Anthraquinones

Anthraquinones are a group of aromatic organic compounds that occur naturally in many medicinal plants – including aloe (Aloe vera), senna leaf (Senna alexandrina), rhubarb (Rheum palmatum), and alder buckthorn (Frangula alnus). Chemically, they belong to the family of quinone-like substances and are known for their characteristic effect on the intestinal tract. In the plant world, they primarily serve as protection against predators and microorganisms; in medicine, they are valued above all for their laxative properties.

The pharmacologically active forms, known as anthranoids or anthraquinone glycosides, are only converted into their active components in the large intestine by gut bacteria. Their effect is well documented, but their use is not without controversy – especially with long-term use. Nevertheless, they have been used for centuries for the short-term treatment of constipation and are also being intensively researched for possible antioxidant, antimicrobial, and cytotoxic properties.

What health benefits are attributed to anthraquinones?

While the various anthraquinones, in the form of the various plants in which they are contained, have already been used for many years for various health problems, studies are now also specifically examining these active compounds. These studies associate anthraquinones with a wide variety of different effects and point to great medical potential. As always, however, the results of the studies should be viewed critically until conclusive statements about their effects can be made. This, however, requires more research. Here are some of the potential effects investigated so far:

  • Strong laxative effect: According to investigations, anthraquinones stimulate the peristalsis of the large intestine and promote water and electrolyte excretion – as a result, they act effectively in acute constipation (1,2).
  • Antimicrobial properties: In studies, some anthraquinones showed growth-inhibiting effects against bacteria, fungi, and even parasites (3,4).
  • Anti-inflammatory potential: In studies, certain anthraquinone derivatives showed anti-inflammatory effects via the inhibition of proinflammatory cytokines (2,4,5,6).
  • Antioxidant effect: Investigations suggest that anthraquinones could inhibit oxidative processes and protect cells from free radicals (6,7).
  • Cancer research: Some synthetically modified anthraquinones are being investigated with regard to their antitumor effects, in particular because of their influence on the cell cycle and apoptosis (2,8,9,10).

How do anthraquinones work in the body?

The effect presumably arises mainly in the large intestine, where the anthraquinones have an irritating effect on the intestinal mucosa and activate the intestinal muscles, which could accelerate the emptying of the bowel. They promote the secretion of water and electrolytes into the intestinal lumen and inhibit their reabsorption – this makes the stool softer. It is important here that the glycoside form is only converted into the active aglycone form by gut bacteria – this explains the delayed effect (6–12 hours after intake) (11).

Side effects and risks

  • Intestinal irritation: With frequent use, abdominal cramps, diarrhea, and mucosal irritation can occur; in addition, the antibacterial effect could also bring negative effects for the microbiome (12).
  • Dependence: Prolonged use can lead to dependence on the laxative and a sluggish bowel (laxative abuse) (12).
  • Electrolyte losses: Potassium loss can lead to muscle cramps or cardiac arrhythmias (12).
  • Melanosis coli: A harmless but noticeable discoloration of the intestinal mucosa can occur (12).
  • Long-term risks: Animal studies have shown indications of possible carcinogenic effects at very high doses – however, this has not been conclusively clarified in humans (12,13,14).

Conclusion

Anthraquinones are potent natural substances that, in the form of various plants, have been used for a wide variety of different problems. In studies, they showed potential as antimicrobial, antioxidant, and anti-inflammatory compounds – with prospects in oncology and infectious disease medicine. However, due to possible side effects, the use of anthraquinone-containing herbal preparations should be limited in time and carried out responsibly, and exclusively under the supervision of medically trained professionals.

