Inhibitors of osteoclast differentiation from Cephalotaxus koreana

Cephalotane diterpenoids: structural diversity, biological activity, biosynthetic proposal, and chemical synthesis

Covering: up to the end of 2023Cephalotane diterpenoids are a unique class of natural products exclusive to the genus Cephalotaxus, featuring a rigid 7,6,5,6-fused tetracyclic architecture. The study of cephalotanes dates back to the 1970s, when harringtonolide (1), a Cephalotaxus troponoid with a peculiar norditerpenoid carbon skeleton, was first discovered. In recent years, prototype C20 diterpenoids proposed as cephalotane were disclosed, which triggered intense studies on this diterpenoid family. To date, a cumulative total of 105 cephalotane diterpenoids with great structural diversity and biological importance have been isolated. In addition, significant advances have been made in the field of total synthesis and biosynthesis of cephalotanes in recent years. This review provides a complete overview of the chemical structures, bioactivities, biosynthetic aspects, and completed total synthesis of all the isolated cephalotane diterpenoids, which will help guide future research on this class of compounds.

Bioinspired Total Synthesis of Cephalotaxus Diterpenoids and Their Structural Analogues

Herein, we present a unified chemical synthesis of three subgroups of cephalotaxus diterpenoids. Key to the success lies in adopting a synthetic strategy that is inspired by biosynthesis but is opposite in nature. By employing selective one-carbon introduction and ring expansion operations, we have successfully converted cephalotane-type C18 dinorditerpenoids (using cephanolide B as a starting material) into troponoid-type C19 norditerpenoids and intact cephalotane-type C20 diterpenoids. This synthetic approach has enabled us to synthesize cephinoid H, 13-oxo-cephinoid H, 7-oxo-cephinoid H, fortalpinoid C, 7-epi-fortalpinoid C, cephanolide E, and 13-epi-cephanolide E. Furthermore, through the development of an intermolecular asymmetric Michael reaction between β-oxo esters and β-substituted enones, we have achieved the enantioselective synthesis of advanced intermediates within our synthetic sequence, thus formally realizing the asymmetric total synthesis of the cephalotaxus diterpenoids family.

Enantioselective Total Synthesis of (-)-Cephalotanin B

Cephalotaxus diterpenoids are attractive natural products with intriguing molecular frameworks and promising biological features. As a structurally unusual member, (-)-cephalotanin B possesses an extraordinarily congested heptacyclic skeleton, three lactone units, and nine consecutive stereocenters. Herein, we report an enantioselective total synthesis of (-)-cephalotanin B based on a divergent asymmetric Michael addition reaction, a novel Pauson-Khand/deacyloxylation process discovered in the development of a second-generation stereoselective Pauson-Khand reaction protocol, and an epoxide-opening/elimination/dual-lactonization cascade to construct the challenging propeller-shaped A-B-C ring system as key transformations.

Kaempferol, a potential neuroprotective agent in neurodegenerative diseases: From chemistry to medicine

Neurodegenerative diseases (NDDs) encompass a range of conditions that involve progressive deterioration and dysfunction of the nervous system. Some of the common NDDs include Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and amyotrophic lateral sclerosis (ALS). Although significant progress has been made in understanding the pathological mechanisms of NDDs in recent years, the development of targeted and effective drugs for their treatment remains challenging. Kaempferol is a flavonoid whose derivatives include kaempferol-O-rhamnoside, 3-O-β-rutinoside/6-hydroxykaempferol 3,6-di-O-β-d-glucoside, and kaempferide. Emerging studies have suggested that kaempferol and its derivatives possess neuroprotective properties and may have potential therapeutic benefits in NDDs. Here, we aimed to provide a theoretical basis for the use of kaempferol and its derivatives in the clinical treatment of NDDs. We systematically reviewed the literature in the PubMed, Web of Science, and Science Direct databases until June 2022 using the search terms "kaempferol," "kaempferol derivatives," "NDDs," "pharmacokinetics," and "biosynthesis" according to the reporting items for systematic review (PRISMA) standard. Based on combined results of in vivo and in vitro studies, we summarize the basic mechanisms and targets of kaempferol and its derivatives in the management of AD, PD, HD, and ALS. Kaempferol and its derivatives exert a neuroprotective role mainly by preventing the deposition of amyloid fibrils (such as Aβ, tau, and α-synuclein), inhibiting microglia activation, reducing the release of inflammatory factors, restoring the mitochondrial membrane to prevent oxidative stress, protecting the blood-brain barrier, and inhibiting specific enzyme activities (such as cholinesterase). Kaempferol and its derivatives are promising natural neuroprotective agents. By determining their pharmacological mechanism, kaempferol and its derivatives may be new candidate drugs for the treatment of NDDs.

