Natural β-Dihydroagarofuran-Type Sesquiterpenoids as Cognition-Enhancing and Neuroprotective Agents from Medicinal Plants of the Genus Celastrus

Molecular networking-guided isolation of melanogenesis inhibitory dihydro-β-agarofuran sesquiterpenoids from Celastrus orbiculatus

Seven previously undescribed dihydro-β-agarofurans (1-7) together with 28 known compounds were isolated from Celastrus orbiculatus fruits using LC-MS/MS-based molecular networking-guided purification. Their structures were elucidated through 1D- and 2D-NMR, HRESIMS analysis, and ECD quantum chemical calculations. The inhibitory effects of all isolated compounds on α-MSH-induced melanin production in B16F0 melanoma cells were tested. Compounds 1, 11, 12, 19-21, 23, 29, 31, 34, and 35 showed significant inhibitory effects on melanin production with IC50 values ranging from 11.3 to 30.1 μM.

Three novel sesquiterpene polyol esters from the root bark of Celastrus angulatus Maxim and their nitric oxide inhibitory activity

Three new sesquiterpene polyol ester compounds angulatin V [1β,15-diacetoxy-2β-(α-methyl)-butanoyloxy-4α,6α-dihydroxy-8α-isobutanoyloxy-9β-benzoxy-β-dihydroagarofuran], angulatin W [1β,2β-diacetoxy-4α,6α-dihydroxy-8-carbonyl-9β-benzoxy-15-isobutanoyloxy-β-dihydroagarofuran], angulatin X [1β,2β,8α-triacetoxy-4α, 6α-dihydroxy-9β-benzoxy-15-nicotinyl-β-dihydroagarofuran] (1-3), together with one known compound Putterine B (4), were isolated from the root bark of Celastrus angulatus Maxim. The structures of compounds 1-3 were elucidated by NMR, HRESIMS, IR data, and comparison with the literature data. The anti-inflammatory activity of all compounds was evaluated by measuring nitric oxide production in RAW264.7 macrophages. Compounds 1-4 showed no significant nitric oxide inhibitory activity at 2.5 and 5 μM concentrations.

Sesquiterpene Polyesters from the Fruits of Euonymus sieboldianus

The MeOH extract from dried immature fruits of Euonymus sieboldianus (Celastraceae) plants yielded nineteen new β-dihydroagarofuran-type sesquiterpene polyesters. The structures of these compounds were established using NMR, MS spectroscopic analysis and chemical evidence.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Dihydro-β-agarofuran-type sesquiterpenoids from the seeds of Tripterygium wilfordii (Thunder God Vine) and evaluation of their anti-osteoclastogenesis and immunosuppressive activities

Extensive phytochemical investigation of the seeds of Tripterygium wilfordii led to the identification of 54 polyesterified dihydro-β-agarofuran-type sesquiterpenoids, including 27 previously undescribed ones, named Tripwilin I-XXVII (1-27). Comprehensive spectroscopic and single-crystal X-ray diffraction analyses, along with electronic circular dichroism (ECD) calculations were used for the structural elucidation of the new compounds. Biological assay revealed that 37 compounds among the isolates exhibited significant inhibition against osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand (RANKL) at 10 µM. Further investigation indicated that Triptogelin C-3 (54), with the most potent osteoclastogenesis inhibitory activity, regulated the osteoclast marker genes (MMP-9, c-Fos, CTSK, and TRAP) and proteins in a dose-dependent manner in vitro. Besides, celaforin D-1 (28), 1α,6β,15-triacetoxy-8α,9α-dibenzoyloxy-2α-hydroxydihydro-β-agarofuran (34), triptogelin A-2 (37), and chiapen D (49) showed moderate suppressive effects on the proliferation of T and B lymphocytes with IC50 values ranging between 8.1 ± 0.8 and 19.0 ± 0.9 μM.

Phytochemistry and pharmacology of Celastrus paniculatus Wild.: a nootropic drug

OBJECTIVES

Celastrus paniculatus Wild is an evergreen climbing shrub. The plant is of great significance in the traditional Indian System of Medicine, such as Ayurveda, Unani, and Siddha. The seeds and their oil are extensively used to treat neurological disorders such as cognitive dysfunction, paralysis, epilepsy, insomnia, and other ailments like rheumatism, arthritis, sciatica, and leprosy. This paper aims to highlight the nootropic activity of C. paniculatus and explore its phytochemistry, traditional uses, and other pharmacological activities.

