by Miroslava Petrikova
General Information: Marigold (Calendula officinalis, Asteraceae) is a plant with distinctive yellow-orange flower petals approximately 30-60 cm high. Marigold easily grows in any kind of soil in sunny locations of temperature regions around the world.
Historical and modern uses: Marigold is a plant with a long medicinal history. The most common usage of marigold has been in the from of external applications to treat variety of acute or chronic skin conditions. Flower heads have been most frequently used for this purpose.
Scientific evidence: The principal compounds identified in marigold are terpenoids and flavonoids, though flavonoid content highly depends on the time and place of cultivation of this plant. Marigold further contains quinones, coumarines, volatile oils, amino acids, carotenoids and other minor compounds. Calendula officinalis has been proposed to posses anti-inflammatory, wound healing, anti-bacterial, anti-fungal, anti-viral and several other effects. Although preclinical data are mainly supportive regarding the marigold’s beneficial effect, the mode of action of these is poorly understood and require more research.
Clinical evidence: Currently there is a lack of human evidence that would support the marigold’s activity shown in animal and in laboratory studies.
Cautions, risk interactions: Although toxicological data with respect to Calendula officinalis extracts are conflicting and do not provide enough evidence to support its safety, marigold have been frequently used in herbal formulations for many years and exhibited low toxicity.
General Information
Calendula officinalis commonly known as marigold, pot marigold or calendula is a plant with a long history of medicinal, culinary and ornamental usage. Marigold is an English name of this plant which derives from the words Mary’s gold as it was considered to be the flower of Virgin Mary. The extension of this name to pot marigold possibly stems from its frequent usage in cooking amongst poor. Alternatively, it may well be linked to the fact that the species is commonly grown in pots? Marigold was used for culinary purposes as a cheaper alternative to saffron (Khalid and Teixeira da Silva, 2012). The name calendula is of a Latin origin and derives from the word calends meaning the first day of each month. This name was linked to marigold due to its extensive flowering period throughout the year. Because marigold flowers bloom during the day and close in the evening these plants have also been referred to as the ‘herbs of the sun’ (Ulbricht, 2006).
There are approximately 25 herbaceous specious belonging to the genus Calendula (Asteraceae) (Arora et al., 2013; Yassen et al., 2010). This genus is native to the Mediterranean, central and eastern European regions (Mohammad and Kashani, 2012). Out of these Calendula officinalis is the most commonly, clinically used plant. It is listed in British Herbal Pharmacopoeia, German Commission E, European Scientific Co-operative on Phytotherapy and in the World Health Organization monographs for anti-inflammatory actions and wound healing (Aurora et al., 2013)
Marigold is an annual or sometimes biennial plant. It is widely grown as an ornamental plant in temperate regions worldwide and cultivated for medicinal usage in southern and eastern Europe (Martin, 2000; Mohammad and Kashani, 2012). Due to its unpretentiousness it easily grows in sunny locations or partial shade ideally in previously cultivated and well-drained positions (Mohammad and Kashani, 2012; 8). However it can thrive in nearly any kind of soil (Chevallier, 1996, Ulbricht, 2006). Research suggests that marigold may benefit from nitrogen (Mohammad and Kashani, 2012) and potassium fertilizers from either potassium sulphate, banana residue or both (Yassen et al., 2010).
Calendula officinalis grows up to a height of about 30-60 cm. Its stem is straight and can branch at the base or higher up. Marigold’s main root is approximately 20 cm long and branches into several thinner roots. Its leaves are organized in alternating arrangement with mostly spatulate shaped leaves at the base while the leaves further up the stem are rather oblong. Marigold’s leaves are covered by tiny soft hair with generously spaced teeth at their borders. This plant has a single flower head with distinctive yellow-orange petals. The head is approximately 5-7 cm wide and a circular disc of tubular flowers can be seen once the outer petals are removed (Arora et al., 2013; Khalid and Teixeira da Silva, 2012).
Historical and Modern Uses
Since approximately the 12th century C.E. Greeks, Egyptians, Arabs and Hindus cultivated and used marigold as medicine (Mohammad and Kashani, 2012). Its traditional usage in medicine was recorded both internally and externally. Marigold has been taken orally to treat fever, gastrointestinal ulcers, cancer, inflammation of internal organs and menstrual irregularities (Mohammad and Kashani, 2012). However the most common usage of marigold has been in the from of external applications. The flower heads of this plant were used to make extracts, balms, salves and tinctures (Bisset and Wichtl, 2001). These preparations were applied directly on the skin to cease inflammation and support wound healing. Marigold has been further used in the form of teas as eyewash or gargle for variety of inflammatory conditions of mucous membranes or skin. Finally marigold has also been used as a homoeopathic treatment for insomnia and mental tension as well as an insect repellent (Khalid and Teixeira da Silva, 2012). Currently marigold extracts are mainly used in topical preparations such as creams, ointments or tinctures for variety of skin complains. In many European regions these preparations are also commonly used in veterinary preparation for example for inflammatory skin conditions in cattle.
Scientific Evidence
Calendula officinalis contain a number of chemical constituents such as terpenoids, flavonoids, quinones, coumarines, volatile oils, amino acids and carotenoids (Muley et al., 2009). The principal compounds identified in marigold are terpenoids and flavonoids (Yoshikawa, 2001).
Studies have suggested that there are at least 8 bioactive terpenoids extracted from the dried flower heads of marigold. These include Faradiol-3-0-palmitate, myristate and laurate, which are the main terpenoid esters found in flowers of marigold (Ulbricht, 2006).
Several different flavonoids have been identified from the ethanolic extract of Calendula officinalis such as quercetin, isorhamnetin, rutin, calendoflaside and many others. Study conducted by Raal and Kirsipuu (2011) showed that the total content of flavonoids isolated from Calendula Officinalis, from different European countries, varied significantly. The researchers concluded that the total flavonoid content highly depends on the time and place of cultivation of this plant.
The main components found in volatile (essential) oil obtained from flower heads of Calendula officinalis were sesquiterpene alcohols such as alpha-cadinol or delta-cadinene and sesqui-terpene hydrocarbones (Khalid and Teixeira da Silva, 2012). The content of volatile oil presented in Calendula officinalis varies depending on the plant’s flowering stage. Okoh. Et al., (2007) found that the highest content of volatile oil in Calendula officinalis is during its full flowering period while the lowest content can be found at its pre-flowering stage.
The yellow-orange colour of marigold flowers suggests its high content of carotenoids. This plant contain different types of carotenoids depending on the part of the plant. Flavoxanthin and auroxanthin are the main carotenoids found in the pollen and petals, whereas leaves and the stem mainly contain lutein and beta-carotene (Bako et al., 2002).
Calendula officinalis further contains 15 different amino acids in their free forms, coumarins such as scopoletin or umbelliferone and many other compounds that contribute to its unique properties (Muley et al., 2009)
Many different properties have been associated with extracts and pure compounds found in marigold. These include anti-inflammatory, wound healing, anti-bacterial, anti-fungal, anti-viral, and several other effects (Ulbricht, 2006).
Anti-inflammatory and anti-oedematous effect
The active compounds responsible for the anti-inflammatory effect are thought to be the triterpenoids especially the monoesters of faradiol (Della-Loggia et al., 1990). Research suggests that this effect may be maintained by an inhibition of inflammatory mediators (Preethi et al., 2009). In study conducted by Ukiya et al., (2006) 9 out of 10 terpenoid glycosides isolated from Calendula officinalis flower heads showed an anti-inflammatory activity in mice. Results from another animal study demonstrated significant reduction of inflammation with similar results in chronic anti-inflammatory model (Preethi et al., 2009). An extract from Calendula officinalis’ flowers showed a substantial inhibition of oedema in animal study. This effect was further supported by an administration of higher dose which increased its effect and thus confirmed marigold extracts’ positive activity on oedema reduction (Zitterl-Eglsser; 1997).
Wound healing effect
Marigold extracts may be beneficial in the care of skin wounds. Study conducted with experimental incision wounds in rats showed decrease in time needed for healing and increased the strength and contraction of the tissue (Rao et al., 1991). An increased wound healing activity was proposed to be achieved due to its antioxidant and anti-microbial properties (Leach, 2008).
Anti-bacterial, anti-fungal and anti-viral effect
An antibacterial effect of an extract from fresh Calendula officinalis was demonstrated in a laboratory study by an inhibition of Staphylococcus aureus (Dumenil et al., 1980). However a study conducted with Calendula officinalis extract on biofilms of child dentifrices did not exhibit any antimicrobial effect against several bacterial strains (Modesto et al., 2000). These are only two examples of many studies which overall could be considered inconclusive regarding the anti-bacterial effect of Calendula officinalis extracts. Furthermore, a study that tested volatile oil from Calendula officinalis against 23 fungal strains suggests that this plant may also possesses anti-fungal properties (Gazim et al., 2008) as well as anti-viral activity which was demonstrated in a laboratory study by suppression of replication of Herpes simplex virus (Silva et al. 2007).
Although many of these studies suggest that marigold extracts may be effective in the prevention or treatment of variety of conditions the mechanism of action of these effects are still poorly understood and require more research (Arora et al., 2013, Ulbricht, 2006). In addition more methodologically well designed studies are needed in order to support these finding. Overall marigold extracts are mainly used in topical preparations for which they show the most effective results.
