Abstract
The purpose of this study is to extract, isolate and elucidate the structure of alkaloid constituents from barks of Alseodaphne pendulifolia Gamb. (Lauraceae) and to determine the biological activities (antiplasmodial, cytotoxicity, antibacterial and antioxidant) against the isolated alkaloids. The samples were collected from Sg. Temau Forest Reserve, Kuala Lipis, Pahang and Sg. Tekam Forest Reserve, Jerantut, Pahang, Malaysia. The isolation and purification of alkaloids were done using various chromatographic techniques including chromatotron, column, preparative thin-layer and thin-layer chromatography. The structure elucidations of the isolated alkaloids were established by NMR spectral data using various 1D-NMR (¹H, ¹³C, and DEPT) and 2D-NMR (COSY, HMQC/HSQC, HMBC, H2BC, HSQC-TOCSY and NOESY) techniques, aided via UV, IR, MS data and also by comparison with data from the literature.Further isolation process of the plants yielded four types of isoquinoline alkaloids: aporphine, aporphine N-oxide, oxoaporphine and bisbenzylisoquinoline. A new aporphine N-oxide; norisocorydine N-oxide 166 with four aporphines; corydine 124, N-methylhernagine 169, oxohernagine 122 and hernagine 123, were successfully isolated from samples collected from Sg. Temau Reserve Forest. Samples from Sg. Tekam Reserve Forest yielded four aporphines: corydine 124, N-methylhernagine 169, hernagine 123 and hernovine 170; an oxoaporphine, oxohernagine 122, was isolated together with a bisbenzylisoquinoline, costaricine 126.Antiplasmodial assay against Plasmodium falciparum on the bark crude extract exhibited active antiplasmodial activity with IC₅₀ value 0.804 μg/mL, while the isolated pure compounds corydine 124, oxohernagine 122 and hernagine 123 showed active antimalarial activity with IC₅₀ values at 1.184, 2.189 and 3.494 μM, respectively. The newly discovered compound, norisocorydine N-oxide showed a moderate effect on cytotoxic assay using leukaemia cell lines HL-60 with IC₅₀ value 11 μg/mL. Norisocorydine N-oxide 166, corydine 124, N-methylhernagine 169, oxohernagine 122 and hernagine 123 exhibited very weak activity with IC₅₀ values more than 500 μg/mL against free radical scavenging effect of antioxidant DPPH assay and were not active against gram-positive bacteria Bacillus subtilis (B145).This is the first report for phytochemical and biological activity studies from barks of Alseodaphne pendulifolia Gamb., which has potential in the determination of other various chemical constituents for new drug discovery