Sources:

  1. Gong X. H., Li Y., Zhang R. Q., Xie X. F., Peng C., Li Y. X. (2015). The synergism mechanism of Rhubarb Anthraquinones on constipation elucidated by comparative pharmacokinetics of Rhubarb extract between normal and diseased rats. Eur. J. Drug Metab. Pharmacokinet. 40, 379–388. 10.1007/s13318-014-0216-7
  2. Wang, D., Wang, X. H., Yu, X., Cao, F., Cai, X., Chen, P., Li, M., Feng, Y., Li, H., & Wang, X. (2021). Pharmacokinetics of Anthraquinones from Medicinal Plants. Frontiers in pharmacology, 12, 638993. https://doi.org/10.3389/fphar.2021.638993
  3. Wang J, Zhao H, Kong W, Jin C, Zhao Y, Qu Y, Xiao X. Microcalorimetric assay on the antimicrobial property of five hydroxyanthraquinone derivatives in rhubarb (Rheum palmatum L.) to Bifidobacterium adolescentis. Phytomedicine. 2010 Jul;17(8-9):684-9. doi: 10.1016/j.phymed.2009.10.009. Epub 2009 Dec 4. PMID: 19962872.
  4. Yadav, A. N., Kour, D., Rana, K. L., Yadav, N., Singh, B., Chauhan, V. S., Rastegari, A. A., Hesham, A. E.-L., & Gupta, V. K. (2019). Metabolic engineering to synthetic biology of secondary metabolites production. In V. K. Gupta & A. Pandey (Eds.), New and future developments in microbial biotechnology and bioengineering (pp. 279–320). Elsevier. https://doi.org/10.1016/B978-0-444-63504-4.00020-7
  5. Li D., Zhang N., Cao Y., Zhang W., Su G., Sun Y., et al. (2013a). Emodin ameliorates lipopolysaccharide-induced mastitis in mice by inhibiting activation of NF-κB and MAPKs signal pathways. Eur. J. Pharmacol. 705, 79–85. 10.1016/j.ejphar.2013.02.021
  6. Zhao, L., & Zheng, L. (2023). A Review on Bioactive Anthraquinone and Derivatives as the Regulators for ROS. Molecules (Basel, Switzerland), 28(24), 8139. https://doi.org/10.3390/molecules28248139
  7. Shia CS, Juang SH, Tsai SY, Chang PH, Kuo SC, Hou YC, Chao PD. Metabolism and pharmacokinetics of anthraquinones in Rheum palmatum in rats and ex vivo antioxidant activity. Planta Med. 2009 Oct;75(13):1386-92. doi: 10.1055/s-0029-1185725. PMID: 19877312.
  8. Lin L., Ni B., Lin H., Zhang M., Li X., Yin X., et al. (2015). Traditional usages, botany, phytochemistry, pharmacology and toxicology of Polygonum multiflorum Thunb.: a review. J. Ethnopharmacol. 159, 158–183. 10.1016/j.jep.2014.11.009
  9. Cui Y., Lu P., Song G., Liu Q., Zhu D., Liu X. (2016). Involvement of PI3K/Akt, ERK and p38 signaling pathways in emodin-mediated extrinsic and intrinsic human hepatoblastoma cell apoptosis. Food Chem. Toxicol. 92, 26–37. 10.1016/j.fct.2016.03.013
  10. Yang N., Li C., Li H., Liu M., Cai X., Cao F., et al. (2019). Emodin induced SREBP1-dependent and SREBP1-independent apoptosis in hepatocellular carcinoma cells. Front. Pharmacol. 10, 709. 10.3389/fphar.2019.00709
  11. Lombardi, N., Bettiol, A., Crescioli, G., Maggini, V., Gallo, E., Sivelli, F., Sofi, F., Gensini, G. F., Vannacci, A., & Firenzuoli, F. (2020). Association between anthraquinone laxatives and colorectal cancer: protocol for a systematic review and meta-analysis. Systematic reviews, 9(1), 19. https://doi.org/10.1186/s13643-020-1280-5
  12. Khan, N. T. (2019). Anthraquinones – A naturopathic compound. Journal of New Developments in Chemistry, 2(2), 25–28. https://doi.org/10.14302/issn.2377-2549.jndc-18-2569
  13. S B Widjanarko, Wijayanti N, Sutrisno A. (2013) Laxative potential of the konjac flour (Amorphophallus muelleri Blume) in treatment of loperamide induced constipation on Sprague Dawley rats. , Int J Med Health Biomed Bioeng Pharm Eng 7(11), 729-733.
  14. Bolen, B. (2024, September 12). Benefits and side effects of anthraquinones. Verywell Health. https://www.verywellhealth.com/anthraquinones-1945348