Digital Database of Absorption Spectra of Diverse Flavonoids Enables Structural Comparisons and Quantitative Evaluations

Flavonoids play diverse roles in plants, comprise a non-negligible fraction of net primary photosynthetic production, and impart beneficial effects in human health from a plant-based diet. Absorption spectroscopy is an essential tool for quantitation of flavonoids isolated from complex plant extracts. The absorption spectra of flavonoids typically consist of two major bands, band I (300-380 nm) and band II (240-295 nm), where the former engenders a yellow color; in some flavonoids the absorption tails to 400-450 nm. The absorption spectra of 177 flavonoids and analogues of natural or synthetic origin have been assembled, including molar absorption coefficients (109 from the literature, 68 measured here). The spectral data are in digital form and can be viewed and accessed at http://www.photochemcad.com. The database enables comparison of the absorption spectral features of 12 distinct types of flavonoids including flavan-3-ols (e.g., catechin, epigallocatechin), flavanones (e.g., hesperidin, naringin), 3-hydroxyflavanones (e.g., taxifolin, silybin), isoflavones (e.g., daidzein, genistein), flavones (e.g., diosmin, luteolin), and flavonols (e.g., fisetin, myricetin). The structural features that give rise to shifts in wavelength and intensity are delineated. The availability of digital absorption spectra for diverse flavonoids facilitates analysis and quantitation of these valuable plant secondary metabolites. Four examples are provided of calculations─multicomponent analysis, solar ultraviolet photoprotection, sun protection factor (SPF), and Förster resonance energy transfer (FRET)─for which the spectra and accompanying molar absorption coefficients are sine qua non.

Kaempferol: Antimicrobial Properties, Sources, Clinical, and Traditional Applications

Flavonoids are a category of plant-derived compounds which exhibit a large number of health-related effects. One of the most well-known and studied flavonoids is kaempferol, which can be found in a wide variety of herbs and plant families. Apart from their anticarcinogenic and anti-inflammatory effects, kaempferol and its associated compounds also exhibit antibacterial, antifungal, and antiprotozoal activities. The development of drugs and treatment schemes based on these compounds is becoming increasingly important in the face of emerging resistance of numerous pathogens as well as complex molecular interactions between various drug therapies. In addition, many of the kaempferol-containing plants are used in traditional systems all over the world for centuries to treat numerous conditions. Due to its variety of sources and associated compounds, some molecular mechanisms of kaempferol antimicrobial activity are well known while others are still under analysis. This paper thoroughly documents the vegetal and food sources of kaempferol as well as the most recent and significant studies regarding its antimicrobial applications.

A nickel(ii)-catalyzed enantioselective all-carbon-based inverse-electron-demand Diels–Alder reaction of 2-pyrones with indenes

An asymmetric IEDDA reaction of 2-pyrones with indenes catalyzed by a chiral N,N′-dioxide/Ni(OTf)2 complex has been disclosed to construct highly functionalized hexahydrofluorenyl bridged-lactone scaffolds in high yields and ee.

Progress in structure, synthesis and biological activity of natural cephalotane diterpenoids

The Cephalotaxus genus is well-known owing to the numerous complex, biologically relevant natural products that can be obtained from its constituent species. The successful identification of various Cephalotaxus alkaloids and natural, structurally diverse cephalotane diterpenoids that exhibit antitumor activities and excellent pharmacological properties has encouraged the discovery of previously undescribed compounds from this genus. The present review summarizes the different strategies for the total synthesis of cephalotane diterpenoids as well as their diverse chemical structures, antitumor activities, structure-activity relationships (SARs), and biosynthetic pathways.

Catalytic Asymmetric Inverse-Electron-Demand Diels-Alder Reactions of 2-Pyrones with Indenes: Total Syntheses of Cephanolides A and B

An inverse-electron-demand Diels-Alder (IEDDA) reaction could complement the conventional normal-electron-demand Diels-Alder reaction in the synthesis of six-membered carbocycles. However, catalytic asymmetric all-carbon-based IEDDA reactions are underdeveloped. Herein, we disclosed a copper-catalyzed asymmetric IEDDA reaction using electron-deficient 3-carboalkoxyl-2-pyrones and electronically unbiased indenes as reactants. This method enables the rapid and enantioselective construction of a wide range of hexahydrofluorenyl bridged-lactone scaffolds. Using this method, asymmetric total syntheses of cephanolides A and B were accomplished.

