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Vibrational circular dichroism (VCD) method has become robust and reliable alternative for the stereochemical characterization of natural products. In this paper, three new serrulatane-type diterpenoids, euplexaurenes A–C (1–3), and a known metabolite, anthogorgiene P (4), were obtained from the South China Sea gorgonian Euplexaura sp. GXWZ-05. The...
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... isolated as a novel skeleton com- pound from a Chinese gorgonian Anthogorgia sp. 12 . Euplexaurenes A-C (1-3) represent the serrulatane-type diterpenoids characterized with a 5,3,6-tricyclic skeleton isolated from nature for the second time. A hypothe- sized biosynthetic pathway of 1-4 starting from geranylgeranyl pyrophosphat (GGPP) was proposed (Fig. 5). A key intermediate (4a) in the biosynthesis derives from GGPP by a ring closure and oxidation. Anthogorgiene P (4) is formed from 4a via aromatic rearrangement to form an unusual 5,3,6-tricyclic nucleus. Then, 4 is oxidized to form euplexaurene C (3), and hydrated to form euplexaurene B (2), respectively. Finally, the epimerization of ...
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... More recently, four spatanes have also been described from soft corals [24][25][26]. Regarding the prenylcubebanes, besides Rugulopteryx algae, the gorgonians Anthogorgia sp. and Euplexaura sp. have yielded terpenoids displaying this skeleton, although the four compounds isolated from these gorgonians were named as serrulatane-type diterpenoids [27,28]. In addition, the species R. okamurae has been the source of a few unique compounds with unprecedented diterpenoid skeletons, such as the dictyterpenoids isolated from Japanese specimens [13] and rugukadiol A from Spanish specimens of the alga [15]. ...
This study aimed to evaluate the anti-inflammatory potential of the different classes of diterpenoids produced by algae of the genus Rugulopteryx. First, sixteen diterpenoids (1–16), including spatane, secospatane, prenylcubebane, and prenylkelsoane metabolites, were isolated from the extract of the alga Rugulopteryx okamurae collected at the southwestern Spanish coasts. Eight of the isolated diterpenoids are new compounds whose structures were determined by spectroscopic means: the spatanes okaspatols A-D (1–4); the secospatane rugukamural D (8); the prenylcubebanes okacubols A (13) and B (14); and okamurol A (16), which exhibits an unusual diterpenoid skeleton featuring a kelsoane-type tricyclic nucleus. Second, anti-inflammatory assays were performed on microglial cells Bv.2 and macrophage cells RAW 264.7. Compounds 1, 3, 6, 12, and 16 caused significant inhibition of the NO overproduction induced by LPS in Bv.2 cells, and compounds 3, 5, 12, 14, and 16 significantly decreased levels of NO in LPS-stimulated RAW 264.7 cells. The most active compound was okaspatol C (3), which completely suppressed the effects of LPS stimulation, both in Bv.2 and in RAW 264.7 cells.
... Thus, 4 serrulatane-type diterpenoids, including new euplexaurenes 77-79 ( Figure 21) and known anthogorgiene P (80) were isolated. The AC followed from a VCD study of 80. 55 The relative stereochemistry of FCdiene 81 ( Figure 22), isolated from fermentation of Saccharomyces cerevisiae, was confirmed by comparison of experimental and predicted 13 C-NMR chemical shifts and the AC followed from its IR and VCD spectra as (6S,7S,11R)-fusicocca-2,10(14)-diene (81). 56 The stereochemistry of a new isopimarane-type diterpenoid, isolated from Callicarpa macrophylla Vahl, was studied by ECD and VCD with the aid of TDDFT calculations confirming the AC as (4S,5S,9S,10S,13S,14S)−14α-hydroxy-7,15isopimaradien-18-oic acid (82) (Figure 22). ...
Although demonstrated in 1975, vibrational circular dichroism (VCD) finally started to popularize during this century as a reliable tool to determine the absolute configuration (AC) of organic molecules. This research field continues to be a very dynamic one, in particular for the study of natural products which are a unlimited source of chiral molecules. It therefore turns of interest to summarize the accomplishments published in recent years and to comment on some eventual difficulties that emerged in rare cases to complete the AC determination task. Therefore the aim of this review is to update VCD results for the AC assignment of natural products published from 2015 to 2019, a period in which VCD was reported in some 126 publications involving almost 300 molecules. They are organized according the type of studied metabolite allowing an easily search. The molecules correspond to 28 monoterpenes concerning 17 papers, to 42 sesquiterpenes in 14 papers, to 51 diterpenes in 19 publications, to 5 other terpenoids in three papers, to 48 aromatic molecules in 15 reports, to 20 polyketides in 10 publications, to 27 miscellaneous formulas also in 10 papers, and to 76 nitrogen containing compounds, which include alkaloids and their synthetic analogs, in 38 articles. The landscape of reviewed molecules is quite wide as it goes from simple monoterpenes, like borneol or camphor, to very relevant biological molecules like the alkaloid cocaine or tadalafil samples to distinguish genuine and counterfeit Cialis ® . In addition, 5 natural products and a simple derivative published outside the reviewed period, were used to illustrate some aspects of density functional theory calculations.
