Macrocarpals: HIV-RTase inhibitors of Eucalyptus globulus

NMR Fingerprints of Formyl Phloroglucinol Meroterpenoids and Their Application to the Investigation of Eucalyptus gittinsii subsp. gittinsii

NMR fingerprints provide powerful tools to identify natural products in complex mixtures. Principal component analysis and machine learning using ¹H and ¹³C NMR data, alongside structural information from 180 published formyl phloroglucinols, have generated diagnostic NMR fingerprints to categorize subclasses within this group. This resulted in the reassignment of 167 NMR chemical shifts ascribed to 44 compounds. Three pyrano-diformyl phloroglucinols, euglobal In-1 and psiguadiols E and G, contained ¹H and ¹³C NMR data inconsistent with their predicted phloroglucinol subclass. Subsequent reinterpretation of their 2D NMR data combined with DFT ¹³C NMR chemical shift and ECD calculations led to their structure revisions. Direct covariance processing of HMBC data permitted ¹H resonances for individual compounds in mixtures to be associated, and analysis of their ¹H/¹³C HMBC correlations using the fingerprint tool further classified components into phloroglucinol subclasses. NMR fingerprinting HMBC data obtained for six eucalypt flower extracts identified three subclasses of pyrano-acyl-formyl phloroglucinols from Eucalyptus gittinsii subsp. gittinsii. New, eucalteretial F and (+)-eucalteretial B, and known, (-)-euglobal VII and eucalrobusone C, compounds, each belonging to predicted subclasses, were isolated and characterized. Staphylococcus aureus and Plasmodium falciparum screening revealed eucalrobusone C as the most potent antiplasmodial formyl phloroglucinol to date.

Acylphloroglucinol-monoterpene meroterpenoids from Eucalyptus tereticornis and their inhibitory activity against ATP citrate lyase

Five undescribed enantiomeric pairs of acylphloroglucinol-monoterpene meroterpenoids ((+)-/(-)-eucateretins A-E) resolved by chiral-phase HPLC were obtained from the leaves of Eucalyptus tereticornis Smith, along with nine known analogues. Their structures were elucidated by spectroscopic methods and ECD calculations. This is the first report of meroterpenoid enantiomers from this plant. Some of the isolates, (-)-eucateretin A, (+)-/(-)-eucateretins E, 7'α-eucalrobusone X, eucalrobusone X, and robustadial B, exhibited inhibitory effects on ATP citrate lyase, and 7'α-eucalrobusone X significantly suppressed the hepatocyte lipogenesis.

Facile Production of (+)-Aristolochene and (+)-Bicyclogermacrene in Escherichia coli Using Newly Discovered Sesquiterpene Synthases from Penicillium expansum

Penicillium expansum, producer of a wide array of secondary metabolites, has the potential to be a source of new terpene synthases. In this work, a platform was constructed with Escherichia coli BL21(DE3) by enhancing its endogenous 2-methyl-d-erythritol-4-phosphate pathway to supply sufficient terpenoid precursors. Using this precursor-supplying platform, we discovered two sesquiterpene synthases from P. expansum: PeTS1, a new (+)-aristolochene synthase, and PeTS4, the first microbial (+)-bicyclogermacrene synthase. To enhance the sesquiterpene production by PeTS1, we employed a MBP fusion tag to improve the heterologous protein expression, resulting in the increase of aristolochene production up to 50 mg/L in a 72 h flask culture, which is the highest production reported to date. We also realized the first biosynthesis of (+)-bicyclogermacrene, achieving 188 mg/L in 72 h. This work highlights the great potential of this microbial platform for the discovery of new terpene synthases and opens new ways for the bioproduction of other valuable terpenoids.

Non-volatile acylphloroglucinol components from Eucalyptus robusta inhibit Zika virus by impairing RdRp activity of NS5

Eucalyptus is a large genus of the Myrtaceae family with high value in various fields of industry. Recently, attention has been focused on the functional properties of Eucalyptus extracts. These extracts have been traditionally used to combat various infectious diseases, and volatile oils are usually considered to play a major role. But the positive effects of non-volatile acylphloroglucinols, a class of specialized metabolites with relatively high content in Eucalyptus, should not be neglected. Herein, non-volatile acylphloroglucinols from leaves of Eucalyptus robusta were evaluated for their abilities to inhibit Zika virus (ZIKV) which is associated with severe neurological damage and complications. The results showed eucalyprobusone G, a new symmetrical acylphloroglucinol dimer, possessed the significant ability to inhibit ZIKV without inducing cytotoxicity. The EC₅₀ values of eucalyprobusone G against the African lineage (MR766) and Asian lineage (SZ-WIV01) of ZIKV were 0.43 ± 0.08 and 10.10 ± 3.84 μM which were 110 times and 5.8 times better than those of the reference compound ribavirin, respectively. Further action mode research showed that eucalyprobusone G impairs the viral binding and RdRp activity of NS5. The results broaden the functional properties of Eucalyptus robusta and indicate acylphloroglucinol dimers could be developed as anti-ZIKV agents.

