Provided is an indole long-chain alcohol, or a hydrate or an isomer thereof, represented by the following formula (I): ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 each independently represent a hydrogen atom, a methyl group, an acetyl group, or a hydroxyl group, and n represents a number from 0 to 20; and a medicinal composition comprising the same. The indole long-chain alcohol (I) exhibits an excellent nerve growth promoting effect, as well as potent antioxidative and anti-tumor effects, and is therefore useful as a prophylactic and/or therapeutic agent for cerebral diseases including dementia diseases, and malignant tumors including brain tumors.