Australine is a pyrrolizidine alkaloid originally isolated fromC. australethat has enzyme inhibitory activities.^1,2,3It is an inhibitor of glucoamylase (IC₅₀= 5.8 µM) that also inhibits glucosidase I, sucrase, maltase, andA. nigerα-glucosidase (IC₅₀s = 20, 28, 35, and 28 µM, respectively).^2,3Australine is selective for these enzymes over glucosidase II, α- and β-mannosidase, and α- and β-galactosidase up to 500 µM, β-glucosidase, with only 5% inhibition at 66 µM, as well as isomaltase and trehalase (IC₅₀= 97 and 160 µM, respectively). Australine (500 µg/ml) inhibits glycoprotein processing of viral glycoproteins in influenza virus-infected MDCK cells and induces the accumulation of glycoproteins.²

1.Molyneux, R.J., Benson, M., Wong, R.Y., et al.Australine, a novel pyrrolizidine alkaloid glucosidase inhibitor from Castanospermum australJ. Nat. Prod.51(6)1198-1206(1988) 2.Tropea, J.E., Molyneux, R.J., Kaushal, G.P., et al.Australine, a pyrrolizidine alkaloid that inhibits amyloglucosidase and glycoprotein processingBiochemistry28(5)2027-2034(1989) 3.Kato, A., Kano, E., Adachi, I., et al.Australine and related alkaloids: easy structural confirmation by 13C NMR spectral data and biological activitiesTetrahedron Asymmetry14(3)325-331(2003)