A patent review of topoisomerase I inhibitors (2016-present)

INTRODUCTION

Topoisomerases are important targets for therapeutic improvement in the treatment of some diseases, including cancer. Inhibitors and poisons of topoisomerase I can limit the activity of this enzyme in its enzymatic cycle. This fact implies an anticancer effect of these drugs, since most cancer cells are characterized by both a higher activity of topoisomerase I and a higher replication rate compared to non-cancerous cells. Clinically approved inhibitors include camptothecin (CPT) and its derivatives. However, their limitations have encouraged different research groups to prepare new compounds, proof of which are the numerous research works and patents, some of them in the last five years.

AREAS COVERED

This review covers patent literature on topoisomerase I inhibitors and their application published between 2016-present.

EXPERT OPINION

The highest contribution toward patent development has been obtained from academics or small biotechnology companies. The most important fields of innovation include the preparation of prodrugs or inhibitors combined with other agents, as biocompatible polymers or antibodies. A promising development of topoisomerase I inhibitors is expected in the next years, directed to the treatment of diverse diseases, specifically toward different types of cancer and infectious diseases, among others.

UPLC-PDA-Q Exactive Orbitrap-MS profiling of the lipophilic compounds product isolated from Eucalyptus viminalis plants

The lipophilic compounds product (LCP), which was isolated and purified from Eucalyptus viminalis plants, has shown earlier broad antimicrobial and anti-inflammatory activities. To study secondary compounds responsible for the pharmacological activities, chemical composition of the LCP was studied with application of ultra-performance liquid chromatography combined with photodiode array detector and high-resolution Q Exactive Orbitrap mass spectrometer (UPLC-PDA-HRMS/MS). There were found thirty two compounds: twenty phloroglucinol derivatives (isopentyl diformyl phloroglucinol, macrocarpals, sideroxylonals, etc.), eight ursane type triterpenoids (loxanic acid, dehydroursolic acid lactone, dehydroursolic acid lactone acetate, two isomers of p-coumaroyl-dehydroursolic acid lactone and two isomers of feruloyl-dehydroursolic acid lactone), sequiterpenoid (S)-β-macrocarpene and three unknown phenolics. The major compounds of the LCP were pharmacologically active macrocarpals A and B, dehydroursolic acid lactone and its derivatives. It is supposed that previously discovered antimicrobial and anti-inflammatory activities of the LCP is due to the high contents of these secondary compounds.

Tyrosinase inhibitors from the leaves of Eucalyptus globulus

A new isoiphionane sesquiterpene, named (3S, 5S, 7S, 10R)-3, 11-dihydroxyisoiphion-4-one (1), two new phloroglucinol glycosides, named eucalglobuside A (2) and eucalglobuside B (3), along with 15 known compounds were isolated from the leaves of Eucalyptus globulus. Their structures were elucidated based on extensive spectroscopic analysis and in comparison with literature data. The absolute configuration of compound 1 was determined by ECD calculation. All isolates were evaluated their inhibitory activities against the mushroom tyrosinase. As a result, three sesquiterpenoids, 1, 5β, 11-dihydroxy-iphionan-4-one (5), and (-)-globulol (8), exhibited the most potent activities with IC₅₀ values of 14.17 μM, 10.08 μM and 9.79 μM, respectively.

New Acylated Phenolic Glycosides with ROS-Scavenging Activity from Psidium guajava Leaves

Reactive oxygen species and subsequent oxidative stress are reported to play important roles in chronic metabolic diseases. Plant-derived polyphenols, especially food-derived phenolics, have attracted a lot of attention due to their potential usage against oxidative stress-related diseases. The leaf of Psidium guajava (known as guava) is regarded as a good resource of polyphenols and its products are commercially available in Japan as functional foods against multiple chronic metabolism disorders. In the course of finding novel polyphenols with antioxidative activities from guava leaf, 11 acylated phenolic glycosides (1-11), including 5 new oleuropeic acid-conjugated phenolic glycosides, named guajanosides A-E (1, 2, and 5-7), along with 17 known meroterpenoides (12-28), were isolated and identified. Their structures were determined by spectroscopic data analysis, chemical degradation, and acid hydrolysis. Compounds 1, 2, and 5-11 displayed potent reactive oxygen species-scavenging activity in lipopolysaccharide-stimulated RAW 264.7 macrophage cells. Western blot revealed that compound 6 markedly increased the expression levels of nuclear factor-erythroid 2-related factor 2 (Nrf2), NAD(P)H quinone dehydrogenase 1 (NQO1), and the glutamate-cysteine ligase catalytic subunit. The current study revealed the presence of oleuropeic acid-derived phenolic glycosides in guava leaf and highlighted the potential usage of this type of phenolics against oxidative stress-related metabolic diseases via activation of the Nrf2 signaling pathway.

