Calaxanthones A-C, three new xanthones from the roots of Calophyllum calaba and the cytotoxicity

Naturally Occurring Xanthones; Biological Activities, Chemical Profiles and In Silico Drug Discovery

Xanthones are widely distributed polyphenols, present commonly in higher plants; Garcinia, Calophyllum, Hypericum, Platonia, Mangifera, Gentiana and Swertia. Xanthone tricyclic scaffold is able to interact with different biological targets, showing antibacterial and cytotoxic effects, as well as potent effects against osteoarthritis, malaria, and cardiovascular diseases. Thus, in this article we focused on pharmacological effects, applications and preclinical studies with the recent updates of xanthon´s isolated compounds from 2017-2020. We found that only α-mangostin, gambogic acid, and mangiferin, have been subjected to preclinical studies with particular emphasis on the development of anticancer, diabetes, antimicrobial and hepatoprotective therapeutics. Molecular docking calculations were performed to predict the binding affinities of xanthone-derived compounds against SARS-CoV-2 M^pro. According to the results, cratoxanthone E and morellic acid demonstrated promising binding affinities towards SARS-CoV-2 M^pro with docking scores of -11.2 and -11.0 kcal/mol, respectively. Binding features manifested the capability of cratoxanthone E and morellic acid to exhibit nine and five hydrogen bonds, respectively, with the key amino acids of the M^pro active site. In conclusion, cratoxanthone E and morellic acid are promising anti-COVID-19 drug candidates that warrant further detailed in vivo experimental estimation and clinical assessment.

Discovery of plant-derived anti-tumor natural products: Potential leads for anti-tumor drug discovery

Natural products represent a paramount source of novel drugs. Numerous plant-derived natural products have demonstrated potent anti-tumor properties, thereby garnering considerable interest in their potential as anti-tumor drugs. This review compiles an overview of 242 recently discovered natural products, spanning the period from 2018 to the present. These natural products, which include 69 terpenoids, 42 alkaloids, 39 flavonoids, 21 steroids, 14 phenylpropanoids, 5 quinolines and 52 other compounds, are characterized by their respective chemical structures, anti-tumor activities, and mechanisms of action. By providing an essential reference and fresh insights, this review aims to support and inspire researchers engaged in the fields of natural products and anti-tumor drug discovery.

Two New Xanthones from the Twigs of Calophyllum membranaceum and Their Anti-Inflammatory Activities in HESC Cells

Two new xanthones, calmemxanthone A (1) and calmemxanthone B (2), along with eleven known compounds were isolated from the dried twigs of Calophyllum membranaceum Gardn. et Champ. The structures of compounds 1 and 2 were established by analysis of spectra and mass spectrometry data. The absolute configuration of compound 1 was confirmed by electronic circular dichroism (ECD) spectral analysis. The anti-inflammation action of these compounds were evaluated on lipopolysaccharide (LPS)-induced inflammatory damage to human endometrial stromal cells (HESCs), and the structure-activities of 1-13 were also discussed. Compound 10 presented the anti-inflammation action with an IC₅₀ value of 20.3 μM, that might be relevant to the regulation of NF-κB signaling pathway via the suppression of TRIF, IKKα, and IκBα.

Staprexanthones, Xanthone-Type Stimulators of Pancreatic β-Cell Proliferation from a Mangrove Endophytic Fungus

This project was focused on the discovery of novel compounds that promote endogenous β-cell regeneration. Screening of extracts identified the fungus Stachybotrys chartarum as a promising candidate. After fermentation and extraction of S. chartarum, we isolated five new prenylated xanthones, namely, staprexanthones A-E (1-5), with staprexanthone A (1) being the first natural xanthone bearing a rare 4,5-dimethyl-1,3-dioxolane moiety. Compounds 1, 2, and 5 significantly increased β-cell numbers in vivo in a zebrafish model. Further analysis revealed that 2 and 5 promoted β-cell mass expansion by increasing proliferation of existing β-cells though promotion of cell-cycle progression at the G1/S transition. These findings indicate that prenylated xanthones are potential new drug leads for antidiabetes therapy by stimulating β-cell regeneration.

Velucarpin D, a new pterocarpan from the stems of Dalbergia velutina and its cytotoxicity

A new pterocarpan, named velucarpin D (1), along with nine known pterocarpans (2-10) were isolated from the stems of Dalbergia velutina. Their structures were determined by spectroscopic analysis. All isolated compounds were evaluated for their cytotoxicity against five human cancer cell lines (KB, HeLa S-3, MCF-7, Hep G2, and HT-29). Compound 2 showed potent cytotoxicity against all the five human cancer cell lines with IC₅₀ values in the range of 4.74-8.46 µM. In addition, compounds 1, 3, 4, 5 and 9 showed moderate cytotoxicity against both KB and HeLa S-3 cells with IC₅₀ values in the range of 14.23-29.35 µM.