METHODS

All available information concerning C. paniculatus has been searched in the internationally accepted scientific databases, including PubMed, ScienceDirect, Scopus, and Google Scholar. Additional knowledge was gathered from the classical Textbooks and Unani Pharmacopoeia.

RESULTS

C. paniculatus is a rich source of several secondary metabolites, such as β-Dihydroagarofuranoids sesquiterpenes, alkaloids (Celastrine, Celapanin, Celapagin, and paniculatin), flavonoids, terpenoid (β-amyrin, Lupeol, Pristimerin), sterols (β-sitosterol, campesterol, stigmasterol, α-tocopherol, γ-Tocopherol), fatty acid (palmitic, stearic, oleic, linoleic, linolenic acids) and non-fatty acids (Benzoic acid, Cinnamic acid). The various study shows that the extracts and active constituent of this plant possess potent nootropic activity. Besides nootropic activity, it has also been reported for anti-Alzheimer, anticonvulsant, antidepressant, antioxidant, analgesic, anti-inflammatory, antiarthritic, gastroprotective, anti-psoriatic, wound healing, antibacterial, antimalarial, and several other properties.

CONCLUSIONS

Several in vitro and in vivo trials confirm the conventional use of C. paniculatus in cognitive dysfunction. However, the relations between the possible mechanisms of other activities and traditional uses of the C. paniculatus remain indistinct. Still, pharmacological studies also explored the effects of C. paniculatus, which were not recognized in ancient times, such as cytotoxic, ACE inhibitor, and antidiabetic activities. These discoveries are may be beneficial in the development of the new drug to treat various diseases. It is also confirmed that the β-dihydroagarofuranoids exhibit significant AChE inhibitory, cytotoxic, antibacterial, and insecticidal effects. This versatile medicine is truly a life elixir. Considering the therapeutic importance of the C. paniculatus and the absence of any reported clinical studies, extensive clinical trials are needed to explore its memory enhancing and other activities.

Bioactive molecular network-guided discovery of dihydro-β-agarofurans from the fruits of Celastrus orbiculatus

A bioactive molecular networking strategy has been applied to discovery of bioactive constituents from the fruits of Celastrus orbiculatus Thunb., which showed significant inhibitory effects on the α-MSH-induced melanin production in B16F0 melanoma cells. In the obtained molecular network, the nodes with relatively high bioactive scores were prioritized for isolation; as a result, 12 undescribed dihydro-β-agarofuran sesquiterpenes together with 15 known compounds were isolated from MeOH extracts of the fruits of C. orbiculatus. Their structures were elucidated based on the interpretation of NMR, HRESIMS, ECD data, and single crystal X-ray diffraction. Among the obtained isolates, celastorbin A and (1R,2S,4R,5S,7S,8S,9R,10S)-1,2,8-triacetoxy-9-cinnamoyloxydihydro-β-agarofuran, which possessed high bioactive scores in the molecular network, exhibited potent inhibitory effects on the α-MSH-induced melanin production in B16F0 cells with IC₅₀ values of 4.1 and 2.0 μM, respectively.

Three new sesquiterpene polyol esters from Celastrus angulatus

Three new sesquiterpene polyol ester compounds angulatins S-U, together with three known compounds were isolated from Celastrus angulatus Maxim. According to mainly 1D NMR and 2D NMR analysis, the structures of the new compounds were completely determined as angulatin S (1β-furoyloxy-2β,8α-diisobutanoyloxy-9β-benzoyloxy-15-acetoxy-4α,6α-dihydroxy-β-dihydroagarofuran), angulatin T (1β,2β,6α-triacetoxy-8β,15-diisobutanoyloxy-9α-benzoyloxy-β-dihydroagrofuran), and angulatin U (1β,6α,15-triacetoxy-8β-isobutanoyloxy-9α-benzoyloxy-β-dihydroagarofuran).

