Provided is a method of treating hypertension, which comprises
administering an effective amount of a compound represented by the
following formula (1) or (2): ##STR00001## wherein, R.sup.1 and R.sup.2
are the same or different and each independently represents hydrogen,
alkyl, alkenyl, cycloalkyl, cycloalkenyl, alkoxyalkyl, aryl, alkylaryl,
aralkyl, or acyl, R.sup.3 represents hydroxyl, ester bond residue, or
amide bond residue, R.sup.4 represents ester bond residue or amide bond
residue, or a pharmaceutically acceptable salt thereof (except ferulic
acid).