Morinda: A plant genus of the family RUBIACEAE. Members contain iridoid glycosides and ANTHRAQUINONES.Iridoids: A type of MONOTERPENES, derived from geraniol. They have the general form of cyclopentanopyran, but in some cases, one of the rings is broken as in the case of secoiridoid. They are different from the similarly named iridals (TRITERPENES).Antispermatogenic Agents: Agents, either mechanical or chemical, which destroy spermatozoa in the male genitalia and block spermatogenesis.Anthraquinones: Compounds based on ANTHRACENES which contain two KETONES in any position. Substitutions can be in any position except on the ketone groups.Plant Extracts: Concentrated pharmaceutical preparations of plants obtained by removing active constituents with a suitable solvent, which is evaporated away, and adjusting the residue to a prescribed standard.