Four 14(13 → 12)-Abeolanostane Triterpenoids with 6/6/5/6-Fused Ring System from the Roots of Kadsura coccinea

Naturally Occurring Norsteroids and Their Design and Pharmaceutical Application

The main focus of this review is to introduce readers to the fascinating class of lipid molecules known as norsteroids, exploring their distribution across various biotopes and their biological activities. The review provides an in-depth analysis of various modified steroids, including A, B, C, and D-norsteroids, each characterized by distinct structural alterations. These modifications, which range from the removal of specific methyl groups to changes in the steroid core, result in unique molecular architectures that significantly impact their biological activity and therapeutic potential. The discussion on A, B, C, and D-norsteroids sheds light on their unique configurations and how these structural modifications influence their pharmacological properties. The review also presents examples from natural sources that produce a diverse array of steroids with distinct structures, including the aforementioned A, B, C, and D-nor variants. These compounds are sourced from marine organisms like sponges, soft corals, and starfish, as well as terrestrial entities such as plants, fungi, and bacteria. The exploration of these steroids encompasses their biosynthesis, ecological significance, and potential medical applications, highlighting a crucial area of interest in pharmacology and natural product chemistry. The review emphasizes the importance of researching these steroids for drug development, particularly in addressing diseases where conventional medications are inadequate or for conditions lacking sufficient therapeutic options. Examples of norsteroid synthesis are provided to illustrate the practical applications of this research.

Four new lanostane triterpenoids featuring extended π-conjugated systems from the stems of Kadsura coccinea

Four new 14(13 → 12)-abeolanostane triterpenoids featuring extended π-conjugated systems, kadcoccitanes E-H (1-4), were obtained from the stems of Kadsura coccinea through using a HPLC - UV-guided approach. Their structural and configurational determination was accomplished through extensive spectroscopic analysis coupled with quantum chemical calculations. Kadcoccitanes E-H were tested for their cytotoxic activities against five human tumor cell lines (HL-60, A-549, SMMC-7721, MDA-MB-231, SW-480) but none of them exhibited activities at the concentration 40 μM.

Lignans and sesquiterpenoids from the stems of Schisandra bicolor var. tuberculate

A pair of new tetrahydrofuran lignan enantiomers, (±)-schibiculatin A [(±)-1], a new enedione lignan, schibiculatin B (2), two new cadinane-type sesquiterpenoids, schibiculatins C (3) and D (4), along with two known seco-cadinane-type sesquiterpenoids (5 and 6) and seven known miscellaneous lignans (7-13) were isolated from the stems of Schisandra bicolor var. tuberculate. The structures of 1-4 were elucidated by comprehensive analysis of their spectroscopic data, quantum chemical calculations, as well as single-crystal X-ray diffraction. A few isolated compounds were tested for their protective activities against corticosterone-induced apoptosis in PC12 cells. Among them, compounds 5 and 6 showed moderate activities.

Chemical Composition and Biological Activities of Essential Oils from the Leaves, Stems, and Roots of Kadsura coccinea

The chemical composition and biological activities of the essential oils from the leaves, stems, and roots of Kadsura coccinea (K. coccinea) were investigated. The essential oils were extracted by hydro distillation and analyzed by gas chromatography mass spectrometry (GC-MS) and gas chromatography with flame ionization detector (GC-FID). Antioxidant activities of the essential oils were examined with DPPH radical scavenging assay, ABTS cation radical scavenging assay, and ferric reducing antioxidant power assay. Antimicrobial activities were evaluated by determining minimum inhibitory concentrations (MIC) and minimum microbiocidal concentrations (MMC). Acetylcholinesterase and butyrylcholinesterase inhibitory activity of the essential oils were also tested. A total of 46, 44, and 47 components were identified in the leaf, stem, and root oils, representing 95.66%, 97.35%, and 92.72% of total composition, respectively. The major compounds of three essential oils were α-pinene (16.60-42.02%), β-pinene (10.03-18.82%), camphene (1.56-10.95%), borneol (0.50-7.71%), δ-cadinene (1.52-7.06%), and β-elemene (1.86-4.45%). The essential oils were found to have weak antioxidant activities and cholinesterase inhibition activities. The essential oils showed more inhibitory effects against Staphylococcus aureus (S. aureus) than those of other strains. The highest antimicrobial activity was observed in the root oil against S. aureus, with MIC of 0.78 mg/mL. Therefore, K. coccinea essential oils might be considered as a natural antibacterial agent against S. aureus with potential application in food and pharmaceutical industries.

