New dammarane triterpenes from the aerial parts of Ibicella lutea grown in Argentina

Two new dammarane triterpenes have been isolated from the aerial parts of Ibicella lutea, 3-acetyl-24-epi-polacandrin (1) and 1,3-diacetyl-24-epi-polacandrin (2), and were obtained along with the known compounds 20S,24S-epoxy-3beta,12beta,25-trihydroxydammarane (3) and apigenin. The structures of compounds 1 and 2 were deduced by spectroscopic studies and by chemical transformations leading to the preparation of derivatives 4-11. The structure and relative stereochemistry of 1 were verified by single-crystal X-ray analysis. The natural compounds and selected semisynthetic derivatives were evaluated against several tumor cells.     

Bioactive dammarane triterpenes from the mangrove plant Bruguiera gymnorrhiza

Three new dammarane triterpenes, bruguierins A-C (1-3), were isolated from a petroleum ether extract of the flowers of Bruguiera gymnorrhiza. Their structures were determined on the basis of physical and spectroscopic data interpretation. With stably transfected HepG2 cells, the three isolates activated antioxidant response element (ARE luciferase activation) with EC(50) values of 7.8, 9.4, and 15.7 microM, respectively. Bruguierin A (1) also inhibited phorbol ester-induced NFkappaB (nuclear factor-kappaB) luciferase activation with an IC(50) value of 1.4 microM and selectively inhibited cyclooxygenase-2 (COX-2) activity with an IC(50) value of 0.37 microM. Compounds 2 and 3 were not active in these bioassays.     

Dammarane-type glycosides from Gynostemma pentaphyllum

Fifteen new dammarane glycosides (1-15), together with four known compounds, gypenosides IV, VIII, LXXI, and XLIX, were isolated from the MeOH extract of the aerial parts of Gynostemma pentaphyllum. Their structures were elucidated by 1D and 2D NMR spectra interpretation as well as by chemical degradation.     

Seco-terpenoids and other constituents from Elateriospermum tapos

Two new taraxerane triterpenes, 2,3-seco-taraxer-14-ene-2,3,28-trioic acid 2,3-dimethyl ester ( 1) and 2,3-seco-taraxer-14-ene-2,3,28-trioic acid 3-methyl ester ( 2), along with two known triterpenes, hopenol B and aleuritolic acid, and five known flavonoids, putraflavone, kaempferol, sequoiaflavone, amentoflavone, and ginkgetin, were isolated from the leaves of Elateriospermum tapos. The stem extract yielded a new cleistanthane diterpene, 2,3-seco-sonderianol ( 3), three known triterpenes, lupeol, lupeol acetate, and 3-acetylaleuritolic acid, and three known diterpenes, yucalexin B-22, yucalexin P-15, and yucalexin P-17. The structures of these compounds were established on the basis of their spectroscopic data. Compound 1 was cytotoxic against NCI-H187 and BC cell lines and also showed in vitro antimycobacterial activity against Mycobacterium tuberculosis.     

Triterpenoids from the floral spikes of Betula platyphylla var. japonica and their reversing activity against multidrug-resistant cancer cells

Four new triterpenes, together with 16 known triterpenes, were isolated from the floral spikes of Betula platyphylla var. japonica in a search for compounds capable of reversing multidrug resistance in cancer cells. The structures of the new triterpenes were elucidated as 3,4-seco-olean-4(23),13(18)-dien-3-oic acid (1), 3,4-seco-urs-4(23),20(30)-dien-3-oic acid (2), 3-O-methylmalonylepiocotillol II (6), and 3-O-methylmalonylcabraleahydroxylactone (16) by spectroscopic examination. The cytotoxicity of the isolated triterpenes against human cancer cell lines as well as multidrug-resistant cancer cell lines was evaluated. Most of the isolated triterpenes showed very weak cellular toxicities. Although no discernible differences were found in the cytotoxicities for the tested compounds against sensitive and resistant cell lines, the cytotoxicities for several triterpenes against multidrug-resistant cancer cell lines (KB-C2 or K562/Adr) were enhanced in the presence of nontoxic concentrations of colchicine or doxorubicin. Compound 10 reversed the cytotoxicity of colchicine against KB-C2 cells at 8.1 microM and showed comparable potency to 5 microM verapamil.     

Antiproliferative triterpenes from Melaleuca ericifolia

Three new 28-norlupane triterpenes, 28-norlup-20(29)-en-3beta-hydroxy-17beta-hydroperoxide (1), 28-norlup-20(29)-en-3beta-hydroxy-17alpha-hydroperoxide (2), and 20 S-17beta,29-epoxy-28-norlupan-3beta-ol (3), were isolated from the leaves of Melaleuca ericifolia along with eight known pentacyclic triterpenes. The structures of the new compounds were elucidated by spectroscopic methods including 1D and 2D NMR spectroscopy and mass spectrometry. The isolated triterpenes were evaluated for antiproliferative activity against the malignant +SA mammary epithelial cell line.     

