Compounds from African Medicinal Plants with Activities Against Selected Parasitic Diseases: Schistosomiasis, Trypanosomiasis and Leishmaniasis

Abstract

Parasitic diseases continue to represent a threat on a global scale, particularly among the poorest countries in the world. This is particularly because of the absence of vaccines, and in some cases, resistance against available drugs, currently being used for their treatment. In this review emphasis is laid on natural products and scaffolds from African medicinal plants (AMPs) for lead drug discovery and possible further development of drugs for the treatment of parasitic diseases. In the discussion, emphasis has been laid on alkaloids, terpenoids, quinones, flavonoids and narrower compound classes of compounds with micromolar range activities against Schistosoma, Trypanosoma and Leishmania species. In each subparagraph, emphasis is laid on the compound subclasses with most promising in vitro and/or in vivo activities of plant extracts and isolated compounds. Suggestions for future drug development from African medicinal plants have also been provided. This review covering 167 references, including 82 compounds, provides information published within two decades (1997-2017).

Keywords: African medicinal plants; Leishmaniasis; Natural products; Parasitic diseases; Schistosomiasis; Trypanosomiasis.

Fig. 1

Global statistics for disease burdens in 2017

Fig. 2

Antiprotozoal naphthylisoquinoline alkaloids

Fig. 3

Aporphine alkaloids with trypanosidal potencies

Fig. 4

Quinoline, indoles and other alkaloids showing activities against Trypanosoma species

Fig. 5

SAR for W. indica compounds inhibiting T. cruzi, T. b. brucei and T. b. rhodesiense

Fig. 6

Sesquiterpenoids which have demonstrated anti-Trypanosoma activities

Fig. 7

Carvotacetones with potent antileishmanial activities

Fig. 8

Diterpenoids and a triterpenoid with selective inhibitory activity against T. brucei GAPDH

Fig. 9

Potent compound with selective activity for L. donovani, when compared with the activity against T. b. brucei

Fig. 10

Triterpenoids with antiparasitic activities

Fig. 11

An antitrypansomal amide and two diarylhepanoids

Fig. 12

Acylphloroglucinols and a xanthone with very potent in vitro antileishmanial activities in the nanomolar range

Fig. 13

Taccalonolides, a rare class of antiprotozoals

Fig. 14

Quiniones and klaivanolide, which showed lower micromolar activities against against several Leishmania species

Fig. 15

Flavonoids and phytosterols with trypanocidal activities