Fluorescent markers for diesel fuels were synthesized from esterification reaction between barakol, which was obtained from the shredded fresh young leaves and flowers of Cassia siamea Lamk, with acid chloride in the presence of triethylamine. These synthetic fluorescent markers were 7-propionyloxy-5-acetony-2-methylchromone (compound 1), 7-butyryloxy-5-acetony-2-methylchromone (compound 2), 7-(2-ethyl)-hexanoyloxy-5-acetony-2-methylchromone (compound 3) and 7-lauroyloxy-5-acetony-2 methylchromone (compound 4). These synthetic fluorescent markers were invisible color in diesel fuels when they were added into diesel at concentration of 2 to 10 ppm and quantitative measurement was carried out using spectrofluorometer. Compound 1-4 gave fluorescence at 612 nm when they were excited at 464 nm. The testing results of fuel properties using the ASTM test methods revealed that the physical properties of the marked diesel fuels were similar to those of the unmarked diesel fuels. Moreover, those synthetic fluorescent markers were found to be stable in diesel fuels for at least three months
