Effects of arbuscular mycorrhiza and phosphorus application on artemisinin concentration in Artemisia annua L.

Abstract

Annual wormwood (Artemisia annua L.) produces an array of complex terpenoids including artemisinin, a compound of current interest in the treatment of drug-resistant malaria. However, this promising antimalarial compound remains expensive and is hardly available on the global scale. Synthesis of artemisinin has not been proved to be feasible commercially. Therefore, increase in yield of naturally occurring artemisinin is an important area of investigation. The effects of inoculation by two arbuscular mycorrhizal (AM) fungi, Glomus macrocarpum and Glomus fasciculatum, either alone or supplemented with P-fertilizer, on artemisinin concentration in A. annua were studied. The concentration of artemisinin was determined by reverse-phase high-performance liquid chromatography with UV detection. The two fungi significantly increased concentration of artemisinin in the herb. Although there was significant increase in concentration of artemisinin in nonmycorrhizal P-fertilized plants as compared to control, the extent of the increase was less compared to mycorrhizal plants grown with or without P-fertilization. This suggests that the increase in artemisinin concentration may not be entirely attributed to enhanced P-nutrition and improved growth. A strong positive linear correlation was observed between glandular trichome density on leaves and artemisinin concentration. Mycorrhizal plants possessed higher foliar glandular trichome (site for artemisinin biosynthesis and sequestration) density compared to nonmycorrhizal plants. Glandular trichome density was not influenced by P-fertilizer application. The study suggests a potential role of AM fungi in improving the concentration of artemisinin in A. annua.

Arbuscular mycorrhizal symbiosis and active ingredients of medicinal plants: current research status and prospectives

“…Interestingly, AM symbiosis formation increased the density of glandular trichome on the upper leaf epidermis of O. vulgare-micropropagated seedlings (Morone Fortunato and Avato 2008), and Copetta et al (2006) have suggested that significantly increased levels of essential oil in O. basilicum colonized by three different AM fungi result from significantly larger numbers of peltate glandular trichomes on the basal and central leaf zones (Copetta et al 2006). In line with this, Kapoor et al (2007) found that two AM fungi increased the density of foliar glandular trichomes in A. annua, and that a strong correlation existed between the density of glandular trichomes on leaves and artemisinin concentrations.…”

“…Some research has also shown that symbiosis with AM fungi results in the increase of terpenoids and phenolic acids, which may result from increased absorption of mineral nutrients, especially P and N (Kapoor et al 2002a, b;Toussaint et al 2007). Finally, changes in the secondary metabolites of mycorrhizal plants may result from changes in levels of phytohormones like cytokinin or gibberellin (Allen et al 1980(Allen et al , 1982Copetta et al 2006;Kapoor et al 2007;Toussaint 2007). However, these and other possibilities all remain to be verified (Toussaint 2007).…”

“…Contents of these unique ingredients can be used as standards for the quality of medicinal plants, such as levels of limonene and carvone in dill (Kapoor et al 2002a), thymol in carum (Kapoor et al 2002a), geraniol and linalool in coriander (Kapoor et al 2002b), anethol in fennel (Kapoor et al 2004), sesquiterpene lactones in Arnica (Jurkiewicz et al 2010), and artemisinin in A. annua (Kapoor et al 2007;Chaudhary et al 2008;Huang et al 2011). Previous research has shown that the AM symbiosis can promote the production of specific secondary metabolites in specific medicinal plants.…”

“…Resisting malaria Kapoor et al 2007;Rapparini et al 2008;Chaudhary et al 2008;Awasthi et al 2011;Huang et al 2011 Echinacea purpurea Antibacterial and antiviral effects Araim et al 2009 Arnica montana Treating bruises, swellings and diseases of the mouth Jurkiewicz et al 2010 Inula ensifolia Diminishing inflammation and antiviral effect Zubek et al 2010 Artemisia umbelliformis Antibacterial and antiviral effects Binet et al 2011 Tagetes erecta Diminishing inflammation, treating cold and cough…”

“…Observations in mycorrhizal A. annua suggest that the increase in artemisinin concentration may not be entirely attributed to enhanced P nutrition (Chaudhary et al 2008;Kapoor et al 2007). Khaosaad et al (2006) also found that essential oil concentration significantly increases in two oregano genotypes associated with G. mosseae, but the levels of essential oil in plants treated with P are not changed, which indicates that the increase in essential oil concentration in mycorrhizal oregano plants is not due to an improved P nutrition, but directly depends on association with the AM fungus.…”