Asymmetric Total Synthesis of (+)-Mannolide C

(+)-Mannolide C is a complex hexacyclic C₂₀ cephalotane-type diterpenoid featuring a highly strained 7/6/6/5 tetracyclic core containing eight consecutive stereocenters and two bridging lactones. The first asymmetric total synthesis of (+)-mannolide C has been accomplished by lipase-mediated resolution, Ru-complex-catalyzed double ring-closing metathesis (RCM) reactions, Ni^II -catalyzed diastereoselective Michael addition, and Mn^III -catalyzed allylic oxidation as the key transformations.

Total Synthesis of (+)-3-Deoxyfortalpinoid F, (+)-Fortalpinoid A, and (+)-Cephinoid H

3-Deoxyfortalpinoid F, fortalpinoid A, and cephinoid H are members of the Cephalotaxus diterpenoids class of natural products, which feature diverse chemical structures and valuable biological activities. We report herein the development of a diastereoselective Pauson-Khand reaction as an effective pathway to access the core tetracyclic skeleton, which is found widely in Cephalotaxus diterpenoids. Furthermore, we enabled the construction of the tropone moiety through a ring-closing metathesis/elimination protocol. Based on the developed strategy, asymmetric synthesis of the title compounds has been achieved for the first time.

Ethnopharmacology, chemodiversity, and bioactivity of Cephalotaxus medicinal plants

Cephalotaxus is the only genus of Cephalotaxaceae family, and its natural resources are declining due to habitat fragmentation, excessive exploitation and destruction. In many areas of China, folk herbal doctors traditionally use Cephalotaxus plants to treat innominate swollen poison, many of which are cancer. Not only among Han people, but also among minority ethnic groups, Cephalotaxus is used to treat various diseases, e.g., cough, internal bleeding and cancer in Miao medicine, bruises, rheumatism and pain in Yao medicine, and ascariasis, hookworm disease, scrofula in She medicine, etc. Medicinal values of some Cephalotaxus species and compounds are acknowledged officially. However, there is a lack of comprehensive review summarizing the ethnomedicinal knowledge of Cephalotaxus, relevant medicinal phytometabolites and their bioactivities. The research progresses in ethnopharmacology, chemodiversity, and bioactivities of Cephalotaxus medicinal plants are reviewed and commented here. Knowledge gaps are pinpointed and future research directions are suggested. Classic medicinal books, folk medicine books, herbal manuals and ethnomedicinal publications were reviewed for the genus Cephalotaxus (Sanjianshan in Chinese). The relevant data about ethnobotany, phytochemistry, and pharmacology were collected as comprehensively as possible from online databases including Scopus, NCBI PubMed, Bing Scholar, and China National Knowledge Infrastructure (CNKI). "Cephalotaxus", and the respective species name were used as keywords in database search. The obtained articles of the past six decades were collated and analyzed. Four Cephalotaxus species are listed in the official medicinal book in China. They are used as ethnomedicines by many ethnic groups such as Miao, Yao, Dong, She and Han. Inspirations are obtained from traditional applications, and Cephalotaxus phytometabolites are developed into anticancer reagents. Cephalotaxine-type alkaloids, homoerythrina-type alkaloids and homoharringtonine (HHT) are abundant in Cephalotaxus, e.g., C. lanceolata, C. fortunei var. alpina, C. griffithii, and C. hainanensis, etc. New methods of alkaloid analysis and purification are continuously developed and applied. Diterpenoids, sesquiterpenoids, flavonoids, lignans, phenolics, and other components are also identified and isolated in various Cephalotaxus species. Alkaloids such as HHT, terpenoids and other compounds have anticancer activities against multiple types of human cancer. Cephalotaxus extracts and compounds showed anti-inflammatory and antioxidant activities, immunomodulatory activity, antimicrobial activity and nematotoxicity, antihyperglycemic effect, and bone effect, etc. Drug metabolism and pharmacokinetic studies of Cephalotaxus are increasing. We should continue to collect and sort out folk medicinal knowledge of Cephalotaxus and associated organisms, so as to obtain new enlightenment to translate traditional tips into great therapeutic drugs. Transcriptomics, genomics, metabolomics and proteomics studies can contribute massive information for bioactivity and phytochemistry of Cephalotaxus medicinal plants. We should continue to strengthen the application of state-of-the-art technologies in more Cephalotaxus species and for more useful compounds and pharmacological activities.