Dihydro-β-agarofuran-type sesquiterpenoids from the seeds of Celastrus virens with lifespan-extending effect on the nematode Caenorhabditis elegans

Twelve dihydro-β-agarofuran-type sesquiterpenoids, including five new ones (1-5), were purified from the seeds of Celastrus virens (Wang et Tang) C. Y. Chent et T. C. Kao. Their chemical structures were characterized via comprehensive spectroscopic analysis, single-crystal X-ray diffraction analysis, and computational prediction of ECD, as well as comparison of observed and reported NMR spectral data. Among the isolates, nine abundant dihydro-β-agarofuran-type sesquiterpenoids were evaluated for their lifespan-extending activity using the nematode Caenorhabditis elegans model. As a result, compounds 1, 2, 5, 6, 8, and 9 (50 μM) significantly extended the mean survival time of C. elegans, respectively, compared with the blank control group (p < 0.05). Further Quantitative RT-PCR showed that the prolonging of lifespan mediated by compounds 1, 6, 8, and 9 were dependent on the transcription factors skn-1 and hsf-1.

First Report on Inhibitory Effect against Osteoclastogenesis of Dihydro-β-agarofuran-Type Sesquiterpenoids

Dihydro-β-agarofuran-type sesquiterpenoids are characteristic metabolites of Celastraceae plants, and the extracts of these plants have been developed into botanical pesticides. In the course of our efforts to find novel natural biologically active products, eight new dihydro-β-agarofuran-type sesquiterpenoids (1-8) were identified from the stems of Celastrus monospermus Roxb. Their structures were elucidated by extensive spectroscopic analysis, single crystal X-ray crystallography, and electronic circular dichroism (ECD) calculations. In consideration of the efficacy of certain Celastrus plants for the treatment of arthritis and arthralgia in folk medicine, the isolates were evaluated for their inhibitory activities against osteoclastogenesis. As a result, compounds 4, 6, and 7 were found to restrain osteoclastogenesis induced by receptor activator of nuclear factor-κB ligand (RANKL) with IC₅₀ values of 0.58, 1.2, and 6.1 μM, respectively. Furthermore, compound 4 was found to inhibit osteoclastogenesis-related gene (c-Fos, MMP-9, CTSK, TRAP) expression and block c-Fos protein expression and inhibited bone resorption of mature osteoclasts induced by M-CSF and RANKL in a dose dependent manner. This is the first report of dihydro-β-agarofuran-type sesquiterpenoid for their potential medical applications in bone metabolic diseases.

Nine new dihydro-β-agarofuran sesquiterpene polyesters from the leaves of Tripterygium wilfordii

Nine previously undescribed dihydro-β-agarofuran type sesquiterpene polyesters, tripteresters A–I (1–9) were isolated from the leaves of Tripterygium wilfordii.

β-Dihydroagarofuran-type sesquiterpenoids from the stems of Celastrus orbiculatus with their cytotoxic activities

Abstract:

A new β-dihydroagarofuran-type sesquiterpenoid named 1α,2α,5α,11-tetraacetoxy-8α-(trans-p-coumaroyl)-β-dihydroagarofuran (1), together with five known compounds (2-6) were isolated from the CHCl3-soluble extract of the stems of Celastrus orbiculatus. The structure of new compound was elucidated with spectroscopic physico-chemical analyses. All isolates were evaluated for in vitro cytotoxic activity against four human cancer lines including HepG2, MCF-7, A549 and HCT-116 cells. Among them, compounds 1 and 6 showed potent cytotoxic activities on HepG2 cells with IC50 values of 8.78 ± 2.31 and 10.28 ± 1.15 μM, respectively. In addition, compound 6 exhibited significant cytotoxic activity on HCT-116 cells with IC50 value of 6.37 ± 2.52 μM

New dihydro-β-agarofuran sesquiterpenoids from Tripterygium wilfordii and their anti-inflammatory activity

Twenty seven dihydro-β-agarofuran sesquiterpenoids, including fifteen new congeners, wilforsinines I-W (1-9, 12-13, 24-27), and twelve known compounds were isolated from the dried root of Tripterygium wilfordii. The structures of the new sesquiterpenoids, wilforsinines I-W, were elucidated by extensive spectroscopic data analysis. The anti-inflammatory activity of isolates 1-27 were evaluated by examining their inhibitory effects on nitric oxide (NO) production in LPS-induced RAW 264.7 macrophage cells. Among them, wilforsinine K (3) and angulatin M (16) exerted optimal inhibitory effects on the production of NO in LPS-induced RAW 264.7 cells. Moreover, Western blot results revealed that their anti-inflammatory activities were correlated with the suppression of the expression of nitric oxide synthase (iNOS) and down-regulation of the level of NF-κB p65 phosphorylation.

