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-1-naphthalenecarbaldehyde, 2-hydroxy-6-hydroxymethyl-7,8-dimethoxy-1-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 IC 50 s 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 ED 50 of 1.5 – 2.4 μg ml −1 .