Two novel cytotoxic and antimicrobial triterpenoids from Pseudolarix kaempferi

Structurally Diverse Triterpene-26-oic Acids as Potential Dual ACL and ACC1 Inhibitors from the Vulnerable Conifer Keteleeria fortunei

A preliminary phytochemical investigation on the 90% MeOH extract from the twigs and needles of the vulnerable conifer Keteleeria fortunei led to the isolation and characterization of 17 structurally diverse triterpen-26-oic acids, including nine previously undescribed ones (fortunefuroic acids A-I, 1-9) featuring a rare furoic acid moiety in the lateral chain. Among them, 1-5 are uncommon 9βH-lanostane-type triterpenoic acids. Friedo-rearranged triterpenoids 6 and 7 feature a unique 17,14-friedo-lanostane skeleton, whereas 9 possesses a rare 17,13-friedo-cycloartane-type framework. Their structures and absolute configurations were elucidated by extensive spectroscopic (e.g., detailed 2D NMR) and computational (NMR/ECD) calculations and the modified Mosher's method. In addition, the absolute structure of compound 1 was ascertained by single-crystal X-ray diffraction analyses. Fortunefuroic acids B (2), G (7), and I (9), along with isomangiferolic acid (12) and 3α,27-dihydroxycycloart-24E-en-26-oic acid (14), exhibited dual inhibitory effects against the adenosine triphosphate (ATP)-citrate lyase (ACL, IC50s: 5.7-11.4 μM) and acetyl-CoA carboxylase 1 (ACC1, IC50s: 7.5-10.5 μM), both of which are key enzymes for glycolipid metabolism. The interactions of the bioactive triterpenoids with both enzymes were examined by molecular docking studies. The above findings reveal the important role of protecting plant species diversity in support of chemical diversity and potential sources of new therapeutics for ACL-/ACC1-associated diseases.

New triterpenoids and PTP1B inhibitory constituents of Pseudolarix amabilis

Six new triterpenoids, pseudolarins A-F (1-6), were isolated from the twigs of Pseudolarix amabilis, together with four known triterpenoids (7-10) and five known diterpenoids (11-15). Their structures were determined by extensive spectroscopic analysis, and the absolute configuration of 1 was assigned by single-crystal X-ray diffraction. Compound 1 is a 3,4:9,10-diseco-cycloartane triterpenoid possessing an unprecedented 5/5/7/6/5/6/5 ring system. Compounds 1, 5, 7, 9-11, and 13 showed inhibition against protein tyrosine phosphatase 1B (PTP1B) in vitro.

Effect of pseudolaric acid B on biochemical and physiologic characteristics in Colletotrichum gloeosporioides

In our previous study on natural products with fungicidal activity, pseudolaric acid B (PAB) isolated from Pseudolarix amabilis was examined to inhibit significantly mango anthracnose (Colletotrichum gloeosporioides) in vivo and in vitro. In the current study, sensitivity of 17 plant pathogenic fungi to PAB was determined. Mycelial growth rate results showed that PAB possessed strong antifungal activities to eleven fungi with median effective concentration (EC₅₀) values ranging from 0.087 to 1.927μg/mL. EC₅₀ of PAB against spore germination was greater than that of mycelium growth inhibition, which suggest that PAB could execute antifungal activity through mycelial growth inhibition. Further action mechanism of PAB against C. gloeosporioides was investigated, in which PAB treatment inhibited mycelia dry weight, decreased the mycelia reducing sugar and soluble protein. Furthermore, PAB induced an increase in membrane permeability, inhibited the biosynthesis of ergosterol, caused the extreme alteration in ultrastructure as indicated by the thickened cell wall and increased vesicles. These results will increase our understanding of action mechanism of PAB against plant pathogenic fungi.

