Three triterpenes and other terpenoids from Catha cassinoides

The investigation of stems and leaves of Catha cassinoides afforded, in addition to sitosterol, β-amyrin, ursolic acid, lup-20(29)-en-3β,30-diol and friedelin, three new pentacyclic triterpenes: 30-hydroxyfriedelan-3-one, 29-hydroxyfriedelan-3-one and 3-oxo-friedelan-29-oic acid. The structures ofthese were determined by spectral studies and correlations, and were confirmed by X-ray analysis of 29-hydroxyfriedelan-3-one acetate.     

Antitumour triterpenes of Maytenus diversifolia

The known compounds maytansine and sitosterol-β-D-glucoside as well as the new triterpenes maytenfoliol and maytenfolic acid were isolated as antileukemic agents from Maytenus diversifolia. Other triterpenes isolated included the new maytensifolin-A and -B as well as the known friedelin, canophyllal, β-amyrin, canophyllol, pachysonol, 29-hydroxyfriedelan-3-one and 30-hydroxyfriedelan-3-one.     

Triterpenoids with antimicrobial activity from Drypetes inaequalis

The air-dried stems and ripe fruit of Drypetes inaequalis Hutch. (Euphorbiaceae) were studied. Four triterpene derivatives, characterized as lup-20(29)-en-3β,6α-diol, 3β-acetoxylup-20(29)-en-6α-ol, 3β-caffeoyloxylup-20(29)-en-6α-ol and 28-β d-glucopyranosyl-30-methyl 3β-hydroxyolean-12-en-28,30-dioate along with 10 known compounds were isolated from the whole stems. One triterpene, characterized as 3α-hydroxyfriedelan-25-al along with six known compounds were isolated from the ripe fruit. Their structures were established on the basis of spectroscopic analysis and chemical evidence. The triterpenes were tested for antimicrobial activity against some Gram-positive and Gram-negative bacteria, and two of them appeared to be modestly active.     

Cytotoxic lupane-type triterpenoids from Acacia mellifera

One new and eight previously described lupane-type metabolites were isolated for the first time from Acacia mellifera (Leguminosae). Based on spectral analyses, the structure of the new compound was elucidated as 28-hydroxy-3-oxo-lup-20-(29)-en-30-al (1), while the known compounds were identified as 3-oxo-lup-20-(29)-en-30-al (2), 3-hydroxy-lup-20-(29)-en-30-al (3), 28-hydroxy-lup-20-(29)-en-3-one (4), lupenone (5), lupeol (6), betulin (7), betulinic acid (8), and betulonic acid (9). Metabolites 2, 3, and 4 are reported for the first time in the Leguminosae family. The cytotoxicity of the isolated metabolites was evaluated on the NSCLC-N6 cell line, derived from a human non-small-cell bronchopulmonary carcinoma. Compounds 1 and 3 exhibited significant levels of activity.     

Anti-inflammatory,antimicrobial and acetylcholinesterase inhibitory activities of friedelanes from Maytenus robusta branches and isolation of further triterpenoids

The new pentacyclic triterpenoids friedel-1-en-3,16-dione (1), 1α,29-dihydroxyfriedelan-3-one (2) and 16β,28,29-trihydroxyfriedelan-3-one (3) were isolated from Maytenus robusta branches in addition to the known, but new for this species, triterpenoid 12α,29-dihydroxyfriedelan-3-one (4). The structures and stereochemistry of the novel triterpenoids were established by IR, 1D/2D NMR and HR-APCIMS spectral data. In addition, the biological activity of compound 2 and the previously isolated friedelanes 5–8 (friedelan-3,16-dione, 29-hydroxyfriedelan-3-one, 29-hydroxyfriedelan-3,16-dione and 16β,29-dihydroxyfriedelan-3-one) was investigated. Compounds 2 and 8 were tested for their acetylcholinesterase properties and antimicrobial activity against the bacteria Staphylococcus aureus, Pseudomonas aeruginosa, Listeria monocytogenes, Citrobacter freundii, and the fungus Candida albicans. Compound 2 was the most active compound for both assays, with values of 32.3% acetylcholinesterase inhibition, 42% activity against the fungus Candida albicans and 34% against the bacterium Pseudomonas aeruginosa. Compounds 5–8 were assayed for their antiedematogenic activity using the carrageenan-induced paw edema assay. At maximum inflammation after three hours, compounds 6 and 8 showed 42% and 57% activity, respectively. After four hours, compounds 5 and 7 showed activity of 71% and 75% compared to 79% of the control indomethacin.     