Phloroglucinols with Immunosuppressive Activities from the Fruits of Eucalyptus globulus

Five new phloroglucinol derivatives, eucalyptins C-G (1-5), together with 13 known analogues (6-18) were isolated from the fruits of Eucalyptus globulus. The structures and absolute configurations of 1-5 were established by means of spectroscopic data analysis, computational calculation methods, and single-crystal X-ray diffraction. Compounds 1-18 were investigated for their immunosuppressive effects in vitro, and 1, 2, 6, and 7 displayed moderate inhibitory activities with IC₅₀ values of 11.8, 10.2, 18.2, and 19.1 μM, respectively. The stimulation index (SI) of 1 was 64.2 and was compared to that of cyclosporine A (SI = 149.57). Further study demonstrated that 1 exhibited an immunosuppressive effect through inducing apoptosis and inhibiting cytokine secretion.

Ozone and Wounding Stresses Differently Alter the Temporal Variation in Formylated Phloroglucinols in Eucalyptus globulus Leaves

Formylated phloroglucinol compounds (FPCs) are a class of plant specialized metabolite present in the Myrtaceae family, especially in the genus Eucalyptus. FPCs are widely investigated due to their herbivore deterrence properties and various bioactivities of pharmaceutical relevance. Despite the increasing number of studies elucidating new FPCs structures and bioactivity, little is known about the role of those compounds in planta, and the effects of environmental stresses on FPC concentration. Ozone (O₃) and wounding are key stress factors regularly confronted by plants. In this study, we investigated how O₃, wounding, and their combination affected individual and total FPC foliar concentration of the economically important species Eucalyptus globulus. Six individual FPCs, including five macrocarpals and one sideroxylonal, showed different response patterns to the single and combined stresses. Total macrocarpals only increased under single O₃ treatment, whereas total sideroxylonals only increased in response to wounding treatment, suggesting different physiological roles played by the two groups of FPCs predominantly existing in E. globulus foliage. Total FPCs increased significantly under individual wounding and O₃ treatments but not under the combined treatment. A principal component analysis indicated that all different treatments had unique FPC fingerprints. Total phenolic contents increased in all O₃ and wounding treatments, and a marginally positive correlation was found between total FPCs and total phenolic contents. We suggest that, depending on the concentration and composition, FPCs play multiple physiological roles in planta, including serving as antioxidants to scavenge the reactive oxygen species brought about by O₃ and wounding stresses.

Littordials A–E, novel formyl-phloroglucinol-β-caryophyllene meroterpenoids from the leaves of Psidium littorale

Littordials A–E (1–5), featuring unusual acyl phloroglucinol units, were isolated from the leaves of Psidium littorale. 2, 3 and 5 exhibited significant cytotoxic activities on MDA-MB-231 and B16 cell lines.

Macrocarpal C isolated from Eucalyptus globulus inhibits dipeptidyl peptidase 4 in an aggregated form

Dipeptidyl peptidase 4 (DPP-4) inhibitors are used for the treatment of type-2 diabetes mellitus. Various synthetic inhibitors have been developed to date, and plants containing natural DPP-4 inhibitors have also been identified. Here, 13 plant samples were tested for their DPP-4 inhibitory activity. Macrocarpals A-C were isolated from Eucalyptus globulus through activity-guided fractionation and shown to be DPP-4 inhibitors. Of these, macrocarpal C showed the highest inhibitory activity, demonstrating an inhibition curve characterised by a pronounced increase in activity within a narrow concentration range. Evaluation of macrocarpal C solution by turbidity, nuclear magnetic resonance spectroscopy and mass spectrometry indicated its aggregation, which may explain the characteristics of the inhibition curve. These findings will be valuable for further study of potential small molecule DPP-4 inhibitors.

