The in vitro activity against herpes simplex virus type 1 of 3-methyl-but-2-enyl caffeate isolated from poplar buds or prepared by synthesis was investigated. Under conditions of one or multiple multiplication cycles, this compound, which is a minor constituent of propolis, was found to reduce the viral titer by 3 log10, and viral DNA synthesis by 32-fold.

In the course of study on Psiadia dentata (CASS.) DC, an endemic species of the Reunion Islands used in traditional medicine to treat abscesses, 2) two methoxylated flavonoids, 3,4Ј-dimethylkaempferol (ermanin) and 3-methylkaempferol (isokaempferide), have been isolated as a result of a bioassay guided fractionation of the antipoliovirus compounds.3) Further investigations of non-flavonoid compounds resulted in the isolation of another active product in minute amounts corresponding to a new 7-prenyloxycoumarin. We report here the isolation and identification of this compound along with the first investigation of its antiviral and cytotoxic activity.Partition of a CHCl 3 extract from dried leaves between hexane and 90% aqueous MeOH, followed by various chromatographic steps, resulted in the isolation of a crystalline solid. This compound (1) showed a strong yellow fluorescence under UV light (366 nm), and was thought to be a coumarin as it was positive to KOH/EtOH and ammonia vapour.The IR spectrum of 1 showed absorption bands at 3296, 3086, 1702 (wide band), 1622, 1566 and 1030 cm Ϫ1 indicating the presence of a hydroxyl group (probably a phenolic one), a diethylenic CH, a conjugated OCO moiety, ethylenic and aromatic CϭC, and a C-O moiety, respectively.High resolution liquid secondary ion mass spectrometry (HR-LSI-MS) revealed [MϩH] ϩ at m/z 277.1076, which corresponds to the molecular formula C 15 H 16 O 5 ; the 68 unit difference between [MϩH] ϩ (m/z 277) and the base peak (m/z 209) corresponded to loss of a C 5 H 8 fragment, which could be due to a Mac-Lafferty 6-center translation mechanism.

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A number of 3-methylbut-2-enyl esters of various 3-amino-3-arylpropionic acids have been synthesized and tested for antiviral activity against HSV-1. Many of these compounds, analoques of the 3-methylbut-2-enyl caffeate, isolated from .poplar buds, show marked anti-HSV-1 activity and are less toxic than the natural ester.