Diterpenoids from Cephalotaxus fortunei var. alpina and their cytotoxic activity

Cephafortunoids A-D (1-4), four new compounds, together with ten known ones (5-14), were isolated from the branches and leaves of Cephalotaxus fortunei var. alpina. 1 and 2 represent the first examples of Cephalotaxus troponoid diterpenoids featured an intact C₂₀ skeleton with CH₃-17 migrating to C-15 and C-13 respectively. 3 and 4 are novel cephalotane-type diterpenoids with an epoxy ring between C-12 and C-13. The structures of isolated compounds were established by extensive spectroscopic methods, electronic circular dichroism (ECD) calculations, and comparison with reported data. In in vitro bioassays, all isolated compounds were evaluated for their cytotoxic activities against human promyelocytic leukemia cells (HL-60), human acute monocytic leukemia cells (THP-1), human breast cancer cells (MDA-MB-231), and human prostate cancer cells (PC-3). 5-9 exhibited prominent cytotoxicity against HL-60 and THP-1 with GI₅₀ values of 0.27-5.48 and 0.48-7.54 μM, respectively. 5-8 showed evident cytotoxicity against MDA-MB-231 and PC-3 with IC₅₀ values of 1.96-10.66 and 2.72-13.99 μM, severally. 6 with an IC₅₀ value of 2.72 ± 0.35 μM displayed stronger cytotoxicity against PC-3 than the positive control etoposide. The structure-activity relationship of these compounds and plausible biogenetic pathways for 1-4 were discussed.

Thermosensitive nanoparticle of mPEG-PTMC for oligopeptide delivery into osteoclast precursors

Transmembrane delivery of biomolecules through nanoparticles plays an important role in targeted therapy. Here, we designed a simple nanoparticle for the delivery of model peptide drug into primary osteoclast precursor cells (bone marrow macrophages) by thermosensitive and biodegradable diblock copolymer monomethoxy poly(ethylene glycol)-block-poly(trimethylene carbonate). The model peptide drug was encapsulated into the nanoparticle by dropping the drug carrier dissolved in dimethylsulfoxide solvent into water containing poly(vinyl alcohol) to achieve temperature response nanoparticles. Through size analysis, we found that the nanoparticles possessed a temperature-sensitive property between 30°C and 40°C. Moreover, flow cytometry and spectrofluorimetry analysis indicated that nanoparticle systems underwent significant cellular uptake. In addition, the evaluation of cell biology showed that nanoparticles have excellent biocompatibility. Thus, the results indicated that the temperature-sensitive nanoparticles have potential application value for targeted delivery of oligopeptide in the treatment process of osteoarthritis.

Advances on the in vivo and in vitro glycosylations of flavonoids

Flavonoids possess diverse bioactivity and potential medicinal values. Glycosylation of flavonoids, coupling flavonoid aglycones and glycosyl groups in conjugated form, can change the biological activity of flavonoids, increase water solubility, reduce toxic and side effects, and improve specific targeting. Therefore, it is desirable to synthesize various flavonoid glycosides for further investigation on their medicinal values. Compared with chemical glycosylations, biotransformations catalyzed by uridine diphospho-glycosyltransferases provide an environmentally friendly way to construct glycosidic bonds without repetitive chemical synthetic steps of protection, activation, coupling, and deprotection. In this review, we will summarize the existing knowledge on the biotechnological glycosylation reactions either in vitro or in vivo for the synthesis of flavonoid O- and C-glycosides and other rare analogs.Key points• Flavonoid glycosides usually show improved properties compared with their flavonoid aglycones.• Chemical glycosylation requires repetitive synthetic steps and purifications.• Biotechnological glycosylation reactions either in vitro or in vivo were discussed.• Provides representative synthetic examples in detail.

Total Synthesis and Stereochemical Confirmation of (-)-Olivil, (+)-Cycloolivil, (-)-Alashinols F and G, (+)-Cephafortin A, and Their Congeners: Filling in Biosynthetic Gaps

For the first time, we describe the stereocontrolled total syntheses of olivil, cephafortin A, 4-des-O-methyl-4-O-rhamnosyl cephafortin A, and alashinol F from a common precursor using a combination of chemoenzymatic and biomimetic methods for the systematic introduction of functional groups on three vicinal stereogenic carbon atoms. We revised the previously assigned stereochemistry of (+)-cephafortin A, which was reported as the enantiomer. Natural and unnatural congeners provide insights into the biogenetic interrelations of members of this family.

