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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.

The first phytochemical investigation of the twig extracts of Maclura fruticosa led to the isolation and identification of a new xanthone, maclurafruticosone (1), together with 14 known compounds (2-15). All compounds were elucidated using spectroscopic methods as well as through comparisons made with data reported in the literature. Some isolated compounds were evaluated for their antioxidant, α-glucosidase inhibitory and cytotoxic activities. Compound 4, 6 and 7 showed significant antioxidant activity against DPPH radicals with IC 50 values ranging from 7.45-16.12 µM. Compound 4 also exhibited potent activity against ABTS + scavenging activity with an IC 50 value of 0.55 ± 0.01 µM which was better than positive control (ascorbic acid, IC 50 2.35 ± 0.17 µM). Compound 12 showed significant α-glucosidase inhibitory activity with an IC 50 value of 0.02 ± 0.37 mM. Compounds 5, 6 and 12 showed weak cytotoxic activities against a colon cancer cell line with IC 50 values ranging from 22.35-47.62 µM.