We report here from Acbilleu fragrantissima (Forssk.) Sch. Bip., a new C-glycosylflavone. When the compound was viewed on paper chromatography in uv light, it exhibited a purple color changing to greenish-yellow with both NH, and naturstoffreagenz-A (NA), indicating a 5,4'-dihydroxyl system. The bathochromic shift, with increased intensity of Band I in NaOMe, confirmed a free 4'-hydroxyl group; moreover, the absence of a bathochromic shift of Band I1 in NaOAc relative to Band I1 in MeOH supported a 7-0-substituent.Acid hydrolysis yielded arabinose and swenisin, which were identified by cochromatography with authentic samples. Ms of the permethylated derivatives gave a molecular ion [MI+ at mlz 690 (rel. int. 45%) confirming swertisin with an 0-arabinosyl moiety. The compound was identified as swertisin 2" arabinoside (6-C-glucosylapigenin 7 methyl ether 2"-arabinoside), a new C-glycoside, by the absence of peaks at mlz [M- 15)+ and [M- 31]+ (5), which were replaced by ions [SO]+ at mlz 5 15 (58%) and [SI+ at mlz 499 (100%) derived from the elimination of a permethylated 2"-O-arabinosyl residue with and without the oxygen atom of the glycosidic bond, respectively (6). The detection of swertisin 2"-arabinoside in A. fragrantissima is not surprising because isoorientin 2"-arabinoside has been reported from AcbiIIeu sibirica ssp. mongo lira (4).