Isolation, Chiral-Phase Resolution, and Determination of the Absolute Configurations of a Complete Series of Stereoisomers of a Rearranged Acetophenone with Three Stereocenters

Natural-derived acetophenones: chemistry and pharmacological activities

Acetophenones are naturally occurring phenolic compounds which have found in over 24 plant families and also fungi strains. They are exist in both free or glycosides form in nature. The biological activities of these compounds have been assayed and reported including cytotoxicity, antimicrobial, antimalarial, antioxidant and antityrosinase activities. Herein, we review the chemistry and biological activity of natural acetophenone derivatives that have been isolated and identified until January 2024. Taken together, it was reported 252 acetophenone derivatives in which the genera Melicope (69) and Acronychia (44) were the principal species as producers of acetophenones.

An epigenetic modifier enhances the generation of anti-phytopathogenic compounds from the endophytic fungus Chaetomium globosporum of Euphorbia humifusa

Endophytic fungi are striking resources rich in bioactive structures with agrochemical significance. In order to maximize the opportunity of search for bioactive compounds, chemical epigenetic manipulation was introduced to enhance the structural diversity of the fungal products, and an UPLC-ESIMS and bioassay-guided separation was used to detect novel bioactive metabolites. Consequently, four previously undescribed compounds including two cyclopentenones (globosporins A and B) and two monoterpenoid indole alkaloids (globosporines C and D), as well as three known compounds, were isolated from the endophytic fungus Chaetomium globosporum of Euphorbia humifusa by exposure to a DNA methyltransferase inhibitor 5-azacytidine. Their structures including the absolute configurations were elucidated by the analysis of NMR spectroscopic data, HRESIMS, and TD-DFT-ECD calculations. The indole alkaloids (globosporines C and D) showed antimicrobial activities against three phytopathogenic microbes (Xanthomonas oryzae pv. oryzae, X. oryzae pv. oryzicola, and Pseudomonas syringae pv. lachrymans) with MICs in the range of 14-72 μg/mL. Mostly, globosporine D was proved to be potently anti-phytopathogenic against X. oryzae pv. oryzae in vitro and in vivo, which suggested that it has the potential to be developed as a candidate for the prevention of rice bacterial leaf blight. This work provides an efficient and environmentally friendly approach for expanding fungal products with agricultural importance.

Molecular networking-based discovery of anti-inflammatory chromene dimers from Melicope pteleifolia

With the aid of a feature-based molecular networking strategy, five undescribed C₂ and C₁ symmetric chromene dimers, namely, melptelchromenes A-E, were isolated from the leaves of Melicope pteleifolia. Four asymmetric dimers were found to be racemates and were resolved by chiral phase HPLC analyses. Their structures, including absolute configurations, were elucidated by HRMS, NMR spectroscopy, and quantum mechanical calculations of ECD spectra and NMR chemical shifts. Melptelchromenes A-D possess a unique ethylidene linkage via two 2H-chromene cores, while melptelchromene E represents the first example of a dimeric chromene featuring a 1,3-diarylbutan-1-ol moiety. Of these compounds, 6,6'-linked dimeric chromenes showed nitric oxide inhibitory activities on lipopolysaccharide-induced RAW 264 cells, and (-)- and (+)-melptelchromene E were the two most potent compounds (IC₅₀, 3.0 and 5.1 μM, respectively).

Natural Enantiomers: Occurrence, Biogenesis and Biological Properties

The knowledge that natural products (NPs) are potent and selective modulators of important biomacromolecules (e.g., DNA and proteins) has inspired some of the world’s most successful pharmaceuticals and agrochemicals. Notwithstanding these successes and despite a growing number of reports on naturally occurring pairs of enantiomers, this area of NP science still remains largely unexplored, consistent with the adage “If you don’t seek, you don’t find”. Statistically, a rapidly growing number of enantiomeric NPs have been reported in the last several years. The current review provides a comprehensive overview of recent records on natural enantiomers, with the aim of advancing awareness and providing a better understanding of the chemical diversity and biogenetic context, as well as the biological properties and therapeutic (drug discovery) potential, of enantiomeric NPs.

New Acetophenones and Chromenes from the Leaves of Melicope barbigera A. Gray

The dichloromethane extract from leaves of Melicope barbigera (Rutaceae), endemic to the Hawaiian island of Kaua'i, yielded four new and three previously known acetophenones and 2H-chromenes, all found for the first time in M. barbigera. The structures of the new compounds obtained from the dichloromethane extract after purification by chromatographic methods were unambiguously elucidated by spectroscopic analyses including 1D/2D NMR spectroscopy and HRESIMS. The absolute configuration was determined by modified Mosher's method. Compounds 2, 4 and the mixture of 6 and 7 exhibited moderate cytotoxic activities against the human ovarian cancer cell line A2780 with IC₅₀ values of 30.0 and 75.7 µM for 2 and 4, respectively, in a nuclear shrinkage cytotoxicity assay.