The roots of the polynesian plant Piper methysticum
, a member of the pepper family, contain alpha pyrones, narcotics which affect spinal rather than cerebral responses. To extract the active ingredients the roots are pounded or emulsified (as the alpha pyrones aren't water soluble). The drink made from the treated roots gives euphoria and relaxation without damaging mental alertness.
This is another plant whose effect isn't precisely an aphrodisiac but is certainly useful in working toward such an outcome.