Antischistosomal, antionchocercal and antitrypanosomal potentials of some Ghanaian traditional medicines and their constituents

Abstract

Background Ghana is endemic for some neglected tropical diseases (NTDs) including schistosomiasis, onchocerciasis and lymphatic filariasis. The major intervention for these diseases is mass drug administration of a few repeatedly recycled drugs which is a cause for major concern due to reduced efficacy of the drugs and the emergence of drug resistance. Evidently, new treatments are needed urgently. Medicinal plants, on the other hand, have a reputable history as important sources of potent therapeutic agents in the treatment of various diseases among African populations, Ghana inclusively, and provide very useful starting points for the discovery of much-needed new or alternative drugs. Methodology/Principal findings In this study, extracts of fifteen traditional medicines used for treating various NTDs in local communities were screened in vitro for efficacy against schistosomiasis, onchocerciasis and African trypanosomiasis. Two extracts, NTD-B4-DCM and NTD-B7-DCM, prepared from traditional medicines used to treat schistosomiasis, displayed the highest activity (IC50 = 30.5 μg/mL and 30.8 μg/mL, respectively) against Schistosoma mansoni adult worms. NTD-B2-DCM, also obtained from an antischistosomal remedy, was the most active against female and male adult Onchocera ochengi worms (IC50 = 76.2 μg/mL and 76.7 μg/mL, respectively). Antitrypanosomal assay of the extracts against Trypanosoma brucei brucei gave the most promising results (IC50 = 5.63 μg/mL to 18.71 μg/mL). Incidentally, NTD-B4-DCM and NTD-B2-DCM, also exhibited the greatest antitrypanosomal activities (IC50 = 5.63 μg/mL and 7.12 μg/mL, respectively). Following the favourable outcome of the antitrypanosomal screening, this assay was selected for bioactivity-guided fractionation. NTD-B4-DCM, the most active extract, was fractionated and subsequent isolation of bioactive constituents led to an eupatoriochromene-rich oil (42.6%) which was 1.3-fold (IC50 <0.0977 μg/mL) more active than the standard antitrypanosomal drug, diminazene aceturate (IC50 = 0.13 μg/mL). Conclusion/Significance These findings justify the use of traditional medicines and demonstrate their prospects towards NTDs drug discovery.

The Activity of Plant Crude Extracts against Schistosoma mansoni

“…Azadirachta indica was tested by four studies, two in vitro [34,35], one in vivo [36], and the third in vitro plus in vivo [37]. Phyllanthus amarus [36,38], Vernonia amygdalina [35,36], Rauwolfia vomitoria [35,39], and Morinda lucida and Nauclea latifolia [35,36] were tested by two studies. The other plants were Mitracarpus frigidus [40], Ozoroa pulcherrima [41], Calotropis procera [42], Ficus elastica [42], Zingiber officinale [42], Punica granatum [43], Tanacetum vulgare [44], Allium sativum (garlic) [45], Allium cepa (onion) [45], Echinops kebericho [46], Hagenia abyssinica [46], Ageratum conyzoides, Alchornea cordifolia, Aloe vera, Alstonia boonei, Anthocleista nobilis, Combretum sp, Khaya senegalensis, Mangifera indica, Mitragyna stipulosa, Momordica charantia, Paulina pinnata, Phyllanthus niruri, Picralima nitida, Smeathmannia sp, Syzygium aromaticum, Tapinanthus bangwensis, Taraxacum officinale, Trichila monadelpha and Xylopia aethiopica [35], Arctium lappa [47], Baccharis trimera [48], Cynara scolymus [49], Ekebergia capensis [37], Chenopodium ambrosioides [50], Conyza dioscorides [50], and Sesbania sesban [50].…”

“…Another group of Ghanaian investigators [35] considered 25 plant species that are used by traditional healers of schistosomiasis. The authors used these plants in formulations of 2-5 plant species in either aqueous herbal preparations or dried powdered forms and evaluated their in vitro activity against newly transformed schistosomula and adult worms of S. mansoni.…”

“…Six plant species were worked on by more than one study. Azadirachta indica was tested by four studies, two in vitro [ 34 , 35 ], one in vivo [ 36 ], and the third in vitro plus in vivo [ 37 ]. Phyllanthus amarus [ 36 , 38 ], Vernonia amygdalina [ 35 , 36 ], Rauwolfia vomitoria [ 35 , 39 ], and Morinda lucida and Nauclea latifolia [ 35 , 36 ] were tested by two studies.…”

Drug development for onchocerciasis-the past, the present and the future

“…Twumasi et al (150), tested a number of traditional herbal preparations from Ghana used locally for treating schistosomiasis and demonstrated activity against O. ochengi mf, adult male and female worms. An aqueous extract of Syzygium aromaticum, Xylopia aethiopica, Tapinanthus bangwensis and Phyllanthus niruri called NTD-B2-DCM, was the most active against female and male adult O. ochengi worms (IC50 = 76.2 mg/mL and 76.7 mg/mL, respectively).…”

Drug discovery research in Ghana, challenges, current efforts, and the way forward

“…For example, compounds synthesised in the Department of Chemistry UG were tested for antimicrobial activity at NMIMR [ 16 ]. In two separate collaborations, semi-synthesis of a natural product and an isolated plant-derived natural product, both carried out in the Department of Chemistry, UG, were assayed for antitrypanosomal activity at the West African Center for Cell Biology of Infectious Pathogens, UG [ 17 , 18 ]. In another study to access the efficacy some medicinal plants for the treatment of mycobacterial infections, stem back extracts isolated from KNUST were tested at NMIMR for antimicrobial activity and cytotoxicity [ 19 ].…”