Abstract: This invention relates to the isolation, and use of a plant extract in the treatment of skin hyper-pigmentation. More particularly, this invention relates to the isolation of a tyrosinase inhibitor in an extract of plant matehal from the Greyia radlkoferi (G. radlkoferi) plant, the extract including 5,7-dihidroxyflavone[(2S)-pinocembrin]; 2?,6?-dihydroxy-4?-methoxydihydrochalcone; 2?,4?,6?-trihydroxyhydrochalcone; 3,5,7-trihydroxyflavone and 4?,5?7-thhydroxyisoflavone.

Abstract: The invention relates to diazepinoindoles of formula: ##STR1## in which R is hydrogen, lower alkyl or lower alkoxy; A is aryl or nitrogen-containing heteroaryl, each of which is optionally substituted by from one to three groups of halogen, lower alkyl, haloalkyl, lower alkoxy and acetamido, or their racemic forms, isomers or pharmaceutically acceptable salts, wherein for the racemic forms of the (S) configuration, A is not phenyl, haloalkyl, or 2-indolyl when R is hydrogen, and for the racemic forms of the (R) configuration, A is not 2-indolyl when R is hydrogen. Also, the invention relates to a method for inhibiting cyclic nucleotide phosphodiesterase activity by administering these compounds to a subject in an amount which is therapeutically effective to inhibit cyclic nucleotide phosphodiesterase activity.