Hypericin, helianthrone and derivatives thereof of general formula (I) wherein the dotted line between positions 11 and 12 represent an optional C11-C12 bond; R is independently selected from the group consisting of hydroxy, C1-C10 alkoxy, NH—C1-C10 alkyl, and NH-hydroxy(C1-C10)alkyl; R′ is independently selected from the group consisting of hydroxy and C1-C10 alkoxy; R″ is independently selected from the group consisting of hydrogen, hydroxy, C1-C10 alkoxy, NH—C1-C10 alkyl, and NH-hydroxy(C1-C10)alkyl; and R1, R2, R3, R4, R5 and R6 are independently selected from the group consisting of hydrogen, hydroxy, chloro, bromo, C1-C10 alkyl, C1-C10 alkoxy, and C1-C10 alkoxycarbonyl, provided that R″ is not hydrogen when there is a C11-C12 bond, are useful as inhibitors of angiogenesis and can be used to prevent formation of metastases and restenosis and for the treatment of angiogenesis-associated ophthalmologic disorders. In addition, the helianthrones of formula (I) can be used for the treatment of tumors in the absence of light irradiation. New compounds include those of formula I which are other than hypericin and known hypericin derivatives and there is either a C11-C12 bond or at least one R″ is other than hydrogen.