Rutacridone-epoxide, a New Acridone Alkaloid from Rut a graveolens *

Several acridone alkaloids have been isolated from roots of Ruta graveolens (for summary see [1, 2]). One of the main alkaloids is rutacridone (1) which seems to be a precursor of several derivatives with hydroxyl or chlorine functions at the isopropyl moiety. As an intermediate an 18,19-epoxide of rutacridone could be postulated [1, 3] that has not yet been identified. Screening for antimicrobial activity of CH2C12 extracts of both, roots of R. graveolens and tissue cultures made from shoots of R. graveolens, showed a yellow zone of distinct antimicrobial activity against the organisms used (Bacillus subtilis, Serratia marcescens, Mycobacterium phlei) when tested by TLCmethods published by Wolters [4]. The substance was isolated and purified by column chroma­ tography on silica gel and subsequent preparative layer chromatography using its antimicrobial activity for detection. The UV spectrum of the substance was similar to those of acridone alkaloids [5] exhibiting maxima at k = 390 nm (log e = 3.08), 329 (3.32), 300 (3.57), 273 (3.95), 263 (3.83), 249 (3.80), 226 (3.57) in EtOEt and thus it is very similar to rutacridone [6], After addition of methanolic FeCl3 reagent a colour change from yellow to green was observed and the substance showed no fluorescence in MeOH; both observations are indicative of a free C-5-OH [5]. The mass spectrum of the compound showed an M+ at m /e 323 (60%) which is 16 daltons