Phloroglucinol Derivatives from the Fruits of Eucalyptus globulus and Their Cytotoxic Activities

A new phloroglucinol derivative, named eucalyptin B (1), along with five related known compounds (2 - 6), was isolated from the fruits of Eucalyptus globulus. Their structures were elucidated by means of 1D- and 2D-NMR spectroscopy, with the absolute configuration of 1 determined by electronic circular dichroism (ECD) calculations. All isolated compounds (1 - 6) were evaluated for their cytotoxic activities against lung (A549), breast (4T1), and skin (B16F10) cancer cell lines. On the basis of cell viability assay, the cytotoxic activity of eucalyptin B (1) was further confirmed by apoptosis assay. Additionally, after treatment with eucalyptin B (1), the apoptosis factor proteins (Bcl2 and Bax) and caspase-3 levels in A549 cells were also determined by Western-blot analysis. By cytotoxic assay, eucalyptin B (1) exhibited potent cytotoxicity against A549 cells with an IC₅₀ value of 1.51 μm and induced concentration dependent apoptosis of up to 49%. Additionally, eucalyptin B (1) inhibited 5-fold and increased 10-folds in the level of Bcl2 and Bax, respectively. Furthermore, the 11-fold increase in the level of caspase-3 confirmed eucalyptin B (1) activated caspase dependent apoptosis pathway. In conclusion, the isolated compound eucalyptin B (1) has promising cytotoxic activity in tumor cells, especially in A549.

Molecular cloning, expression, and characterization of acyltransferase from Pseudomonas protegens

The formation of C-C bonds by using CoA independent acyltransferases may have significant impact for novel methods for biotechnology. We report the identification of Pseudomonas strains with CoA-independent acyltransferase activity as well as the heterologous expression of the enzyme in E. coli. The cloning strategies and selected expression studies are discussed. The recombinant acyltransferases were characterized with regard to thermal and storage stability, pH,- and co-solvent tolerance. Moreover, the impact of bivalent metals, inhibitors, and other additives was tested. Careful selection of expression and working conditions led to obtain recombinant acyltransferase form Pseudomonas protegens with up to 11 U mL^-1 activity.

Biological, medicinal and toxicological significance of Eucalyptus leaf essential oil: a review

The genus Eucalyptus L'Heritier comprises about 900 species, of which more than 300 species contain volatile essential oil in their leaves. About 20 species, within these, have a high content of 1,8-cineole (more than 70%), commercially used for the production of essential oils in the pharmaceutical and cosmetic industries. However, Eucalyptus is extensively planted for pulp, plywood and solid wood production, but its leaf aromatic oil has astounding widespread biological activities, including antimicrobial, antiseptic, antioxidant, chemotherapeutic, respiratory and gastrointestinal disorder treatment, wound healing, and insecticidal/insect repellent, herbicidal, acaricidal, nematicidal, and perfumes, soap making and grease remover. In the present review, we have made an attempt to congregate the biological ingredients of leaf essential oil, leaf oil as a natural medicine, and pharmacological and toxicological values of the leaf oil of different Eucalyptus species worldwide. © 2017 Society of Chemical Industry.

Psiguajadials A-K: Unusual Psidium Meroterpenoids as Phosphodiesterase-4 Inhibitors from the Leaves of Psidium guajava

Bioassay-guided fractionation of the ethanolic extract of the leaves of Psidium guajava led to the isolation of 11 new Psidium meroterpenoids, psiguajadials A–K (1–11), along with 17 known ones (12–28). Their structures and absolute configurations were elucidated by spectroscopic methods and comparison of experimental and calculated ECD. Compounds 1 and 2 represent two unprecedented skeletons of 3,5-diformyl-benzyl phloroglucinol-coupled sesquiterpenoid, while 3 is the first example of Psidium meroterpenoids coupling via an oxepane ring. Putative biosynthetic pathways towards 1 and 2 are proposed. Compounds 1–13 and 16–26 exhibited moderate inhibitory activities against phosphodiesterase-4 (PDE4), a drug target for asthma and chronic obstructive pulmonary disease, with IC₅₀ values in the range of 1.34–7.26 μM.

Eucalrobusone C suppresses cell proliferation and induces ROS-dependent mitochondrial apoptosis via the p38 MAPK pathway in hepatocellular carcinoma cells

BACKGROUND

Eucalyptus extracts have anti-cancer activity against various cancer cells. Formyl-phloroglucinol meroterpenoids (FPMs), which are typical secondary metabolites of the genera Eucalyptus, have many important pharmacological activities.

PURPOSE

Eucalrobusone C (EC), a new bioactive phytochemical, was first isolated from the leaves of Eucalyptus robusta in our laboratory. EC is a FPM, and our previous research revealed that EC showed strongest cytotoxicity in three cancer models than other compounds isolated from the leaves of E. robusta. This study investigated its anti-tumor effects on human hepatocellular carcinoma (HCC) and its underlying mechanisms.

METHODS

Cell viability was measured by MTT assay. Cell cycle, apoptosis and mitochondrial transmembrane potential were determined by flow cytometry. Immunofluorescence was determined by a laser scanning confocal microscope. Protein levels were analyzed by Western blotting.

RESULTS

Our results showed that EC exerted strong anti-proliferative activity against HCC cells in a concentration- and time-dependent manner. EC markedly induced apoptosis through the caspase-dependent mitochondrial pathway, and the cell cycle was arrested at S phase. SB203580, a p38 MAPK inhibitor, effectively decreased cell death caused by EC. Moreover, the ROS scavenger N-acetyl cysteine (NAC) significantly attenuated apoptosis induced by EC and reversed EC-induced p38 MAPK activation.