Dihydro-β-agarofuran-Type Sesquiterpenoids from the Seeds of Celastrus virens and Their Multidrug Resistance Reversal Activity against the KB/VCR Cell Line

Twenty-nine dihydro-β-agarofuran-type sesquiterpenoids, including 17 new and 12 known compounds, were obtained from the seeds of Celastrus virens. The structures of the new isolates were characterized by spectroscopic methods and X-ray diffraction analysis. Among these, 20 sesquiterpenoids were evaluated for their multidrug resistance (MDR) reversal activity against the KB/VCR cell line. As a result, compounds 6 and 8 were found to exhibit MDR-reversal activity of more than 10-fold at a concentration of 2 μM, and the reversal fold (RF) ratios of compounds 19, 21, and 24 were >97.9 at a 20 μM nontoxic concentration level.

Stereocontrolled Total Synthesis of (-)-Isocelorbicol and Its Elaboration to Natural Dihydro-β-agarofuran Esters

The first total synthesis of four naturally occurring dihydro-β-agarofuran esters has been accomplished via a highly stereocontrolled 14-step access to their common core triol, (-)-isocelorbicol. A semipinacol rearrangement of an epoxy alcohol to install a quaternary carbon, diastereoselective conjugate reduction of a spirocyclic butenolide for the establishment of a methyl-bearing chiral center, and ring-closing metathesis to construct the decalin ring system were exploited as the key steps for the high-yielding synthesis of (-)-isocelorbicol.

Modified lanostane-type triterpenoids with neuroprotective effects from the fungus Inonotus obliquus

Six undescribed lanostane triterpenoids (1-6), together with three known compounds (7-9) were isolated from Inonotus obliquus. Compounds 3-5 are the rare natural compounds featuring a 4,5-seco-lanostane core with a 5,7,9-trien-21,24-cyclopentane moiety. The structure elucidation of the compounds was conducted by spectroscopic techniques and the ECD method. The absolute configuration of compound 1 was confirmed by single-crystal X-ray diffraction analysis. All isolated compounds were assayed for their neuroprotective activity against H₂O₂-induced cell injury using human neuroblastoma SH-SY5Y cells. Compound 9 exhibited the most potent neuroprotective activity and the flow cytometry analysis indicated that 9 could protect SH-SY5Y cells from oxidative damage by inhibiting cell apoptosis.

Siphonagarofurans A-J: Poly-O-acylated β-dihydroagarofuran sesquiterpenoids from the fruits of Siphonodon celastrineus

Ten poly-O-acylated β-dihydroagarofuran sesquiterpenoids, siphonagarofurans A-J, were obtained from the fruits of Siphonodon celastrineus using chromatographic techniques. Their structures were elucidated by extensive use of 2-D NMR spectroscopic methods. The absolute configurations of siphonagarofurans A-J were assigned following analysis of calculated and experimental ECD spectra. The absolute configuration of siphonagarofuran A was also confirmed by X-ray crystallographic analysis. Selected compounds were evaluated for their cytotoxic activity against KB, Vero and Hela cell lines with siphonagarofuran J identified as the most active compound, with IC₅₀ values ranging from 14 to 27 μM.

Polyesterified Sesquiterpenoids from the Seeds of Celastrus paniculatus as Lifespan-Extending Agents for the Nematode Caenorhabditis elegans

Eighteen new polyesterified dihydro-β-agarofurans, celaspaculins A-R, as well as 11 known ones, were purified from the seeds of Celastrus paniculatus. The structures of new isolates were identified by extensive spectroscopic analysis and X-ray diffraction studies. The lifespan-extending activity of the dihydro-β-agarofuran-enriched fraction and 10 abundant polyesterified dihydro-β-agarofurans was evaluated on the nematode Caenorhabditis elegans model. Consequently, the dihydro-β-agarofuran-enriched fraction and compounds 5, 14, and 21 notably increased the average survival time of C. elegans by 23%, 16%, 18%, and 17%, respectively, compared with the blank control group (p < 0.0001).