Bioactive constituents of Lindernia crustacea and its anti-EBV effect via Rta expression inhibition in the viral lytic cycle

ETHNOPHARMACOLOGICAL RELEVANCE

Lindernia crustacea (L.) F.Muell. (Scrophulariaceae) was selected for phytochemical investigation owing to its traditional use against human herpes virus infection and its anti-Epstein-Barr virus (EBV) effect.

AIMS OF THE STUDY

The present study focused on the phytochemical investigation of L. crustacea including the isolation and structure determination of its biologically active compounds. Compounds with anti-EBV effects were also investigated.

MATERIALS AND METHODS

The EtOH extract of L. crustacea was subsequently partitioned using different solvents. The EtOAc fraction was subjected to several chromatographic methods to obtain pure compounds. The structures of all isolates were established by spectroscopic analysis and compared with previously reported physical data. The anti-EBV effect was evaluated in an EBV-containing Burkitt's lymphoma cell line (P3HR1) to study the expression of EBV lytic proteins.

RESULTS

Thirty-three compounds, including one diterpene (1), four anthraquinones (2-5), two ionones (6 and 7), fourteen phenylpropanoid glycosides (8-21), five flavonoids (22-26), one lignan glycoside (27), one phenethyl alcohol glycoside (28), one phenylpropene glycoside (29), one glucosyl glycerol derivative (30), one furanone (31), and two cinnamic acid derivatives (32 and 33), were isolated from the ethanolic extract of the plant. All isolated compounds were obtained for the first time from Lindernia sp. The evaluation of the anti-EBV activity of L. crustacea crude extract, partitioned fractions, and constituents was performed for the first time. Phytol (1), aloe-emodin (2), byzantionoside B (7), a mixture of trans-martynoside (8) and cis-martynoside (9), a mixture of trans-isomartynoside (10) and cis-isomartynoside (11), luteolin-7-O-β-D-glucopyranoside (24), and apigenin-7-O-[β-D-apiofuranosyl (1→6)-β-D-glucopyranoside] (25) exhibited significant inhibitory effects on the EBV lytic cycle at 20 μg/mL in the immunoblot analysis. On the other hand, (6R,7E,9R)-3-oxo-α-ionol-β-D-glucopyranoside (6) and a mixture of trans-dolichandroside A (12) and cis-dolichandroside A (13) showed moderate anti-EBV activity at 20 μg/mL.

CONCLUSIONS

L. crustacea and its active isolates could be developed as potential candidates against EBV. Our findings provide scientific evidence for the traditional use of L. crustacea for its antiviral effects.

17- nor-Cephalotane-Type Diterpenoids from Cephalotaxus fortunei

Seventeen new 17- nor-cephalotane-type diterpenoids, fortalpinoids A-Q (1-17), were isolated from the seeds of Cephalotaxus fortunei var. alpine. Compound 12 represents the first 17- nor-cephalotane-type diterpenoid featuring an 8-oxabicyclo[3.2.1]oct-2-ene moiety. The absolute configuration of fortunolide A (18) was determined for the first time, and the structure of cephinoid Q was revised to 14- epi-cephafortoid A (24) by X-ray crystallographic data analysis. Some of the compounds showed significant cytotoxicity against A549 and HL-60 cells, and the structure-activity relationship of this compound class is discussed.

Bioactive norditerpenoids from Cephalotaxus fortunei var. alpina and C. lanceolata

Twenty-eight naturally occurring Cephalotaxus tropone analogues, including 19 previously undescribed ones, were identified from Cephalotaxus fortunei Hook. var. alpina H. L. Li and C. lanceolata K. M. Feng. The presence of the C20 cephinoids A-E revealed that these tropones were assigned to the norditerpenoids and were perhaps derived from labdane-type diterpenoids. These norditerpenoids showed excellent cytotoxicity against human cancer cells (IC₅₀, 20-0.1 μM) in vitro. The SAR (structure-activity relationship) analysis disclosed that the tropone moiety and the lactone ring were crucial structural features for the observed activities. Further SAR analyses led to a new candidate, cephinoid H, which demonstrated an inhibition of 49.0% by administration to zebrafish at a dose of 60.0 ng/mL, compared to cisplatin (DDP, 22.4%) at 15.0 μg/mL. These compounds might affect the NF-κB signaling pathway rather than binding to microtubules. Additionally, the isolated norditerpenoids showed almost equal anti-inflammatory activities compared to the positive control, MG132.

