Plant Profiler

Blessed thistle (Cnicus benedictus)

Blessed thistle (Cnicus benedictus) Image
Synonyms / Common Names / Related Terms
Bitter thistle, cardin, Carbenia benedicta, Chardon Benit, Cardo Santo, carduus benedictus, Cnici benedicti Herba, Cnicus, holy thistle, Kardo-benedictenkraut, St. Benedict thistle, spotted thistle.

Combination product example: Essiac® (blessed thistle, burdock root, Indian rhubarb, sheep sorrel, inner bark of slippery elm, watercress, red clover, and kelp).

Note: Blessed thistle should not be mistaken for milkthistle or other members of the thistle family.

Mechanism of Action


  • Constituents: The chemical constituents of blessed thistle include sesquiterpene lactone glycosides such as cnicin (0.2-0.7%), polyacetylen13, and absinthin14; triterpenoids such as a-amyrenone, a-amyrin acetate, a-amyrine, and multiflorenol acetate14,15; lignans such as trachelogenin, arctigenin, and nortracheloside16; flavonoids; polyenes; tannins (8%); and essential/volatile oils (0.3%) such as p-cymene, fenchon, citral and cinnamaldehyde.3 Salonitenolide has also been found to be present.13 Lignans such as trachelogenin may contribute to the bitter characteristics of blessed thistle. Cnicin has also been identified as a principal bitter ingredient in blessed thistle.17
  • Anti-microbial effects: Antimicrobial activity of blessed thistle has been attributed to cnicin and polyacetylene constituents. 2,3,4 Antibacterial activity of cnicin and the essential oil of blessed thistle herb have been observed in vitro against Bacillus subtilis, Brucella species, Escherichia coli, Proteus species, Pseudomonas aeruginosa, Staphylococcus aureus and Streptococcus faecalis.2,4,3 Other studies have demonstrated no activity against Klebsiella, Pseudomonas, S. aureus, S. tyhpi, or yeast.18,19,20 Several lignans have also been under investigation as antiviral (particularly anti-HIV) and anticancer agents.7,8,21,22
  • Anti-inflammatory effects: In the standard rat paw model of inflammation, cnicin had mild anti-inflammatory effects.12 Lignans such as arctigenin and trachelogenin appear to exert inhibitory effects on cyclic AMP, phosphodiesterase, and histamine release in rat mast cells.1 Antagonist activities against calcium ions and platelet activation factor have also been observed.1
  • Anti-proliferative effects: Cnicin and arctigenin have exhibited cytotoxic activity against some tumor cell lines including leukemia (HL-60), hepatomas, and sarcomas via inhibition of cellular DNA, RNA or protein synthesis.5,6,7,8,9,10,4 Arctigenin has been noted to induce differentiation in mouse myeloid leukemia cell lines.11 Blessed thistle is included in some brands of the unproven anti-cancer herbal remedy, Essiac®.


  • Following oral ingestion of blessed thistle by rats, the lignans arctiin and tracheloside are metabolized to their genins, arctigenin and trachelogein. Peak serum levels are reached at four hours for arctigenin and at eight hours for trachelogenin.1


  1. Nose, M., Fujimoto, T., Nishibe, S., and Ogihara, Y. Structural transformation of lignan compounds in rat gastrointestinal tract; II. Serum concentration of lignans and their metabolites. Planta Med 1993;59(2):131-134. 8387675
  2. Vanhaelen-Fastre, R. [Antibiotic and cytotoxic activity of cnicin isolated from Cnicus benedictus L]. J Pharm Belg. 1972;27(6):683-688. 4665015
  3. Vanhaelen-Fastre, R. [Constitution and antibiotical properties of the essential oil of Cnicus benedictus (author's transl)]. Planta Med 1973;24(2):165-175. 4765454
  4. Vanhaelen-Fastre, R. and Vanhaelen, M. [Antibiotic and cytotoxic activity of cnicin and of its hydrolysis products. Chemical structure - biological activity relationship (author's transl)]. Planta Med 1976;29(2):179-189. 948519
  5. Barrero, A. F., Oltra, J. E., Morales, V., Alvarez, M., and Rodriguez-Garcia, I. Biomimetic cyclization of cnicin to malacitanolide, a cytotoxic eudesmanolide from Centaurea malacitana. J Nat Prod  1997;60(10):1034-1035. 9358646
  6. Cobb E. Antineoplastic agent from Cnicus benedictus. Patent Brit 1973;335:181.
  7. Eich, E., Pertz, H., Kaloga, M., Schulz, J., Fesen, M. R., Mazumder, A., and Pommier, Y. (-)-Arctigenin as a lead structure for inhibitors of human immunodeficiency virus type-1 integrase. J Med Chem 1-5-1996;39(1):86-95. 8568830
  8. Hirano, T., Gotoh, M., and Oka, K. Natural flavonoids and lignans are potent cytostatic agents against human leukemic HL-60 cells. Life Sci 1994;55(13):1061-1069. 8084211
  9. Moritani S, Nomura M, Takeda Y, and et al. Cytotoxic components of Bardanae Fructus (Goboshi). Biol Pharm Bull 1996;19:1515-1517.
  10. Ryu SY, Ahn JW, Kang YH, and et al. Antiproliferative effect of arctigenin and arctiin. Arch Pharm Res 1995;18(6):462-463.
  11. Umehara K, Sugawa A, Kuroyanagi M, and et al. Studies on the differentiation-inducers from Arctium fructus. Chem Pharm Bull 1993;41:1774-1779.
  12. Mascolo N, Autore G, Caspasso F, and et al. Biological screening of Italian medicinal plants for antiinflammatory activity. Phytother Res 1987;1:28-31.
  13. Vanhaelen-Fastre R. [Polyacetylen compounds from Cnicus benedictus]. Planta Medica 1974;25:47-59.
  14. Kataria H. Phytochemical investigation of medicinal plant Cnicus wallichii and Cnicus benedictus L. Asian J Chem 1995;7:227-228.
  15. Ulbelen A and Berkan T. Triterpenic and steroidal compounds of Cnicus benedictus. Planta Medica 1977;31:375-377.
  16. Vanhaelen M and Vanhaelen-Fastre R. Lactonic lignans from Cnicus benedictus. Phytochemistry 1975;14:2709.
  17. Schneider, G. and Lachner, I. [Analysis and action of cnicin]. Planta Med 1987;53(3):247-251. 3628557
  18. Perez C and Anesini C. Inhibition of Pseudomonas aeruginosa by Argentinean medicinal plants. Fitoterapia 1994;65(2):169-172.
  19. Perez, C. and Anesini, C. In vitro antibacterial activity of Argentine folk medicinal plants against Salmonella typhi. J Ethnopharmacol 1994;44(1):41-46. 7990503
  20. Recio M, Rios J, and Villar A. Antimicrobial activity of selected plants employed in the Spanish Mediterranean area. Part II. Phytother Res 1989;3:77-80.
  21. Maeda Y and Mitsuya H. Antiretroviral chemotherapy against AIDS. Med Biol Environ 1995;23:267-278.
  22. Yang L, Lin S, Yang T, and et al. Synthesis of anti-HIV activity of dibenzylbutyrolactone lignans. Bioorg Med Chem Lett 1996;6(8):941-944.

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