Crystal structure and configuration revision of 9-hydroxy-7,8-dehydro-sarcotrocheliol and sarcotrocheliol

Pyrane-based cembranoid and 2-dehydro-4-peroxy-sarcophine: two new diterpenes from Sarcophyton glaucum

Soft corals, particularly Sarcophyton sp. are rich in metabolites with variety of biological activities. In this study, a pyran-based 9-exo-methylene-10-hydroxy-sarcotrocheliol (1) and 2-dehydro-4-peroxy-sarcophine (2), two new cembranoide diterpenes, were isolated together with 9-hydroxy-10,11-dehydro-sarcotrocheliol, sarcotrocheliol, sarcotrocheliol acetate, sarcophine, (+)-7α,8β-dihydroxydeepoxysarcophine, (±)-sarcophytonine B, and peridinin from the organic extract of Sarcophyton glaucum collected at the coasts of Hurghada, Egypt. The structures of the new diterpenes 1-2 were identified based on cumulative analyses of HRESIMS and NMR (1D/2D NMR) spectra. The relative configurations of both compounds were verified by NOESY spectra and comparison with our recently reported analogues. The compounds showed no antimicrobial activity against a set of diverse tested microorganisms.

Marine natural products

Covering: January to December 2021This review covers the literature published in 2021 for marine natural products (MNPs), with 736 citations (724 for the period January to December 2021) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1425 in 416 papers for 2021), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. An analysis of the number of authors, their affiliations, domestic and international collection locations, focus of MNP studies, citation metrics and journal choices is discussed.

The Soft Coral Sarcophyton trocheliophorum: A Warehouse of Terpenoids with Structural and Pharmacological Diversity

The soft coral Sarcophyton trocheliophorum, which was frequently encountered on Indo-Pacific and Red Sea coral reefs, furnished a wealth of secondary metabolites. Notably, terpenoids dominated the chemical profile of this species. In this review, we summarized the discovery of 156 terpenoids from the soft coral S. trocheliophorum specimens in different geographical areas. The structures comprised 13 terpenoidal classes with various functionalities. We covered the era from the first report of S. trocheliophorum-derived metabolites in 1976 up to October 2022. The biological effects of these chemical compositions on a vast array of potential pharmacological activities such as protein tyrosine phosphatase 1B (PTP1B) inhibitory, neuroprotective, cytotoxic, anti-inflammatory, antibacterial, antivirus, and immunomodulatory activities were also presented. This review also revealed an immense demand to explore the terpene biosynthetic gene clusters of this species besides the chemo- and bio-investigations.

Diterpenes and sterols from the Red Sea soft coral Sarcophyton trocheliophorum and their cytotoxicity and anti-leishmanial activities

The ethyl acetate and dichloromethane-soluble fractions, from a soft coral Sarcophyton trocheliophorum total methanolic extract, exhibited significant anti-leishmanial and cytotoxic activities. These active fractions yielded a new cembranoid diterpene (1), two known analogues [sarcotrocheliol (2) and sarcophine (3)], and two sterols [(24S)-24-methylcholesterol (4) and gorgosterol (5)]. The structure of the new diterpene (1) was determined via a detailed analysis of its spectroscopic data. Compounds 3 and 5 demonstrated noticeable cytotoxicity on A549 (IC₅₀ 17.4 ± 1.9 µg/ml) and HepG2 (IC₅₀ 17.7 ± 1.5 µg/ml) cell lines, respectively. None of the isolates 1‒5 showed detectable anti-leishmanial activity (IC₅₀ >100 µg/ml).

Pitfalls in the structural elucidation of small molecules. A critical analysis of a decade of structural misassignments of marine natural products

Covering: July 2010 to August 2021This article summarizes more than 200 cases of misassigned marine natural products reported between July 2010 and August 2021, sorting out errors according to the structural elements. Based on a comparative analysis of the original and the revised structures, major pitfalls still plaguing the structural elucidation of small molecules were identified, emphasizing the role of total synthesis, crystallography, as well as chemical- and biosynthetic logic to complement spectroscopic data. Distinct "trends" in natural product misassignment are evident between compounds of marine and plant origin, with an overall much lower incidence of "impossible" structures within misassigned marine natural products.

Ximaoglaucumins A - F, new cembranoids with anti-inflammatory activities from the South China Sea soft coral Sarcophyton glaucum

Six new cembrane-type diterpenoids, namely ximaoglaucumins A-F (1-6), along with fifteen known related ones (7-10 and 14-24), have been isolated from the soft coral Sarcophyton glaucum collected off the Ximao Island in the South China Sea. Their structures, including absolute stereochemistry, were elucidated by extensive spectroscopic analysis, quantum mechanical nuclear magnetic resonance (QM-NMR) methods, X-ray diffraction analysis, chemical methods, as well as comparison with the reported data in the literature. Further, detailed analysis of spectroscopic data of 7 not only clarified the confusions regarding 7, 11 (sarcophytolol) and 12/13 (sarcotrocheliol) in the literature, but also led to revise the structure of 11, which was mis-assigned due to careless/erroneous interpretation of the 2D NMR spectra, and to correct the structures of 12/13, which were both wrongly depicted. In in vitro bioassay, compounds 8 and 20 exhibited potent inhibitory effects on lipopolysaccharide (LPS)-induced inflammatory responses in BV-2 microglial cells.

Marine natural products

This review covers the literature published in 2019 for marine natural products (MNPs), with 719 citations (701 for the period January to December 2019) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1490 in 440 papers for 2019), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. Methods used to study marine fungi and their chemical diversity have also been discussed.