri (ATCC 22822), Kloeckera africana (ATCC 20111), and Kluyveromyces marxianus var. lactis (ATCC 2628) to yield 7α-hydroxypsiadin. Their structures have been established on the basis of spectral data. The structure and relative stereochemistry of 7α-hydroxypsiadin was confirmed by single-crystal X-ray analysis.

Daucane sesquiterpenes from Ferula hermonis

The roots of Ferula hermonis Boiss yielded two new daucane esters, 14-(4'-hydroxybenzoyloxy)dauc-4,8-diene (1) and 14-(4'-hydroxy-3'-methoxybenzoyloxy)dauc-4,8-diene (2), together with the four known sesquiterpenes jaeschkeanadiol p-hydroxybenzoate (3), jaeschkeanadiol benzoate (4), jaeschkeanadiol (5), and epoxyjaeschkeanadiol (6). The identities of the isolated compounds were ascertained primarily using NMR and MS data. Compounds 1 and 3 exhibited antimicrobial activity against Staphylococcus aureus with IC(50) 1.5 and 3.5 microg/mL, respectively, and against Methicillin-resistant S. aureus with IC(50) 2.0 and 4.0 microg/mL, respectively.

New eudesmane sesquiterpenes from Plectranthus cylindraceus

Three new eudesmane sesquiterpenes, plectranthone (1), desacetylplectranthone (2), isodeacetylplectranthone (3), and the three known flavonols pachypodol, casticin, and chrysosplenol D were isolated for the first time from the aerial parts of Plectranthus cylindraceus. Their structures have been established on the basis of spectral data. The structures and relative stereochemistries of 1 and 2 were confirmed by single-crystal X-ray analysis.

Microbial metabolism of artemisitene

Studies on the microbial transformation of the sesquiterpene endoperoxide artemisitene have revealed that artemisitene was metabolized by Aspergillus niger (NRRL 599) to yield 11-epi-artemisinin, 9 beta-hydroxydeoxy-11-epi-artemisinin and 9 beta-hydroxy-11-epi-artemisinnin. These metabolites were characterized on the basis of their spectral data.

New products from the reactions of artemisinin with ammonia and amines

Reaction of artemisinin (1) with ammonia, methylamine, dimethylamine, and allylamine afforded five unexpected products 2-6, in addition to the previously reported compounds 7-12. The identities of the new compounds were established from their spectral data, by chemical derivatization and by comparison with published reports. The stereochemistries of compounds 5 and 6 were confirmed by single-crystal X-ray analysis.

Artemisinin-derived sesquiterpene lactones as potential antitumour compounds: cytotoxic action against bone marrow and tumour cells

We determined the in vitro cytotoxic activity of the sesquiterpene lactone endoperoxide artemisinin (1) and some chemically prepared derivatives, which have been found to display cytotoxicity to cloned murine Ehrlich ascites tumour (EAT) cells and human HeLa cells and against murine bone marrow using a clonogenic assay for committed progenitor cells of the granulocyte-monocyte lineage (CFU-GM assay). Comparing artemisinin (1) to deoxyartemisinin (2), the endoperoxide group appeared to play a role in cytotoxicity to CFU-GM cells. Dimers of dihydroartemisinin and dihydrodeoxyartemisinin revealed that the stereochemistry of the ether linkage of the dimers was a more important determinant for this cytotoxic activity. The nonsymmetrical dimer of dihydroartemisinin (3) and the corresponding endoperoxide-lacking dimer of dihydrodeoxyartemisinin (5) were equally cytotoxic to CFU-GM cells. Despite the differences between both systems, it may be stated that most compounds displayed higher cytotoxicity to CFU-GM cells than to EAT cells. Dimers of dihydroartemisinin (3, 4) were selected as potential antitumour compounds and subjected to the National Cancer Institute drug-screening programme consisting of about sixty human cancer cell lines derived from nine different tissues. Both compounds displayed the same specific cytotoxicity pattern. Throughout the screen dimer 3 was more active than 4.

Glucose-conjugation of the flavones of Psiadia arabica by Cunninghamella elegans

Microbial transformation of psiadiarabin and its 6-desmethoxy analogue 5,3' dihydroxy-7,2',4'5'-tetramethoxyflavone by Cunninghamella elegans NRRL 1392 gave the 3'-glucoside conjugates of the two flavones. Structural elucidation of these two new metabolites was achieved using 1D and 2D NMR spectroscopy and CIMS.

Stereochemistry-dependent cytotoxicity of some artemisinin derivatives

We determined the cytotoxicity of some artemisinin derivatives against EN2 tumor cells using the MTT assay. Artemisinin (1) was clearly more cytotoxic than deoxyartemisinin (2), which lacks the endoperoxide bridge. Ether-linked dimers of dihydroartemisinin with defined stereochemistry were found to differ in the extent of cytotoxic effect on EN2 cells. The nonsymmetrical dimer (3) was more cytotoxic than the symmetrical dimer (4). The nonsymmetrical dimer of dihydrodeoxyartemisinin (5) lacking the endoperoxide bridges was also effective in the MTT assay, although less cytotoxic than 3 and 4. Similarly, the symmetrical dimer (6) was less effective than 5. Epoxides of artemisitene also showed that stereochemistry was an important factor for cytotoxicity. The results suggested that the endoperoxide bridge was not crucial for cytotoxicity to the tumor cells, but contributed to the cytotoxic effect apparently exerted by the ether linkage of the dimers. Flow cytometry data indicated that the dimers 3 and 4 caused an accumulation of the cells in the G1-phase of the cell cycle. In contrast, artemisinin (1) caused a slight increase of S-phase cells.

Antitumor germacranolides from Anvillea garcinii

The aerial parts of Anvillea garcinii yielded two new germacranolides, 9 alpha-hydroxy-1 beta, 10 alpha-epoxyparthenolide (4) and parthenolid-9-one (5), in addition to the known 9 alpha-hydroxyparthenolide (1), 9 beta-hydroxyparthenolide (2), and 9 beta-hydroxy-1 beta, 10 alpha-epoxyparthenolide (3). The structures of the new compounds were elucidated from their spectral data (IR, MS, 1H- and 13C-NMR, 1H-1H COSY, and 1H-13C HETCOR) and by chemical derivatization. The hitherto unreported 13C-NMR data and carbon atom assignments of the previously isolated lactones 1, 2, and 3 were given. The in-vitro antitumor and anti-HIV activities were evaluated for the isolated compounds.

Alkaloids of Daphnandra dielsii. I. Tertiary Bases. Isolation and Structural Determination of Dielsine

The isolation and structural determination of the new alkaloid dielsine (3), which belongs to the small group of repanduline-type bases, are described.