Dimeric naphtho-γ-pyrones and further diverse bioactive metabolites from the marine-derived Aspergillus flavus Af/MMA 2018

Abstract

Background and objective Sponge-associated fungi are known for their production of structurally diverse secondary metabolites, many of which exhibit different pharmacological activities. Materials and methods Isolation and identification of fungal isolate from the marine sponge Echinodictyum flabelliforme collected from the Red Sea coast of Hurghada, Egypt, was done. Working up and purification with the ethyl acetate extract produced by the marine-derived Aspergillus flavus Af/MMA 2018 afforded nine bioactive compounds. Structure of the isolated compounds was determined on the basis of NMR (1D and 2D) and mass (EI, ESI, HRESI MS) spectra and by comparison with the corresponding literature studies. Biologically, the antimicrobial, antioxidant, and antitumor activities (using Ehrlich cells) of compounds were studied in comparison with the original extract. Results and conclusion Working up and purification of the ethyl acetate-extracted residue produced by the marine-derived A. flavus Af/MMA 2018 afforded nine diverse bioactive compounds: five dimeric naphtho-γ-pyrones, that is, aurasperone A (1), aurasperone B (2), aurasperone D (3), aurasperone F (4), and aurasperone E (5), along with β-sitosterol glucoside (6), cerebroside C (7), glyceryl linoleate (8), and linoleic acid (9). Cerebroside C showed strong antimicrobial activity against different test organisms, whereas aurasperone E showed maximum DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) scavenging activity (67.41%) after 1 h, and by using different concentrations, giving 98.99% at 1000 μg/ml. The maximum antitumor activity against Ehrlich ascites carcinoma cells (70.9%) was attributed to the dimeric naphtho-γ-pyrone aurasperone E.