DISCOVERY OF COUMARIN AS THE PREDOMINANT ALLELOCHEMICAL IN GLIRICIDIA SEPIUM

A crude methanol extract of Gliricidia sepium (Fabaceae) leaves inhibited the growth of lettuce (Lactuca sativa) radicles. To isolate and characterise the inhibitory compound, the extract was fractionated based on the total activity on lettuce radicle elongation. The n-hexane-soluble fraction obtained by liquid-liquid partitioning of the crude methanol extract showed strong inhibitory activity. A compound corresponding to the major peak in high performance liquid chromatography was isolated from the fraction and identified as coumarin. The EC50 of coumarin for the growth of lettuce radicles was 23.3 μmol L-1. On the basis of the coumarin content (11.6 mmol kg-1 fresh weight) and the total activity of coumarin (500) in G. sepium, we concluded that the inhibitory activity of G. sepium was primarily due to coumarin. Ekstrak metanol mentah bagi daun Gliricidia sepium (Fabaceae) merencat pertumbuhan radikel salad (Lactuca sativa). Untuk mengasing dan mencirikan sebatian perencat ini, ekstrak menjalani pemeringkatan berdasarkan aktiviti pemanjangan radikel salad. Pecahan yang larut dalam n-heksana yang diperoleh daripada pemeringkatan cecair-cecair ekstrak metanol mentah menunjukkan aktiviti perencatan yang kuat. Sebatian yang sepadan dengan puncak utama dalam kromatografi cecair prestasi tinggi diasingkan daripada pecahan dan dikenal pasti sebagai kumarin. Nilai EC50 kumarin bagi pertumbuhan radikel salad ialah 23.3 μmol L-1. Berdasarkan kandungan kumarin (11.6 mmol kg-1 berat basah) dan aktiviti kumarin (500) dalam G. sepium, kami membuat keputusan yang aktiviti perencatan G. sepium disebabkan terutamanya oleh kumarin.