Asthma,Euphorbia Hirta and Its Anti-Inflammatory Properties
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per cent of asthma sufferers are children and 5% are adults. Asthma mortality in Asthma, Euphorbia hirta and its the United States amounted to some 5000 persons in the year 2000. The global prevalence of the disease is expected to anti-inflammatory properties rise to 400 million by the year 2025.3 Most of the available pharmacological O.E. Ekpo* and E. Pretorius*‡ therapies simply control the known mechanisms by which the disease occurs. There is no complete cure for asthma. UPHORBIA HIRTA IS A PLANT USED IN TRADI- that the flavonoids quercitrin (converted to Pharmaceutical products have been the tional medicine for a variety of diseases, quercetin in the alimentary canal) and main source of anti-asthma treatment but Esuch as cough, asthma, colic dysentery myricitrin, as well as the sterols 24-methy- some of these have recently been associated and genito-urinary infection. This plant, be- lene-cycloartenol and -sitosterol, exert note- with serious adverse effects. longing to the family Euphorbiaceae, is also worthy and dose-dependent anti-inflam- known as the Australian asthma herb or matory activity. The triterpene β-amyrin also It is estimated that there are about 27 Queensland asthma weed, and is not toxic seems to exert a similar anti-inflammatory million consumers of indigenous medicine when taken in typical dosages. In South Africa, activity. Tannins and tannic acid derivatives, in southern Africa, a large number of it is commonly used for asthma, which is one also present in the plant, have antiseptic whom consult traditional healers for of the most common respiratory complaints. effects and the two triterpenoids, taraxerone potentially life-threatening conditions.4,5 Although corticosteroids are considered the (EH-1) and 11α,12α-oxidotaraxerol (EH-2), in An estimated 60% of the South African best means of defence against this debilitating E. hirta demonstrate antibacterial and anti- population is reported to consult traditional illness, many people, especially in poor coun- fungal properties. The effectiveness of E. hirta healers.6 Moreover, the steady increase in tries, rely on herbal remedies for its treatment. in treating asthma may lie predominantly in We discuss recently published results to the synergistic relationships between the incidence of asthma has, as with any assess the effect of the plant using the BALB/c flavonoids, sterols and triterpenoids. chronic condition, opened up a new era murine asthma model. We also review the where sufferers are resorting to alternative 7 different compounds found in plant extracts, Introduction treatments. in an attempt to understand the reason for its Asthma is one of the most common One of the herbs used against asthma in anti-inflammatory properties. We conclude respiratory complaints in the world today. southern Africa is Euphorbia hirta (family *Department of Anatomy, Faculty of Health Sciences, It affects an estimated 300 million people Euphorbiaceae), also known as the Austra- University of Pretoria, P.O.Box 2034, Pretoria 0001, South worldwide, of whom about 50 million live lian asthma herb or Queensland asthma Africa. weed, cat’s hair, hairy spurge, spurge or ‡Author for correspondence. in Africa, 15 million in the U.S., 5 million in E-mail: [email protected] the U.K. and 2 million in Australia.1,2 Ten milkweed. In India, the plant is used for 202 South African Journal of Science 103, May/June 2007 News & Views Table 1.Summary of mean white blood cell counts in blood smears obtained from control group, asthmatic mice, to possess several proven medicinal asthmatic mice treated with low and high hydrocortisone (HC) doses, as well as asthmatic mice treated with Euphorbia hirta (5 areas from each blood smear, and 5 smears from each individual mouse, were counted; there properties including anti-inflammatory, were 6 mice per group). antioxidant, anti-allergic, antibacterial 6 Control group Asthma group Low HC High HC E. hirta and antiviral activity. The most abun- 20,21 (100 mg/kg) (125 mg/kg) (0.01 ml of 62.5 mg/kg dant flavonoid in E. hirta is quercetin, plant material) which has been reported to be the main Neutrophil 39 336 36 91 31 agent that addresses the inflammatory 20 Eosinophil 13 104 10 3 4 component of asthma. Flavonoids have Basophil 7 58 3 2 1 been proposed to exert beneficial effects Lymphocyte 144 1203 41 81 82 in many diseases, including asthma. Monocyte 203 737 32 63 113 Many of the biological actions of flavonoids have been attributed to their antioxidant properties, either through treating a variety of diseases, such as hydrocortisone lowered the white blood their reducing capacities or as a result of cough, asthma, colic dysentery and counts in the mice, as did the plant extract. their possible influence on intracellular genito-urinary conditions.8–13 In East and The neutrophils, eosinophils and basophils redox status.22 Flavonoids can also inter- West Africa, extracts of