Stephania japonica, known in Australia as the Snake Vine is a common scrambler, often seen in sheltered areas near the sea.Greenish small flowers form on compound umbels, growing from the leaf axils in the warmer months. Inflorescences are 4 to 8 cm long.

A widespread vine seen as far south as Eden, New South Wales, north through Queensland. Also seen in Japan, India and many other areas of south-east Asia and the Pacific region. The original specimen was collected in Japan, hence the specific epithet “japonica”.

Two new hasubanan alkaloids, 16-oxoprometaphanine and 16-oxohasubanonine, were obtained from Stephaniajaponica as minor components. A hasubanan alkaloid stephasunoline was converted into metaphanine via prometaphanine.

Complete and unambiguous NMR analysis of several benzylisoquinoline alkaloids including (-)-ayuthianine (4) and the X-ray crystal structure of the methiodide derivative of (-)-amurine (9).