Antibacterial, insecticidal, and α-glucosidase inhibitory constituents of Cyclea racemosa Oliv.

Three undescribed isoquinolines, Cycleanoside A (1), (4-methoxybenzyl)-7-hydroxy-8-O-β-D-glucopyranosyl-1-phenoxyisoquinoline (2), and (4-hydroxy-3,5-dimethoxybenzyl)-7-hydroxy-1-benzoate-isoquinoline (3), alongside 21 known compounds, were purified from Cyclea racemosa Oliv. rhizomes (95% ethanol extract). The identification of their structures relied on HR-ESI-MS, NMR experiments, and CD spectroscopic data. Northalifoline (4), steponine (7), p-hydroxybenzaldehyde (11), p-hydroxyphenylacetic acid (12), cinnamic acid (14), and N-trans-feruloyltyramine (15) displayed strong α-glucosidase inhibition, with IC50 values measured between 50 ± 2 and 640 ± 12 μmol/L. Coclaurine (9) showed limited antibacterial potency, and the minimum inhibitory concentrations were determined as 25 μmol/L against Listeria monocytogenes and 51 μmol/L against Staphylococcus aureus, respectively. Cycasin (20) demonstrated potent insecticidal activity against the citrus psyllid at 1 g/L, achieving 56.99 ± 1.92% inhibition.