Two new ɑ-pyrone derivatives from the endophytic Diaporthe sp. ECN371

Natural ten-membered lactones: sources, structural diversity, biological activity, and intriguing future

Covering: 2012 to 2022Ten-membered lactones (TMLs) are an interesting and diverse group of natural polyketides that are abundant in fungi and, to a lesser extent, in bacteria, marine organisms, and insects. TMLs are known for their ability to exhibit a wide spectrum of biological activity, including phytotoxic, cytotoxic, antifungal, antibacterial, and others. However, the random discovery of these compounds by scientific groups with various interests worldwide has resulted in patchy information about their distribution among different organisms and their biological activity. Therefore, despite more than 60 years of research history, there is still no common understanding of the natural sources of TMLs, their structural type classification, and most characteristic biological activities. The controversial nomenclature, incorrect or erroneous structure elucidation, poor identification of producing organisms, and scattered information on the biological activity of compounds - all these factors have led to the problems with dereplication and the directed search for TMLs. This review consists of two parts: the first part (Section 2) covers 104 natural TMLs, published between 2012 and 2022 (after the publishing of the previous review), and the second part (Section 3) summarizes information about 214 TMLs described during 1964-2022 and as a result highlights the main problems and trends in the study of these intriguing natural products.

Insights from the Endophytic Fungi in Amphisphaeria (Sordariomycetes): A. orixae sp. nov. from Orixa japonica and Its Secondary Metabolites

Endophytic fungi are a remarkably diverse group of microorganisms that have imperceptible associations with their hosts for at least a part of their life cycle. The enormous biological diversity and the capability of producing bioactive secondary metabolites such as alkaloids, terpenoids, and polyketides have attracted the attention of different scientific communities, resulting in numerous investigations on these fungal endophytes. During our surveys of plant-root-based fungi in the mountain areas of Qingzhen, Guizhou Province, several isolates of endophytic fungi were identified. In this study, a novel endophytic fungus was discovered in the roots of a medicinal plant (Orixa japonica) in Southern China and introduced as a new species (Amphisphaeria orixae) based on morphological evidence and molecular phylogenetic analysis (combined ITS and LSU sequence data). To the best of our knowledge, A. orixae is the first reported endophyte as well as the first hyphomycetous asexual morph in Amphisphaeria. A new isocoumarin, (R)-4,6,8-trihydroxy-5-methylisochroman-1-one (1), and 12 known compounds (2-13) were isolated from the rice fermentation products of this fungus. Using 1D- and 2D-NMR, mass spectrometry, and ECD studies, their structures were identified. The antitumor activity of these compounds was tested. Unfortunately, none of the compounds tested showed significant antitumor activity.

Diaporpyrone E, an undescribed α-pyrone from the endophytic fungus Diaporthe sp. CB10100

An undescribed α-pyrone diaporpyrone E (1), and three known nucleotides, 5'-O-acetyl uridine (2), 5'-O-acetyl thymidine (3), and adenine (4), were identified from Diaporthe sp. CB10100, an endophytic fungus isolated from the medicinal plant Sinomenium acutum. The structure of 1 was determined by extensive analysis of its HRMS, 1D and 2D NMR spectroscopic data, as well as electronic circular dichroism calculations and comparison. The in vitro cytotoxic and antibacterial assays of 1 revealed that it has a 30.2% inhibitory effect on HepG2 cells at 50 μM, while no antibacterial activities against Staphylococcus aureus and Klebsiella pneumoniae at 64 μg/mL.