the decoction of specifically were also lowered; these cells act selectively within the mitogen-acti- the flowering and fruiting plants are used are known to be active in inflammation. vated protein (MAP) kinase signalling in the treatment of asthma and respira- Platelets and fibrin networks also play a pathway.22–24 tory tract infections and are sometimes fundamental role in asthma. Pretorius combined with bronchial sedatives such and co-workers showed that control mice Possible anti-asthmatic effects of as Grindelia robusta in preparations for possess major thick fibres and minor thin quercetin inhalation.14,15 The plant is also employed fibres as well as tight round platelet Quercitrin (3-rhamnosylquercetin), found in the treatment of coughs, chronic bron- aggregates with typical pseudopodia in E. hirta, is a bioflavonoid with anti- chitis and pulmonary disorders, especially formation.17 Minor fibres of asthmatic oxidant and anti-inflammatory proper- in Australia.16 mice have a net-like appearance, covering ties.25 It is converted in the alimentary Since this plant is used as herbal medicine the major fibres, whereas platelets appear canal to quercetin (3-O-α-L-rhamno- and is not cytotoxic when taken in typical to form loosely connected, granular aggre- pyranoside), which is the aglycone prod- amounts, Pretorius and co-workers inves- gates. Both concentrations of hydrocorti- uct of the former.26–29 It is this converted tigated its effect in the treatment of sone made the fibrin more fragile, and product, quercetin, that is a potent anti- asthma.17 The BALB/c murine asthma platelet morphology changed from a tight inflammatory chemical, and is believed to model was used to investigate the conse- platelet aggregate to a more granular be the most important constituent in the quences for mice exposed to low-dose assembly, not closely fused to one another. plant responsible for the anti-asthmatic hydrocortisone (HC) (100 mg/kg), mice Furthermore, it was claimed in the article effects. exposed to higher-dose HC (125 mg/kg), that E. hirta does not influence the fragility and mice subjected to physiologically of the fibrin and that it prevents the minor Sterols comparable levels of E. hirta (0.01 ml of fibres forming the dense net-like layer Sterols that have been isolated from 62.5 mg/kg plant material). over the major fibres, as is observed in E. hirta and have been chemically charac- White blood cell counts are a reliable untreated asthmatic mice. Furthermore, it terized include cycloarternol, 24-methy- measure of asthmatic status. The process seems that E. hirta does not render the lene-cycloarternol, β-sitosterol, euphorbol of inflammation in asthma is viewed as an fibrin fibres as fragile as is found with the hexacozonate, 1-hexacosanol, tinyaloxin, inflammatory cascade, which is divisible HC-treated mice and it also does not alter campesterol and stigmasterol.8,29,30 The into seven phases: sensitization, stimula- the integrity and morphology of the compounds 24-methylene-cycloartenol tion, cell signalling, migration, cell activa- platelets as was found in HC-treated and β-sitosterol have also been found to tion, tissue stimulation or damage, and mice. An important result is that E. hirta exert significant and dose-dependent resolution. In humans, eosinophil numbers reduces inflammatory cells to the same anti-inflammatory effects, when treating are elevated in the airways of asthmatics level as that achieved by hydrocortisone, acetate-induced ear inflammation.31 and these cells release basic proteins and suggesting that the plant, indeed, has growth factors that may damage airway anti-inflammatory properties. Tannins and triterpenoids epithelial cells, and cause airway remod- The question that now arose is, what Tannins are not widely known for their elling.18 Additionally, neutrophil popula- components give the plant these proper- anti-inflammatory potential; E. hirta tion is usually found to increase in the ties? A review of the relevant available possesses a few such chemicals. Phyto- airways and in sputum of patients with literature now follows. chemicals work synergistically, however, severe asthma. It is therefore useful to and therefore these tannins may assist in examine these counts, to determine if an Chemical compounds of Euphorbia the anti-inflammatory action of the plant. anti-asthmatic product is effective, partic- hirta Euphorbia hirta presents three hydrolys- ularly when compared with results from Phytochemical analyses of E. hirta reveal able tannins, namely, dimeric hydro- exposure to hydrocortisone (which, in flavonoids, sterols, tannins and triter- lyzable tannin, euphorbin E and the our case, was used as a positive control) penoids in the bark and leaves. dimeric dehydroellagitannins, euphorbin and reduces white blood counts in A and euphorbin B.32 Chen also isolated asthma. Table 1 shows that the mice in the Flavonoids the following tannins from the leaves of asthmatic group (made asthmatic and not Two flavonoids have been isolated from E.