It is intended to find a compound that is structurally simpler than yohimbine, a pentacyclic condensed heterocyclic compound, and has an effect similar to that of yohimbine. The present invention relates to a pharmaceutical or food composition for .alpha..sub.2 receptor blockage comprising a compound represented by the formula (I) or a pharmaceutically acceptable salt thereof: ##STR00001## (wherein R.sup.1 represents a hydrogen, alkyl group, alkenyl group, alkynyl group, aromatic group, aralkyl group, acyl group, arylsulfonyl group, alkylsulfonyl group, or hydroxyl group; R.sup.2 represents a hydrocarbon group; R.sup.3, R.sup.4, R.sup.5, R.sup.6, and R.sup.7 are the same or different and represent a hydrogen, halogen, alkyl group, or alkoxy group; R.sup.8 represents a hydrogen or acyl group; n represents an integer of 1 to 6; and a and b are the same or different and represent 1 or 0).