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Technical report | Chemical Investigations of the Castor Bean Plant Ricinus communis

Abstract 

In 2009 a National Security Science and Technology grant was awarded to the Human Protection and Performance Division for the investigation of several forensic aspects of the castor bean plant Ricinus communis. A major focus of this grant was to understand the chemical composition of the seeds, and to ascertain if these differences could be used for provenance classification. This technical report will discuss progress made during these investigations.

Executive Summary

Ricinus communis (commonly known as the castor bean plant) is an introduced species that now grows wild in Australia. There are approximately 250 cultivars known. In addition to castor oil, the seeds also produce the toxic lectin ricin. Ricin is declared by the Chemical Weapons Convention as a Schedule 1 agent. These are chemicals that are highly toxic and have no legitimate uses. Consequently, ricin is of interest to state and national law enforcement agencies. Given the above information, strategies that are able to determine cultivar and provenance of an extract from R. communis seeds are of interest to these agencies.In 2009, Human Protection and Performance Division (HPPD) was awarded a Prime Minister and Cabinet (PM&C) National Security Science and Technology (NSST) grant to study R. communis and establish forensic methods for dealing with potential ricin white powder incidents. A particular focus of this work was to investigate if there are any chemical signatures in the seed extracts that would allow for provenance classification. In particular, the following aims were proposed:

  • to gain an understanding of the different cultivars present throughout Australia via an extensive national collection program;
  • to establish analytical methods to provenance extracts of R. communis through the understanding of both the inorganic [Inductively Coupled Plasma Mass Spectrometry (ICPMS)] and organic [via Liquid Chromatography Mass Spectrometry (LCMS) and proton Nuclear  Magnetic Resonance (1H NMR) spectroscopy] chemical fingerprints; and
  • to interrogate the collected data using multivariate statistical analysis for the identification of inorganic and organic markers of provenance.  

During the collection program, a great morphological diversity in specimens of R. communis was observed in Victoria, New South Wales and South Australia. In particular, many specimens were sighted and collected that had variations in leaf size, shape and colour, stem and inflorescence colour, as well as seed pod colour, seed size and seed shape. Conversely, it appeared from our field observations that Queensland and Western Australia have virtually no diversity in their R. communis populations. It was also noted that during these collection efforts no specimens of R. communis were sighted in Darwin, Northern Territory.

The chemical analysis of the extracts of R. communis yielded some interesting results. Firstly it was found that analysing the 2% acidic R. communis extracts was not readily applicable to IRMS and ICPMS techniques due to interference from residual acetic acid. However, Laser Ablation-Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS) of the whole seed allowed for provenance determination. The 2% acidic R. communis extracts were able to be analysed by LCMS with no subsequent loss in sensitivity. However, only cultivar of R. communis extracts analysed was determined using this method.

1H NMR is a non-destructive, non-selective analysis which is able to detect every compound in a mixture containing protons. In the field of metabolomics, it has been identified as a prudent starting point for any metabolomic investigation. NMR also has the advantage of being an inherently quantitative technique. An NMR spectrum therefore allows for an estimation of the relative amounts of compounds present in a mixture. NMR also allows for compound structural information to be ascertained to at least a functional group level. When applied in conjunction with LCMS, a greater understanding of the chemical composition of the mixture is achieved. This combination of 1H NMR and LCMS, when applied to the analysis of the 2% acidic R. communis extracts, allowed for cultivar and provenance determinations to be made with a high degree of certainty.This technical report documents the progress made against the chemistry milestones contained in the NSST grant. This report will inform the clients of this work program (AFP, Chemical Warfare Agent Laboratory Network (CWALN) members, other national security clients) of some of the capability that HPPD has for handling these extracts, and the type of information that is able to be extracted from them.

Key information

Author

Simon P. B. Ovenden, Christina K. Bagas, David J. Bourne, Eloise J. Pigott and Warren Roberts

Publication number

DSTO-TR-2786

Publication type

Technical report

Publish Date

December 2012

Classification

Unclassified - public release

Keywords

Chemical Analysis; Chromatography; Research; Spectrometry; Spectroscopy

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