Differentiating Dyes: A Spectroscopic Investigation into the Composition of Scarlet Bloodroot (Haemodorum coccineum R.Br.) Rhizome

Abstract

Haemodorum coccineum, commonly known as scarlet bloodroot, is a plant native to New Guinea and the northern most parts of Australia. The highly coloured H. coccineum is used by communities in Larrakia country for dyeing garments and occasionally to treat snake bites. Previous studies into H. coccineum have focused on its taxonomic classification, with this being the first evaluation of the chemical composition of the plant. Haemodoraceae plants are reported to contain phenylphenalenones (PhPs), which are highly conjugated polycyclic oxygenated aromatic hydrocarbons. We report the characterisation of 20 compounds extracted from the rhizome of H. coccineum: four sugars and 16 compounds belonging to the PhP family. The compounds include five aglycones and seven glycosylated compounds, of which four contain malonate esters in their structures. Characterisation of these compounds was achieved through 1D and 2D NMR, MS analysis and comparison to the known phytochemistry of other species from the Haemodorum genus. Preliminary anti-microbial activity of the crude extract shows significant inhibition of the growth of both gram-positive and gram-negative bacteria, but no activity against Candida albicans.

Keywords: Haemodorum coccineum; natural products; phenylphenalenones; traditional medicine; xanthanes.

Figure 1

Compound isolation flowchart. The numbers in black represent the percentage of methanol (aq) used to elute that SPE fraction. Compound numbers in orange indicate compounds characterised from sample mixtures. Compounds in green were characterised as single compounds.

Figure 2

Structures of phenylphenalenone, benzo[de]isochromenone, allophanyl, malonate and compounds 4, 4′, 5, 5′, 19 and 19′. (Please refer to Supplementary Information for clarification on naming and numbering of structures).

Figure 3

Structures of all compounds isolated from the rhizome of H. coccineum.