Academics/Researcher, University of Port Harcourt, Nigeria
A novel antiplasmodial depside from a Nigerian foliose lichen
Major setbacks to the eradication of malaria globally have been resistance to the conventional drugs. This study reported the isolation, and structural elucidation of a novel anti-plasmodial depside (antiplasmodial IC50 =25µg/mL; mammalian cell toxicity (IC50 >100 µg/mL) from the Nigerian foliose lichen Dirinaria picta epiphytic on the oil palm tree. The structure of the purified depside was elucidated using spectroscopic techniques. Anti-plasmodial activity was done in vitro using the PLDH assay method with chloroquine as reference drug for comparison. Mammalian cell toxicity assay was done in vitro against HeLa cells line with emetine as reference drug for comparison. This study revealed the potential of Nigerian lichens in the management of malaria infection.
Abstract: Mimosa pigra L. (Fabaceae-Mimosoideae) is a large shrub native to tropical America and economically important as a medicinal plant; it is also an invasive plant and a noxious weed. M. pigra leaves were air-dried, pulverised and extracted with 96 % ethanol. The ethanol extract (MPEE) was partitioned with diethyl ether (DEE) and ethyl acetate (EA) in succession to yield DEE fraction (DEEF), EA fraction (EAF) and EA insoluble fraction (EAIF). Sephadex LH-20 gel filtration chromatography (GFC) of the EAF and semi-preparative HPLC purification of the GFC sub-fractions afforded two new acylated flavonol glycosides [myricetin (2”-O-galloyl)-3-O-α-L rhamnopyranoside, I; and quercetin (2”-O-galloyl)-3-O-α-L-rhamnopyranoside, II] in M. pigra. Alongside three other flavonol glycosides (myricetin 3-O-α-L-rhamnopyranoside, III; quercetin 3-O-α-L-rhamnopyranoside, IV; and quercetin 3-O-α-L-arabinopyranoside, V). The structures of compounds I–V were assigned by ultraviolet/visible (UV) spectroscopy, 1D and 2D 1H and 13C NMR spectroscopy and liquid chromatography-electrospray-mass spectrometry (LC-ESI-MS). Myricetin, quercetin and their glycoside derivatives are strong antioxidants; and elicit cytotoxic effect on human cancer cell lines among other pharmacological activities. The isolation of acylated flavonoids in M. pigra provided an important insight on the evolutionary trend of the medicinal plant. While the dominance of flavonols, may account for the various ethnomedicinal uses of the herb and the mechanism and mode of its confirmed pharmacological actions.
Pub.: 20 Aug '16, Pinned: 25 Jun '17
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