Although pycnantha is perhaps the 'correct' identity for "golden wattle", common names are unreliable, and other Acacias such as longifolia are also commonly called golden wattle. You could theoretically call most of them that, because of their golden yellow flowers, so what I'm saying is, your post doesn't tell what species you're actually working with.
AND, Hegnauer did not report what was claimed above. Heganuer's work was purely literature reviews and summaries, often incomplete, and simply referred to White's earlier finding of less than 0.01% alkaloids (of unidentified type) in leaf.