Molluscicidal Activity of Butanol Fraction of Meryta denhamii Flowers Against Lymnaea natalensis and Biomphalaria alexandrina

The molluscicidal activity of methyl extract of Meryta denhamii fruits and flowers against Lymnaea natalensis and Biomphalaria alexandrina snails were studied. The two extracts exhibited similar effects on Biomphalaria snails, LD50 was 85 mg/L for both flowers and fruits. While flowers extract was more active against Lymnaea snails; LD50 were 72.4 & 100 mg/L for flowers and fruits, respectively. The molluscicidal activity of flower fractions (Butanol, chloroform, petroleum ether and ethyl acetate) was screened. Butanol fraction was the most potent one against the two snail species, LD50 were 26.4 & 39.8 mg/L and LD90 were 70.8 & 79.4 mg/L for L. natalensis and B. alexandrina, respectively. While ethyl acetate fraction was inactive. Biochemical assays showed elevation in the glucose concentration and protein content in both haemolymph and soft tissues of treated snails. Although, glycogen content in soft tissues increased in treated L. natalensis it was decreased in treated B. alexandrina. Three monodesmosidic saponins were isolated from butanol fraction oiMeryta denhamii flowers. Their structures were established by spectroscopic methods (ʹHNMR and 13NMR) as oleonolic acid-3-0 -a- arabinopyranoside, oleonolic acid-3-O-[3-glucopyranoside and hedragenin-3-O-a-rhamnopyranoside In conclusion,flowers butanol fraction of M denhamii could be successfully used as a botanical molluscicide.