Dimeric Erythrina alkaloids as well as their key units from Erythrina variegata

Abstract

Ten dimeric and two monomeric Erythrina alkaloids, all of them are undescribed, were isolated from the bark of Erythrina variegata L. and named as erythrivarines O–Z. Their structures were determined on the basis of NMR and UV-spectroscopy and mass spectrometry. Dimeric Erythrina alkaloids with a C-10/11′ linkage in erythrivarine O and a C-7/10′ connectivity in erythrivarines P–U are not yet reported. The two identified monomeric alkaloids may be the precursors of the described dimeric derivatives. These co-occurring dimeric and monomeric alkaloids enabled us to propose a possible biosynthetic pathway leading to these dimers. Their effects of preventing hearing loss were additionally evaluated and erythrivarine T showed as a potential protector of the House Ear Institute-Organ of Corti 1 (HEI–OC–1) cells against neomycin.