CONCLUSION

Our findings indicate that EC induces mitochondrial-dependent apoptosis in HCC cells through ROS generation and p38 MAPK activation, making EC a promising candidate for further development as an anticancer agent for HCC cells.

Myrtucomvalones A–C, three unusual triketone–sesquiterpene adducts from the leaves of Myrtus communis ‘Variegata’

The first examples of triketone–cubebane adducts (1 and 2) with an unusual skeleton were isolated from Myrtus communis ‘Variegata’.

New Formyl Phloroglucinol Meroterpenoids from the Leaves of Eucalyptus robusta

Seven new formyl phloroglucinol meroterpenoids (FPMs), namely eucalrobusones J-P (1–7), as well as three known ones (8–10) were isolated from the leaves of Eucalyptus robusta. Their structures were elucidated by spectroscopic data analysis, and their absolute configurations were determined by applications of the Snatzke’s helicity rule and the electron circular dichroism (ECD) calculation. These FPMs are diverse in coupling patterns between phloroglucinol and sesquiterpenoid units, forming novel polycyclic ring systems. Compound 1 possesses a new carbon skeleton that a 1-oxaspiro[5.6]dodecane core is formed through C-14 rather than C-4 of the aromadendrane moiety. Compound 2 features a novel 6/7/5 ring-fused 6-oxabicyclo[3.2.2]nonane skeleton. Compounds 3–5 are rare aristolane-based FPMs. By forming different oxo bridges, compound 3 is the first sample of FPM with benzo-dihydrofuran structure, and compound 4 possesses a novel 6/6/6/6/3-fused pentacyclic skeleton. Compounds 1, 6, and 8 exhibited significant antifungal activities against Candida glabrata with MIC₅₀ values of 2.57, 1.95, and 2.49 μg/mL, respectively.

(1) H NMR-Guided Isolation of Formyl-Phloroglucinol Meroterpenoids from the Leaves of Eucalyptus robusta

Nine formyl-phloroglucinolmeroterpenoids (FPMs), namely, eucalrobusones A-I (1-9), were isolated from the leaves of Eucalyptus robusta by tracking the phenolic hydroxyl (1) H NMR peaks. The Snatzke helicity rules for the Cotton effects of twisted benzene rings were applied to elucidate the absolute configurations of the FPMs. These findings, along with NMR spectroscopy, the circular dichroism (CD) exciton chirality method, and CD calculations, allowed complete structures for the FPMs to be assigned. Eucalrobusones A-F (1-6) are novel adducts formed between a formyl-derived carbon atom on the phloroglucinol ring and monoterpene and sesquiterpene components. Eucalrobusones G-I (7-9) are the first examples of FPMs with cubebane part structures connected by an unusual 1-oxaspiro[5.5]undecane subunit. Among these isolates, eucalrobusone C (3) showed significant cytotoxicity against HepG2, MCF-7, and U2OS cancer cell lines, with IC50 values less than 10 μm. Compound 3 significantly blocks cell proliferation in MCF-7 cells and induces MCF-7 cell death through apoptosis.

Eucarobustols A-I, Conjugates of Sesquiterpenoids and Acylphloroglucinols from Eucalyptus robusta

Nine new conjugates of sesquiterpenoids and acylphloroglucinols, named eucarobustols A-I (1-9), as well as 11 known analogues were isolated from the leaves of Eucalyptus robusta. The sesquiterpenoid motifs furnishing the new conjugates included four structural types of aristolane (1 and 2), guaiane (3), eudesmane (4), and aromadendrane (5-9) moieties. Compounds 1 and 2 were found to represent the first examples of conjugates of aristolane and acylphloroglucinol units. In turn, compound 3 features a new coupling model of guaiane and acylphloroglucinol via the C-4-C-7' bond. Compounds 1, 7, and 9 showed inhibitory activities against protein tyrosine phosphatase 1B (PTP1B) with IC50 values of 1.3, 1.8, and 1.6 μM, respectively.

Gold catalysis in total synthesis – recent achievements

The most recent achievements of gold catalysed transformations applied in total synthesis of natural products are reviewed and analysed.

Guajavadimer A, a Dimeric Caryophyllene-Derived Meroterpenoid with a New Carbon Skeleton from the Leaves of Psidium guajava

Guajavadimer A (1), a dimeric sesquiterpene-based meroterpenoid which possessed an unprecedented two caryophyllenes, a benzylphlorogulcinol, and a flavonone-fused complicated stereochemical skeleton, was isolated from the leaves of Psidium guajava L. Its structure and absolute configuration were elucidated on the basis of spectroscopic data and X-ray crystallography. Guajavadimer A (1) showed moderate hepatoprotective activity against N-acetyl-p-aminophenol (APAP)-induced toxicity in HepG2 cells.