Diterpenoids and Lignans from Cephalotaxus fortunei

Five new diterpenoids including two Cephalotaxus troponoids (1 and 2), two 17-nor-cephalotane-type diterpenoids (3 and 4), and an abietane-type diterpenoid (5), two new lignans (6 and 7), and a new trisnorneoligan (8) along with eight known compounds were identified from the twigs and leaves of Cephalotaxus fortunei. The structure of 11-hydroxyhainanolidol was revised as 10-hydroxyhainanolidol (9) by X-ray crystallographic data. Compounds 3 and 4 are the first examples of 17-nor-cephalotane-type diterpenoids that are likely the biosynthesis precursors of the co-occurring troponoids (e.g., 1, 2, and 9). Compound 1 exhibited cytotoxic activities against HL-60 and A-549 cells with IC₅₀ values of 0.77 ± 0.05 and 1.129 ± 0.057 μM, respectively.

Cephalotanins A-D, Four Norditerpenoids Represent Three Highly Rigid Carbon Skeletons from Cephalotaxus sinensis

Four polycyclic norditerpenoids, cephalotanins A-D (1-4) representing three unprecedented carbon skeletons with highly rigid ring systems, were isolated from Cephalotaxus sinensis and structurally characterized by a combination of various methods. Compounds 1 and 2 are new skeletal norditerpenoid trilactones, while 3 and 4 are two norditerpenoids featuring different new carbon skeletons. Biosynthetic pathways for 1-4 were proposed by involving diverse and very fascinating chemical events with the coexisting cephalotane troponoids as the precursors. Compound 1 exhibited good NF-κB inhibition with an IC50 value of 4.12±0.61 μΜ.

Five New Alkaloids from Cephalotaxus lanceolata and C. fortunei var. alpina

Five new alkaloids (1-5) were isolated from the leaves and twigs of Cephalotaxus lanceolata and C. fortunei var. alpina along with 24 known alkaloids. The new structures were elucidated based on spectroscopic data including 1D and 2D NMR, FTIR, UV and MS. These new alkaloids showed no cytotoxicity to HeLa, SGC-7901 gastric cancer, and A-549 lung cancer cell lines.

Mannolides A-C with an Intact Diterpenoid Skeleton Providing Insights on the Biosynthesis of Antitumor Cephalotaxus Troponoids

Three new diterpenoids, mannolides A-C (1-3), and two new Cephalotaxus troponoids, 4 and 5, were isolated from Cephalotaxus mannii and structurally characterized by spectroscopic data and X-ray crystallography. The discovery of compounds 1-3 featuring a new intact carbon skeleton, proposed as cephalotane, sheds new light on the biogenesis of Cephalotaxus troponoids, a rare class of antitumor C19 norditerpenoids. Antitumor tests showed that the tropone motif is essential for the activity.

Asymmetric transfer hydrogenation of γ-aryl α,γ-dioxo-butyric acid esters

Six ferrocene-based chiral ligands were prepared and applied in ATH reaction of multiple-carbonyl compounds as RuCl(p-cymene)[Ts-DPEN] did.

New Sulphated Flavonoids from Wissadula periplocifolia (L.) C. Presl (Malvaceae)

Wissadula periplocifolia (L.) C. Presl (Malvaceae) is commonly used in Brazil to treat bee stings and as an antiseptic. The antioxidant properties of its extracts have been previously demonstrated, thus justifying a phytochemical investigation for its bioactive phenolic constituents. This has yielded five new sulphated flavonoids: 8-O-sulphate isoscutellarein (yannin) (1a); 4′-O-methyl-7-O-sulphate isoscutellarein (beltraonin) (1b); 7-O-sulphate acacetin (wissadulin) (2a); 4′-O-methyl-8-O-sulphate isoscutellarein (caicoine) (2b) and 3′-O-methyl-8-O-sulphate hypolaetin (pedroin) (3b) along with the known flavonoids 7,4′-di-O-methyl-8-O-sulphate isoscutellarein (4), acacetin, apigenin, isoscutellarein, 4′-O-methyl isoscutellarein, 7,4′-di-O-methylisoscutellarein, astragalin and tiliroside. The compounds were isolated by column chromatography and identified by NMR (¹H, ¹³C, HMQC, HMBC and COSY) and LC-HRMS. A cell based assay was carried out to evaluate the preliminary cytotoxic properties of the flavonoids against UVW glioma and PC-3M prostate cancer cells as well as non-tumour cell lines. The obtained results showed that acacetin, tiliroside, a mixture of acacetin + apigenin and the sulphated flavonoids 2a + 2b exhibited inhibitory activity against at least one of the cell lines tested. Among the tested flavonoids acacetin and tiliroside showed lower IC₅₀ values, presenting promising antitumor effects.