Cancer chemopreventive activity of serratane-type triterpenoids from Picea jezoensis

To search for cancer chemopreventive agents from natural sources, 13alpha,14alpha-epoxy-21alpha-methoxyserratan-3-one, 21alpha-methoxyserrat-13-en-3-one, and 21alpha-hydroxy-3beta-methoxyserrat-14-en-30-al isolated from the cuticle of Picea jezoensis (Sieb. et Zucc.) Carr. var. jezoensis (Pinaceae) were investigated for inhibitory effects in a two-stage mouse skin carcinogenesis test on mouse skin with 7,12-dimethylbenz[a]anthracene (DMBA) as initiator and 12-O-tetradecanoylphorbol-13-acetate (TPA) as promoter. 21Alpha-hydroxy-3beta-methoxyserrat-14-en-30-al and 13alpha,14alpha-epoxy-21alpha-methoxyserratan-3-one were found to exhibit strong antitumor-promoting activities in the in vivo carcinogenesis test.     

Cross-conjugated carotenoid aldehydes in Rhodopseudomonas viridis

Two carotenoid aldehydes isolated from Rhodopseudomonas viridis (Rhodospirillaceae) have been identified as lycopen-20-al (13-cis-ψ, ψ-caroten-20-al) and the novel 3,4-didehydro-1,2-dihydrolycopen-20 (or 20′)-al (3,4-didehydro-1,2-dihydro-ψ,ψ-caroten-20-al or 3′, 4′-didehydro-1′,2′-dihydro-ψ,ψ-caroten-20-al). Some extracts also contained acetonyl derivatives, probably artefacts produced from the cross-conjugated carotenoid aldehydes and acetone under alkaline conditions. The distribution of cross-conjugated caroten-20-als in photosynthetic bacteria is discussed.     

A new compound, 21α-hydroxyfriedel-4(23)-en-3-one and other triterpenoids from Phyllanthus reticulatus

The petrol extracts of the stems and leaves of Phyllanthus reticulatus both gave friedelin and sitosterol, and that of the former also friedelan-3β-ol, glochidonol, 21α-hydroxyfriedelan-3-one and a new compound, which was proved to be 21α-hydroxyfriedel-4(23)-en-3-one. The ethanol extract of the stems yielded betulinic acid.     

A lupane derivative and the 13C NMR chemical shifts of some lupanols from Pleurostylia opposita

A new lupane derivative isolated from Pleurostylia opposita has been assigned the structure 6,β-hydroxy-lup-20(29)-en-3-one, using spectral evidence and chemical interconversions. The ¹³C NMR spectral assignments of 20-hydroxy-lupan-3-one, 6β, 20-dihydroxy-lupan-3-one, 6β,28-dihydroxy-lup-20(29)-en-3-one and 20-hydroxy-lupane-3, 6-dione previously isolated from the same plant are also reported.     

Biologically active abietane and ent-kaurane diterpenoids and other constituents from Erythroxylum suberosum

Bioassay-guided fractionation of the ethanol extract from the branches of Erythroxylum suberosum, which was toxic to brine shrimp larvae, afforded five diterpenes bearing abietane and ent-kaurane-type skeletons from an active fraction. From these, four were new, 7-oxo-16-hydroxy-abiet-15(17)-en-19-al, 16-hydroxyabiet-15(17)-en-7-one, 7α,16-dihydroxy-abiet-15(17)-en-19-al and ent-12α-hydroxy-kaur-16-en-19-al, while methyl ent-7α,15β-dihydroxy-kaur-16-en-19-oate is reported for the first time as a natural product. This is also the first reported occurrence of abietane-type diterpenes in the genus Erythroxylum. The flavonoid ombuin-3-rutinoside was isolated from an inactive fraction, while rutin (quercetin-3-rutinoside) was obtained from the non-toxic ethanol extract of the leaves. The structures of the new and known compounds were established by analyses of 1D- and 2D-NMR and mass spectrometry data.     

