Neo-clerodane Diterpenes Research Articles

Phytochemical Characterization of the Aerial Parts of Teucrium nuchense K. Koch: An Endemic Species of Caucasian Flora

Background: The genus Teucrium L. is frequently employed in traditional medicine, primarily for addressing disorders of the digestive and respiratory systems. Biological investigations focused on essential oils have substantiated their antibacterial, antioxidant, anti-tumor, anti-diabetic, and anti-rheumatic properties. Objective: The aim of the study was to assess the chemical composition and biological activities of the aerial parts of the endemic species Teucrium nuchense K. Koch. Methods: The chemical composition of the essential oil was analyzed using gas chromatography-mass spectrometry (GC-MS). The antioxidant activity was evaluated through the Oxygen Radical Absorbance Capacity (ORAC) assay and tested on normal skin fibroblasts (WS-1). Additionally, the antiinflammatory efficacy was assessed by monitoring nitric oxide production. The total phenolic content in the aqueous, methanolic, and chloroformic extracts was quantified using the Folin-Ciocalteu reagent. Individual compounds were isolated using preparative high-performance liquid chromatography. Their identification was accomplished using high-resolution mass spectrometry (HRMS) with an ESI-Q-TOF detector in conjunction with nuclear magnetic resonance (NMR) spectroscopy. Results: The essential oil yield was 0.32 ml/kg. Caryophyllene oxide, constituting 15.19 %, and 1- octen-3-ol, constituting 8.75%, emerged as the primary components in the essential oil. Oxygenated sesquiterpenes dominated the terpenic compounds, representing 25.1 % of the essential oil. The aqueous and methanolic extracts displayed a notable phenolic content, with percentages of 27 ± 2 % and 35 ± 0.1 %, respectively. Both the aqueous and methanolic extracts demonstrated robust antioxidant activity in the ORAC test and in vitro assessments using WS-1 cells. The methanolic extract, at a concentration of 160 μg/ml, inhibited NO formation by 90 %, without toxicity in RAW 264.7. Individual compounds, teucrioside from the phenylethanoid glycoside class, two neo-clerodane diterpenes, teucrin A, and 6-alpha-hydroxyteuscordine, were isolated. Conclusion: The essential oil extracted from the aerial parts of Teucrium nuchense is characterized by the presence of caryophyllene oxide and 1-octen-3-ol. The methanolic extract exhibits notable antioxidant as well as anti-inflammatory properties, whereas the aqueous extract demonstrates high antioxidant activity. Additionally, three compounds of teucrioside, teucrin A, and 6-α- hydroxyteuscordine have been isolated and characterized.

New neo-clerodane diterpenes from Teucrium polium subsp. capitatum

Phytochemical investigation of a methanolic extract from the aerial parts of Teucrium polium subsp. capitatum afforded six acetoxylated neo-clerodane diterpenes, including 20-acetylauropolin and 6-acetylteucjaponin A, along with four previously undescribed congeners. The compounds were isolated by a combination of silica gel column chromatography and preparative HPLC-ESIMS. Their structures were determined by extensive NMR analysis, HRESIMS, and by comparison with literature data of related compounds. The absolute configuration of 20-acetylauropolin was confirmed by X-ray crystallographic diffraction analysis. Some of the isolated diterpenes possess structural features unusual in the class of neo-clerodane diterpenes, such as a rare C-20 hemiacetal function which forms an oxepane ring to C-7 of the trans-decalin core structure.

In Vitro Hypoglycemic Diterpenoids from the Roots of Croton yunnanensis.

Fifteen compounds including nine new diterpenes were isolated from the roots of Croton yunnanensis. By HRESIMS, NMR, ECD data, and X-ray diffraction analysis, the new compounds were characterized as eight neo-clerodane diterpenes (compounds 1-8) and one 15,16-dinor-ent-pimarane diterpene (9). All diterpenes were assayed for their hypoglycemic activities. Compounds 1-4, 6, 7, and 10 promoted glucose uptake activity in insulin-resistant 3T3-L1 adipocytes. Compounds 1 and 6 showed insulin sensitizing activity, potentiating conspicuously their glucose uptake activity at a concentration of 20 μM when treated synergistically with low-concentration insulin at 1 nM.