A new naphthalene glycoside from Chimaphila umbellata inhibits the RANKL-stimulated osteoclast differentiation

A new naphthalene glycoside was isolated from the leaves and stems of Chimaphila umbellata Barton. Its chemical structure was elucidated to be 2,7-dimethyl-1,4-dihydroxynaphthalene-1-O-β-D-glucopyranoside (DMDHNG), based on spectroscopic evidence. DMDHNG significantly inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced tartrate-resistant acid phosphatase (TRAP) activity and the formation of multinucleated osteoclasts in a dose-dependent manner. In addition, the new glycoside inhibited the RANKL-induced mRNA expression of osteoclast-associated genes that encode TRAP, cathepsin K, and another transcription factor-nuclear factor of activated T-cells c1. We believe that the inhibitory effects of DMDHNG on the osteoclast differentiation may be exploited for a therapeutic benefit.

Synthesis of Naturally Occurring Tropones and Tropolones

Tropones and tropolones are an important class of seven-membered non-benzenoid aromatic compounds. They can be prepared directly by oxidation of seven-membered rings. They can also be derived from cyclization or cycloaddition of appropriate precursors followed by elimination or rearrangement. This review discusses the types of naturally occurring tropones and tropolones and outlines important methods developed for the synthesis of tropone and tropolone natural products.

Catechin-7-O-xyloside induces apoptosis via endoplasmic reticulum stress and mitochondrial dysfunction in human non-small cell lung carcinoma H1299 cells

The medicinal plant Ulmus davidiana var. japonica has significant potential as a cancer chemoprevention agent. Catechin-7-O-xyloside (C7Ox) was purified from ultrafine U. davidiana var. japonica ethanol extract. In the present study, we investigated the apoptotic effect of C7Ox in the non-small cell lung cancer (NSCLC) cell line H1299. C7Ox treatment induced cell death and decreased plasma membrane integrity, an event typical of apoptosis. C7Ox-induced apoptosis was associated with the proteolytic activation of caspase-6, cleavage of poly(ADP-ribose) polymerase (PARP) and loss of mitochondrial membrane potential. C7Ox also induced the endoplasmic reticulum (ER) stress-regulated pro-apoptotic transcription factor CHOP. The suppression of CHOP expression significantly decreased C7Ox-induced cell death, LDH leakage and caspase-6 activation. Antitumor effects, evaluated based on protracted tumor regression, were observed when nude-mice bearing H1299 xenografts were treated with C7Ox. C7Ox-induced tumor regression was accompanied by enhanced expression of CHOP mRNA. Our data suggest that C7Ox can trigger mitochondrial-mediated apoptosis, and that ER stress is critical for C7Ox-induced apoptosis in H1299 NSCLC cells.

Anti-inflammatory properties of a triterpenoidal glycoside from Momordica cochinchinensis in LPS-stimulated macrophages

Two triterpenoidal saponins were isolated from the seeds of Momordica cochinchinensis Sprenger (Cucurbitaceae). Identification of chemical structures has been performed by (1)H- and (13)C-NMR spectroscopy and gas chromatography (GC). One of the saponins is a new gypsogenin glycoside, named as gypsogenin 3-O-β-D-galactopyranosyl(1→2)-[α-L-rhamnopyranosyl(1→3)]-β-D-glucuronopyranoside (compound 1), which is reported for the first time from natural resources. The other saponin is a quillaic acid glycoside (compound 2), which showed anti-inflammatory activities in RAW 264.7 cells. The mechanistic understanding of anti-inflammatory activities demonstrates that compound 2 inhibits lipopolysaccharide-induced expression of nitric oxide and IL-6 via NF-κB pathway.

