Main immunomodulatory constituents of Eastern Nigeria Mistletoe,Loranthus micranthus Linn

Objective:In our continued efforts to isolate the active immunomodulatory and antiviral constituents of Loranthus micranthus Linn parasitic on Kola acuminata,we set out to fractionate the crude aqueous methanol extract of the plant.The establishment of the most potent fraction(s) as well as the isolation of the pure active secondary metabolite responsible for the immune stimulatory and antiviral activities in Eastern Nigeria mistletoe has become very needful.This will enable us prove our assumption that this particular specie is different from the European version,Viscum album.Methods:Five solvents of varying polarity namely n-hexane,chloroform, ethylacetate,acetone and methanol were successively employed in the complete fractionation of the crude aqueous -methanol extract of Eastern Nigerian mistletoe,Loranthus micranthus Linn.,harvested from Kola acuminata in that order.The fractions were dried in-vacuo using a rotary evaporator maintained at a temperature of(40±5)℃.The different fractions were screened for immunomodulatory activity using a universal model:the cellular - mediated delayed type hypersensivity test in experimental mice.This was performed by administering two different dose levels:250 mg/kg and 500 mg/kg of each fraction against standard positive and negative control. Results:Results of the study established dose-dependent immunostimulatory(upregulatory) effects of the five fractions of the extract as the model used in the study with different percentage stimulations compared to controls.At the dose levels of 500 mg/kg and 250 mg/kg body weight,the percentage stimulation observed were as following:chloroform fraction 311.11%and 122.22%,ethyl acetate fraction 193.38%and 95. 56%,n-hexane 155.56%and 3.50%,acetone fraction 95.56%and 51.11%and methanol fraction 68. 89%and 24.44%respectively.Levamisole,a known potent immunostimulant,afforded a stimulation of 68. 89%at a dose of 2.5 mg/kg.Conclusion:The study showed that the order of immunomodulatory potency is chloroform fraction > ethylacetate fraction > hexane fraction > acetone fraction > methanol fraction.Bioassayguided fractionation and purification of the active extracts led to the isolation of pure compounds phytochemically characterized as sterols and flavonoids.This work indicates that the main constituents of our local mistletoe responsible for immunostimulation are the flavonoids,terpenoids and or steroids.Glycosides,carbohydrates, tannins and alkaoids appear to augment the measured activities.

Immunomodulation and Nigerian mistletoe immunomodulatory activities of n-hexane and methanol extracts of Loranthus micranthus Linn,parasitic on Parkia biglobosa.

Loranthus micranthus is the species of mistletoe peculiar to the eastern province of Nigeria.It has been shown to possess anti-diabetic,anumotility,antimicrobial and antihypertensive activities which are host-tree dependent. The antimicrobial activity was found to vary with the season during which the plant was harvested.We are of the opinion that this species should possess immunomodulating potentials as have been reported for the European species,Viscum album.In our efforts to establish the bio-activities and active principles in our local mistletoe, the immunomodulatory activity of n-hexane and methanol extracts from Loranthus micranthus parasitic on Persea americana was assessed at three dose levels ranging from 100 to 400 mg/kg body weight using delayed type hypersensitivity reaction(DTHR) and cyclophosphamide-induced myelosuppression models in mice.This was compared with responses from a standard immunostimulatory drug,levamisole.Preliminary phytochemical analysis of the plant showed the presence of tannins,flavonoids,alkaloids,terpenoids,carbohydrates and saponins.Regression analysis indicated a dose-dependent response relationship in the parameters measured with over 170%increase for both extracts at the highest dose level.The one way ANOVA test showed significant variation in the parameters between the controls and the different dose levels.However,at 95%confidence level,(P【0.05),there was no statistically significant difference between the two extracts, an indication that the active immunomodulant(s) could be both in the polar and non-polar crude extract.In conclusion,the present results have established some immune stimulating actions of the Eastern Nigeria mistletoe, Loranthus micranthus thus indicating that this variant of the semi parasitic plant holds a strong promise as an immunostimulatory candidate.There is therefore,a basis for further detailed investigation on the fractions and specific constituents.Thus,these extracts from Loranthus micranthus possess pronounced immune stimulating action comparable to Levamisole in mouse-based models.