17 June 2019

Echimidine - A weed by any other name – Paterson’s Curse or Salvation Jane?

Natural toxin

Echium plantagineum is a plant that has caused much debate within Australia for over a 100 years

“But Patterson's flower displayed a distressing ignorance of the value of self-restraint (if inanimate nature can be so charged), and soon overran the limits of the pioneer's garden”
* Quote from the Albury Banner and Wodonga Express, 1905, issue 39 [1].

Figure 1: Photos showing Paterson Curse Morphology and Invasive Spread [2]

Echium plantagineum, commonly known as Patterson’s Curse, is a noxious plant that has taken hold in Australian pastureland. It is native to the Iberian Peninsula, in the eastern regions of Spain and Portugal and is now found over much of  Southern Australia, the Mediterranean, USA and South Africa [3]. The plant was introduced to Australia in the 1880’s, supposedly by the Paterson’s of Cumberoona NSW, as an ornamental plant [2]. As early as 1894 there were warning reports that the plant had become invasive, as it spread like wildfire and outcompeted other plant pasture species. It was considered useless as fodder, non-poisonous and medicinally used for purifying blood and snakebites. A Bill was introduced in 1901, that encouraged farmers to pull up the plants before germination and burn them, to stop the spread [1]. However, contrasting opinions emerged as some farmers found that their livestock would willingly feed upon the plant in drought conditions, when other pasture species had died, leading to the name Salvation Jane.

Echium plantagineum belongs to the borage family and is a bristly annual plant. It grows from 20-200cm tall, with large base leaves, narrow stem leaves and small rosette leaves. The flowers are 2-3cm long, usually purple and shaped like a curved trumpet (Figure 1) [4]. Today it covers millions of hectares of land from Western Australia to New South Wales and is responsible for an estimated loss of $250 million to the agricultural industry, through lost productivity in pastures, control costs and wool contamination [2, 3].

Echimidine is a pyrrolizidine alkaloid produced in the leaves, stems, flowers and seeds. The toxin has limited effect on ruminant livestock species, only experiencing intoxication after long exposure periods or large doses [5]. A study exposed merino wethers to pelleted diets containing 80% Echium plantagineum for four, 12 week periods and found only marginally reduced liver function [6]. It is not palatable to horses, hindgut fermenters, with intoxication occurring with at a small dose [2, 7]. Echimidine is metabolised by hepatic microsomal enzymes into pyrrole derivatives. These derivatives are hepatotoxic and inhibit cellular replication, protein synthesis and cause megalocytes in the liver [5]. Symptoms include weakness, weight loss, lethargy, yawning, depression and photosensitivity (unpigmented skin). Currently it is advised that it should not be used for fodder for any livestock for the above reasons and should be actively managed through good biosecurity practises; biological and chemical [2]. 

Figure 2: Structural Formula of (a) Echimidine [8] and (b) Shikonin [9]. Click figure for 3D image of Echimidine.

A bonus secondary metabolite produced, are bioactive naphthoquinones (NQ’s) formed in the roots. Recent studies of the rhizosphere have demonstrated that red-coloured NQ’s are produced in the periderm of the primary, secondary roots and seedling root hairs, exuding copious quantities [3]. The production and accumulation suggest that they play an important role in plant defence, interference and its invasion success. Interestingly, invasive plants have a 2-fold higher concentration of NQ’s, than plants growing in native regions, suggesting that the invasive plants are more bioactive. In medical literature NQ’s are referred to as shikonins, and are researched for their antioxidant, anthelminthic, purgative and wound healing properties [3].

In conclusion, Echium plantagineum is a plant that has caused much debate within Australia for over a 100 years, historically a salvation for some and a lingering curse for most. At the very least, it is a curse that is easy on the eye.

SMILES and CAS Number:

Echimidine: 520-68-3 [C@@H]12N(CC=C1COC(=O)[C@@](C(C)(O)C)(O)[C@H](C)O)CC[C@H]2OC(=O)/C(=C\C)/C

Shikonin: 517-89-5

Further Reading:

  1. Macinnis P. 2015. A short history of Paterson's Curse [Cited 13/06 2019]. Available from: https://oldblockwriter.blogspot.com/2015/07/a-short-history-of-patersons-curse.html
  2. Development DoPIaR. 2017. Paterson's Curse: what you should know. [Cited 13/06 2019]. Available from: https://www.agric.wa.gov.au/biological-control/patersons-curse-what-you-should-know
  3. Zhu X, Skoneczny D, Weidenhamer JD, Mwendwa JM, Weston PA, Gurr GM, Callaway RM, Weston LA. 2016. Identification and localization of bioactive naphthoquinones in the roots and rhizosphere of Paterson’s curse (Echium plantagineum), a noxious invader. Journal of Experimental Botany 67:3777-3788. DOI: 10.1093/jxb/erw182.
  4. Rymer L. 2009. What is a Weed, or ‘Salvation Jane’ May be ‘Paterson's Curse’. Environmental Conservation 7:269-270. DOI: 10.1017/S0376892900007979.
  5. 2012. Hepatopathy, Chronic Megalocytic. In Wilson DA, ed, Clinical Veterinary Advisor. W.B. Saunders, Saint Louis, pp 262-263.
  6. Culvenor CCJ, Jago MV, Peterson JE, Smith LW, Payne AL, Campbell DG, Edgar J, Frahn JL. 1984. Toxicity of Echium plantagineum (Paterson's Curse). 1. Marginal toxic effects in Merino wethers from long-term feeding.
  7. 2014. Chapter 2 - Conditions of the liver, spleen and pancreas. In McAuliffe SB, ed, Knottenbelt and Pascoe's Color Atlas of Diseases and Disorders of the Horse (Second Edition). W.B. Saunders, pp 84-104.
  8. KNApSAck. 2007. Echimidine. [Cited  13/06 2019]. Available from: http://www.knapsackfamily.com/knapsack_jsp/information.jsp?mode=r&word=C00002085&key=2
  9. KNApSAck 2007. Shikonin. [Cited  13/06 2019]. Available from: http://www.knapsackfamily.com/knapsack_jsp/information.jsp?word=C00000859