Cycloartane triterpenes isolated from Combretum quadrangulare in a screening program for death-receptor expression enhancing activity

In our screening program for natural products that increase DR5 (death-receptor 5) expression, nine new cycloartane triterpenes, combretanones A-G (1-7), combretic acid A (8), and combretic acid B (9), were isolated from a MeOH extract of Combretum quadrangulare leaves. The known oleanane triterpenes (10, 11) and six known flavonols (12-17) were also isolated. The structures of 1-9 were elucidated by spectroscopic studies. Compounds 7, 9, 12, 16, and 17 enhanced DR5 expression, and 16 showed TRAIL-resistance abrogating activity.     

Friedolanostanes and lanostanes from the leaves of Garcinia hombroniana

Five new triterpenes, one 17,14-friedolanostane (garcihombronane F, 1), three 17,13-friedolanostanes (garcihombronanes G-I, 2-4), and one lanostane (garcihombronane J, 5), were isolated from the leaves of Garcinia hombroniana together with nine known compounds including five triterpenes, two ionone-derived glycosides, and two flavonoid glucosides. Their structures were identified by analysis of spectroscopic data and comparison of the NMR data with those previously reported.     

Bioactive 3,4-seco-Triterpenoids from the Fruits of Acanthopanax sessiliflorus

Eight new 3,4-seco-lupane triterpenes and glycosides, acanthosessiligenins I and II (1, 3) and acanthosessiliosides A-F (2, 4-8), as well as six known 3,4-seco-lupane triterpenes (9-14) were isolated from an ethanolic extract of Acanthopanax sessiliflorus fruits. The chemical structures of 1-8 were determined by spectroscopic data interpretation. All isolated compounds were tested for their cytotoxicity against six human cancer cell lines and their ability to inhibit LPS-induced nitric oxide production in RAW 264.7 macrophages.     

Highly hydroxylated triterpenes from Salvia kronenburgii

The three new triterpenes (1-3) and five known triterpenes and a sterol were isolated from the acetone extract of a Turkish collection of Salvia kronenburgii. The structures of the new triterpenes were established as 1beta,2alpha-dihydroxy-3beta-acetoxy-11-oxours-12-ene (1), 2alpha,20beta-dihydroxy-3beta-acetoxyurs-9(11),12-diene (2), and 1beta,2alpha-dihydroxy-3beta-acetoxyurs-9(11),12-diene (3) on the basis of spectral analyses, including 1D and 2D NMR and mass spectroscopy. It is probable that compounds 2 and 3 are artifacts from dehydration of the corresponding allylic alcohols. 1beta,2alpha,3beta,11alpha-Tetrahydroxyurs-12-ene (5), the most abundant compound in the extract, was found to be highly cytotoxic to renal, non-small cell lung, and breast cancer cell lines.     

Antineoplastic agents. 489. Isolation and structures of meliastatins 1-5 and related euphane triterpenes from the tree Melia dubia

The bark of the giant neem tree Melia dubia was found to contain 11 euphane-type triterpenes. Five new compounds, meliastatins 1-5 (1-5), proved to inhibit growth of the P388 lymphocytic leukemia cell line (ED(50) 1.7-5.6 microg/mL). Four of the others, the previously known methyl kulonate (8), kulinone (9), 16-hydroxybutyrospermol (10), and kulactone (11), were also found to inhibit (ED(50) 2.5-6.2 microg/mL) the P388 cancer cell line. In addition, two new euphane triterpenes were isolated and named dubione A (6) and dubione B (7). Structures for each of the 11 euphane triterpenes were established by spectral techniques that included HRMS and 2D NMR.     

Triterpene saponins from Gynostemma cardiospermum

Six new dammarane glycosides (1-6) and four known compounds, rutin, kaempferol, quercetin, and linalool 3-O-beta-D-glucopyranoside, were isolated from an ethanol extract of the aerial parts of Gynostemma cardiospermum. The structures of 1-6 were elucidated by 1D and 2D NMR spectroscopic interpretation as well as by chemical degradation. Triterpene aglycons containing carbonyl groups at both C-21 and C-28, as found in compounds 1-5, are being reported in the family Cucurbitaceae for the first time.     

Absolute stereostructures of new arborinane-type triterpenoids and inhibitors of nitric oxide production from Rubia yunnanensis

The aqueous acetone extract from the roots of a Chinese herbal medicine, Rubia yunnanensis, showed a potent inhibitory effect on nitric oxide production in lipopolysaccharide-activated macrophages. Five new arborinane-type triterpenes, rubianols-a (1), -b (2), -c (3), -d (4), and -e (5), and a new arborinane-type triterpene glycoside, rubianoside I (6), were isolated from the herbal crude extract together with 10 known compounds. The absolute stereostructures of 1-6 were determined on the basis of chemical and physicochemical evidence, including the application of the modified Mosher's method. The effects of the isolated constituents on nitric oxide production in lipopolysaccharide-activated macrophages were examined, and several triterpenes were found to show inhibitory activity.     

Triterpenes from Agarista mexicana as potential antidiabetic agents.

