The subject invention provides a myricanol compound that is in predominant form of (+)-αR,11S-myricanol as compared to (−)-αS,11R-myricanol. In one embodiment, the (+)-αR,11S-myricanol is isolated from Myrica cerifera, and is in about 86% enantiomeric excess of (−)-αS,11R-myricanol. The subject invention also pertains to therapeutic compositions and methods for treatment of neurodegenerative diseases, in particular, neurodegenerative diseases associated with abnormal accumulation of protein tau. Specifically exemplified herein is the therapeutic use of myricanol and myricanone isolated from root barks of Myrica species. Also provided are methods for preparing extracts of the subject invention from Myrica species.