Nematicidal and quantitative phytochemical analysis of Allamanda cathartica chromatographic fractions

Abstract

The environmental pollution of synthetic nematicides is enormous, due to their residual effects and non-degradability. This study investigated the possibility of a green alternative to replace the pollution problems of synthetic nematicides. The activity of plant secondary metabolites against plant parasitic nematodes was tested in-vitro using chromatographic isolates from the stem and leaves of Allamanda cathartica. Four isolates from the extracted plant materials were tested at various concentrations (0 mg/mL, 10 mg/mL, 20 mg/mL and 30 mg/mL) against Meloidogyne incognita juveniles and eggs via inhibition of egg hatch and larval mortality tests. The result showed that egg hatch was totally inhibited among all the isolates, few hatches were recorded in the 10mg/ml (0.26%) concentration while the control (0mg/ml) had 48.39% hatch on day 5. Isolate four showed strong nematicidal effect, with percentage mortality of 16.87 % after one hour of exposure comparable with the synthetic nematicide (carbofuran). A hundred percent juvenile mortality was achieved in all the isolates on day 2. However, the leaves of A. cathartica were more effective than the stem. Phytochemical screening revealed that the quantities of secondary metabolites were more in the leaves of A. carthatica than in the stems. Infra-red spectroscopic data of three of the isolates revealed the presence of alkanes (2930, 2923 and 1460 cm-1) aldehydes (2855, 2851 and 1733cm-1) and phenols at (3650, 1115cm-1). Aliphatic amines (3200, 1460 and 1600 cm- 1) and non-cyclic ethers (1310, 1300, 1240 and1000 cm-1) are present in isolate four. This study showed that the leaves of A. cathartica could serve as a bio-nematicide to reduce environmental pollution.