Macrocarpal-like Compounds from Eugenia umbelliflora Fruits and Their Antibacterial Activity

Certain members of the genus Eugenia are used as foods. One of these species is Eugenia umbelliflora, which is used for its fruits. The aim of the study was to isolate the constituents of the CH2Cl2 fraction obtained from E. umbelliflora O. Berg (Myrtaceae) and also to evaluate its antimicrobial properties. Two new meroterpenoids, eugenial C (3) and eugenial D (4) were isolated from the unripe fruits of E. umbelliflora and their structures established mainly by extensive NMR spectroscopy. In previous studies, the CH2Cl2 extract showed significant antibacterial activity, which can be attributed to meroterpenoids isolated in this study. The compounds eugenials C and D exhibited potent activity against Bacillus subtilis and Staphylococcus aureus and different strains of MRSA and activity similar to those of the antibiotics used in antimicrobial therapies.

Biological activity of natural sesquiterpenoids containing a gem-dimethylcyclopropane unit

The biological activity of sesquiterpenes containing the gem-dimethylcyclopropane unit is described.

Biomimetic synthesis of (+)-ledene, (+)-viridiflorol, (-)-palustrol, (+)-spathulenol, and psiguadial A, C, and D via the platform terpene (+)-bicyclogermacrene

(+)-Bicyclogermacrene is a strained bicyclic and common sesquiterpene found in several essential oils. A short and good yielding synthesis of bicyclogermacrene proceeding in seven steps is reported. This terpene is used as key platform intermediate for a biomimetic access to several aromadendrene sesquiterpenoids, such as ledene, viridiflorol, palestrol, and spathulenol. Furthermore, bicyclogermacrene is shown to be the terpene component in the synthesis of the meroterpenoids psiguadial A, C, and D.

Gold(I) as an artificial cyclase: short stereodivergent syntheses of (-)-epiglobulol and (-)-4β,7α- and (-)-4α,7α-aromadendranediols

Three natural aromadendrane sesquiterpenes, (-)-epiglobulol, (-)-4β,7α-aromadendranediol, and (-)-4α,7α-aromadendranediol, have been synthesized in only seven steps in 12, 15, and 17 % overall yields, respectively, from (E,E)-farnesol by a stereodivergent gold(I)-catalyzed cascade reaction which forms the tricyclic aromadendrane core in a single step. These are the shortest total syntheses of these natural compounds.

Eucalmaidials A and B, phloroglucinol-coupled sesquiterpenoids from the juvenile leaves of Eucalyptus maideni

Eucalmaidials A and B, representing a new skeleton of phloroglucinol-coupled iphionane, were isolated from the juvenile leaves of Eucalyptus maideni.

Semisynthesis of macrocarpal C and analogues by selective dehydration of macrocarpal A or B

Macrocarpals A and C are structurally related compounds that have been extracted from different Eucalyptus species. Although macrocarpal C is of biological interest, its isolation in pure form is difficult to achieve. We report herein an efficient method for the semisynthesis of macrocarpal C by selective exo-dehydration of another member of the macrocarpal family, macrocarpal A. We also report the semisynthesis of three new macrocarpal structures derived from either macrocarpal A or B.

Nudibaccatumone, a trimer comprising a phenylpropanoid and two sesquiterpene moieties from Piper nudibaccatum

A new complex natural product with a C39 skeleton, named nudibaccatumone, and the known sesquiterpenes (+)-spathulenol, (-)-4β,10α-aromadendranediol, and ent-T-muurolol, as well as the phenylpropanoid hydroxychavicol, were isolated from the aerial parts of Piper nudibaccatum. The structure and absolute configuration of nudibaccatumone were elucidated using spectroscopic methods and ECD calculations. A 1,8-Michael addition reaction and an intermolecular, inverse electron demand Diels-Alder reaction are proposed as the key steps in the biosynthesis of nudibaccatumone.

Potent HGF/c-Met axis inhibitors from Eucalyptus globulus: the coupling of phloroglucinol and sesquiterpenoid is essential for the activity

Eucalyptin A (1), together with two known compounds 2 and 3 exhibiting potent inhibition on HGF/c-Met axis, was discovered from the fruits of Eucalyptus globulus. 1 possessed an unprecedented carbon framework of phloroglucinol-coupled sesquiterpenoid, and its structure was elucidated by spectroscopic method and ECD calculation. A brief structure-activity relationship discussion indicated that the coupling of a phloroglucinol and a sesquiterpenoid is essential for the activity.

