Antiplasmodial, antimalarial activities and toxicity of African medicinal plants: a systematic review of literature.

BACKGROUND: Malaria still constitutes a major public health menace, especially in tropical and subtropical countries. Close to half a million people mainly children in Africa, die every year from the disease. With the rising resistance to frontline drugs (artemisinin-based combinations), there is a need to accelerate the discovery and development of newer anti-malarial drugs. A systematic review was conducted to identify the African medicinal plants with significant antiplasmodial and/or anti-malarial activity, toxicity, as wells as assessing the variation in their activity between study designs (in vitro and in vivo). METHODS: Key health-related databases including Google Scholar, PubMed, PubMed Central, and Science Direct were searched for relevant literature on the antiplasmodial and anti-malarial activities of African medicinal plants. RESULTS: In total, 200 research articles were identified, a majority of which were studies conducted in Nigeria. The selected research articles constituted 722 independent experiments evaluating 502 plant species. Of the 722 studies, 81.9%, 12.4%, and 5.5% were in vitro, in vivo, and combined in vitro and in vivo, respectively. The most frequently investigated plant species were Azadirachta indica, Zanthoxylum chalybeum, Picrilima nitida, and Nauclea latifolia meanwhile Fabaceae, Euphorbiaceae, Annonaceae, Rubiaceae, Rutaceae, Meliaceae, and Lamiaceae were the most frequently investigated plant families. Overall, 248 (34.3%), 241 (33.4%), and 233 (32.3%) of the studies reported very good, good, and moderate activity, respectively. Alchornea cordifolia, Flueggea virosa, Cryptolepis sanguinolenta, Zanthoxylum chalybeum, and Maytenus senegalensis gave consistently very good activity across the different studies. In all, only 31 (4.3%) of studies involved pure compounds and these had significantly (p = 0.044) higher antiplasmodial activity relative to crude extracts. Out of the 198 plant species tested for toxicity, 52 (26.3%) demonstrated some degree of toxicity, with toxicity most frequently reported with Azadirachta indica and Vernonia amygdalina. These species were equally the most frequently inactive plants reported. The leaves were the most frequently reported toxic part of plants used. Furthermore, toxicity was observed to decrease with increasing antiplasmodial activity. CONCLUSIONS: Although there are many indigenous plants with considerable antiplasmodial and anti-malarial activity, the progress in the development of new anti-malarial drugs from African medicinal plants is still slothful, with only one clinical trial with Cochlospermum planchonii (Bixaceae) conducted to date. There is, therefore, the need to scale up anti-malarial drug discovery in the African region.

A systematic review of anti-Entamoeba histolytica activity of medicinal plants published in the last 20 years.

Amoebiasis has emerged as a major health problem worldwide. It is endemic in the present scenario is different and sub-tropical regions especially in Asia, Latin America and also in Africa. Causative of amoebiasis is a protozoan known as Entamoeba histolytica. We screened all the databases such as PubMed, Science Direct, Medline and Google Scholar by using the keywords 'anti-Entamoeba histolytica activity of medicinal plants, anti-Entamoeba histolytica activity of herbal drugs, the anti-amoebic activity of natural drugs'. In the present study, we found 7861 articles, where all articles were screened for bias analysis and included 32 full-matching articles in total reporting the use of medicinal plants as a remedy for amoebiasis. Through these articles, we found 42 herbs having anti-amoebic activity. In bias analysis, we also found four articles under high bias risk. In our study, seven medicinal plants were concluded to possess the most potent anti-amoebic activity based on their IC50 value, which was less than 1 µg mL−1. On bias analysis, we found four articles with high bias risk, hence these studies can be repeated for better results.