Hypericum lanceolatum (Hypericaceae) as a potential source of new anti-malarial agents: a bioassay-guided fractionation of the stem bark

Abstract

BackgroundMalaria is a major public health threat in Africa, and traditional medicine continues to play a key role in its control especially in rural areas. A bioassay-guided fractionation was carried out in order to evaluate the anti-malarial potential and the safety of the methanol extract of the Hypericum lanceolatum stem bark.MethodsThe anti-plasmodial activity was assayed by the lactate dehydrogenase method (pLDH) against the multidrug-resistant W2mef laboratory strain, and a field isolate (SHF4) of Plasmodium falciparum. Cytotoxicity tests were carried out using the LLC-MK2 monkey kidney epithelial cells.ResultsFive compounds were isolated from the most active and least cytotoxic ethylacetate sub-extract: betulinic acid (HLT1), 2,2',5,6'-tetrahydroxybenzophenone (HLT2), 5-hydroxy-3-methoxyxanthone (HLT3), 3-hydroxy-5-methoxyxanthone (HLT4) and HLT0 (yet to be identified). Three of the tested compounds presented significant anti-plasmodial activities (with 50% inhibitory concentration, IC50 < 5 μM), with 5-hydroxy-3-methoxyxanthone exerting the highest activity, followed by HLT0 and betulinic acid. All the compounds with significant anti-plasmodial activity were non-cytotoxic, except betulinic acid which showed a 50% cytotoxic concentration, CC50 of 25 μg/mL.ConclusionsThese findings justify the use of H. lanceolatum stem bark as anti-malarial by traditional healers of Western Cameroon, and could constitute a good basis for further studies towards development of new drug candidates or phytomedicines for malaria.

In vivo antioxidant assessment of two antimalarial plants–Allamamda cathartica and Bixa orellana

“…10% TCA was added to the liver homogenate and blood samples separately, and were centrifuged. A volume of 1.0 mL of the supernatant was treated with 0.5 mL Ellman's reagent (19.8 2 O dissolved in 500 mL distilled water). The absorbance was read at 412 nm and the GSH contents calculated from the standard graphs generated.…”

“…People living in the poorest countries are the most vulnerable to malaria and are most dependent on plant resources for malaria management, especially in the population of West Africa [1,2] . However, do all the plants employed by the local population have therapeutic prowess for treating Malaria?…”

A New Squeaker Frog (Arthroleptidae: Arthroleptis) from Bioko Island, Equatorial Guinea

“…Even so, the exploitation of the montane scrub and subalpine grasslands in the region has been primarily restricted to hunting of game. Recent findings by Zofou et al (2011), however, justified the use of stem bark from Hypericum laceolatum (Hypericaceae), found in the upper montane zone of the BFH (Table 2), for the treatment of malaria, and suggest that it will likely yield new anti-malarial drug candidates. Given the gravity of malaria infection worldwide, further positive results may lead to local overexploitation similar to that of another montane species, the red stinkwood (Prunus africana), whose bark is used to treat prostate hyperplasia (Ingram and Nsawir, 2007;Charlotte, 2010).…”

Bioprospecting of “New” or “Old” Plant Species?

“…The bioassay of stem bark extract from Hypericum lanceolatum Lam., used by traditional healers in Cameroon, indicated some new metabolites with anti-plasmodial activity [14]. The species could be considered as a potential source of new anti-malarial phytomedicines.…”