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DOI: 10.1055/s-0030-1264427
Immunomodulatory and antioxidant constituents of Eastern Nigeria mistletoe, Loranthus micranthus Linn. (Loranthaceae) parasitic on Cola acuminata Schott et Endl.
Our recent reported data established mistletoe harvested from Cola acuminata Schott et Endl. as the most potent in terms of immunostimulation [1, 2]. Further bioassay-guided fractionation of the crude extract showed potency in the order of chloroform fraction >> ethylacetate fraction > n-hexane fraction [3]. Our continued efforts to isolate and characterize these active constituents led to the isolation of nine major compounds, epimeric β-carotenoids and eight lipophilic fractions. Two notable steroids, 5α-16, 16-dimethyl-androstan-17-one and 6β-hydroxy-17-oxo-4, 5-secoandrostan-4-oic acid were identified in the lipophilic fractions. A novel sesquiterpene-like compound; 2, 3-dimethoxy-benzo [a, b] cyclopentenyl-31, 31, 51-trimethyl pyran-4-carboxylic acid and an alkaloid, CFO were isolated from the chloroform fraction. Stigmast-7, 20 (21)-diene-3β-hydroxy-6-one, 3β-Hydroxy- stigmast- 23-ene (Stigmast-23-ene-3β-ol), 21β-hydroxy- 5, 9(10), 24-triene-21-nor-dammaren-3-one, lupeol and other steroids, HF4, HF6, HF7 were isolated from the n-hexane fraction while dibutyl phthalate and a flavonoidal EA2 were confirmed in the ethylacetate fraction. All isolated compounds were subjected to cell proliferation studies using cell line (C57Bl/6 splenocytes) and flow cytometry techniques against Lipopolysaccharide and Concanavalin A standards. The results showed that of all the major compounds isolated; only CFO, EA2 and HF7 exhibited immunostimulatory activity. Specifically, EA2 and CFO were the most potent with activity index of 91.49±0.22% and 69.84±0.19% respectively compared to 34.01±0.32% recorded for the two standards. The antioxidant potentials of these compounds showed that EA2 was most potent with an effective concentration (EC50) value of 55.42±0.99mg/ml against ascorbic acid value of 17.6±1.78mg/ml.
Acknowledgements: The authors acknowledge Mr. A. Ozioko of BDCP, Nsukka, Enugu State Nigeria for providing the plant material.
References: 1. Osadebe PO, et al (2009)J Ethnopharmacol., 125:287–293.
2. Osadebe et al (2008), RPRM Vol 27: 473–485.
3. Omeje EO et al (2009) Asian Pacific J.Tropical Med., 2(4): 11–18.