(Also known as: comfrey steeping; comfrey tea; Symphytum officinale extract)
Hazard alerts
The following Pesticide Hazard Tricolour (PHT) alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement. The alerts for Highly Hazardous Pesticides (HHPs) are based on applying the FAO/WHO (Type 1) and the PAN (Type II) criteria to PPDB data. Further details on the HHP indicators are given in the tables below. Neither the PHT nor the HHP hazard alerts take account of usage patterns or exposure, thus they do not represent risk.
PHT: Environmental fate
PHT: Ecotoxicity
PHT: Human health
Highly Hazardous Pesticide
Human health Moderate alert: Mammals acute toxicity: Moderate; Possible Carcinogen; Genotoxic
Warning: Significant data are missing
GENERAL INFORMATION
Description
A plant extract that is primarily used as a fertiliser and soil condition but which also has use as an insect repellent, plant elicitor and biostimulant.
Example pests/issues controlled
Aphids and other insects; Common fungi; Growth; Stress
Example applications
Fruit trees; Grass; Vegetables
Efficacy & activity
Very little literature or data is available to evaluate efficacy. Main action appears to be as a biofertiliser with small studies observing improved seed germination & growth with lettuce, tomato and peppers. Regarding stress resiliance data is largely observational and anecdotal.
As an insect repellent mode of action appears to be due to the strong odour. As a biostimulant the mechanism is unclear but appears to be associated with is activity as a biofertilizer and nutrient uptake promotion.
Insecticide behavioural & physiological effects
-
Substance source
Extracted from the comfrey plant (Symphytum officinale , L.)
Mixture composition
The exact composition of comfrey extract varies depending on factors such as the plant part utilised, growing conditions, extraction method, and specific variety. The key bioactive compounds are various phenolic / polyphenol compounds and in particular rosmarinic acid (approx. 0.2%). Allantoin, typically present at around 0.6-4.7% in roots but less in leaves, is also bioactive. Other components include caffeine acid and its derivatives as well as chlorogenic acid, tannins, triterpenes and phytosterols. The most notable group is pyrrolizidine alkaloids (PAs; around 0.013-1.2%), which are toxic and hepatotoxic and are potentially carcinogenic.
Example manufacturers & suppliers of products using this active now or historically
Greenprotech
Example products using this active
Formulation and application details
Usually supplied as a dispersible concentrate for spraying or seedling watering
Commercial production
Comfrey extract is commercially produced by harvesting the roots and leaves of Symphytum species which are rich in beneficial compounds like allantoin, rosmarinic acid, and mucilage. The plant material is first dried and ground, then subjected to solvent extraction using ethanol or water to draw out the active constituents. For higher purity and efficiency, some manufacturers use supercritical CO₂ extraction, which allows for selective isolation of bioactives without residual solvents. The resulting extract is filtered, concentrated, and standardised to ensure consistent levels of key compounds.
Impact on climate of production and use
-
ENVIRONMENTAL FATE
Property
Value
Source; quality score; and other information
Interpretation
Solubility - In water at 20 °C at pH 7 (mg l⁻¹)
-
-
-
Solubility - In organic solvents at 20 °C (mg l⁻¹)
-
-
-
Melting point (°C)
-
-
-
Boiling point (°C)
-
-
-
Degradation point (°C)
-
-
-
Flashpoint (°C)
-
-
-
Octanol-water partition coefficient at pH 7, 20 °C
P
-
-
-
Log P
-
-
-
Fat solubility of residues
Solubility
-
-
-
Data type
-
-
-
Density (g ml⁻¹)
-
-
-
Dissociation constant pKa) at 25 °C
-
-
-
-
Vapour pressure at 20 °C (mPa)
-
-
-
Henry's law constant at 25 °C (Pa m³ mol⁻¹)
-
-
-
Volatilisation as max % of applied dose lost
From plant surface
-
-
-
From soil surface
-
-
-
Maximum UV-vis absorption L mol⁻¹ cm⁻¹
-
-
-
Surface tension (mN m⁻¹)
-
-
-
Degradation
Property
Value
Source; quality score; and other information
Interpretation
General biodegradability
-
Soil degradation (days)
DT₅₀ (typical)
-
-
-
DT₅₀ (lab at 20 °C)
-
-
-
DT₅₀ (field)
-
-
-
DT₉₀ (lab at 20 °C)
-
-
-
DT₉₀ (field)
-
-
-
DT₅₀ modelling endpoint
-
-
-
Note
-
Soil mineralisation
Aerobic (at 20 °C)
-
-
-
Anaerobic (at 20 °C)
-
-
Dissipation rate RL₅₀ (days) on plant matrix
Value
-
-
-
Note
-
Dissipation rate RL₅₀ (days) on and in plant matrix
Value
-
-
-
Note
-
Aqueous photolysis DT₅₀ (days) at pH 7
Value
-
-
-
Note
-
Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7
Value
-
-
-
Note
-
Water-sediment DT₅₀ (days)
-
-
-
Water phase only DT₅₀ (days)
-
-
-
Sediment phase only DT₅₀ (days)
-
-
-
Air degradation
As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.
Decay in stored produce DT₅₀
-
Soil adsorption and mobility
Property
Value
Source; quality score; and other information
Interpretation
Linear
Kd (mL g⁻¹)
-
-
-
Koc (mL g⁻¹)
-
Notes and range
-
Freundlich
Kf (mL g⁻¹)
-
-
-
Kfoc (mL g⁻¹)
-
1/n
-
Notes and range
-
pH sensitivity
-
Known metabolites
None
ECOTOXICOLOGY
Terrestrial ecotoxicology
Property
Value
Source; quality score; and other information
Interpretation
Mammals - Acute oral LD₅₀ (mg kg⁻¹)
> 1800
Q3 Q = Miscellaneous data from online sources 3 = Unverified data of known source
Rat
Moderate
Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)
-
-
-
Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)
A0 A = Chromosome aberration (EFSA database) 0 = No data
;
B0 B = DNA damage/repair (EFSA database) 0 = No data
;
C0 C = Gene mutation (EFSA database) 0 = No data
;
D0 D = Genome mutation (EFSA database) 0 = No data
;
E2 E = Unspecified genotoxicity type (miscellaneous data source) 2 = Mixed/ambiguous results
No data found
Reproduction / development effects
Acetyl cholinesterase inhibitor
Neurotoxicant
No data found
No data found
No data found
Respiratory tract irritant
Skin irritant
Skin sensitiser
No data found
No data found
No data found
Eye irritant
Phototoxicant
No data found
No data found
General human health issues
Comfrey extracts can contain pyrrolizidine alkaloids, some of which re suspected hepatoxins, genotoxins and carcinogens Links with heptic veno-occlusive disease have been demonstrated
Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242
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Human health
Warning:
