Quantitative multi-tissue profiling of tryptamines, phenethylamines, and β-carbolines across 53 species of Australian Acacia

The genus Acacia , comprising approximately 1000 native Australian species, represents a major contributor to the biodiversity of the continent. Some species of Acacia are known to contain bioactive alkaloids, including the popular psychedelic N,N-dimethyltryptamine (DMT). However, systematic phytochemical characterisation across different species of Acacia and tissue types remains limited. Here we used a validated LC–MS/MS method to quantify various tryptamines, phenethylamines, and β-carbolines in 150 tissue samples from 53 species of Acacia , primarily obtained from the Australian Botanical Garden (Mount Annan, New South Wales). Ten analytes were quantified: hordenine, phenethylamine, tryptamine, N-methyltryptamine, DMT, DMT-N-oxide, harmalol, 2-methyl-1,2,3,4-tetrahydro-β-carboline (2-MTHBC), harmol, and harmane. Phenethylamine was the most prevalent analyte (quantified in 93 samples from 41 species) and a major determinant of phytochemical variation. Hordenine (84 samples from 39 species), and tryptamine (84 samples from 35 species) were also frequently quantified. By contrast, DMT and β-carbolines were detected less frequently with high species-specificity. Flowers often contained the highest concentrations of analytes followed by leaves and stems. DMT was quantified at high concentrations in the flowers and phyllodes of Acacia courtii , an endangered species subject to illicit harvesting. Acacia complanata also displayed a unique profile with relatively high tryptamine and β-carboline concentrations in flowers and leaves. Multivariate analysis indicated that species identity, rather than tissue type, was the primary driver of phytochemical diversity. This study represents the first quantitative, multi-tissue, survey of alkaloids in diverse examples of Australian Acacia . The high concentrations of analytes in the flowers of select species is notable, and the destructive bark harvesting of threatened species to obtain psychedelic substances appears unnecessary given the enriched alkaloid content in flowers and leaves.