Eucalyptals D and E, new cytotoxic phloroglucinols from the fruits of Eucalyptus globulus and assignment of absolute configuration

Two new phloroglucinols, named eucalyptals D (1) and E (2), along with a related known compound (euglobal-In-3, 3) were isolated from the fruits of Eucalyptus globulus. Their structures were established on the basis of extensive spectroscopic studies, revealing that they share a common 3,5-diformyl-isopentyl phloroglucinol unit, but each is instead coupled to a different sesquiterpenoid skeleton (aromadendrene in 1, cadinene in 2, and a spirosesquiterpene in 3). Compound 1 possessed an unusual seven-membered D ring with an ether bridge between C-2 of the aromadendrene moiety and C-2' of the aromatic unit. The absolute configuration of the isolates was defined by the comparison of experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1-3 exhibited significant in vitro cytotoxicities against a few human cancer cell lines (Huh-7, Jurkat, BGC-823, and KE-97) using the CellTiter-Glo^™ luminescent cell viability assay method.

Antibacterial sideroxylonals and loxophlebal A from Eucalyptus loxophleba foliage

Loxophlebal A, a new antibacterial formylated phloroglucinol was isolated from the mother liquor obtained after separation of sideroxylonals from the chloroform-methanol extract of leaves of Eucalyptus loxophleba ssp lissophloia. The structure of loxophlebal A was determined to be 3-desformyl sideroxylonal A by spectroscopic methods including 1D- and 2D-NMR. The stereochemistry of loxophlebal A was determined by chemical correlation with sideroxylonal A. This article also reports an efficient, simple and economic method for large scale isolation of sideroxylonals in a purity of >90% from the leaves of Eucalyptus loxophleba ssp lissophloia.

Synthesis and anti-HIV activity of alkylated quinoline 2,4-diols

Naturally occurring quinolone alkaloids, buchapine (1) and compound 2 were synthesized as reported in literature and evaluated for anti-HIV potential in human CD4+ T cell line CEM-GFP, infected with HIV-1(NL4.3) virus by p24 antigen capture ELISA assay. The compounds 1 and 2 showed potent inhibitory activity with IC(50) value of 2.99 and 3.80microM, respectively. Further, 45 alkylated derivatives of quinoline 2,4-diol were synthesized and tested for anti-HIV potential in human CD4+ T cell line CEM-GFP. Among these, 13 derivatives have shown more than 60% inhibition. We have identified three most potent inhibitors 6, 9 and 23; compound 6 was found to be more potent than lead molecule 1 with IC(50) value of 2.35microM and had better therapeutic index (26.64) as compared to AZT (23.07). Five derivatives 7, 19a, 19d, 21 and 24 have displayed good noticeable anti-HIV activity. All active compounds showed higher CC(50) values which indicate that they have better therapeutic indices.

Psidials A-C, three unusual meroterpenoids from the leaves of Psidium guajava L

Three novel sesquiterpenoid-based meroterpenoids of psidials A-C (1-3) have been isolated from the leaves of Psidium guajava L. Their complete structures were elucidated by spectral and chemical methods, and that of 1 was confirmed by single-crystal X-ray diffraction analysis. Psidial B (2) and C (3) represented the new skeleton of the 3,5-diformylbenzyl phloroglucinol-coupled sesquiterpenoid. A possible biosynthetic pathway for 2-3 was postulated. 2-3 showed activity to enzyme PTP1B in 10 microM.

Antimicrobial activity of five herbal extracts against multi drug resistant (MDR) strains of bacteria and fungus of clinical origin

Antimicrobial activities of the crude ethanolic extracts of five plants were screened against multidrug resistant (MDR) strains of Escherichia coli, Klebsiella pneumoniae and Candida albicans. ATCC strains of Streptococcus mutans, Staphylococcus aureus, Enterococcus faecalis, Streptococcus bovis, Pseudimonas aeruginosa, Salmonella typhimurium, Escherichia coli, Klebsiella pneumoniae and Candida albicans were also tested. The strains that showed resistance against the maximum number of antibiotics tested were selected for an antibacterial assay. The MDR strains were sensitive to the antimicrobial activity of Acacia nilotica, Syzygium aromaticum and Cinnamum zeylanicum, whereas they exhibited strong resistance to the extracts of Terminalia arjuna and Eucalyptus globulus. Community-acquired infections showed higher sensitivity than the nosocomial infections against these extracts. The most potent antimicrobial plant was A. nilotica (MIC range 9.75-313 microg/ml), whereas other crude plant extracts studied in this report were found to exhibit higher MIC values than A. nilotica against community acquired as well as nosocomial infection. This study concludes that A. nilotica, C. zeylanicum and S. aromaticum can be used against multidrug resistant microbes causing nosocomial and community acquired infections.