Flavonoids and Acid-Hydrolysis derivatives of Neo-Clerodane diterpenes from Teucrium flavum subsp. glaucum as inhibitors of the HIV-1 reverse transcriptase–associated RNase H function

Bioassay-guided fractionation of the ethyl acetate extract from Teucrium flavum subsp. glaucum, endowed with inhibitory activity towards the HIV-1 reverse transcriptase–associated RNase H function, led to the isolation of salvigenin (1), cirsimaritin (2) and cirsiliol (3) along with the neo-clerodanes teuflavin (4) and teuflavoside (5). Acid hydrolysis of the inactive teuflavoside provided three undescribed neo-clerodanes, flavuglaucins A-C (7-9) and one known neo-clerodane (10). Among all neo-clerodanes, flavuglaucin B showed the highest inhibitory activity towards RNase H function with a IC50 value of 9.1 μM. Molecular modelling and site-directed mutagenesis analysis suggested that flavuglaucin B binds into an allosteric pocket close to RNase H catalytic site. This is the first report of clerodane diterpenoids endowed with anti-reverse transcriptase activity. Neo-clerodanes represent a valid scaffold for the development of a new class of HIV-1 RNase H inhibitors.

Synthetic Studies of Neoclerodane Diterpenes from Salvia divinorum: Design, Synthesis, and Evaluation of Analogues with Improved Potency and G-protein Activation Bias at the μ-Opioid Receptor.

Previous structure-activity relationship (SAR) studies identified the first centrally acting, non-nitrogenous μ-opioid receptor (MOR) agonist, kurkinorin (1), derived from salvinorin A. In an effort to further probe the physiological effects induced upon activation of MORs with this nonmorphine scaffold, a variety of analogues were synthesized and evaluated in vitro for their ability to activate G-proteins and recruit β-arrestin-2 upon MOR activation. Through these studies, compounds that are potent agonists at MORs and either biased toward β-arrestin-2 recruitment or biased toward G-protein activation have been identified. One such compound, 25, has potent activity and selectivity at the MOR over KOR with bias for G-protein activation. Impressively, 25 is over 100× more potent than morphine and over 5× more potent than fentanyl in vitro and elicits antinociception with limited tolerance development in vivo. This is especially significant given that 25 lacks a basic nitrogen and other ionizable groups present in other opioid ligand classes.

Ethnomedicinal Uses, Phytochemistry, Pharmacology, and Toxicology of Species from the Genus Ajuga L.: A Systematic Review.

The present review is aimed at providing a comprehensive summary of the botanical characteristics, ethnomedicinal uses, phytochemical, pharmacological, and toxicological studies of the genus Ajuga L. The extensive literature survey revealed Ajuga L. species to be a group of important medicinal plants used for the ethnomedical treatment of rheumatism, fever, gout, sclerosis, analgesia, inflammation, hypertension, hyperglycemia, joint pain, palsy, amenorrhea, etc., although only a few reports address the clinical use and toxicity of these plants. Currently, more than 280 chemical constituents have been isolated and characterized from these plants. Among these constituents, neo-clerodane diterpenes and diterpenoids, phytoecdysteroids, flavonoids, and iridoids are the major bioactive compounds, possessing wide-reaching biological activities both in vivo and in vitro, including anti-inflammatory, antinociceptive, antitumor, anti-oxidant, antidiabetic, antimicrobial, antifeedant, antidiarrhoeal, hypolipidemic, diuretic, hypoglycaemic, immunomodulatory, vasorelaxant, larvicidal, antimutagenic, and neuroprotective activity. This review is aimed at summarizing the current knowledge of the ethnomedicinal uses, phytochemistry, biological activities, and toxicities of the genus Ajuga L. to reveal its therapeutic potentials, offering opportunities for future researches. Therefore, more focus should be paid to gathering information about their toxicology data, quality-control measures, and the clinical application of the bioactive ingredients from Ajuga L. species.

