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Euroticins C–E (1–3), three pairs of salicylaldehyde derivative enantiomers, were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. They represent two types of salicylaldehyde derivatives bearing unprecedented highly constructed 6/6/6/6 tetracyclic structures. Their structures were established by comprehensive spectroscopic analyses, X-ray diffraction, and electronic circular dichroism calculations. Compounds (+)-1 and (−)-1 showed significant antioxidative activity and moderate cytotoxic activity.

Two pairs of salicylaldehyde derivative enantiomers, euroticins A and B (1 and 2), were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Compound 1 possesses a highly constructed 6/6/6/5/7 pentacyclic structure featuring an unprecedented 2,11-dioxatricyclo[5.3.1.04,8]undecane core. Compound 2 represents the first example of 6/6/6/6 tetracyclic salicylaldehyde derivative. Their structures were established by spectroscopic analyses, X-ray diffraction, and electronic circular dichroism (ECD) and 13C NMR calculations. Compounds (+)-2 and (-)-2 exhibited remarkable antioxidative activities.

To enlarge the chemical diversity of Eurotium sp. SCSIO F452, a talented marine-derived fungus, we further investigated its chemical constituents from a large-scale fermentation with modified culture. Four pairs of new salicylaldehyde derivative enantiomers, euroticins F-I (1–4), as well as a known one eurotirumin (5) were isolated and characterized. Compound 1 features an unprecedented constructed 6/6/6/5 tetracyclic structures, while 2 and 3 represent two new types of 6/6/5 scaffolds. Their structures were established by comprehensive spectroscopic analyses, X-ray diffraction, 13C NMR, and electronic circular dichroism calculations. Selected compounds showed significant inhibitory activity against α-glucosidase and moderate cytotoxic activities against SF-268, MCF-7, HepG2, and A549 cell lines.

(±)-Eurotone A [(±)- 1 ], a pair of new enantiomeric polyketide dimers, as well as six known biogenetically related polyketides ( 2 – 7 ) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by comprehensive spectroscopic methods, X-ray diffraction and quantum chemical calculations. Compound 1 represented the first pair of spirodihydrobenzanthracene enantiomers isolated from marine fungi with their absolute configurations assigned. A plausible biosynthetic pathway involving a key acid-mediated dimerization was proposed for 1 . The antioxidative activities of the new enantiomers were evaluated.

Two pairs of new salicylaldehyde derivative enantiomers, salicylaldehydiums A and B (1 and 2), along with five known analogues were isolated and identified from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures and absolute configuration were determined by extensive spectroscopic analysis and electronic circular dichroism (ECD) calculations. All the new optical pure enantiomers [(+)-1, (-)-1, (+)-2, (-)-2] were evaluated for their cytotoxic and antioxidative activities. Compound (-)-1 exhibited weak cytotoxic activity.

Three pairs of new spirocyclic alkaloid enantiomers eurotinoids A–C (1–3), as well as a known biogenetically related racemate dihydrocryptoechinulin D (4) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by spectroscopic analyses and electronic circular dichroism (ECD) calculations. Compounds 1 and 2 represent the first two “meta” products from a non-stereoselective [4 + 2] Diels-Alder cycloaddition presumably between an enone group of a diketopiperazine alkaloid and a diene group of a benzaldehyde derivative via a new head-to-tail coupling mode biosynthetically, while 3 and 4 were “ortho” products. Their enantiomers exhibited different antioxidative and cytotoxic activities. The modes of action were investigated by a preliminary molecular docking study.

Three pairs of spirocyclic diketopiperazine enantiomers, variecolortins A-C (1-3), were isolated from marine-derived fungus Eurotium sp. SCSIO F452. Compound 1 possesses an unprecedented highly functionalized seco-anthronopyranoid carbon skeleton featuring a 2-oxa-7-azabicyclo[3.2.1]octane core. Compounds 2 and 3 represent rare examples of a 6/6/6/6 tetracyclic cyclohexene-anthrone carbon scaffold. Their structures were determined by spectroscopic analyses, X-ray diffraction, and ECD calculations. Their enantiomers exhibited different antioxidative and cytotoxic activities, and their modes of action were investigated.