The π-A isotherms for monolayers of three amphiphilic rutin esters, rutin-4”’-O-stearate (RS), rutin-4”’-O-laurate (RL) and rutin-4”’-O-caproate (RC), were measured at the air-water interface and an air-aqueous aluminum sulfate solution interface. The properties of the monolayers of three rutin esters were related to the carbon number of alkyl, the compression rate and the property of substrate. Although RS and RL showed scant water solubility, they formed monolayers with the liquid-expanded phase when spread on water. While RC could not form insoluble monolayer at the air-water interface, which may be due to the larger water solubility of RC. Appropriately low compression rate was critical to form relatively stable monolayers. When spread on an aqueous aluminum sulfate solution, the formation of a complex between the aluminum ions and the rutin ester resulted in higher values of acoll for RS and RL monolayers compared with their values on water, and RC could spread as liquid-expanded phase monolayer. The results described in this paper provide valuable information for investigating the interaction of flavonoids and biomembranes and the anti-oxidant mechanism of flavonoids.
