UV absorbent, marmesin, from the bark of Thanakha, Hesperethusa crenulata L.

Abstract

We used solvent extractions, SiO2 column chromatographies, and HPLC to isolate from the bark of Thanakha (Hesperethusa crenulata L.) an active crystalline compound for absorbing UV-A radiation (320 to 380 nm). Analyses of low- and high-resolution FAB-MS revealed a compound, named marmesin, with a formula Of C14H14O4 and a molecular mass of 246. To determine its chemical structure, we conducted 300 MMz NMR analyses using various probes, H-1, C-13, and DEPT C-13. Our NMR data showed a structure of 2,3-dihydro-2(1-hydroxy-1-methylethyl)-furanocoumarin. This active compound contains UV-absorbing chromophores, an aromatic ring, a double bond at C3-C4, and a carbonyl at C2. Its lambda(max) is 335 nm, indicating that marmesin could be commercially useful as a natural UV-A-filtering product.