**2. Medicinal plants with demonstrated anti-malarial activity**

Malaria is one of the world's most important parasitic disease and a leading cause of death especially in developing countries [4]. It is endemic in about 100 developing countries, leading to about 1.2 million estimated deaths each year in Africa [5], with pregnant women and children below 5 years being mostly affected [6]. A wide range of medicinal plants is employed for the treatment of malaria, since majority of the people who get infected cannot afford the existing expensive orthodox medicines [7]. The problem of resistance to existing antimalarial agents by parasite has necessitated the search for new and potent agents, and the focus of researchers is on natural products especially medicinal plants since active compounds like quinine and artemisinin were isolated from plants and have been lead compounds for antimalarial drug development [8, 9]. Various medicinal plants have been investigated for their anti-malarial activity and some with demonstrated potent *in vitro* activity have been reviewed below.

#### **2.1** *Cryptolepis sanguinolenta*

 *C. sanguinolenta* (Lindl.) Schlechter (Apocynaceae) is known by Ghanaians as 'Ghana quinine' and specifically by the Asantes and Ewes as 'Nibima' and 'Kadze,' respectively [10]. It is a twining and scrambling thin-stemmed shrub, indigenous to Africa, with much ethno-medicinal importance and interest in the West African sub-region [11]. It is used traditionally for the treatment of malaria, upper respiratory and urinary tract infections, diarrhea, hypertension and as cicatrizant of wounds [12, 13]. The ethanolic and aqueous extracts of *C. sanguinolenta* exhibited an *in vitro*  antiplasmodial activity against multi-drug resistance *Plasmodium falciparum* (K1) strain, with all the extracts inhibiting 90% of parasite growth at concentrations below 23 μg/mL. The ethanolic roots and leaves extracts showed potent activity with IC50 of 0.895 ± 0.02 and 3.01 ± 0.02 μg/mL, respectively. While the aqueous roots and leaves extracts had IC50 of 2.32 ± 0.3 and 13.5 ± 0.7 μg/mL, respectively [14]. Evaluating the clinical efficacy of a tea bag formulation of the root of *C. sanguinolenta* in patients with uncomplicated malaria showed that within 72 h, Fifty percent (50%) of the patients had their *P. falciparum* parasitaemia cleared, and all patients, by Day 7. By Day 3, all presenting symptoms such as fever, chills, nausea and vomiting were completely no more. The overall cure rate when one tea bag of *C. sanguinolenta* was taken three times a day for 5 days was 93.5%, due to two cases of recrudescence on Days 21 and 28 [15].

#### **2.2** *Terminalia ivorensis*

*T. ivorensis* A. Chev. belongs to the family Combretaceae and is commonly known as 'black afara' and by the Asantes as 'amire.' It is a large deciduous forest tree of 15–46 m high, normally grown as timber plantation in many tropical countries [16]. In traditional medicine, various parts of the plant is used to treat malaria, yellow fever, pile, stomach ulcer, wounds and other infections [17, 18]. A study by Komlaga

et al. [19] revealed an active *in vitro* antiplasmodial activity of *T. ivorensis* aqueous leaf extract, against *P. falciparum* chloroquine-sensitive (3D7) and chloroquine resistant (W2) strains with IC50 of 0.64 ± 0.14 and 10.52 ± 3.55 μg/mL, respectively. The ethanolic stem bark extract also showed an *in vitro* antimalarial activity against chloroquine-resistant strains of *P. falciparum* with an IC50 of 6.949 μg/mL [20].
