Talcarpones A and B: bisnaphthazarin-derived metabolites from the Australian fungus Talaromyces johnpittii sp. nov. MST-FP2594.

Talcarpones A (1) and B (2) are rare bisnaphthazarin derivatives produced by Talaromyces johnpittii (ex-type strain MST-FP2594), a newly discovered Australian fungus, which is formally described and named herein. The talcarpones were isolated along with the previously reported monomeric naphthoquinone, aureoquinone (3), suggesting a biosynthetic link between these metabolites. Talcarpone A is a lower homologue of hybocarpone (4), which was first isolated from a mycobiont of the lichen Lecanora hybocarpa. The structures of 1 and 2 were elucidated by detailed spectroscopic analysis, molecular modelling and comparison with literature data. Talcarpones 1 and 2 exhibited moderate antifungal activity (MIC 0.78-3.1 µg ml-1) and weak activity against Gram-positive bacteria (MIC 13-25 µg ml-1). The talcarpones also demonstrated noteworthy chemical reactivities, with 2 converting rapidly to 1, which in turn converted slowly to the highly coloured 3. These post-biosynthetic reactions point to a potential ecological role for the talcarpones in providing ongoing (slow-release) physicochemical protection for T. johnpittii against solar irradiation.

Turonicin A, an Antifungal Linear Polyene Polyketide from an Australian Streptomyces sp.

Turonicin A (1) was isolated from Streptomyces sp. MST-123921, which was recovered from soil collected on the banks of the Turon River in New South Wales, Australia. Turonicin A (1) is an amphoteric linear polyene polyketide featuring independent pentaene and tetraenone chromophores and is structurally related to linearmycins A-C (2-4). The structure of 1 was determined by detailed spectroscopic analysis and comparison to literature data. Bioinformatic analysis of the linearmycin biosynthetic gene cluster also allowed the previously unresolved absolute stereostructures of 2-4 to be elucidated. Turonicin A (1) exhibited very potent activity against the fungi Candida albicans (MIC 0.0031 µg/mL, 2.7 nM) and Saccharomyces cerevisiae (MIC 0.0008 µg/mL, 0.7 nM), moderate activity against the bacteria Bacillus subtilis (MIC 0.097 µg/mL, 85 nM) and Staphylococcus aureus (MIC 0.39 µg/mL, 340 nM), and no cytotoxicity against human fibroblasts, making it an attractive candidate for further development as a potential next-generation antibiotic scaffold.

Fuligopyrones from the Fruiting Bodies of Myxomycete Fuligo septica Offer Short-Term Protection from Abiotic Stress Induced by UV Radiation.

The myxomycete Fuligo septica, colloquially referred to as "dog vomit fungus", forms vibrant yellow fruiting bodies (aethalia) on wood chips during warm and humid conditions in spring. In 2018, ideal climatic conditions in Sydney, Australia, provided a rare opportunity to access abundant quantities of F. septica aethalia, which enabled the isolation, purification, structure elucidation, and biological screening of two avenalumamide pyrones, fuligopyrone (1) and fuligopyrone B (2). While 1 and 2 did not exhibit any appreciable biological activity, their significant UV absorption at 325 nm suggested they may be acting as transient sunscreens to help protect the fruiting mass from exposure to sunlight. In support of this hypothesis, exposing a solution of 2 to direct sunlight for 5 min resulted in rapid equilibration with a mixture of 2E,4Z-fuligopyrone B (10) and 2Z,4E-fuligopyrone B (11) photoisomers.