Commonly known as “pot marigold,” Calendula officinalis is one of the numerous members of the aster or daisy family.1Anyone who has ever had a flower garden tends to wrinkle his or her nose when thinking of marigolds, due to the pungent, unpleasant fragrance they produce. However, this flowering plant, native to the Mediterranean, has a long history of multiple medicinal uses. Marigold is reportedly found in more than 200 cosmetics around the world, not to mention many undocumented compounds. 


Background


C. officinalis blooms profusely throughout spring, summer and fall. The marigold boasts a variety of bright yellow and orange flowers and dark-green, thick, fernlike leaves. Researchers have documented its medicinal properties, which include antiviral, anti-HIV and anti-inflammatory effects.2 Studies discussing the potential antitumor activity of C. officinalis suggest additional medicinal uses. 


Science


Both the blossom and the leaves of C. officinalis contain 
flavonol glycosides, triterpene oligoglycosides, oleanane-type triterpene glycosides, saponins and a sesquiterpene glucoside.3 Science is beginning to see more in-depth uses for these anti-inflammatory chemicals. 


Bench researchers are aggressively studying C. officinalis extracts for their anticarcinogenic potential. In one study using cultured human cell lines, two of the triterpene glycosides exhibited potent cytotoxic effects against colon cancer, leukemia and melanoma.3

In a broader study, a laser-activated calendula extract (LACE) was used to study its effects on multiple types of neoplastic cells.2 Trial results demonstrated that the LACE extract showed an in vitro inhibition of tumor cell growth that ranged from 70%-100%.2 The mechanisms of action observed were apoptosis and cell cycle arrest.3

In patients undergoing radiation therapy, C. officinalis extracts have mitigated painful dermatitis experienced by up to 80% of patients.

 

One study enrolled more than 250 patients being treated for breast cancer with postoperative radiation.4 These patients were blindly randomized to either trolamine or calendula in a petroleum-jelly base. The participants were given instructions to apply the compound to the affected area a minimum of twice daily. A positive response was considered a 20% reduction in dermatitis.

A significant finding at the end of treatment was that patients who had used the calendula ointment experienced over 20% fewer cases of radiation dermatitis of grade 2 or higher.4 This along with other studies has earned calendula an evidence rating of “B” (good scientific evidence for use) for use in cases of radiation skin protection.5,6

Marigold compounds have also been studied as potential remedies for such gastric conditions as irritable bowel syndrome, chronic constipation and cramping. In a study using a rabbit intestine, researchers induced a spastic response on the tissue and then applied the calendula extract.7,8 The results showed a marked spasmolytic effect and subsequent smooth muscle relaxation.7 The action appeared to be induced by a calcium channel blockade, similar to that of verapamil (Calan, Covera, Isoptin, Verelan).7,8

Other conditions for which calendula may be beneficial include venous stasis ulcers of the leg, generalized wound healing and otitis media. A lack of human trials gives calendula use in these ailments a weak-evidence rating.9 Claims of antiviral and antibacterial activity also fall below the required evidence level for credible use.9

Safety, interactions


In clinical trials, allergic reactions to C. officinalis occur in just over 2% of participants.10 Overdoses of C. officinalis have produced a tranquilizer-like sedation as well as hepatic and renal overload, as evidenced by elevated alanine transaminase and elevated blood urea nitrogen.11 Calendula is not recommended for use in children or infants or in pregnant or nursing women.11

How supplied, dosage


Topical ointments of 2% to 5% strength, applied three to four times daily, are used for skin irritations.11 Liquid drops are available in compound with other agents, and may be used in cases of otitis media.12

Summary


Calendula products are a long way from mainstream use. The most promising application of C. officinalis ointment for radiation dermatitis definitely warrants further study. Other claims— while supported in small, in vitro studies—are lacking in clinical data and, therefore, are not recommended. 


Sherril Sego, FNP-C, DNP, is a staff clinician at the VA Hospital in Kansas City, Mo., where she practices adult medicine and women’s health. She also teaches at the nursing schools of the University of Missouri and the University of Kansas.

 References

  1. About herbs, botanicals & other products: calendula page. Memorial Sloan-Kettering Cancer Center website. 
  2. Jiménez-Medina E, Garcia Lora A, Paco L, et al. A new extract of the plant Calendula officinalis produces a dual in vitro effect: cytotoxic anti-tumor activity and lymphocyte activation. BMC Cancer. 2006;6:119-133.

  3. Ukiya M, Akihisa T, Yasukawa K, et al. Anti-inflammatory, anti-tumor-promoting, and cytotoxic activities of constituents of marigold (Calendula officinalis) flowers. J Nat Prod. 2006;69:1692-1696.

  4. Pommier P, Gomez F, Sunyach MP, et al. Phase III randomized trial of Calendula officinalis compares with trolamine for the prevention of acute dermatitis during irradiation for breast cancer. J Clin Oncol. 2004;22:1447-1453.

  5. Basch E, Bent S, Foppa I, et al. Marigold (Calendula 
officinalisL.): An evidence-based systematic review by the Natural Standard Research Collaboration. J Herb Pharmacother. 2006;6:135-159.

  6. McQuestion M. Evidence-based skin care management in radiation therapy. Semin Oncol Nurs. 2006;22:163-173.

  7. Bashir S, Janbaz KH, Jabeen Q, Gilani AH. Studies on spasmogenic and spasmolytic activities of Calendula 
officinalis flowers. Phytother Res. 2006;20:906-910.

  8. Mohammad SM, Kashani HH. Pot marigold (Calendula officinalis) medicinal usage and cultivation. Sci Res Essays. 2012;7:1468-1472.

  9. Reider N, Komericki P, Hausen BM, et al. The seamy side of natural medicines: contact sensitization to arnica (Arnica Montana L.) and marigold (Calendula officinalisL.). Contact Dermatitis. 2001;45:269-272.

  10. Silva EJ, Goncalves ES, Aguiar F, et al. Toxicological studies on hydroalcoholic extract of Calendula officinalis. L.Phytother Res. 2007;21:332-336.

  11. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. American Botanical Council. Austin, Tx.; 1998. 

  12. Sarell EM, Cohen HA, Kahan E. Naturopathic treatment for ear pain in children. Pediatrics. 2003;111(5 Pt 1): e574-e579.

  13. All electronic documents accessed August 6, 2012.