Medicinal plants used in the treatment of sickle cell disease in Western Africa

Sickle cell disease is a serious problem in Africa where the required medication is often not available or too expensive for local Africans. Other possibilities have to be investigated, like traditional medication in the form of medicinal plants to control the symptoms of the disease. By screening scientific articles, a big table in Excel was made, containing 93 species which all have a potential effect against sickle cell disease. Cajanus cajan, Carica papaya, Piper guineense, Pterocarpus osun, Sorghum bicolor, Syzygium aromaticum, Zanthoxylum zanthoxyloides, Justicia secunda, Moringa oleifera and Vinga unguiculata seem to be the most promising species for treatment. To solve the problem of unaffordable medication, a closer look should be taken to the common food crops in the table which have a possible effect against sickle cell disease. Introduction Sickle cell disease (SCD), also known as drepanocytosis, is a genetic blood disorder in which red blood cells form an abnormal sickle or crescent shape. This genetic disease is due to a mutation in the β-globin gene in which the 17th nucleotide is changed from thymine to adenine and the sixth amino acid in the βglobin chain of hemoglobin whereby glutamic acid, a polar amino acid, is replaced by valine, a non-polar amino acid. This mutation decreases the affinity of hemoglobin for oxygen. At low oxygen tension the mutant hemoglobin, called hemoglobin S, polymerizes inside the red blood cells leading to a severe decrease in the red cell deformability. Polymerization and precipitation of hemoglobin S within the red blood cells cause the change of their shape from their normal disc-like form into one resembling a sickle (Mehanna, 2001; Bender, 1993; Rees, 2010). In Figure 1, part A shows normal red blood cells flowing freely in a blood vessel. The inset image shows a cross-section of a normal red blood cell with normal hemoglobin. Part B shows abnormal, sickled red blood cells blocking blood flow in a blood vessel. The inset image shows a cross-section of a sickle cell with abnormal hemoglobin forming abnormal strands. (http://www.nhlbi.nih.gov/health/health-topics/topics/sca/) Figure 1. Normal and sickled red blood cells. http://www.nhlbi.nih.gov/health/health-topics/topics/sca/ The symptoms which are caused by the sickle shaped cells are due to a shortage of good functioning blood cells, which causes anemia, blood clotting and blockage of blood vessels. They vary from fatigue, to dizziness and headaches, during a mild sickle cell crisis. A drastic sickle cell crisis is an acute episode of severe pain. These crises occur when sickled red blood cells block the blood flow to the limbs and organs, which causes the pain and eventually irreversible organ damage (Steinberg, 1999; Bender, 1993). SCD cannot be cured, so the goal of treatment is to manage and control symptoms, and to limit the number of crises (www.nhlbi.nih.gov). Patients with SCD need continuous treatment, even when they are not experiencing a painful crisis. The treatment includes pain medicines, fluids for hydration, blood transfusion to replace the sickled cells, multiple vaccines and antibiotics. The last two are necessary because of acute splenic sequestration, which occurs mostly in young patients. Sickle cells clump inside the spleen, which then becomes enlarged and cannot function properly anymore. This makes the patients more viable for infections and needy of the vaccines and antibiotics (Emond et al., 1985). In a crisis situation, multiple operations may be necessary for the transplantation of damaged organs. Also a bone marrow transplant can be performed, where the bone marrow stem cells are replaced by those of a donor and the newly made red blood will not form into a sickled shape (http://www.hematologienederland.nl/sikkelcelziekte). The problem Sickle cell disease is prevalent in tropical Africa. In Northern and Southern Africa, 1-2% of the population is a carrier of the disease, a heterozygote. In countries such as Congo, Gabon, Benin, Ghana and Nigeria this percentage reaches up to 20-30%. The geographic distribution of the sickle cell trait is similar to that of malaria. This is because heterozygotes actually have an advantage, above people without SCD, as they are protected against the severe form of malaria. Consequence is that people who are heterozygous reach maturity more often than those who are not. In countries, where the percentage of carriers is higher than 20%, about 2% of the population is born with SCD, the