Thymus algeriensis (Boiss. et Reut.) is an aromatic species of the Labiatae family growing in North Africa (endemic species) known as "zhitra" [1]. In Algerian folk medicine the leaves and flowering branches are used as condiment, stomachic, diaphoretic, antispasmodic specifically for whooping cough, stimulant for the blood circulation, and aphrodisiac [2].Previously isolated constituents were essential oil [3,4] and the flavonoids: taxifolin, eriodictyol, 5,6-dihydroxy-7-3′,4′-trimethoxyflavone, and 5,6,4′-trihydroxy-7,3′-dimethoxyflavone [5].Aerial parts of flowering T. algeriensis were collected from the Jijel region (eastern of Algeria) in June 1998. A voucher specimen has been deposited in the herbarium of the laboratory of natural substances and organic synthesis, University of Constantine under No. 05/ 1998/ L.T.A/03.Dried powder of aerial parts (85 g) of flowering T. algeriensis was extracted with 70% MeOH solution, which was concentrated to dryness under reduced pressure. The residue (20 g) was dissolved in dist. H 2 O (100 mL) stored in the cold and filtered after 24 hrs. The filtrate was extracted successively with EtOAc (2 g) and n-BuOH (8 g).After PC (Whatman® N1) tests with 15% AcOH (system Ia), 30% AcOH (system Ib), and BAW (n-BuOH-AcOH-H 2 O, 4 : 1 : 5 top layer (system II)), the EtOAc and n-BuOH extracts were combined (10 g) and subjected to CC on polyamide MN-SC6 eluted with a gradient of toluene-MeOH with increasing polarity; 54 fractions of 100 mL were collected and analyzed by cellulose TLC in the above systems in which similar fractions were combined to get only 12 fractions.By preparative PC (Whatman® 3MM) using the above solvent systems some compounds were isolated. Purification of each compound for spectral analysis was carried out over a Sephadex LH-20 column eluted with MeOH. Three flavonoids are well identified by chromatography behavior, spectral data, and by co-chromatography with an authentic sample when possible and confirmed by comparison with literature data [6,7]. Compound 1 was identified by spectroscopic techniques (UVvisible, 1 H NMR, 13 C NMR, DEPT, COSY, HMQC, and HMBC), while 2 and 3 were identified by UV-visible, 1 H NMR, and 13 C NMR spectra and acid hydrolysis [6].Compound 1. C 19 H 18 O 7 ; mp 188-191°C; R f 0.25 (system Ib), 0.95 (system II) UV (λ max , nm), MeOH: 338, 276, 240sh; +NaOH: 385sh, 329, 286; +AlCl 3 : 366, 287, 260; +HCl: 363, 260, 287; +NaOAc: 336, 277; +H 3 BO 3 : 337, 275. Mass spectrum (ES APCI), m/z (I rel , %): 358 [M] + (10), 357 [M-1] + (45), 343 [M-15] + (100), 328 [M-2×15] + (90), 313 [M-3×15] + (92), 298 [M-4×15] + (40). 1 H NMR (300 MHz, CDCl 3 , δ, ppm, J/Hz): 12.68(1H, s, OH-5), 7.44 (1H, dd, J = 9, J = 2, H-6′), 7.25 (1H, d, J = 2,