Dihydro-β-agarofuran sesquiterpenoid derivatives with neuroprotective activity from the leaves of Tripterygium wilfordii

A phytochemical investigation on the leaves of Tripterygium wilfordii Hook. F. was conducted, leading to the isolation of five undescribed dihydro-β-agarofuran sesquiterpenoids (1-5) and one known analogue (6). Their structures were determined by comprehensive spectroscopic analyses. The absolute configurations of the compounds were determined by comparison of the experimental ECD with the calculated data. In addition, all the compounds were evaluated for their neuroprotective activities against H₂O₂-induced cell injury in human neuroblastoma SH-SY5Y cells, and 3 showed the better protective effect with 76.63% cell viability comparing with the positive control Trolox (69.84%) at 12.5 μM.

Dihydroagarofuran sesquiterpenoid derivatives from the leaves of Tripterygium wilfordii with potential neuroprotective effects against H2O2-induced SH-SY5Y cell injuries

In this study, eight undescribed sesquiterpenoid esters and four known analogues were isolated and their absolute configurations were determined by ECD calculations and single-crystal X-ray diffraction analysis.

Triterpenes and Aromatic Meroterpenoids with Antioxidant Activity and Neuroprotective Effects from Ganoderma lucidum

Reactive oxygen/nitrogen species generated in the human body can cause oxidative damage associated with many degenerative diseases such as atherosclerosis, dementia, coronary heart diseases, aging, and cancer. There is a great interest in developing new antioxidants from Ganoderma fungus due to its low toxicity. As part of our ongoing search for antioxidative constituents from the fruiting bodies of Ganoderma lucidum, the chemical constituents were investigated and seven secondary metabolites, including one new lanostane triterpene (1), two known aromatic meroterpenoids (6–7), and four known triterpenes (2–5), were isolated by a series of chromatographic methods. The structures of the seven compounds were elucidated by spectroscopic techniques. The isolated compounds were tested in vitro for antioxidant potencies and neuroprotective activities against H₂O₂ and aged Aβ-induced cell death in SH-SY5Y cells. As a result, compounds 1, 6, and 7 exhibited potent antioxidant and neuroprotective activities. Additionally, all isolated compounds were tested for radical scavenging activities. Compounds 6 and 7 showed the comparable free radical scavenging activities with the standard drug in both ABTS (2, 2’-azobis (3-ethylbenzothiazole-6-sulfonaic acid)) and ORAC (oxygen radical absorbance capacity) experiments. The results from this study suggested that G. lucidum and its metabolites (especially the meroterpenoids) may be potential functional food ingredients for the antioxidation and prevention of neurogenerative diseases.

Neuroprotective Dihydro-β-agarofuran-Type Sesquiterpenes from the Seeds of Euonymus maackii

Twenty-one dihydro-β-agarofuran derivatives were purified from the seeds of Euonymus maackii, and eight compounds (1-8) were identified as new natural products. Their structures were deduced by extensive spectroscopic analysis, X-ray diffraction studies, and comparison of observed and reported NMR data. Compounds 10, 12, 17, and 18 significantly increased the cell viability of Aβ_25-35-treated SH-SY5Y cells with effects similar to that of epigallocatechin gallate (EGCG). In addition, the abundant compound 9 reduced the seizure-like locomotor activity of zebrafish at 10 μM compared with a pentylenetetrazol-treated group.

Traditional uses, secondary metabolites, and pharmacology of Celastrus species - a review

ETHNOPHARMACOLOGICAL RELEVANCE

Plants of genus Celastrus (Celastraceae) have been widely used in traditional Chinese medicine (TCM) and Indian medicine to treat cognitive dysfunction, epilepsy, insomnia, rheumatism, gout, and dyspepsia for thousands of years.

AIM OF STUDY

We critically summarized the current evidence on the botanic characterization and distribution, ethnopharmacology, secondary metabolites, pharmacological activities, qualitative and quantitative analysis, and toxicology of Celastrus species to provide perspectives for developing more attractive pharmaceuticals of plant origin.

MATERIALS AND METHODS

The relevant information on Celastrus species was gathered from worldwide accepted scientific databases via electronic search (Web of Science, SciFinder, PubMed, Elsevier, SpringerLink, Wiley Online, China Knowledge Resource Integrated, and Google Scholar). Information was also obtained from the literature and books as well as PhD and MSc dissertations. Plant names were validated by "The Plant List" (www.theplantlist.org).

