Abstract:
Ethnopharmacological relevance: Leishmaniasis is one of the neglected tropical disease caused
by a protozoan of the genus Leishmania transmitted by sandflies. High cost and lack of oral
formulation of existing drugs, rapid developments of resistance by the parasite coupled with
serious side effects require new treatments to augment or replace currently available therapies.
The major merits of herbal medicine seem to demonstrate perceived efficacy, low incidence of
serious adverse effects and low cost. Erythrophleum plants possess beneficial biological properties
and, as such, characterization of the bioactive components of these plants is imperative. Previous
work has shown an overwhelming presence of cassaine alkaloids in these plants. However,
amongst these plants, the African based specie (Erythrophleum ivorense) is the least studied.
Objective: In the current study, the in vitro anti-leishmanial activity of the crude extract, its
fractions and isolated compounds were evaluated using direct counting assay of promastigotes of
Leishmania donovani using amphotericin B as positive control.
Materials and methods: The anti-leishmanial activity of E. ivorense extract was evaluated in
vitro against the promastigote forms of Leishmania Donovani using a direct counting assay
based on growth inhibition. Different crude extracts from ethyl acetate, pet-ether, and methanol as well
as pure isolated compounds of E. ivorense: Erythroivorensin, Eriodictyol and Betulinic acid were screened. To know the possible components of the active methanolic extract, attempt was made to
elucidate the extract using ultra-performance liquid chromatography quadrupole time of flight
mass spectrometry (UHPLC-QTOF-MS/MS).
Results: This afforded a weak pet-ether fraction, a moderately active ethyl acetate fraction and a
significantly active methanol fraction (IC50 = 2.97 μg/mL) compared to Amphotericin B (IC50 =
2.40±0.67μg/mL). The novel diterpene erythroivorensin, betulinic acid and the flavanone
Eriodictyol, from the ethyl acetate fraction, showed weak activity. UPLC-QTOF-MS/MS was used
to identify the cassaine diterpenoids from the active methanol fraction. Here, 10 compounds of this
type were putatively identified from the ethanol crude extract.
Conclusion: The fragmentation mechanism of these metabolites is also proposed and are expected
to serve as reference template for identification of these and related compounds in future. The
presence of these compounds is an indication that they are an inherited and evolutionary
component of plants belonging to the Erythrophleum genus. Our results further present another
dimension where these compounds and their relative abundances can be used as chemo-
taxonomical bio-markers of the genus. The present study also successfully demonstrated/re-
affirmed the use of UPLC-QTOF-MS/MS as a robust technique for the characterization of natural
products.
