Mirabiquinone, a new unsymmetrical binaphthoquinone from the sea urchin Scaphechinus mirabilis

Mirabiquinone [7,5'-anhydroethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin)], a new unsymmetrical binaphthoquinone, was isolated from the sea urchin Scaphechinus mirabilis along with the known symmetrical binaphthoquinones ethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin) and 7,7'-anhydroethylidene-6,6'-bis(2,3,7-trihydroxynaphthazarin). The structure of mirabiquinone was established using 1H NMR, C-13 NMR, HSQC and HMBC data, along with a spectroscopic analysis of its pentamethoxy derivative. Mirabiquinone and the symmetrical binaphthoquinones demonstrated excellent scavenging of the 2,2-dipheny1-1-picrylhydrazyl (DPPH) radical. (C) 2014 Elsevier Ltd. All rights reserved.