Formosins A-F: Diterpenoids with Anti-microbial Activities from Excoecaria formosana

Three new halimane-type diterpenoids formosins A-C (1-3), and three clerodane-type diterpenoids formosins D-F (4-6), were isolated from the twigs of Excoecaria formosana. Their structures were assigned on the basis of spectroscopic data analysis. Compounds 1 and 4 showed moderate anti-microbial activities against Bacillus subtilis (MIC = 50 and 50 μg/mL, respectively). Compound 6 exhibited moderate anti-microbial activities against two strains of Helicobacter pylori (Hp-SS1 and ATCC 43504) with MIC values of 50 and 50 μg/mL, respectively.

Antifungal activity of compounds extracted from Cortex Pseudolaricis against Colletotrichum gloeosporioides

Cortex Pseudolaricis is the root bark of Pseudolarix amabilis Rehder, found only in China, and has been widely used in folk antifungal remedies in traditional Chinese medicine. In order to find the natural antifungal agents against mango anthracnose, eight compounds, namely pseudolaric acid A (1), ethyl pseudolaric acid B (2), pseudolaric acid B (3), pseudolaric acid B-O-β-d-glucoside (4), piperonylic acid (5), propionic acid (6), 3-hydroxy-4-methoxybenzoic acid (7), and 4-(3-formyl-5-methoxyphenyl) butanoic acid (8) were isolated from the ethanol extracts of Cortex Pseudolaricis by bioassay-guided fractionation and evaluated for in vitro antifungal activity against Colletotrichum gloeosporioides Penz. Results demonstrated that all of the eight compounds inhibited the mycelial growth of C. gloeosporioides at 5 μg/mL. Among them, pseudolaric acid B and pseudolaric acid A showed the strongest inhibition with the EC50 values of 1.07 and 1.62 μg/mL, respectively. Accordingly, both Pseudolaric acid B and Pseudolaric acid A highly inhibited spore germination and germ tube elongation of C. gloeosporioides. Dipping 100 μg/mL pseudolaric acid B treatment exhibited more effective suppression on postharvest anthracnose in mango fruit when compared to the same concentration of carbendazim. Scanning electron microscopy observations revealed that pseudolaric acid B caused alterations in the hyphal morphology of C. gloeosporioides, including distortion, swelling, and collapse. Pseudolaric acid B caused the mycelial apexes to show an abnormal growth in dimensions with multiple ramifications in subapical expanded areas with irregular shape. These findings warrant further investigation into optimization of pseudolaric acid B to explore a potential antifungal agent for crop protection.

Cytotoxic dinorditerpenoids from Drypetes perreticulata

Four hitherto unknown dinorditerpenoids, dryperreins A-D of the pimarane class, together with eight known triterpenoids, were isolated from twigs and leaves of Drypetes perreticulata. The structures of dryperreins A-D were elucidated on the basis of detailed spectroscopic analysis as (10S)-11,12-dihydroxy-6-methoxy-15,16-dinorpimara-5,8,11,13-tetraene-3,7-dione, (10S)-6,11,12-trihydroxy-15,16-dinorpimara-5,8,11,13-tetraene-3,7-dione, (10S)-11,12-dihydroxy-6-methoxy-15,16-dinorpimara-1,5,8,11,13-pentaene-3,7-dione, and (10S)-6,11,12-trihydroxy-15,16-dinorpimara-1,5,8,11,13-pentaene-3,7-dione, respectively. Dryperreins C and D exhibited strong cytotoxicity in vitro against HL-60 human tumor cell line. The structure-activity relationship of the cytotoxic compounds was briefly discussed.

Lipase inhibitory and LDL anti-oxidative triterpenes from Abies sibirica

A methanol extract of Abies sibirica Ladeb, a Mongolian medicinal plant, had an inhibitory effect on both lipase activity in mouse plasma and LDL anti-oxidative activity, which are preventative factors for arteriosclerosis. The extract was fractionated by silica gel column chromatography and its active constituents were sought. From lipid soluble fractions, 20 terpenoids including seven hitherto unknown triterpenes were isolated. The latter triterpenes had either a γ-lactone ring with a lactol or a derivative thereof. Their chemical structures were determined by spectroscopic methods. The lipase inhibitory activity and LDL anti-oxidative activity of these compounds were evaluated. Some constituents (either lipase inhibitory or LDL anti-oxidative activities) had moderate inhibitory activities.

