Three naphthalenes from root bark of Hibiscus syriacus

Abstract

Three new naphthalenes, designated as syriacusins A-C, were isolated from the root bark of Hibiscus syriacus. These compounds were identified as 2,7-dihydroxy-6-methyl-8-methoxy-l-naphthalenecarbaldehyde, 2-hydroxy-6- hydroxymethyl-7,8-dimethoxy-l-naphthalenecarbaldehyde, 1-carboxy-2,8- dihydroxy-6-methyl-7-methoxynaphthalenecarbolactone (1 → 8), respectively, on the basis of various spectral studies. The compounds inhibited lipid peroxidation with IC50s of 0.54,5.90 and 1.02 μg ml-1, respectively. The first compound also showed cytotoxicity against some human cancer cell lines with an ED50 of 1.5-2.4 μg ml-1.