Triterpenoids from ten Lithocarpus species of Hong Kong

From the petrol extracts of the leaves and stems of ten Lithocarpus species (L. attenuata, L. cornea, L. elizabethae, L. glabra, L. haipinii, L. hancei, L. harlandi, L. irwinii, L. litchioides, and L. polystachya) of the Fagaceae family, were isolated 23 different triterpenoids, and sitosterol and stigmasterol. Of the triterpenoids, 11 belonged to the oleanane and rearranged oleanane group [β-amyrin, friedelin, friedelan-3β-ol, glutinol, taraxerone, taraxerol and its acetate, canophyllol (28-hydroxyfriedelan-3-one), friedelan-2,3-dione (3-hydroxyfriedel-3-en-2-one), pachysandiol-A (2α,3β-dihydroxyfriedelane) and a new compound lithocarpic lactone C₃₀H₅₀O₂]. Four compounds were from the lupane and rearranged lupane group (lupenone, lupeol, betulin and taraxasterol), 2 from the hopane group (22-hydroxyhopan-3-one and 3β,22-dihydroxyhopane), and 6 were probably new compounds.     

Triterpenes from the leaves of Pleurostylia opposita

Friedelin, friedelan-3β-ol, sitosterol, α-amyrin, 6β,20-dihydroxylupan-3-one, lup-20(29)-en-3β,6β-diol, 6β,28-dihydroxylup-20(29)-en-3-one and dulcitol were isolated from the leaves of Pleurostylia opposita. The distribution of lupanes in the Celastraceae and their chemotaxonomic significance is discussed.     

Antibacterial triterpenoids from Dillenia papuana and their structure-activity relationships

Two new oleanene-type triterpenoids, dillenic acids D and E, have been isolated from the leaves and stems of Dillenia papuana together with the new natural product 3-oxoolean-12-en-30-oic acid. Together with these compounds, the known compound, betulinic acid (3β-hydroxy-20(29)-lupen-28-oic acid) was isolated as the major component of the fractions studied. Dillenic acids D and E were characterized as 2,3-seco-2-oxoolean-12-en-3-methylester-30-oic acid and 1,3β-dihydroxyolean-12-en-30-oic acid and their nuclear magnetic resonance data were unambiguously assigned using two-dimensional nuclear magnetic resonance techniques. A comparison of antibacterial activities of these compounds with the earlier reported dillenic acids A-C indicated that, aside from a double bond in γ- or δ-position to a carboxylic group, a ketone function in ring A of an oleanene-skeleton may be required for the observed activity.     

Three new oxygenated triterpenoids of the lupane series from Gymnosporia wallichiana

Two new epimeric triterpenoid acids, gymnosporic acid, 3β-hydroxy-(20R)-lupan-29-oic acid, wallichianic acid, 3β-hydroxy-(20S)-lupan-29-oic acid and a new diol wallichianol, (20S)-lupane-3β,29-diol have been isolated from Gymnosporia wallichiana, in addition to β-amyrin, friedelin, 3β-hydroxy-29-norlupan-20-one and dulcitol.     

Secondary metabolites from two species of Pulicaria and their cytotoxic activity

Two new compounds, the sesquiterpene (1E,5E)-8β-acetoxy-4α-hydroxy-7βH-germacra-1(10),5-dien-14-oic acid (2), and a nor-sesquiterpene, (5E)-8β-acetoxy-4α-hydroxy-7βH-germacr-5-en-10-one (3), were isolated from Pulicaria canariensis ssp. lanata, along with ten known compounds, including the flavonoid 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (4). From Pulicaria burchardii, we isolated seven known compounds; the physical and spectroscopic data of the triterpenoid 3β-hydroxytaraxaster-20-en-30-al (1) are reported. The structures of compounds 1-3 were determined on the basis of HR-MS, and 1D- and 2D-NMR studies. The structure of 2 was corroborated by X-ray crystal diffraction. Cell viability experiments revealed that the semisynthetic flavonoid 4b was the most cytotoxic compound against human leukemia cells, and the cytotoxicity was caused by induction of apoptosis, as determined by microscopy of nuclear changes.     