Asymmetric synthesis of the oxygenated polycyclic system of (+)-harringtonolide

A straightforward asymmetric synthesis of the cage oxygenated structure of (+)-harringtonolide has been accomplished for the first time. The key steps involved (i) a templated stereoselective IMDA reaction to build a highly functionalized cyclohexene ring D, (ii) functionalization of the cycloadduct, (iii) ring-closing metathesis providing the five-membered ring C, and finally (iv) a challenging one-step cascade cyclization of an epoxy-alcohol toward the target structure, whose mechanism was investigated.

ent-Kaurane diterpenoids from Croton tonkinensis stimulate osteoblast differentiation

Four new ent-kaurane diterpenoids (1-4) were isolated from the leaves of Croton tonkinensis by bioactivity-guided fractionation using an in vitro osteoblast differentiation assay. Their structures were identified as ent-11β-acetoxykaur-16-en-18-ol (1), ent-11α-hydroxy-18-acetoxykaur-16-ene (2), ent-14β-hydroxy-18-acetoxykaur-16-ene (3), and ent-7α-hydroxy-18-acetoxykaur-16-ene (4). Compounds 1-4 significantly increased alkaline phosphatase activity and osteoblastic gene promoter activity. Compounds 1-3 also increased the levels of ALP and collagen type I alpha mRNA in C2C12 cells in a dose-dependent manner. These results suggest that ent-kaurane diterpenoids from C. tonkinensis have a direct stimulatory effect on osteoblast differentiation and may be potential therapeutic molecules against bone diseases such as osteoporosis.

Constituents of Dalbergia sissoo Roxb. leaves with osteogenic activity

One new isoflavone glucoside, caviunin 7-O-[β-d-apiofuranosyl-(1→6)-β-d-glucopyranoside] (10) and a new itaconic derivative, (E)-4-methoxy-2-(3,4-dihydroxybenzylidene)-4-oxobutanoic acid (15) along with series of isoflavones and flavonols with their glucosides (1-9 and 11-14) and a lignan glucoside (16) were isolated from the ethanolic extract of Dalbergia sissoo leaves. The structures of these compounds were established on the basis of IR, UV, (1)H and (13)C NMR, DEPT, COSY, HSQC, HMBC and MS data. All compounds (1-16) were assessed for osteogenic activity in primary calvarial osteoblast cultures. Compounds 1-4 and 10 increased alkaline phosphatase activity and mineralization thus resulting in significant osteogenic activity.

Effects of Sideritis euboea (Lamiaceae) Aqueous Extract on IL-6, OPG and RANKL Secretion by Osteoblasts

The water extract obtained from the aerial parts of Sideritis euboea (Lamiaceae), which is known in Greece as ‘mountain tea’, was investigated by determining the in vitro effect of this extract on the IL-6, OPG and RANKL secretion by osteoblasts, three important molecules in osteoblast-osteoclast interplay. The results showed that this extract reduced significantly the secretion of IL-6 by KS-483 osteoblasts, while it also suppressed RANKL secretion, with both effects being dose-dependent and more potent at the higher concentrations tested (50, 100 μg/mL). We further determined the chemical profile of the extract by applying an analytical U-HPLC-DAD-ESIMS/MS method using the high resolution hybrid LTQ-Orbitrap Discovery spectrometer. An ESI source in negative mode was employed. The analysis indicated that the water extract of S. euboea is rich in flavonoid glycosides, and phenylpropanoid glycosides.

Total Synthesis of (±)-Agastinol

A synthesis of the tetrahydrofuran lignan (±)-agastinol, starting from the cheap Vanillin, has been developed based on Stobbe reaction with diethyl succinate to give the skeleton of lignan, which was then reduced to afford meso- and threo-(±)-secoisolanciresinol. threo-(±)-Secoisolanciresinol was treated with DDQ in acetic acid to give the 2-aryl tetrahydrofuran lignan, and which was then condensed with ferulic acid to give (±)-agastinol for the first time.

Flavonoid Glycosides from the Seeds of Litchi chinensis

Seven flavonoid glycosides, including one new (1) and five previously uncharacterized (3-7), were obtained from the seeds of lychee ( Litchi chinensis Sonn. cv. Heiye) by means of repetitive column chromatography and high-performance liquid chromatography (HPLC) preparation. They were identified as litchioside D (1), (-)-pinocembrin 7-O-neohesperidoside (2), (-)-pinocembrin 7-O-rutinoside (3), taxifolin 4'-O-β-d-glucopyranoside (4), kaempferol 7-O-neohesperidoside (5), tamarixetin 3-O-rutinoside (6), and phlorizin (7) on the basis of spectroscopic analysis and comparison of their data to the values reported in the literatures. Among them, compounds 1, 4, and 5 showed in vitro antitumor activity against A549, LAC, Hep-G2, and HeLa cell lines in the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) colorimetric assay.