... Meanwhile, the stereochemistry of molecules has become one of the most important features of chiral natural products, which play a fundamental role in biology, chemistry and medicine. Thus, assigning the stereochemical characterizations attracted more and more attentions in the field of natural medicinal chemistry [4,5]. In our research on structurally-unique and biologically-active metabolites from the marine-derived fungi, the fungal strain Penicillium polonicum HBU-114, whose EtOAc extract exhibited the original thin-layer chromatography (TLC) and high performance liquid chromatography-under voltage (HPLC-UV) profiles of the secondary metabolites, differed from the other fungi, attracted our attention. ...
... In our research on structurally-unique and biologically-active metabolites from the marine-derived fungi, the fungal strain Penicillium polonicum HBU-114, whose EtOAc extract exhibited the original thin-layer chromatography (TLC) and high performance liquid chromatography-under voltage (HPLC-UV) profiles of the secondary metabolites, differed from the other fungi, attracted our attention. HPLC-guided separation resulted in the isolation of three new quinazoline alkaloids, polonimides A-C (1-3) and four known analogues, aurantiomide quinazoline alkaloids, polonimides A−C (1−3) and four known analogues, aurantiomide C (4) [6], anacine (5) [6], aurantiomide A (6) ( Figure S24) [6] and aurantiomide B (7) ( Figure S25) [6] (Figure 1). Herein, we report the isolation, absolute configurations and bioactivity of these compounds. ...
... It should be noted that the chemical structure of 3 could be found in the Scifinder database with the cas registry number 154725-83-4. However, the chemical structure of cas 154725-83-4 was the same as anacine (5), which was originally proposed as a benzodiazepine structure by Mantle and co-workers [7] but was revised as a quinazoline structure by Sim and co-workers [8]. ...
Three new quinazoline-containing diketopiperazines, polonimides A-C (1-3), along with four analogues (4-7), were obtained from the marine-derived fungus Penicillium polonicum. Among them, 2 and 4, 3 and 5 were epimers, respectively, resulting the difficulty in the determination of their configurations. The configurations of 1-3 were determined by 1D nuclear overhauser effect (NOE), Marfey and electron circular dichroism (ECD) methods. Nuclear magnetic resonance (NMR) calculation with the combination of DP4plus probability method was used to distinguish the absolute configurations of C-3 in 3 and 5. All of 1-7 were tested for their chitinase inhibitory activity against OfHex1 and OfChi-h and cytotoxicity against A549, HGC-27 and UMUC-3 cell lines. Compounds 1-7 exhibited weak activity towards OfHex1 and strong activity towards OfChi-h at a concentration of 10.0 μM, with the inhibition rates of 0.7%-10.3% and 79.1%-95.4%, respectively. Interestingly, 1-7 showed low cytotoxicity against A549, HGC-27 and UMUC-3 cell lines, suggesting that good prospect of this cluster of metabolites for drug discovery.
... GXWZ-05. (Weizhou Island sea area, China) yielded three new diterpenes with the serrulatane skeleton, euplexaurenes A-C (69-71) (Fig. 6) [69], and a known metabolite, anthogorgiene P. Moreover, the absolute configuration of euplexaurenes A-C (69-71) was confirmed by vibrational circular dichroism (VCD) analysis. ...
Gorgonian corals are considered as a rich source of secondary metabolites with unique structural features and biological activities. A large number of novel metabolites with potent pharmacological properties were isolated from gorgonian corals. Some of these compounds have exhibited to possess new mechanisms of action, which hold great promises as potential lead compounds in future marine drug development. This review aims to provide an overview in chemical constituents and biological activities of gorgonian corals from 2015 to December, 2019. Some 145 metabolites, including 16 sesquiterpenoids, 62 diterpenoids, 62 steroids and 5 alkaloids were reported during this period and their pharmacological activities were investigated. Moreover, the peculiar structure and potential medicinal value of these new compounds are discussed in this review.
