Table 1.

Review of elicitor compounds tested in Echinacea to enhance secondary metabolite content.

Type	Elicitor	Concentration used	Variety	Effects	Reference
Abiotic	Titanium (IV) ascorbate	Foliar spray – 10 μM	PPA	Increased caftaric, chlorogenic acid in roots, and increased root mass	Kuzel et al. 2009
Biotic	Yeast extract elicitor	1mg/mL	PPA	Increased production of phenolics, including novel phenolics	Li and Barz 2006
Growth Regulator	Dimethyl amino hexanoate (with 0.3 mg/L IBA)	0.08 mg/L for petioles, 0.16 mg/L for leaves, 0.01 mg/L for roots	PPA	Enhanced shoot regeneration, increased plant growth and final biomass	Chen et al. 2013
	Gibberellic acid	0.025 μM	PPA	Thicker roots, increased overall biomass, increased levels of anthocyanins and cichoric acid	Abbasi et al. 2012
		150 μM	PPA	Increase in caftaric acid in early culture stage	Jones et al. 2009
	Indole-3-butyric acid (IBA)	1 mg/mL	PLL	Induces root regeneration, increases CAD content	Wu et al. 2012
		2 mg/L	ANG	Increased final weight of root cultures, increased total phenolics and flavanoids	Wu et al. 2006
		15 μM	PPA	increased levels of cichoric and caftaric acid, and detectable levels of echinacoside	Murch et al. 2006
Herbicide	Glyphosate treatment + l-tryptophan feeding	0.5 mM glyphosate, 0.5 mM l-tryptophan	PPA	Higher levels of CADs, phenols, and flavanoids	Mobin et al. 2015
	Palcobutrazole + Gibberellic acid	100 μM Palcobutrazol, 50 μM GA	PPA	Increased caftaric and cichoric acid in roots, slight drop in shoots	Jones et al. 2009
Stress Response Molecule	Acetylsalicylic acid	Foliar spray – 10 μM	PPA	Increased caftaric acid in tops	Kuzel et al. 2009
	Jasmonic acid	10–40 μM	PPA, ANG, PLL	Several fold increase in alkylamides, but decreased root growth	Romero et al. 2009
	Methyl Jasmonate	5 μM	PPA	Increased production of phenolics, including novel phenolics	Li and Barz 2006
	Methyl Jasmonate, Methyl salicylate	200 μM	ANG	Increase of of echinacoside and cichoric acid	Baque et al. 2012
		100 μM	ANG	Increased polyphenolics, flavanoids, and CADs in root culture	Cui et al. 2013
		Foliar spray – 10 μM	PPA	Increased caftaric acid in tops, cichoric and chlorogenic acid in roots, and mass of roots	Kuzel et al. 2009
	Salycilic acid	Foliar spray – 10 μM for tops, 1000 μM for roots	PPA	Increased cichoric and caftaric acid in tops, and cichoric acid, and mass in roots	Kuzel et al. 2009
	Sodium nitroprusside	100 μM	PPA	Increased phenolics, flavanoids, CADS, and antioxidant potential	Wu et al. 2007c

E. purpurea: PPA; E. angustifolia: ANG; E. pallida: PLL.