Rutacridone epoxide

An antimicrobial alkaloid that was isolated from roots of Ruta graveolens and from callus tissue cultures proved to be rutacridone epoxide (31).17 The structure was determined by 2H and 13C n.m.r. and by mass spectroscopy, although the configurations at C-2 and C-18 are not known. The epoxide, rather than rutacridone (37), is a major root alkaloid clearly, the plant is chemically different from that studied previously, but the reason for the variation is unknown. 

A number of alkaloids have been demonstrated to act as phytoalexins (Brooks and Watson, 1985). Among these are lupanine in Lupinus species and rutacridone epoxide in Ruta graveolens. 

Rutacridone epoxide (24) from Ruta graveolens was shown to possess antimicrobial activity against several organisms (Nahrstedt et al., 1980 Wink, 1993). Cultures of Ruta graveolens produced 50-fold more rutacridone epoxide and hydroxyrutacridone epoxide when treated with fruigi not specific to the host (Brooks and Watson, 1985 Ellis, 1988). 

Rutacridone epoxide 1 1-OH, 10-Me, 2 -C(Me) —CHg O Boenninghausenia albiflora [25], Ruta graveolens [44], Ruta callus cultures (R. bracteosa, R. chalepensis, R. macrophylld) [26], Thamnosma montana (cell suspension cultures) [28]... 

Nahrstedt A, Eilert U, Wolters B, Wray V 1981 Rutacridone-epoxide, a new acridone alkaloid from Ruta graveolens. Z Naturforsch Ser C 36 200-203... 

The formation of isatins has been reported during decomposition studies of the structure or reactivity of natural products. In this manner, the attempted epoxidation of rutacridone led to A-methyl isatin67 (Scheme 24). 

Paulini, H., and O. Schimmer. 1989. Mutagenicity testing of mtac-ridone epoxide and rutacridone, alkaloids in Ruta graveolens L., using the Salmonella/mictosome assay. Mutagenesis 4(l) 45-50. 

In the biosynthesis of rutacridone, it is proposed that 1,3-dihydroxyacri-done is first formed from anthranilic acid and three C2 units, then the N-10 nitrogen is methylated to form 1,3-dihydroxy-N-methylacridone. Next, a C5 unit, IPP or DMAPP, is attached to 1,3-dihydroxy-N-methylacridone to fc>rm glycocitrine II, which is probably oxidized to produce an as-yet-uniden-tified epoxide. The epoxide is cyclized and dehydrated to give rutacridone [4]. Though rutacridone is a small molecule, as in the case of the quinoline alkaloids, three main biosynthetic precursors are involved in the biosynthesis of this alkaloid. Namely, the shikimic acid, the polyketide, and probably the iso-prenoid pathways all provide precursors for the biosynthesis of rutacridone. 

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