homozygotes (http://www.afro.who.int). The required medication to treat SCD is often not readily available to most rural Africans, especially in the poorest countries. They cannot afford the available treatments, as they always need continuous medication, because SCD cannot be cured, only controlled. In Congo for example, where the average daily wage is less than 1 US dollar, people cannot afford the cheapest available haemoglobin S test, which is about 2.5 US dollars (Tshilolo et al., 2009). Buying this test means they cannot eat for one or probably more days, and the treatments are not even included yet. All these factors make SCD a large problem in Africa which should be taken seriously. Because of the expensive tests, medication and treatments, rural Africans often rely on traditional medicine to treat this disease, which comes in the form of plant extracts. It is not clear though, which plant species actually have an positive effect on the sickled cells or the symptoms of SCD and may function as a treatment for the disease. Experiments have been done on several African plant species to evaluate their effect against SCD, but no clear overview exists about which species have been tested and actually have a proven effect. Aim of the research The aim of this research is to review which plant species are being used in Africa for the treatment of SCD, and which of those are promising species to effectively treat this disease. This is very important to determine, as African people who suffer from SCD may benefit greatly from further testing of these species. Using effective medicinal plants can be an affordable way for them to treat the symptoms of SCD and cope with the disease. Mainand sub research questions Which plants are used to treat sickle cell anemia in Western Africa? 1. Have these plants been studied pharmacologically for their potential to treat sickle cell disease related ailments? 2. Which plants have a potential to reduce sickle cell anemia related health problems? 3. How do Africans view the cause and treatment of sickle cell disease? Method The first step of this research was to search for scientific articles in Google scholar (http://scholar.google.nl/) and Pubmed (http://www.ncbi.nlm.nih.gov/pubmed) about the treatment of sickle cell disease in Africa by plants, and make a clear summary of the results described in these papers. I used the search terms ‘drepanocytose’ and ‘sickle cell’ in combination with the terms ‘disease’, ‘anemia’, ‘Africa’, ‘plants’, ‘herbs’, ‘traditional medicine’, ‘medicinal plants’, ‘anti-sickling’ and ‘anthocyanins’. In order to do this I made an Excel table, containing the collected plant species, family, countries where the species was used in to treat SCD, whether the species had an anti-sickling effect of the red blood cells according to the article, if the anti-sickling or other mentioned effects of the species were proven by means of an in vivo or in vitro test and the active principle in the plant which according to authors, was responsible for the anti-sickling effect. Since many Africans think the colour of the plant affects its effectiveness, they believe that red plant medicines will cure red blood (Cocks et al., 2002). Therefore, I noted whether any part of the plant (roots, stem, leaves, fruit, flowers) had a red, pink or purple colour. This information was acquired from literature or by typing in the species in www.google.com and then clicking ‘Images’, or from images from www.wikipedia.com. Species names were updated by using The Plant List (www.theplantlist.org). I also collected information from unpublished plant use databases from Ghana by postdoc researcher Tinde van Andel, from Benin and Gabon by PhD Candidate Alexandra Towns and from Julie-Anne Borm. Julie-Anne has been a project leader of the Association of Cooperating Parent and Patient Organizations (‘Vereniging van Samenwerkende Ouderen Patiëntenorganisaties’, VSOP) in the Netherlands. When I listed a species from these databases, I mentioned it in the references as ‘Unpublished’, together with the name of the person of my source. I retrieved all the information in the excel table from the articles, except the tabs ‘Family’, ‘Genus and Species THEPLANTLIST.ORG’ and ‘Red colour’. I got the information of the first two tabs from www.theplantlist.org. I held an interview with Julie-Anne Borm, who is knowledgeable on SCD and who could tell me her field experiences about African people that use plants in order to treat this disease. This I did to have a better understanding in the thoughts of Africans related to SCD.