Antinociceptive effect of neo-clerodane diterpenes obtained from Baccharis flabellata

We report here for the first time antinociceptive effects of extracts from Baccharis flabellata. Two extracts in this analysis, one obtained in summer and the other during winter time. Our results indicate that both extract show strong antinociceptive effects, being the extracts obtained during the summer significantly more active.Our results suggest that this activity is mainly due to the presence of the diene-acid clerodane ent-15,16-epoxy-19-hydroxy-1,3,13(16),14-clerodatetraen-18-oic acid (DAC) and its dimer called DACD. Employing naloxone as an antagonist of opioid receptors, we demonstrated that both compounds act on opioid receptors, being the antinociceptive effect of DACD stronger than DAC. Thus, the antinociceptive activity of DACD was almost two times stronger than DAC (44.8 over 24.6 s in the hot-plate test) after one hour of treatments.In order to better understand the mechanism of action at molecular level of these compounds, we conducted a molecular modeling study analyzing the molecular interactions of DAC and DACD complexes with the κ-ORs. Our results suggest interactions for both DAC and DACD with Gln115, Val118, Tyr119, Asn122 and Tyr313 stabilizing their complexes; however, these interactions are significantly stronger for DACD with respect to DAC. This finding could explain why DACD have a higher affinity for the κ-ORs. These results are in agreement with the obtained antinociceptive effect. In addition, our results indicate that these neoclerodanes would have a mechanism of action similar to that of salvinorin A; such information can be very useful for the design of new inhibitors of κ-ORs.

In vivo photoinduced [4 + 2] dimerization of a neo-clerodane diterpene in Baccharis flabellata. ROS and RNS scavenging abilities

Secondary metabolites play a major role in the adaptation of plants to the environment. Furan neo-clerodane diterpenes are characteristic secondary metabolites in Baccharis flabellata Hook. & Arn. var. flabellata. One of the main compounds is the diene ent-15,16-epoxy-19-hydroxy-1,3,13(16),14-clerodatetraen-18-oic acid (DAC). In this work a new dimeric compound (DACD) has been isolated and identified by NMR and MS techniques. The presence of other minor dimers was also observed in the same plant methanolic extracts. Assuming that they may be the products of [4 + 2] condensation of two monomeric moieties, the formation of adducts by photochemical dimerization was checked by inducing the in vitro [4 + 2] cycloaddition of DAC. Moreover, the DAC and DACD accumulation rates in aerial parts of B. flabellata specimens were analyzed monthly during a complete phenological cycle. The accumulation of monomer depends on the plant phonological stage; meanwhile the dimer proportion arises in detriment of the monomer as the solar UV radiation increases. Since plants exposed to strong UV intensities produce radical species, the scavenger properties of these compounds toward reactive nitrogen species (RNS), and reactive oxygen species (ROS), were analyzed. Albeit DAC and DACD show significant superoxide radical scavenger activities, the monomer proved to be more effective than the dimer toward ROS, while DACD was an excellent RNS scavenger.

Neo-clerodane diterpenes and phytoecdysteroids from Ajuga decumbens Thunb. and evaluation of their effects on cytotoxic, superoxide anion generation and elastase release in vitro

Five novel compounds, including four neoclerodane diterpenoids, named ajugacumbins KN (1–4) along with a phytoecdysterone, named ajugacetalsterone E (5), were isolated from the whole herbs of Ajuga decumbens (Labiatae). Their structures were elucidated on the basis of detailed spectroscopic analysis including IR, HRESIMS, CD, 1D and 2D NMR spectroscopic experiments. Compounds 1–5 were evaluated for their cytotoxic activities and the effects on superoxide anion generation and elastase release in FMLP/CB-induced human neutrophils.

