Phenolic Constituents from the Branch of Firmiana simplex

From the branch of Firmiana simplex, eleven phenolic compounds, ethyl caffeate, butyl caffeate, methyl caffeate, caffeic acid, ethyl cinnamate, kaempferol, astragalin, afzelin, quercetin, (+)-pinoresinol, and (+)-isolariciresinol were isolated. Their structures were determined by 1D and 2D nuclear magnetic resonance (NMR) and mass spectroscopy analysis. Furthermore, all the isolated compounds (1-11) were tested for antimicrobial activity against methicillin-resistant Staphylococcus aureus (MRSA). Firmiana simplex (aogiri in Japanese) is a tall deciduous tree of the family Sterculiaceae, which is widely distributed in eastern Asia, Taiwan, China, and throughout Japan from Okinawa to Honshu [1,2]. The previous chemical investigations of F.simplex led to the isolations of flavonoids [3], neolignans [4], and naphthoquinone [5]. The fresh branch of F.simplex was exhaustively extracted with MeOH at room temperature for 3 months. The MeOH extract was partitioned between EtOAc and H2O. The EtOAc-soluble portion (20 g) was separated by ordinary-phase silica gel and reverse-phase silica gel to furnish ethyl caffeate (1, 100 mg), butyl caffeate (2, 15 mg), methyl caffeate (3, 25 mg), caffeic acid (4, 180 mg), ethyl cinnamate (5, 27 mg) [6], kaempferol (6, 170 mg), astragalin (7, 150 mg), afzelin (8, 12 mg), quercetin (9, 200 mg) [7], (+)-pinoresinol (10, 18 mg), and (+)-isolariciresinol (11, 12 mg) [8].