Clerodane and labdane diterpenoids from Nuxia sphaerocephala

Seven diterpenoids including four clerodane and three labdane derivatives, (13S)-ent-7beta-hydroxy-3-cleroden-15-oic acid (1), ent-7beta-hydroxy-2-oxo-3-cleroden-15-oic acid (2), ent-2,7-dioxo-3-clero-den-15-oic acid (3), ent-18-(E)-caffeoyloxy-7beta-hydroxy-3-cleroden-15-oic acid (4) (13S)-ent-18-(E)-coumaroyloxy-8(17)-labden-15-oic acid (5), ent-18-(E)-caffeoyloxy-8(17)-labden-15-oic acid (6), ent-15-(E)-caffeoyloxy-8(17)-labden-18-oic acid (7), have been isolated from an ethyl acetate extract of the leaves of Nuxia sphaerocephala, together with 17 known compounds. 3-Oxolup-20(29)-en-30-al (3-oxolupenal) (8) and 3beta-hydroxylup-20(29)-en-30-al (3beta-hydroxy-lupenal) (9) showed the best inhibitory activity against Plasmodium falciparum with the IC(50) values between 1.55 and 4.67 microg/ml in vitro, respectively. The structure and the relative stereochemistry of the compounds were established on the basis of their spectroscopic properties. The absolute configuration at C-13 of 1 and 5 was determined by the PGME amide procedure.     

Three new triterpenoids from Salacia hainanensis Chun et How showed effective anti-α-glucosidase activity

To identify the chemical constituents with hypoglycemic activity in Salacia hainanensis Chun et How, this study was carried out on the roots of S. hainanensis. By means of a bioassay-guided method, three new triterpenoids (2β,3β-dihydroxylup-20(29)-ene [compound 1], 30-hydroxy-D:A-friedo-olean-1-en-3-one [compound 2], and 24,25,26-trihydroxytirucall-7-en-3-one [compound 3]) along with three known compounds (olibanumol J [compound 4], 21α-hydroxy-D:A-friedo-olean-3-one [compound 5], and 29-hydroxy-D:A-friedo-olean-3-one [compound 6]) were isolated from the EtOAc part and were shown to have effective α-glucosidase inhibitory activity. Their structures were established on the basis of spectral analysis, especially according to the data obtained by two dimensional nuclear magnetic resonance spectroscopic and high-resolution mass spectra experiments. All compounds with the exception of compound 2 showed much stronger inhibitory activity against α-glucosidase than did the positive control (acarbose, IC₅₀ 1.02 μM).     

Evaluation of Cytotoxicity and Antifungal Activity of Friedelanes from Salacia elliptica Roots

Plants from Salacia genus are used in traditional medicine for a wide range of diseases. Previous studies reported bioactive pentacyclic triterpenoids from S. elliptica leaves and branches. In this study, the novel pentacyclic triterpenoid 7α,15α-dihydroxyfriedelan-3-one ( 1 ) was obtained from the roots of Salacia elliptica, along with seven known compounds: friedelan-3-one ( 2 ), friedelan-3β-ol ( 3 ), friedelan-1,3-dione ( 4 ), friedelan-3,15-dione ( 5 ), 15α-hydroxyfriedelan-3-one ( 6 ), 15α,26-dihydroxyfriedelan-3-one ( 7 ), and 26-hydroxyfriedelan-3,15-dione ( 8 ). Additionally, one steroid, spinasterol ( 9 ), was also identified. The chemical structures of all compounds were established through ¹H and ¹³C-NMR. Compound 1 was analysed by additional 2D experiments (HMBC, HSQC, COSY, and NOESY) for complete elucidation. Furthermore, the cytotoxicity of compounds 2 , 3 , 6 , 7 and 8 against the A549 lung cancer cells model was evaluated. The flow cytometry analysis revealed a significant cytotoxic activity similar to that exhibited by the triterpenoid lupeol. Additionally, compounds 2 , 3 , 6 , and 7 were tested for in vitro antifungal activity against Candida, Cryptococcus and Sporothrix strains. However, all compounds showed no activity at the tested concentrations.     

Isolation of dihydroxylupene and dihydroxylupane from the bark of Lawsonia inermis

Two pentacyclic triterpenes isolated from the bark of henna were identified as 3β, 30-dihydroxylup- 20(29)-ene (hennadiol), and (20S)-3β, 30-dihydroxylupane. The assignment of the C-20 configuration in the latter compound was supported by the analysis of Eu(fod)₃-induced ¹H NMR chemical shifts in the two C-20 epimers synthesized from lupeol.