RESULTS

Comprehensive analysis of the above mentioned databases and other sources confirmed that ethnomedical uses of plants of Celastrus genus had been recorded in China, India, and other countries in Southern Asia. The phytochemical investigation revealed the presence of β-dihydroagarofuranoids, diterpenoids, triterpenoids, tetraterpenes, phenylpropanoids, alkaloids, flavonoids, lignans, and others. The crude extracts and isolated constituents have exhibited a wide range of in vitro and in vivo pharmacological effects, including antitumor, cytotoxic, insecticidal, antimicrobial, anti-rheumatoid arthritis (RA), anti-inflammatory, anti-ageing and antioxidative, and neuroprotective activities.

CONCLUSION

Plants of genus Celastrus have been confirmed to show a strong potential for therapeutic and health-maintaining effects, in light of their long traditional use and the phytochemical and pharmacological studies summarized here. Currently, pharmacological studies of this genus mainly focus on Celastrus paniculatus Willd. and Celastrus orbiculatus Thunb. Therefore, more pharmacological investigations should be implemented to support traditional uses of other medicinal plants of the genus Celastrus. Moreover, studies on the toxicity, bioavailability, and pharmacokinetics, in addition to clinical trials, are indispensable for assessing the safety and efficacy of the secondary metabolites or extracts obtained from plants belonging to this genus.

Dihydro-β-agarofurans from the Australian rainforest plant Denhamia celastroides that inhibit leucine transport in prostate cancer cells

Four new dihydro-β-agarofurans, denhaminols K-N (4-7), along with three known secondary metabolites, denhaminols A-C (1-3) were obtained from the large-scale isolation studies of the leaves of the Australian endemic rainforest plant, Denhamia celastroides. The structures of the previously undescribed compounds were determined by detailed 1D and 2D nuclear magnetic resonance spectroscopy, mass spectrometry, ultraviolet, and infrared data analysis. All compounds were found to inhibit the activity of leucine transport in a human prostate cancer cell line with IC50 values ranging from 5.1-74.9 μM. Dihydro-β-agarofurans 1-7 showed better potency than the L-type amino acid transporter family inhibitor, 2-aminobicyclo[2.2.1]-heptane-2-carboxylic acid (BCH).

Dihydro-β-agarofurans from the roots of the Australian endemic rainforest tree Maytenus bilocularis act as leucine transport inhibitors

Phytochemical studies of the roots of the Australian plant, Maytenus bilocularis, resulted in the identification of six previously undescribed dihydro-β-agarofuran sesquiterpenoids, bilocularins D-I, along with three known natural products, namely 1α,2α,6β,15-tetraacetoxy-9β-benzoyloxydihydro-β-agarofuran, pristimerin, and celastrol. The structures of all compounds were characterized via analysis of 1D/2D NMR and MS data. The absolute configuration of bilocularin D was defined by X-ray crystallography analysis. Bilocularins D and G, 1α,2α,6β,15-tetraacetoxy-9β-benzoyloxydihydro-β-agarofuran, and celastrol inhibited leucine transport in the human prostate cancer cell line LNCaP with IC₅₀ values ranging from 2.5-27.9 μM, which were more potent than the L-type amino acid transporter (LAT) family inhibitor 2-aminobicyclo[2,2,1]-heptane-2-carboxylic acid (BCH). Bilocularins D-F are the first examples of dihydro-β-agarofurans bearing a hydroxyacetate group.

Neuroprotective Dihydroagarofuran Sesquiterpene Derivatives from the Leaves of Tripterygium wilfordii

Thirteen dihydroagarofuran derivatives, including 12 new sesquiterpenoid esters and one known sesquiterpenoid alkaloid, were obtained from the leaves of Tripterygium wilfordii. Spectroscopic techniques and the ECD method were used for the structure elucidation of the compounds. The structures of compounds 1 and 8 were confirmed by single-crystal X-ray crystallographic analyses. Compounds 8, 9, 11, 12, and 13 increased cell viability of the okadaic acid treated PC12 cells from 60.4 ± 23.0% to 72.4 ± 14.1, 71.5 ± 11.5, 75.7 ± 15.6, 81.2 ± 13.1, and 86.2 ± 25.5% at 10 μM, respectively.