... Trichodermanin C, a diterpenes obtained from a fungal strain Trichoderma harzianum OUPS-111D-4 derived from sponge Halichondria okadai, exhibited significant cytotoxic activity (Yamada et al. 2017). In our ongoing research on the marine invertebrates and their symboitic microorgnisms, 101 terpenoids including 43 new compounds with novel structures were isolated, which exhibited antibacterial, cytotoxic and antifouling activities (Cao et al. , 2017Li et al. 2012a). ...
... From the gorgonian Euplexaura sp. GXWZ-05, three new serrulatane-type diterpenoids, 139-141 (euplexaurenes A-C), and a known metabolite, 142 (anthogorgiene P) (Fig. 26), were isolated (Cao et al. 2017). The absolute configurations of C-11 in 139-142 were difficult to determine by common methods due to the high conformational flexibility of the eight-carbon aliphatic chain attached at C-4. ...
... By vibrational circular dichroism (VCD), their absolute configurations were determined. Compounds 139-142 displayed selective cytotoxic activities against the human laryngeal carcinoma (Hep-2) cell line (IC 50 = 1.95, 7.80, 13.6 and 5.85 μmol/L, respectively) (Cao et al. 2017). ...
Metabolites from marine organisms have proven to be a rich source for the discovery of multiple potent bioactive molecules with diverse structures. In recent years, we initiated a program to investigate the diversity of the secondary metabolites from marine invertebrates and their symbiotic microorganisms collected from the South China Sea. In this review, representative cases are summarized focusing on molecular diversity, mining, and application of natural products from these marine organisms. To provide a comprehensive introduction to the field of marine natural products, we highlight typical molecules including their structures, chemical synthesis, bioactivities and mechanisms, structure–activity relationships as well as biogenesis. The mining of marine-derived microorganisms to produce novel secondary metabolites is also discussed through the OSMAC strategy and via partial chemical epigenetic modification. A broad prospectus has revealed a plethora of bioactive natural products with novel structures from marine organisms, especially from soft corals, gorgonians, sponges, and their symbiotic fungi and bacteria.
Five new suberosanone-purine hybrids, namely subergorgines A–E (1–5), were isolated from the South China Sea gorgonian Subergorgia suberosa. Their structures were elucidated on the basis of extensive spectroscopic data and the absolute configurations were clarified by the theoretical ECD calculation. Compounds 1–5 were rare purine alkaloids merged with the same suberosanone moiety via different C (6)–N bridges. Cytotoxic activities of the isolates were tested. Compound 4 was found to be the most active against the HL-60 cancer cell line with an IC50 value of 14.3 μM. A plausible biosynthetic pathway for suberosanone-purine hybrids was also discussed.
Aquatic invertebrates are a major source of biomaterials and bioactive natural products that can find applications as pharmaceutics, nutraceutics, cosmetics, antibiotics, antifouling products and biomaterials. Symbiotic microorganisms are often the real producers of many secondary metabolites initially isolated from marine invertebrates; however, a certain number of them are actually synthesized by the macro-organisms. In this review, we analysed the literature of the years 2010-2019 on natural products (bioactive molecules and biomaterials) from the main phyla of marine invertebrates explored so far, including sponges, cnidarians, molluscs, echinoderms and ascidians, and present relevant examples of natural products of interest to public and private stakeholders. We also describe omics tools that have been more relevant in identifying and understanding mechanisms and processes underlying the biosynthesis of secondary metabolites in marine invertebrates. Since there is increasing attention on finding new solutions for a sustainable large-scale supply of bioactive compounds, we propose that a possible improvement in the biodiscovery pipeline might also come from the study and utilization of aquatic invertebrate stem cells.
Chemical investigation of the South China Sea soft coral Lemnalia sp. afforded 13 structurally diverse terpenoids, including three new neolemnane sesquiterpene lineolemnene, E–G (1–3); a new aristolane-type sesquiterpenoid, 2-acetoxy-aristolane (4); four new decalin-type bicyclic diterpenes, named biofloranate A−D (5−8); a new serrulatane, named euplexaurene D (9); and a new aromadendrane-type diterpenoid cneorubin K (10), together with three known related compounds (11−13). The structures of the new compounds were elucidated by NMR spectroscopy, the Mosher’s method, and ECD analysis. Compounds 1–13 were tested in a wide panel of biological assays. Lineolemnene J (3) showed weak cytotoxicity against the CCRF-CEM cancer cell line. The isolated new diterpenes, except euplexaurene D (9), demonstrated moderate antimicrobial activity against Bacillus subtilis and Staphylococcus aureus with a MIC of 4−64 μg/mL. Compound 2 exhibited a mild inhibitory effect against influenza A H1N1 virus (IC50 = 5.9 µM).
