Bioassay-directed isolation of oxytocic principles from the methanol extract of Monechma ciliatum

The hot methanol extract (HME) of Monechma ciliatum which has been reported to have potent oxytocic activity was purified by fractionation in an attempt to isolate the oxytocic principle. Thin layer analysis indicated that the oxytocic fraction was very polar. A positive reaction with ninhydrin-spray suggested that it is an amino acid/protein. Repeated column chromatography (CC) on silica gel followed by sephadex LH-20 column, accompanied by bioassay of the fractions on the rat isolated uterus enabled partial isolation of the oxytocic principle (P3) to be achieved. Although the exact structure of P3 could not be identified from the present study, various spectral analyses suggest that it is a small peptide made up of tyrosine, leucine and a third component which is probably serine. It is interesting to note that the parent compound, oxytocin, is also a peptide with tyrosine and leucine in its structure.