Two New β-Dihydroagarofuran Sesquiterpenes from Celastrus orbiculatus Thunb and Their Anti-Proliferative Activity

Two new β-dihydroagarofuran-type sesquiterpenes (1-2) were isolated and identified from the fruit of Celastrus orbiculatus Thunb, together with seventeen known compounds (3-19). The structures of the isolated new compounds were elucidated based on extensive spectroscopic analyses. The cytotoxic activities of the 19 sesquiterpenes on three cell lines, human acute promyelocytic leukemia HL-60, human leukemic K562, and human colon cancer HCT-116 cells, were evaluated in vitro. Compound 4 exhibited potent cytotoxic activity against HL-60, K562, and HCT116 cell lines with IC50 values of 3.61 μΜ, 17.13 μΜ and 10.15 μΜ, respectively, and the other compounds displayed moderate activity.

New arbutin derivatives from the leaves of Heliciopsis lobata with cytotoxicity

Heliciopsis lobata is a medicinal plant, which is exclusively used to treat tumor in Li folk region. Two new arbutin derivatives, 6'-((E)2-methoxy-5-hydroxycinnamoyl) arbutin (1) and 2'-((E)2, 5-dihydroxycinnamoyl) arbutin (2) along with five known compounds (3-7), were isolated from the leaves of Heliciopsis lobata. Their structures were elucidated on the basis of extensive spectroscopic interpretations. They were evaluated for their potential anticancer activity. Compounds 6 and 7 exhibited cytotoxicity against MGC-803 cells with IC₅₀ values being 44.1 and 11.3 μg·mL^-1, respectively. Additionally, compounds 1, 2 and 5-7 exhibited a moderate inhibition of MGC-803 cells invasion; compound 2 at 20 μg·mL^-1 inhibited the invasion of MGC-803 cells by 43.0%, compared with the controls.

β-Dihydroagarofuran-Type Sesquiterpenes from the Seeds of Celastrus monospermus and Their Lifespan-Extending Effects on the Nematode Caenorhabditis elegans

Seventeen β-dihydroagarofuran-type sesquiterpenes were isolated from the seeds of Celastrus monospermus, and, among them, 15 (1-15) were identified as new natural products. Nine isolates were evaluated for their lifespan-extending effect using the standard model animal nematode Caenorhabditis elegans. As a result, all of the tested compounds prolonged the lifespan of C. elegans when compared to the blank control group (p < 0.0001). Among them, celaspermin E (5) extended the average lifespan and maximum lifespan of C. elegans, with effects similar to those of rapamycin, a positive control that has been found experimentally to delay the aging process of yeasts, worms, fruit flies, and mice.

Caffeoyl Triterpenoid Esters as Potential Anti-ischemic Stroke Agents from Celastrus orbiculatus

Three new triterpenoids, celastrusins A-C (1-3), together with 3-O-caffeoyl-α-amyrin (4) were isolated from the root bark of Celastrus orbiculatus. Their structures were identified by spectroscopic analysis, X-ray crystallography using Cu Kα radiation, and the comparison of both observed and reported spectroscopic data. An in vitro bioassay revealed that the caffeoyl triterpenoid esters 1, 3, and 4 possess neuroprotective effects against oxygen-glucose deprivation (OGD) induced SH-SY5Y cell damage. Further animal studies indicated that compound 1 significantly reduced brain infarction after transient middle cerebral artery occlusion (MCAO) in rats using a 10 mg/kg (i.v.) dose.

Absolute Configuration of Dihydro-β-agarofuran Sesquiterpenes from Maytenus jelskii and Their Potential Antitumor-Promoting Effects

Chemoprevention of human cancer appears to be a feasible strategy for cancer control, especially when chemopreventive intervention is involved during early stages of the carcinogenesis process. As a part of our ongoing research program into new chemopreventive agents, herein are reported the isolation, structural elucidation, and biological evaluation of 10 new (1-10) and three known (11-13) sesquiterpenes with a dihydro-β-agarofuran skeleton from the leaves of Maytenus jelskii Zahlbr. Their stereostructures have been elucidated by means of spectroscopic analysis, including 1D and 2D NMR techniques, ECD studies, and biogenetic considerations. The isolated metabolites and eight previously reported sesquiterpenes (14-21) were screened for their antitumor-promoting activity using a short-term in vitro assay for Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA). Six compounds from this series (4, 5, 11, and 13-15) were found to exhibit higher efficacies than β-carotene, used as reference inhibitor for EBV-EA activation. In particular, promising antitumor activity was observed for compound 5, exhibiting inhibition even at the lowest concentration assayed (10 mol ratio/TPA). Preliminary structure-activity relationship analysis revealed that the acetate, benzoate, and hydroxy groups are the most desirable substituents on the sesquiterpene scaffold for activity in the EBV-EA activation assay.

