1.0 Background of the study
Medicinal plants have been identified and used throughout human history (Tapsell et al., 2006). Plants have the ability to synthesize a wide variety of chemical compounds that are used to perform biological functions. The chemical compounds in plants mediate their effects on the human body through processes identical to those already well understood for the chemical compounds in conventional drugs (Tapsell et al., 2006). Herbal medicines do not differ greatly from conventional drugs in terms of how they work and this enables them to be as effective as conventional/orthodox drugs, and also gives them the same potential to cause harmful side effects (Lai et al., 2004). Many of the pharmaceuticals currently available to physicians have a long history of use as herbal remedies this includes aspirin, digitalis, quinine and opium (swain et al., 1968). With this upsurge in the use of herbal medicines alongside orthodox medicine, there is a shift in the use of mono-therapy to multi-drug therapy as seen in the treatment of malaria, tuberculosis, cancer, diabetes, etc. This practice has become inevitable as the rise in the use of herbal remedies most especially has gone global with more than 80% of the people in west Africa (Nigeria precisely), Asia and an increasing number in some western countries using this method of treatment. Malaria, a life threatening blood disease caused by the anopheles mosquito, is a major tropical disease with high mortality and morbidity rate. It is responsible for the death of about 1.24 to 1.82 million patients mainly among children and pregnant women (WHO, 2010). Malaria has been shown to be a contributor to the economic burden in communities where it is endemic and is responsible for annual economic loss. Due to the ineffectiveness of anti-malarial drugs in combating malaria, several studies have been made which produced a new and effective anti-malaria drug, artemisinin. Artemisinin can be used alone but this leads to high rate of recrudescence (return of parasites) after which other drugs are required to clear the body of all parasites and prevent recurrence. This led the World Health Organization to recommend artemisinin combination therapies (ACT) to be the first-line therapy for Plasmodium falciparum malaria worldwide. These combinations are effective because the artemisinin component kills the majority of the parasites at the start of the treatment while the partner drug, which is more slowly eliminated, clears the remaining parasites (White, 2004). The artemisinin has a short half-life while the partner drug has a long half-life e.g mefloquin, lumefantrine, piperaquine, amodiaquine and pyronaridine (Krudsood et al., 2010). Despite the recorded success with the use of ACTs, patients often fall back to using herbal therapies in combination prior to after orthodox anti-malaria therapy (Ijarotimi et al., 2010) which is mostly done without the knowledge of a health personnel. Combination of drugs may predispose the body to pharmacodynamic or pharmacokinetic interactions which may result in drug toxicity or therapeutic failure (Fasinu et al., 2012). With regards to malaria, one of the anti-plasmodial herbs often used in combination with orthodox drugs is Hippocratea africana root bark extract alongside Eremomastax speciosa leaf extract which is believed to be anti-anaemic. This combination is commonly practiced by the people of the south-eastern part of Nigeria. The Hippocratea africana root extract has also been used traditionally in the treatment of ailments such as diabetes, fever, malaria, diarrhea, anemia (Okokon et al., 2006). It has been reported to possess anti-plasmodial activities with lethal dosage (LD50) of 2.45 mg/kg body weight in mice (Ndem et al.,2010). Further studies carried out also shows that the ethanolic extract of H. africana possesses promising schizonticidal activity (Ndem et al., 2013). Eremomastax speciosa leaf extract has also been reported to cause increase in hematological parameters and prevent malaria anemia which is common in areas endemic to malaria (Okokon et al., 2007). The leaves are also used to treat fracture, hemorrhoids, irregular menstruation and urinary tract infections (Adjanohoun et al., 1996).