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Gonioridleylactam (1), a new compound, is a unique dimeric aristolactam isolated from the EtOAc extract of the twigs of Goniothalamus ridleyi King. The structure of gonioridleylactam (1) consists of two different aristolactams linked together with two methylenedioxy bridges at C–3/C–3′ and C–4/C–4′, generating a ten-membered ring of [1,3,6,8]tetraoxecine. A new natural product, gonioridleyindole (3-hydroxymethyl-1-methyl-1H-benz[f]indole-4,9-dione, 2), together with eight known compounds (3–10) were also isolated from this plant. Their structures were extensively characterized by spectroscopic methods and comparisons were made with the literature. Compounds 1–4, 7, and 9 were evaluated for their α-glucosidase inhibitory activity. Of these, 3,5-demethoxypiperolide (7) displayed the highest α-glucosidase inhibitory activity, with an IC50 value of 1.25 µM.

Two new oxoprotoberberine alkaloids, amocurine A and B (1 and 2), a new aporphine alkaloid, amocurine C (3), along with three known compounds (46) were isolated from the roots of Amoora cucullata. Their structures were determined by analysis of spectroscopic data. The isolated compounds were evaluated for their antiproliferative activity against three human cancer cell lines (KB, oral cavity; MCF-7, breast cancer; and NCI-H187, small cell lung cancer). Compounds 3 showed the most potent activities against KB and MCF-7 cell lines with IC50 values 3.5 and 4.2 M, respectively.

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