Acute rosmarinic acid treatment enhances long-term potentiation, BDNF and GluR-2 protein expression, and cell survival rate against scopolamine challenge in rat organotypic hippocampal slice cultures

BACKGROUND

Rosmarinic acid (RA) is a polyphenolic ester of caffeic acid and is commonly found in the Nepetoideae subfamily of flowering mint plants. Because RA has previously exhibited antioxidant, neuroprotective, and antidepressant-like effects, we evaluated its influences on cellular functions in neuronal cultures.

OBJECTIVE

To elucidate possible mechanisms of RA, we investigated the influences of acute RA administration on long-term potentiation (LTP), plasticity-related protein expression, and scopolamine-induced cell death in organotypic hippocampal slice cultures.

METHODS

LTP analysis in organotypic hippocampal slice cultures (OHSCs) was carried out with various ion channel blockers, such as AP5 (10 μM), CNQX (10 μM), niflumic acid (100 μM), and scopolamine (300 μM) in response to RA (1, 10 or 100 μg/mL) treatment. Protein expression and cell death assays in the presence of scopolamine were examined to observe the effects of RA. For LTP analysis, baseline field excitatory postsynaptic potentials (fEPSPs) were recorded in CA1 by a 60-channel multielectrode array (MEA) every min for 40 min before 15 min of high-frequency stimulation (HFS) to the Schaffer collaterals and commissural pathways, followed by a successive 50 min of recording. For protein expression measurements, anti-BDNF and anti-GluR2 antibodies were used for Western blotting assays in whole-hippocampal tissue homogenate. Finally, for cell death assays, OHSCs were exposed to a culture medium containing propidium iodide (PI) for 24 or 48 h, followed by the assessment of cell death by fluorescent image analysis of PI uptake.

RESULTS

and discussion: Our results indicate that RA treatment enhances fEPSPs following HFS in CA1 synapses at 1 and 10 μg/ml RA, an effect that was inhibited by CNQX and NFA but not by AP5. RA treatment also increases the expression of BDNF and GluR-2 proteins and prevents cell death of scopolamine-exposed OHSCs. Our results suggest the possibility that rosmarinic acid can enhance neural plasticity by modulating glutamatergic signaling pathways, as well as providing neuroprotection with reduced cholinergic activity.

Bioactive Dihydro-β-agarofuran Sesquiterpenoids from the Australian Rainforest Plant Maytenus bilocularis

Chemical investigations of the CH2Cl2 extract obtained from the leaves of the Australian rainforest tree Maytenus bilocularis afforded three new dihydro-β-agarofurans, bilocularins A-C (1-3), and six known congeners, namely, celastrine A (4), 1α,6β,8α-triacetoxy-9α-benzoyloxydihydro-β-agarofuran (5), 1α,6β-diacetoxy-9α-benzoyloxy-8α-hydroxydihydro-β-agarofuran (6), Ejap-10 (11), 1α,6β-diacetoxy-9β-benzoyloxydihydro-β-agarofuran (12), and Ejap-2 (13). The major compound 1 was used in semisynthetic studies to afford four ester derivatives (7-10). The chemical structures of 1-3 were elucidated following analysis of 1D/2D NMR and MS data. The absolute configurations of bilocularins A (1) and B (2) were determined by single-crystal X-ray diffraction analysis. All compounds were evaluated for cytotoxic activity against the human prostate cancer cell line LNCaP; none of the compounds were active. However, several compounds showed similar potency to the drug efflux pump inhibitor verapamil in reversing the drug resistance of the human leukemia CEM/VCR R cell line. In addition, similar to verapamil, compound 5 was found to inhibit leucine uptake in LNCaP cells (IC50 = 15.5 μM), which was more potent than the leucine analogue 2-aminobicyclo[2.2.1]heptane-2-carbocyclic acid. This is the first report of secondary metabolites from Maytenus bilocularis.