Antiplasmodial evaluation of extracts of selected Ghanaian medicinal plants and other bioactivities of isolates of polyalthia longifolia var. pendula (annonaceae)
Loading...
Date
2014
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Malaria is one of the most important tropical infectious diseases. About half of the world’s
population is at risk of developing malaria. It is a major public health challenge as well as a
significant economic burden on many developing countries, especially in the African region.
Most malaria patients are usually anaemic and also experience reduced or compromised immune
systems which therefore predispose them to secondary bacterial and fungal infections. People
living in extreme poverty are the most vulnerable to these infectious diseases simultaneously.
This affects their ability to make a living and move out of poverty. Many of these people rely on
herbs for treatment of the disease due to lack of access to efficacious antimalarial drugs against,
especially the fast spreading multidrug-resistant Plasmodium falciparum. However, very few of
these folklore herbs have been scientifically investigated and authenticated for used in the
management of malaria and other infectious diseases. This study therefore sought to investigate
and validate or otherwise the traditional uses of some Ghanaian plants for treating malaria. The
ethanolic extracts of ten plant species which were selected based on their traditional medical
application were screened against the multidrug resistant P. falciparum (K1 strain) by the parasite
lactate dehydrogenase (pLDH) assay. Seven of the plant species (Adenia cissampeloides Planch.
ex Hook. Anthocleista nobilis G. Don, Elaeis guineensis Jacq., Entandrophragma angolense
(Welw.) CDC, Mallotus oppositifolius (Geisel.) Müll. Arg., Sarcocephalus latifolius (J.E.Sm) E.
A Bruce and Polyalthia longifolia var. pendula) showed potent antiplasmodial activity with IC50
< 50 μg/ml. The extracts P. longifolia exhibited the most potent activity (IC50 < 23 μg/ml).
Bioassay guided fractionation of P. longifolia extracts yielded four clerodane diterpenes [16-
hydroxycleroda-3,13-dien-16,15-olide (1) and its acetylated derivative acetyl-16-oxycleroda-
3,13-dien-16,15-olide (1a), 16-oxocleroda-3,13E-dien-15-oic acid (2) and 3,16-
dihydroxycleroda-4(18),13(14)Z-dien-15,16-olide (3)], a steroid [β-Stigmasterol (4)] and two
vii
alkaloids [Darienine (5) and L-Stepholidine (6)]. Even though the steroid and the alkaloids
showed weak antiplasmodial activity (IC50: 22 -105 μg/ml), the clerodane diterpenes exhibited
significantly (p < 0.005) potent blood schizonticidal activity (IC50: 3 - 6 μg/ml) against the
multidrug resistant malaria parasite. Although the isolated clerodane diterpenes 1a, 2 and 3 are
known compounds, this is the first report of their antiplasmodial activity especially against the
multi-drug resistant Plasmodium falciparum. The clerodane diterpenes also displayed potent
antibacterial and antifungal activities (MIC ranged between 3.13 and 50.00 μg/ml) against
Staphylococcus aureus (ATCC 25923), Streptococcus pneumoniae (clinical isolate), Bacillus
subtilis (NCTC 10073), Pseudomonas aeruginosa (ATCC 4853), Salmonella typhi (NCTC 8385),
Escherichia coli (NCTC 25922) and Candida albicans (NCPF 3179). The study therefore
appeared to lend support to the traditional uses of these plants as remedies for malaria in Ghana
and formulations containing especially P. longifolia extracts will be highly beneficial in treating
mixed infections associated with malaria.
Description
A thesis submitted to the Department of Pharmaceutics Faculty of Pharmacy and Pharmaceutical Sciences College of Health Sciences in fulfillment of the requirements for the degree of Doctor of Philosophy