Effect of eucalyptus extract chewing gum on periodontal health: a double-masked, randomized trial

BACKGROUND

Studies in vitro showed that eucalyptus extracts possess antibacterial activity against cariogenic and periodontopathic bacteria; however, the clinical effects with respect to periodontal health in humans remain unproven. The objective of this study was to evaluate the effect of chewing gum containing eucalyptus extract on periodontal health in a double-masked, randomized, controlled trial.

METHODS

Healthy humans with gingivitis but not deep periodontal pockets were randomly assigned to the following groups: high-concentration group (n=32): use of 0.6% eucalyptus extract chewing gum for 12 weeks (90 mg/day); low-concentration group (n=32): use of 0.4% eucalyptus extract chewing gum for 12 weeks (60 mg/day); and placebo group (n=33): use of chewing gum without eucalyptus extract for 12 weeks. Plaque accumulation (PLA), gingival index (GI), bleeding on probing (BOP), periodontal probing depth (PD), and clinical attachment level (CAL) were measured at weeks 0, 4, 8, 12, and 14. Significance was analyzed with repeated-measures two-way analysis of variance followed by the Games-Howell pairwise comparison test.

RESULTS

The interaction between the effects of eucalyptus extract chewing gum and the intake period was statistically significant for PLA, GI, BOP, and PD but not for CAL. The low- and high-concentration groups exhibited statistically significant (P <0.05) improvements compared to the placebo group for PLA, GI, BOP, and PD.

CONCLUSIONS

Eucalyptus extract chewing gum had a significant effect on PLA, GI, BOP, and PD. The use of eucalyptus extract chewing gum may promote periodontal health.

Intestinal permeability of antivirus constituents from the fruits of Eucalyptus globulus Labill. in Caco-2 Cell Model

The uptake and transepithelial transport of the three main constituents macrocarpal A (M-A), macrocarpal B (M-B), and cypellocarpa C (Cy-C) from the fruits of Eucalyptus globulus Labill. were investigated. Monolayers of the human intestinal epithelial cancer cell line Caco-2 were incubated with M-A, M-B, and Cy-C to model its intestinal absorption and transport, respectively. The determination of compounds was performed by HPLC. The apparent permeability coefficients (P(app)) for M-A, M-B, and Cy-C in the apical-to-basolateral direction of a Caco-2 monolayer were (1.70+/-0.06)x10(-6), (1.99+/-0.10)x10(-6), and (6.08+/-0.41)x10(-6)cm/s, respectively. In the presence of iodoacetamide, the P(app) of Cy-C were both reducted in apical-to-basolateral and basolateral-to-apical directions. M-A and M-B appear to accumulate in the epithelial cells. The intestinal absorption of M-A, M-B, and Cy-C was passive diffusion as the dominating process and Cy-C was partly ATP-dependent.

Inhibitory effects of macrocarpals on the biological activity of Porphyromonas gingivalis and other periodontopathic bacteria

BACKGROUND/AIMS

Macrocarpals, which are phloroglucinol derivatives contained in eucalyptus leaves, exhibit antimicrobial activity against a variety of bacteria including oral bacteria. This study examined effects of macrocarpals A, B, and C on periodontopathic bacteria, especially Porphyromonas gingivalis.

METHODS

Macrocarpals A, B, and C were purified from a 60% ethanol-extract of Eucalyptus globules leaves. To investigate antibacterial activity, representative periodontopathic bacteria were cultured in media with or without various amounts of macrocarpals; subsequently, the optical density at 660 nm was measured. Macrocarpal inhibition of P. gingivalis Arg- and Lys-specific proteinases was assessed by spectrofluorophotometric assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. The effect of macrocarpals on P. gingivalis binding to saliva-coated hydroxyapatite beads was examined with (3)H-labeled P. gingivalis.

RESULTS

Growth of P. gingivalis was inhibited more strongly than growth of Prevotella intermedia or Prevotella nigrescens and Treponema denticola by macrocarpals, however, Actinobacillus actinomycetemcomitans and Fusobacterium nucleatum were much more resistant. Macrocarpals inhibited P. gingivalis Arg- and Lys-specific proteinases in a dose-dependent manner. The enzyme-inhibitory effect of macrocarpals was confirmed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis in which hemoglobin degradation by P. gingivalis proteinase was inhibited by macrocarpals. P. gingivalis binding to saliva-coated hydroxyapatite beads was also strongly attenuated by macrocarpals.

CONCLUSIONS

Macrocarpals A, B and C demonstrated antibacterial activity against periodontopathic bacteria. Among tested bacteria, P. gingivalis displayed the greatest sensitivity to macrocarpals; additionally, its trypsin-like proteinase activity and binding to saliva-coated hydroxyapatite beads were inhibited by macrocarpals. These results indicate that eucalyptus leaf extracts may be useful as a potent preventative of periodontal disease.