Marmesin, an UVA Absorbing Compound from the Bark of Thanakha, Hesperethusa crenulata

Abstract

From barks of Thanakha (Hesperethusa crenulata L.), an active compound for absorbing UV A(320 - 360nm) was isolated as a crystal by solvent extractions, SiO2 column chromatographies and HPLC. Analyses of low and high resolution FAB MS revealed that the molecular weight of the active compound is 246 whose formula is C14H14O4. To determine the chemical structure of the active compoud, 300MHz NMR analyses using various probes, 1H, 13C, DEPT 13C, 1H-1H COSY and 1H-13C COSY were carried out. NMR data provided that the structure of the active compound is 2,3-dihydro-2(1-hdroxy-1-methyl)-furocoumarin, marmesin. Marmesin contained UV absorbing chromophores, an aromatic ring, a double bond at C3-C4 and a carbonyl at C2 in the structure. The λmax of marmesin was 335nm, indicating that marmesin could be commercially useful for a natural UV A filtering compound as it is. Also, it is thought that marmesin can be used as a leading compound to synthesize more strong UV A filtering compounds by structural modifications.