Chemical constituents from the aerial part of Sheareria nana S. Moore

Seventeen compounds were isolated from the aerial parts of Sheareria nana S. Moore. Their structures were elucidated by spectroscopic methods and by comparison of the reported spectral data. They consisted of two sterols (1 and 12), five triterpenoids (2–6), two lignanoids (7 and 16), two diterpenoids (8 and 9), two phenylpropanoids (10 and 11), three flavonoids (13, 15 and 17) and one quinone (14). The taxonomic influence of these compounds in the position of this species within the Compositae family was discussed. As the result, the neo-clerodane diterpenes (soulidiol and soulidiol 18-O-β-D-glucoside), sterol (α-spinasterol-3-O-β-D-glucoside) and triterpenoids (urs-12-ene and olean-12-ene) might depict the taxonomic position for S. nana in Compositae and demonstrate the relationships between S. nana and some species of Astereae and Inuleae.

Constituents from Scutellaria barbata Inhibiting Nitric Oxide Production in LPS-Stimulated Microglial Cells.

The arial parts of Scutellaria barbata D. Don (Lamiaceae) efficiently inhibited NO production in BV2 microglial cells, and the active constituents were further isolated based on activity-guided isolation using silica-gel column chromatography, RP-C18 MPLC and prep-HPLC. As the results, 2 flavonoids including 6-methoxynaringenin (1) and 6-O-methylscutellarein (5), and 6 neo-clerodane diterpenes such as scutebarbatine W (2), scutebatas B (3), scutebarbatine B (4), scutebarbatine A (6), 6-O-nicotinolylscutebarbatine G (7), and scutebarbatine X (8) were isolated. The structures of these compounds were elucidated based on NMR and MS data, and the comparison of literature values. All the compounds except compound 7 inhibited NO production efficiently with IC50 values of lower than 50μm. Particularly, compounds 1 and 8 were the most efficient with IC50 values of 25.8 and 27.4μm, respectively. This is the first report suggesting the potential of S.barbata on the reduction of neuroinflammation.

Phytochemical, cytotoxic and chemotaxonomic study on Ajuga forrestii Diels (Labiatae)

A phytochemical investigation of Ajuga forrestii Diels led to the isolation of 14 compounds, including eight neo-clerodane diterpenes (1–8), two phytoecdysteroids (9, 11), one stigmastane sterol (10) and three iridoid glycosides (12–14). The structures of these compounds were identified by spectroscopic methods and a comparison of their data with those reported in the literature. This is the first report of compounds 1–14 from A. forrestii. The cytotoxic activities of the aqueous extract of A. forrestii and several compounds have been studied and the chemotaxonomic significance of isolated compounds has also been summarised.

6 Clerodane diterpene化合物の絶対配置について : X線解析及びCDスペフトルの矛盾する結果に対する立体配座からの解明

6 Clerodane diterpene化合物の絶対配置について : X線解析及びCDスペフトルの矛盾する結果に対する立体配座からの解明

Stachaegyptin A-C: Neo-clerodane diterpenes from Stachys aegyptiaca

Phytochemical investigation of Stachys aegyptiaca resulted in the characterization of three new diterpenes (1-3) together with eleven known compounds including four neo-clerodane diterpenes and seven flavonoid aglycones. Structure elucidation was performed by spectroscopic analysis by HRFABMS, 1D and 2D NMR and X-ray. Isolated compounds were screened for anti-inflammatory activity using a lipopolysaccharide-induced nitric oxide inhibition assay employing murine macrophage cells. Among the assayed compounds, 13 (calycopterin) showed a concentration-dependent inhibition of LPS-induced nitric oxide release with a IC50 of 62.5μM.

Synthetic Studies of Neoclerodane Diterpenes from Salvia divinorum: Identification of a Potent and Centrally Acting μ Opioid Analgesic with Reduced Abuse Liability.