Discovery of structurally diverse and bioactive compounds from plant resources in China

This review describes the major discoveries of structurally diverse and/or biologically significant compounds from plant resources in China, mainly from the traditional Chinese medicines (TCMs) since the establishment of our research group in 1999. In the past decade, a large array of biologically significant and novel structures has been identified from plant resources (or TCM) in our laboratory. The structural modification of several biologically important compounds led to more than 400 derivatives, some of which exhibited significantly improved activities and provided opportunities to elucidate the structure-activity relationship of the related compound class. These findings are important for drug discovery and help us understand the biological basis for the traditional applications of these plants in TCM.

Screening of 42 medicinal plants for in vivo anthelmintic activity against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus)

In the present study, methanol extracts of 42 traditional medicinal plants with potent anthelmintic activity against Dactylogyrus intermedius (Monogenea) in goldfish (Carassius auratus) were investigated. Cinnamomum cassia, Lindera aggregata, and Pseudolarix kaempferi exhibited 100% activity and were selected for further evaluation by applying five solvents (petroleum ether, chloroform, ethyl acetate, methanol, and water) for the extraction of the samples, followed by the in vivo bioassay. Among the extracts tested, water and methanol extracts of C. cassia showed the highest efficacies with EC(50) values of 13.2 and 12.3 mg L(-1), showing 100% efficacy against D. intermedius at 30.0 and 40.0 mg L(-1), followed by methanol extract of L. aggregata which demonstrated 100% efficacy at 60.0 mg L(-1) with EC(50) value of 17.1 mg L(-1) after 48 h of exposure. Methanol and ethyl acetate extract of P. kaempferi, which exhibited a 100% efficacy against D. intermedius at 60.0 and 50.0 mg L(-1), revealed similar activity with EC(50) values of 23.5 and 23.3 mg L(-1), respectively. Acute toxicity of these active extracts was investigated on goldfish for 48 h and the corresponding median lethal concentrations (LC(50)) of 56.9, 31.3, 88.7, 168.2, and 165.7 mg L(-1), respectively. These findings indicated that these extracts of the three plants can be developed as preferred natural antiparasitic agents for the treatment of D. intermedius.

Rapid separation and identification of major constituents in Pseudolarix kaempferi by ultra-performance liquid chromatography coupled with electrospray and quadrupole time-of-flight tandem mass spectrometry

A rapid and reliable method based on ultra-performance liquid chromatography (UPLC) coupled with photodiode-array detection (PDA) and electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-Q-TOF-MS/MS) has been developed for separation and identification of major constituents in extracts of root bark of Pseudolarix kaempferi Gordon (PKG). Identification of the constituents was carried out by interpretation of their retention times, UV absorption spectra, MS and MS/MS spectra, as well as the data provided by authentic standards and literatures. A total of 20 components were separated in only 8.0 min on a small particle size C18 column (1.7 microm). These components included nine diterpene acids, seven glycosides and four triterpenoids, among which pseudolaric acid C-O-beta-D-glucopyranoside and pseudolaric acid C2-O-beta-D-glucopyranoside were separated and identified for the first time in this study. Furthermore, the fragmentation patterns of the three types of compounds were elucidated for the first time. This established UPLC-PDA/Q-TOF-MS/MS method is reliable and effective for the separation and identification of the 20 compounds and will be useful for quality control of the crude materials of Pseudolarix kaempferi Gordon and their related preparations.

Limonoids from Khaya ivorensis

Four limonoids, 1-O-deacetyl-6-deoxykhayanolide E (1), 1-O-deacetyl-2 alpha-hydroxykhayanolide E (2), 3-acetyl-khayalactone (3), 11 alpha-acetoxy-2 alpha-hydroxy-6-deoxy-destigloylswietenine acetate (4), along with 12 known limonoids, were isolated from the stems of Khaya ivorensis. Their structures were elucidated on the basis of spectroscopic analysis.

