Indolediketopiperazine Alkaloids from Eurotium cristatum EN-220, an Endophytic Fungus Isolated from the Marine Alga Sargassum thunbergii

Abstract

Four new indolediketopiperazine derivatives (1–4), along with nine known congeners (5–13), were isolated and identified from the culture extract of Eurotium cristatum EN-220, an endophytic fungus obtained from the marine alga Sargassum thunbergii. The structures of thesecompounds were elucidated on the basis of extensive spectroscopic analysis and the absolute configurations of compounds 1–4 were established by NOESY experiments and by chiral HPLC analyses of their acid hydrolysates. The absolute configuration of C-8 (a quaternary carbon substituted with a hydroxyl group) in 5 of preechinulin class was firstly determined by electronic circular dichroism (ECD) calculations. All these compounds were evaluatedfor brine shrimp (Artemia salina) lethality and nematicidal activity as well as antioxidativeand antimicrobial potency.

New Indole Diketopiperazine Alkaloids from Soft Coral‐Associated Epiphytic Fungus Aspergillus sp. EGF 15‐0‐3

“…In addition, the HMBC from H‐20 ( δ (H) 3.83) to C‐10 ( δ (C) 167.1)/C‐12 ( δ (C) 163.6) was elucidated the nitrogen methyl group located at N‐11 ( Figure ). The lower‐filed shifted methine proton signal for H‐8 at δ (H) 8.01 (s, H−C(8), 1H) of 1 implied that this proton was influenced by the deshielding effect of the C=O group, which suggested the double bond at C‐8 has ( Z )‐geometry . Above all, the planar structure of 1 was identified and named as 11‐methylneoechinulin E.…”

Biologically Active Echinulin-Related Indolediketopiperazines from the Marine Sediment-Derived Fungus Aspergillus niveoglaucus

“…Cryptoechinuline D (2), which was previously reported to have strong DPPH-radical scavenging activity [25], also demonstrated antioxidant effects in a PQ-induced Neuro-2a cell model, where pretreatment with 2 could suppress ROS upregulation (Table 1). Compounds 3-6 had activities similar to those of 2 in both the PQ and DPPH [25,26] assays (Table 1), whereas the radical-scavenging properties of neoechinulin (7) have not been previously investigated. Thus, we showed for the first time that neoechinulin (7) binds DPPH free radicals with an IC 50 of 62.6 µM (Table 1).…”

Chemical diversity and biological function of indolediketopiperazines from marine-derived fungi

“…Compound 101 exhibited lethal activity against brine shrimp with an LD 50 value of 74.4 μg/mL (Du et al 2012). Five years later, four new IDPs (122-125) were reported from the same strain (Du et al 2017). In the subsequent bioactivity assays, compound 123 showed better activities than others.…”