Opioids are widely used to treat millions suffering from pain, but their analgesic utility is limited due to associated side effects. Herein we report the development and evaluation of a chemical probe exhibiting analgesia and reduced opioid-induced side effects. This compound, kurkinorin (5), is a potent and selective μ-opioid receptor (MOR) agonist (EC50 = 1.2 nM, >8000 μ/κ selectivity). 5 is a biased activator of MOR-induced G-protein signaling over β-arrestin-2 recruitment. Metadynamics simulations of 5's binding to a MOR crystal structure suggest energetically preferred binding modes that differ from crystallographic ligands. In vivo studies with 5 demonstrate centrally mediated antinociception, significantly reduced rewarding effects, tolerance, and sedation. We propose that this novel MOR agonist may represent a valuable tool in distinguishing the pathways involved in MOR-induced analgesia from its side effects.

Neo-Clerodane diterpenoids from the aerial parts of Teucrium fruticans cultivated in China

Seven neo-clerodane diterpenes, teufruintins A–G (1–7), together with eight known compounds (8–15) were isolated from the CHCl3-soluble fraction of the aerial parts of Teucrium fruticans cultivated in China. The chemical structures of the isolated compounds were elucidated using different spectroscopic methods. All of the isolated diterpenes were evaluated for their cytotoxic activities on three human cancer cell lines, and for their ability to inhibit LPS-induced nitric oxide production in RAW 264.7 macrophages. None of the compounds displayed cytotoxic activities on the cancer cell lines, and only 15 showed weak NO inhibitory activity.

Methoxyflavones from Stachys glutinosa with binding affinity to opioid receptors: in silico, in vitro, and in vivo studies.

Fractionation of the bioactive dichloromethane extract from the aerial parts of Stachys glutinosa led to the isolation of four flavones, xanthomicrol (1), sideritoflavone (2), 8-methoxycirsilineol (3), and eupatilin (4), along with two neo-clerodane diterpenes, roseostachenone (8) and a new compound, 3α,4α-epoxyroseostachenol (7). In order to study structure-activity relationships, two methoxyflavones [5-demethyltangeretin (5) and tangeretin (6)] were synthesized by the methoxylation of xanthomicrol. The isolated compounds (1-4, 7, and 8) as well as the xanthomicrol semisynthetic derivatives (5 and 6) were evaluated for their binding affinity to the μ and δ opioid receptors. Xanthomicrol was the most potent binder to both μ and δ receptors, with a Ki value of 0.83 and 3.6 μM, respectively. Xanthomicrol administered intraperitoneally in mice at a dose of 80 mg/kg significantly reduced morphine-induced antinociception in the tail flick test. Our results suggested that xanthomicrol is a μ opioid receptor antagonist. Docking experiments were carried out to acquire a deeper understanding about important structural aspects of binding of xanthomicrol. In summary, these data suggest that xanthomicrol is a valuable structure for further development into a potential μ opioid receptor antagonist.

Structure and Antifeedant Activity Relationship of neo-Clerodane Diterpenes Against Colorado Potato Beetle Larvae

Structure and Antifeedant Activity Relationship of neo-Clerodane Diterpenes Against Colorado Potato Beetle Larvae

An Approach to the Bicyclic C‐5–C‐17/C‐19–C‐20 (BC) Portion of Neoclerodane Diterpenes by Intramolecular Diels–Alder Reaction

AbstractUsing a highly diastereoselective intramolecular acrylate [4+2] cycloaddition as the key step, a short route from 3‐furaldehyde to a bicyclic building block for the synthesis of neoclerodane diterpenes was developed. A first attempt featuring a conjugate methylation of a dienyl lactone failed, but a streamlined sequence using an all‐encompassing intramolecular Diels–Alder reaction of a sterically congested 1,3‐diene was successful.

Neo-Clerodane diterpenes from Ajuga decumbens and their inhibitory activities on LPS-induced NO production

A phytochemical investigation of the whole plants of Ajuga decumbens led to the isolation of three new (1, 2a, and 2b) and three known (3a−3c) neo-clerodane diterpenes. Their structures were elucidated by spectroscopic data analysis (IR, ESIMS, HR-ESIMS, 1D and 2D NMR), and the structure of 1 was confirmed by X-ray crystallography. The inhibitory activities on LPS-induced NO production of the six diterpenes were evaluated and compounds 2a, 2b, and 3a showed inhibitory effects.