Clinical Evidence
Extracts from marigold have been submitted to several clinical trials mainly examining its activity for the improvement of skin conditions. Calendula officinalis has been tested in an open phase 3 clinical trial as an agent to prevent erythema (redness of the skin) and dermatitis (inflammation of the skin) pain during radiation therapy. Participants in this study were 254 women treated for breast cancer. An ointment containing marigold extract was compared to trolamine. Marigold ointment was shown to be more effective in preventing skin radiation dermatitis than trolamine (Pommier et al., 2004). However, results from this study can only be considered preliminary due to methodological limitations. Another human study examined Calendula officinalis effect on skin burns, dermatitis, abrasions and varicose ulcers. Participants from this study did not respond to conventional treatment. Complete healing of burns was reported within 2-6 days in all 15 patients that participated in this study whereas complete healing of varicose ulcers was demonstrated in 8 out of 12 patients within 30 days. Patients suffering from chronic dermatitis or abrasions experienced substantial improvement of these conditions within 10 days (Netto et al., 1996). However this study was poorly described and lacked statistically analysed data. Calendula officinalis was further examined in a clinical study where it showed to be the most effective solution for the treatment of 2nd and 3rd degree of burns in comparison with two other preparations (Lievre et al., 1992). Again this study was rather poorly designed and described.
Overall currently there is a lack of human evidence that would support the marigold’s activity shown in animal and laboratory studies (Arora et al., 2013). Therefore well designed human studies are needed to demonstrate marigold’s beneficial effect before a strong conclusion regarding its efficacy can be reached.
Cautions, Risk Interactions
Extracts from marigold are reported to be used in approximately 200 herbal preparations, including clinical use for the treatment of various ailments (Arora et al., 2013). An animal study regarding the acute toxicity of Calendula officinalis extracts showed it to be relatively non-toxic. Skin irritation, sensation and phototoxicity tests in animal models showed minimal positive effect and therefore were generally considered safe and non-irritant. Only one formulation exhibited minimal ocular irritation. Water extract from Calendula officinalis was found non-genotoxic as well as saponins derived from this plant proved to be non-mutagenic. However saponins obtained from Calendula officinalis tested in a laboratory study exhibited cytotoxic properties. Calendula officinalis extract was also found to be genotoxic in another study. Hence published data are conflicting and do not provide enough evidence to support the safety of marigold extracts in such preparations (Ulbricht, 2006). Nevertheless, Calendula officinalis extracts have been frequently used in herbal formulations for many years and exhibited low toxicity (Arora et al., 2013).
Allergy to marigold is rather uncommon condition. However its use should be avoided by individuals with known allergy to plants from Asteraceae such as daisies, chrysanthemums or rag-weed (Dietz, 1998). Sensitivity to marigold was observed in the study in 9 out of 443 participants (Reider et al., 2001).
Although no other complains than allergy have been reported some laboratory and animal studies suggest that marigold may also possess certain undesirable effects. A severe decrease of blood glucose as well as reduction in serum lipids and proteins has been demonstrated in one small animal study (Ulbricht, 2006). Hence it is important to consider consumption of marigold extracts by patients treated for diabetes as they may increase the activity of insulin and hypoglycemic mediators. Likewise patients treated with cholesterol-lowering drugs should be cautious with consumption of marigold extracts. Calendula officinalis further exhibited uteronic effect in a laboratory study which was based on anecdotal reports of mariglod’s abortifacient and spermatocide activity (Agarwal et al., 2011). Therefore its consumption during pregnancy and lactation is considered unsafe. Use of topical preparations during these periods is unclear. Marigold was further reported to act as sedative and so its possible additive effect should be taken into account if one is using other sedatives. Some animal studies also demonstrated anti-hypertensive effects of Calendula officinalis extracts. Thus again patients treated with anti-hypertensive drugs should be aware of its possible hypotensive activity (Ulbricht, 2006).
Conclusion
Marigold is a widely used medicinal and ornamental plant that easily grows in sunny locations around the world. It has been used for centuries in traditional Ayurvedic medicine and in many European countries. The most common usage of marigold has been and still is in the form of external applications for variety of skin complains. Many different properties have been associated with extracts and pure compounds found in marigold such as anti-inflammatory, wound healing, anti-bacterial and several other effects. Although, there is a lack of human clinical evidence that would support the marigold’s activity conclusively, animal and laboratory studies have demonstrated relevant effects of frequently used herbal formulations containing marigold.
In this essay we do not advise or recommend herbs for medicinal or health use. This information is intended for educational purposes only and should not be considered as a recommendation or an endorsement of any particular medical or health treatment. The use of any such product should be based on the appropriate advice of a health care professional or based on the information available in the patient information leaflets (i.e. for THR products).
© 2015 Miroslava Petrikova
Short note about the author, Miroslava Petrikova
I am a master degree student at the University College London studying Pharmacognosy (Msc). I have previously graduated from the University of Roehampton and earned a Bachelor’s degree in Human Nutrition and Health. During my studies at the university, chemistry and nutrition (particularly molecular and biochemical) were the subjects that have fascinated me right from the beginning of my undergraduate study. I have always had a strong belief in the remedial power of plants, I grew up in a mountain area where many plants are collected for tea production. Therefore I decided to dedicate myself to a field of study that focuses on medicinal plants, their use in medicine, nutritional food and supplement production.
If you have any questions regarding the medicinal plant mentioned above or any other queries please do not hesitate to contact the author by using the CONTACT FORM on this website.
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