A critical review on the use of DP4+ in the structural elucidation of natural products: the good, the bad and the ugly. A practical guide

Covering: 2015 up to the end of 2020Even in the golden age of NMR, the number of natural products being incorrectly assigned is becoming larger every day. The use of quantum NMR calculations coupled with sophisticated data analysis provides ideal complementary tools to facilitate the elucidation process in challenging cases. Among the current computational methodologies to perform this task, the DP4+ probability is a popular and widely used method. This updated version of Goodman's DP4 synergistically combines NMR calculations at higher levels of theory with the Bayesian analysis of both scaled and unscaled data. Since its publication in late 2015, the use of DP4+ to solve controversial natural products has substantially grown, with several predictions being confirmed by total synthesis. To date, the structures of more than 200 natural products were determined with the aid of DP4+. However, all that glitters is not gold. Besides its intrinsic limitations, on many occasions it has been improperly used with potentially important consequences on the quality of the assignment. Herein we present a critical revision on how the scientific community has been using DP4+, exploring the strengths of the method and how to obtain optimal results from it. We also analyze the weaknesses of DP4+, and the paths to by-pass them to maximize the confidence in the structural elucidation.

A new triterpenoid from the stems of Kadsura coccinea with antiproliferative activity

A series of schiartane C₂₉ nortriterpenoids with 5/5/7/6/5 membered consecutive rings (1‒5) with an unique schinortriterpenoid skeleton including a new, kadcoccilactone V (1), together with four known ones (2‒5) and three known triterpenoids (6‒8) were identified from stems of Kadsura coccinea (Lem.) A. C. Smith. The structures of 1 and known compounds were elucidated by interpretation of 1D and 2D NMR, and HR-ESI-MS data as well as comparing those data in the literature. All the isolated compounds were examined for cytotoxic effects against six human cancer cell lines [(HCT-15 (colon), NUGC-3 (stomach), NCI-H23 (lung), ACHN (renal), PC-3 (prostate), and MDA-MB-231 (breast)]. Among them, compound 6 showed potent cytotoxicity against NCI-H23 (GI₅₀ 1.28 µM) and NUGC-3 (GI₅₀ 1.28 µM), and significantly inhibited on PC-3, MDA-MB-231, ACHN, HCT-15 with GI₅₀ values around 2.33 to 2.67 µM.

Neuroprotective schinortriterpenoids from Schisandra neglecta collected in Medog County, Tibet, China

Schisdilactones K-U (1-11), a series of previously unreported 16,17-secopreschisanartane-type schinortriterpenoids (SNTs), were isolated from the leaves and stems of Schisandra neglecta A. C. Smith. Their structures were mainly established through analysis of their spectroscopic data. Besides, schisdilactones K (1), O (5) and R (8) were confirmed by single-crystal X-ray crystallographic analysis, and the configurations of schisdilactones T and U (10 and 11) were elucidated via quantum chemical calculation of their NMR chemical shifts and electronic circular dichroism (ECD) spectra. Schisdilactones L-S (2-8) and U (11) were found to exhibit moderate protective activities against corticosterone-induced apoptosis of PC12 cells at 20 μM, with cell viability in the range of 62.95-66.97%.

Towards Knowledge Maintenance in Scientific Digital Libraries with the Keystone Framework

Scientific digital libraries speed dissemination of scientific publications, but also the propagation of invalid or unreliable knowledge. Although many papers with known validity problems are highly cited, no auditing process is currently available to determine whether a citing paper's findings fundamentally depend on invalid or unreliable knowledge. To address this, we introduce a new framework, the keystone framework, designed to identify when and how citing unreliable findings impacts a paper, using argumentation theory and citation context analysis. Through two pilot case studies, we demonstrate how the keystone framework can be applied to knowledge maintenance tasks for digital libraries, including addressing citations of a non-reproducible paper and identifying statements most needing validation in a high-impact paper. We identify roles for librarians, database maintainers, knowledgebase curators, and research software engineers in applying the framework to scientific digital libraries.

Kadsura coccinea: A rich source of structurally diverse and biologically important compounds

Kadsura coccinea belongs to medicinally important genus Kadsura from the Schisandraceae family. It has been used in traditional Chinese medicine (TCM) for the treatment of rheumatoid arthritis and gastroenteric disorders. The initial phytochemical work focused on the identification of some structurally novel and diverse natural products, which turned the attention of many researchers towards this plant. Thus far, 202 compounds have been reported in this plant. Lignans and terpenoids were found as the main chemical constituents of this plant. Some of the triterpenoids and sesquiterpenoids with novel structures are of particular interest for natural product researchers. The isolated compounds of this plant have shown different bioactivities including anti-tumor, anti-HIV, anti-inflammatory, nitric oxide (NO) production inhibitory and other pharmacological effects. This review systematically summarizes all the phytochemical and pharmacological work done so far on K. coccinea, and can be used as a reference for future research on this plant.

Characterization of Leptazolines A-D, Polar Oxazolines from the Cyanobacterium Leptolyngbya sp., Reveals a Glitch with the "Willoughby-Hoye" Scripts for Calculating NMR Chemical Shifts

The bioactivity-guided examination of a Leptolyngbya sp. led to the isolation of leptazolines A-D (1-4), from the culture media, along with two degradation products (5 and 6). Density functional theory nuclear magnetic resonance calculations established the relative configurations of 1 and 2 and revealed that the calculated shifts depended on the operating system when using the "Willoughby-Hoye" Python scripts to streamline the processing of the output files, a previously unrecognized flaw that could lead to incorrect conclusions.