Hypoglycaemic activity-guided fractionation together with chemical analysis led to the isolation of 12-ursene and a novel triterpene 23,24 dimethyl-24-ethyl-stigmast-25-ene from the chloroform extract of the dried stem of A. mexicana. Identification was based on spectroscopic methods. The isolated triterpenes were tested for hypoglycaemic activity in normal and alloxman-diabetic CD1 mice 25-30 g at a dose of 50 mg/kg body weight. The blood glucose levels were determined before and 1.5, 3, 4.5 and 24 h after intraperitoneal drug administration. The results showed that the triterpenes produced a significant hypoglycaemic effect in normal as well as in diabetic mice. Comparison was made between the action of the triterpenes and a known hypoglycaemic drug, tolbutamide (50 mg/kg). The 12-ursene was found to be slow and less effective than tolbutamide, and the 23,24 dimethyl-24-ethyl-stigmast-25-ene was shown to be more effective than tolbutamide.     

Triterpene, antioxidant, and antimicrobial compounds from Melissa officinalis

Six new triterpenes (1- 6) and four known compounds have been isolated from dried stems and leaves of Melissa officinalis. The known compounds were identified as quadranoside III, salvianic acid A, rosmarinic acid, and luteolin. The structures of compounds 1- 6 were established by analysis of spectroscopic data. Free radical scavenging and antimicrobial activities of the extracts and of rosmarinic acid, the major component, were evaluated.     

Triterpenes from Garcia parviflora. Cytotoxic evaluation of natural and semisynthetic friedelanes

Three new friedelane-type triterpenes, 1,2-dehydro-2,3-secofriedelan-3-oic acid (1), 1β-hydroxyfriedelin (2), and 3β-hydroxyfriedelan-23-oic acid (3), and the known compounds friedelin-3,4-lactone (4), acetyl aleuritolic acid (5), 4-hydroxy-5-propionyl-1,3-di-O-methylpyrogallol, elemicin, and (-)-syringaresinol were isolated from the leaves of Garcia parviflora. The structures of 1-3 were elucidated by spectroscopic methods, including 1D and 2D NMR, HREIMS, X-ray, and CD analysis. Some derivatives of 2 (6-14) were prepared via oxidation, reduction, and esterification. The natural triterpenes and the semisynthetic friedelane derivatives were tested for cytotoxic activity against human cancer cell lines U251, PC-3, K562, HCT-15, MCF-7, and SKLU-1. Compound 5 was cytotoxic against U251 cells.     

Three new oleanane-type triterpenes from Ludwigia octovalvis with cytotoxic activity against two human cancer cell lines

Three new oleanane-type triterpenes, (23Z)-coumaroylhederagenin (1), (23E)-coumaroylhederagenin (2), and (3Z)-coumaroylhederagenin (3), together with two known triterpene acids, oleanolic acid and ursolic acid, have been isolated from the whole plant of Ludwigia octovalvis, and their structures have been elucidated by spectroscopic methods. All three new triterpenes showed significant cytotoxicity against two human tumor cell lines, namely, oral epidermoid carcinoma KB and colorectal carcinoma HT29, and gave IC(50) values in the range 1.2-3.6 microM.     

Bacterial biofilm inhibitors from Diospyros dendo

One new (1) and four known (2-5) ursene triterpenes with potent inhibition of the formation of the bacterial biofilm Pseudomonas aeruginosa PA01 were obtained from Diospyros dendo using a high-throughput natural products chemistry procedure. These compounds were isolated as mass-limited samples. The miniaturization of the structure elucidation and dereplication was performed primarily utilizing a capillary-scale NMR probe.     

Plant antitumor agents, 19. Novel triterpenes from Maprounea africana

Four new pentacyclic triterpenes have been isolated from Maprounea africana. These triterpenes are members of the previously unknown urs-12-en-29-oic acid series. The structures of these compounds were deduced from spectral and chemical evidence. The parent compound, maprounic acid, was identified as 3B-hydroxyurs-12-en-29-oic acid. The remaining three triterpenes were identified as maprounic acid 3-p-hydroxybenzoate, 7 beta-hydroxymaprounic acid 3-p-hydroxybenzoate, and 2 alpha-hydroxymaprounic acid 2,3-bis-p-hydroxybenzoate. Of the four triterpenes, only the 7 beta-hydroxy derivative exhibited in vivo P-388 activity.     

Stellettins L and M, cytotoxic isomalabaricane-type triterpenes, and sterols from the marine sponge Stelletta tenuis

Two new isomalabaricane-type triterpenes, stellettins L (1) and M (2), and three new sterols (3-5) were isolated from the marine sponge Stelletta tenuis collected in the South China Sea. Chemical structures were established from spectroscopic data and comparison with known compounds. In addition, spectroscopic data reported for the known sterol 24-methylene-27-methylcholest-5-en-3beta-ol-7-one (6) were revised. Compounds 1 and 2 exhibited significant cytotoxic activity against stomach cancer (AGS) in vitro.