Preparative isolation of pseudolaric acids A and B, and their glucosides from the root bark of Pseudolarix kaempferi using high-speed counter-current chromatography

In order to provide the chemical markers for the quality control of herbal medicines, four diterpenoids, pseudolaric acids A and B (PAA and PAB), and their glucosides were isolated from the methanol extract of the Chinese herb Pseudolarix kaempferi using high-speed counter-current chromatography (HSCCC). The diphase solvent system was n-hexane/EtOAc/MeOH/H(2)O which was used at two ratios (5:5:5:5 and 1:9:4:6 by volume) in the separation of pseudolaric acids and their glycosides, respectively. As a result, PAA (14 mg), PAB (129 mg), PAA-O-beta-D-glucopyranoside (8 mg, PAAG), and PAB-O-beta-D-glucopyranoside (42 mg, PABG) were obtained from 0.5 g of the crude extract. Their purities were determined to be above 97% by HPLC analysis. Their chemical structures were confirmed by( 1)H and( 13)C NMR analysis or HPLC comparison with the reference compounds.

Limonoids from the stem bark of Khaya grandifoliola

Three limonoids, deacetylkhayanolide E (1), 6S-hydroxykhayalactone (2), and grandifolide A (3), along with three known ones, were isolated from stem bark of the Nigerian medicinal plant Khaya grandifoliola. Their structures were characterized on the basis of the application of spectroscopic methods. In vitro antimicrobial and cytotoxic activities of the isolates were also tested, but were all found to be inactive.

Simultaneous determination of seven major diterpenoids in Pseudolarix kaempferi by high-performance liquid chromatography DAD method

A reversed phase high-performance liquid chromatography method was established for the first time to simultaneously qualify the seven major diterpenoids in Pseudolarix kaempferi, namely pseudolaric acid B O-beta-D-glucopyranoside (1), pseudolaric acid C2 (2), pseudolaric acid C1 (3), deacetylpseudolaric acid A (4), pseudolaric acid A O-beta-D-glucopyranoside (5), pseudolaric acid B (6) and pseudolaric acid A (7). The optimal conditions of separation and detection were achieved on an Inertsil ODS-3 column with gradient elution of methanol and 0.5% aqueous acetic acid (v/v) at the flow rate of 0.6 ml min(-1) within 40 min and detection wavelength set at 262 nm. All calibration curves showed good linear regression (r2>0.9999) within test ranges. This method provided good accuracy with recoveries in the range of 94.3-106.1% and good precision with R.S.D.s of repeatability and intermediate precision less than 0.57% and 4.67%, respectively. The method was successfully applied to qualitative and quantitative determination of 20 P. kaempferi among the 54 samples collected from different areas. The results revealed that the commercial crude drugs were seriously confused and the developed HPLC assay could be used as a suitable qualitative and quantitative determination method for P. kaempferi.

In vitro and in vivo activities of Chios mastic gum extracts and constituents against Helicobacter pylori

The extracts and pure major constituents of Chios mastic gum (resin of Pistacia lentiscus var. chia) were tested for their activities against Helicobacter pylori. A total mastic extract without polymer (TMEWP) was prepared after removal of the contained insoluble polymer in order to ameliorate solubility and enhance in vivo activity. Administration of TMEWP to H. pylori SS1-infected mice over the period of 3 months with an average dose of 0.75 mg/day led to an approximately 30-fold reduction in the H. pylori colonization (1.5 log CFU/g of tissue). However, no attenuation in the H. pylori-associated chronic inflammatory infiltration and the activity of chronic gastritis was observed. To further characterize potential active mastic constituents, the TMEWP was separated into an acidic and a neutral fraction. Both were extensively characterized by nuclear magnetic resonance and mass spectroscopy to elucidate the structure of the components contained within each fraction. After chromatographic separation, the acid fraction gave the major triterpenic acids, while the neutral fraction gave several triterpenic alcohols and aldehydes. Mastic extracts and isolated pure triterpenic acids were tested for in vitro activity against a panel of 11 H. pylori clinical strains. The acid fraction was found to be the most active extract (minimum bactericidal concentration [MBC], 0.139 mg/ml), and the most active pure compound was isomasticadienolic acid (MBC, 0.202 mg/ml [0.443 mM]). Our results show that administration of TMEWP may be effective in reducing H. pylori colonization and that the major triterpenic acids in the acid extract may be responsible for such an activity.

