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DOI: 10.1055/s-0030-1264259
Potent immunostimulatory and antioxidant activities of three – (–) catechin-O-rhamnosides from Eastern Nigeria mistletoe
Mistletoes of Eastern Nigeria origin, Loranthus micranthus, harvested from our local Kola tree, Kola acuminata, was recently reported to be the most potent specie in terms of antidiabetic [1], immunostimulatory activities [2, 3]. Furthermore, an unpublished data showed that this mistletoe possesses pronounced in vitro antioxidant activities when compared to ascorbic acid. In bid to study the chemical composition of this specie of mistletoe, elaborate bioassay-guided fractionation and purification led to the isolation of three rhamnoside based glycosides namely; – (–) catechin-7-O-rhamnoside, – (–) catechin-3-O- rhamnoside and a 4′-methoxy derivative of the 7-O-rhamnoside. Characterization and unequivocal structural assignments of these compounds were achieved by a combination of UV/visible, IR, NMR, MS, COSY experiments including, HMBC and HQSC. These flavonoid glycosides exhibited very potent immunostimulatory activity on cell line (C57Bl/6 splenocytes) against Lipopolysaccharide and Concanavalin A standards. Their measured antioxidant potentials in terms of effective concentration at 50% reduction in diphenyl picrazyl hydrazyl radical activity (EC50) were remarkably high (< or=to 55. 42±0.99mg/ml) when compared to ascorbic acid (17.6±1.78mg/ml) We are herein reporting, for the first time, the presence and some biological activities of three catechin-based rhamnoside glycoside in mistletoe harvested from Eastern Nigeria
Acknowledgements: The authors specially acknowledge Mr. Alfred Ozioko of BDCP, Nsukka for collection and identification of the plant material.
References: 1. Osadebe PO, et al (2004)J Ethnopharmacology, 95: 133–138.
2. Osadebe PO, et al (2009)J Ethnopharmacology, 125:287–293.
3. Osadebe et al (2008), RPMP Vol 27: 473–485.