The present invention relates to a compound represented by formula (I) wherein R.sup.1 represents optionally protected hydroxy or oxo, indicates .alpha.-configuration, .beta.-configuration or a mixture of these in an arbitary proportion, n represents an integer of 1 to 3, and m represents 0 or an integer of 1 to 10; and wherein two or more R.sup.1's are not bound to the same carbon atom other than the terminal carbon atom, a salt thereof or a prodrug thereof. The compounds represented by formula (I) have an ability to improve astrocyte function, and they are useful as a preventive and/or therapeutic agent for a brain infarction, neuronal dysfunction by brain infarction, Parkinson's disease, Parkinson's syndrome, amyotrophic lateral sclerosis or Alzheimer's disease.