Novel Antibacterial Diterpenoids fromLarix chinensis Beissn

Two novel labdane-type diterpenoids, butanedioic acid mono[(13S)-13-hydroxylabda-8(17),14-dien-19-yl] ester (1) and butanedioic acid bis[(13S)-13-hydroxylabda-8(17),14-dien-19-yl] ester (2), along with the eleven known diterpenoids 3-13 and three other known compounds, were isolated from the bark of Larix chinensis. Their structures were elucidated both spectroscopically and chemically. The major diterpenoids 1-9, 11, and 13, as well as the very abundant phenolic compound 16, were subjected to antibacterial and cytotoxic bioassays. Compounds 7 and 9 showed remarkable in vitro inhibition of Staphylococcus aureus and S. epidermidis (MIC = 37-73 microM).

Chemical constituents fromPseudolarix Kaempferi

A novel degraded triterpenoid isopseudolaritone A (1) and one new oligosaccharide, 1-O-isopropyl-6-O-[2-O-methyl-alpha-L-rhamnopyranosyl(1 --> 6)]-beta-D-glucopyranose (2), two new artefacts, 9-O-formacyl cedrusin (5) and 9,9'-O-diformacyl cedrusin (6), as well as 12 known phenolic Compounds (3-4, 7 16), were isolated from the root bark of Pseudolarix kaempferi. Their structures were elucidated mainly by spectroscopic methods.

Antibacterial prenylflavone derivatives from Psoralea corylifolia, and their structure–activity relationship study

Three new prenylflavonoids, namely corylifols A-C (1-3), together with 13 known ones, were isolated from the seeds of Psoralea corylifolia. Their structures were elucidated by spectral methods including 1D and 2D NMR techniques. All the isolates were tested on antibacterial assays, and nine of them showed significant antibacterial activities against two pathogenic bacteria Staphylococcus aureus and S. epidermidis. The antibacterial structure-activity relationship of these prenylflavonoids (1-16) was also briefly discussed.

Antifungal diterpenoids of Pseudolarix kaempferi, and their structure-activity relationship study

The in vitro antifungal activities of 19 structurally diversified analogues of pseudolaric acids tested against the major pathogenic fungus Candida albicans has led to the establishment of a very clear structure-activity relationship of pseudolaric acids derivatives. Pseudolaric acid A was first found to be a potent antifungal component comparable with pseudolaric acid B. Among the tested 19 diterpenoids, pseudolaric acids A2 (1), B2 (3), B3 (4) and methyl pseudolarate A2 (2) are new isolates of the root bark of Pseudolarix kaempferi, and their structures were elucidated mainly by 2D-NMR techniques and chemical methods. Compounds 12-19 were first semi-synthesized by efficient routines from pseudolaric acid B.

Five new diterpenoids from Pseudolarix kaempferi

Five new diterpenoids, pseudolaric acids F (1), G (2), and H (3), 2',3'-dihydroxy-1'-propoxypseudolarate B (4), and 6'-O-acetylpseudolaric acid B O-beta-D-glucopyranoside (5), along with nine known diterpenoids, pseudolaric acids A, B, and C(1), deacetylpseudolaric acid C(2), deacetylpseudolaric acid A, methyl pseudolarate A, methyl pseudolarate B, pseudolaric acid A-O-beta-D-glucopyranoside, and pseudolaric acid B-O-beta-D-glucopyranoside, were isolated from the root bark of Pseudolarix kaempferi. Their structures and stereochemistry were elucidated mainly by spectral data, especially 2D NMR techniques.