24-epibrassinolide

24-epibrassinolide	Last updated: 03/02/2026
(Also known as: epibrassinolide)

SUMMARY

24-epibrassinolide is a naturally occurring plant hormone. It has a low aqueous solubility but is more soluble in organic solvents. It has a low volatility tends to be moderately persistent in soil systems. It may be more persistent in water depending upon conditions. 24-epibrassinolide is moderately toxic to most aquatic species. This substance has a low oral mammalian toxicity.

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
Environmental fate Moderate alert: Moderately persistent Warning: Significant data are missing	Ecotoxicity Moderate alert: Daphnia acute ecotoxicity: Moderate; Bees acute contact ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate Warning: Significant data are missing	Human health Low alert

GENERAL INFORMATION

Description

An activator that enhances the plants ability to protect against abiotic stresses and to improve plant health. Although it is effective against some fungal infections it has no direct fungicidal or antagonistic effects.

Example pests controlled

Grey mold; Downy mildew; Bottom rot; Leaf spot; Stress

Example applications

Wine and table grapes; Leafy vegetables e.g. endive, chicory, spinach; Pumpkin; Lettuce; Cucumber; Sugarbeet

Efficacy & activity

Effectiveness demonstrated in plant trials. Disease severity and incidence tend to be reduced rather than cured. Studies have shown that 24-epibrassinolide has a significant effect on seed germination, seedling growth, and plant development by interacting with specific receptors in plants and activating signalling pathways that regulate growth and development processes.

Appearance and life cycle

Taxonomic classification

GB regulatory status

GB COPR regulatory status

Not approved

Date COPR inclusion expires

Not applicable

GB LERAP status

No UK approval for use as a plant protection agent

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Austria

Date EC 1107/2009 inclusion expires

31/03/2036

EU Candidate for substitution (CfS)

Listed in EU database

Yes

Approved for use (✓) under EC 1107/2009 in the following EU Member States

ATAustria	BEBelgium	BGBulgaria	CYCyprus	CZCzech Republic	DEGermany	DKDenmark	EEEstonia	ELGreece

ESSpain	FIFinland	FRFrance	HRCroatia	HUHungary	IEIreland	ITItaly	LTLithuania	LULuxembourg

LVLatvia	MTMalta	NLNetherlands	PLPoland	PTPortugal	RORomania	SESweden	SISlovenia	SKSlovakia

Approved for use (✓) under EC 1107/2009 by Mutual Recognition of Authorisation and/or national regulations in the following EEA countries

ISIceland	NONorway

Additional information

Also used in

USA (pending)

Chemical structure

Isomerism

24-epibrassinolide exhibits stereoisomerism, specifically epimerism, which is a subtype of diastereomerism. It is an epimer of brassinolide, differing only in the configuration at the C-24 carbon atom in the side chain of the steroidal structure. While brassinolide has the hydroxyl group at C-24 in one spatial orientation, 24-epibrassinolide has it in the opposite configuration.

Chemical formula

C₂₈H₄₈O₆

Canonical SMILES

CC(C)C(C)C(C(C(C)C1CCC2C1(CCC3C2COC(=O)C4C3(CC(C(C4)O)O)C)C)O)O

Isomeric SMILES

International Chemical Identifier key (InChIKey)

IXVMHGVQKLDRKH-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C28H48O6/c1-14(2)15(3)24(31)25(32)16(4)18-7-8-19-17-13-34-26(33)21-11-22(29)23(30)12-28(21,6)20(17)9-10-27(18,19)5/h14-25,29-32H,7-13H2,1-6H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
24-epibrassinolide	-

General status

Biopesticide type

Fungicide; Other substance

Other bioactivity & uses

Elicitor; Plant activator; Biostimulant - improved abiotic stress resiliance & enhanced growth

Substance groups

Plant hormone; Plant-derived substance

Minimum active substance purity

900 g kg⁻¹

Known relevant impurities

EU dossier 2018: None declared

Substance origin

Natural

Mode of action

An elicitor of the plant’s self-defence mechanisms against fungal diseases

Substance source

It was first discovered in rape (Brassica napus) pollen and has since been identified in many other plant tissues including Brassica juncea and Camellia sinensis.

Uses

Target pests

Target host

Farming system suitability

CAS RN

78821-43-9

EC number

639-387-1

CIPAC number

None allocated

US EPA chemical code

PubChem CID

Molecular mass

480.68

PIN (Preferred Identification Name)

(22R,23R,24R)-2a,3a,22,23-tetrahydroxy-24-methyl-ß-homo-7-oxa-5-cholestan-6-one

IUPAC name

(22R,23R,24R)-2α,3α,22,23-tetrahydroxy-24-methyl-β-homo-7-oxa-5-cholestan-6-one

CAS name

24-epibrassinolide

Global Governance status: Listed (✓) under

UK Poisons List Order 1972	Rotterdam Convention	Montreal Protocol
XNo The Poisons List Order 1972	XNo Rotterdam Convention	XNo Montreal Protocol
Stockholm Convention	OSPAR	EU Water Framework Directive
XNo Stockholm Convention	XNo OSPAR	XNo EU Water Framework Directive

Relevant Environmental Water Quality Standards

Forever chemical

Highly Hazardous Pesticide (HHP)

Type I

Type II

Other status information

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

White to cream coloured powdery solid

Related substances & organisms

brassinolide

brassinolide-ethyl

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1979, discovered

Example manufacturers & suppliers of products using this active now or historically

Suntton
Jinan Ponder Chemical Co. Ltd.
Sichuan Xinlanyue Biotechnology

Example products using this active

Sunergist

Formulation and application details

Available in a range of formulations including liquids, powders and microencapsulated forms

Commercial production

24-epibrassinolide can be produced commercially via two main processes. Chemical synthesis is the usual approach. This often begins with ergosterol, a sterol found in fungi. Methyl sulfonylation of ergosterol followed by hydrolysis and oxidation forms intermediate ketones. Ring modifications build the brassinosteroid skeleton. Stereoselective reactions follow to ensure correct configuration at multiple chiral centres. Finally, the material is purified using chromatography and crystallisation. Alternatively, the substance can be produced by microbial biotransformation. Uses genetically engineered microbes (e.g., Saccharomyces cerevisiae) to convert sterols into brassinosteroids.

Impact on climate of production and use

While it is marketed as a low-risk substance, the environmental impact of 24-epibrassinolide production, especially in terms of GHGs, remains unclear. Generally, fungicide production creates 11 to 30 kg of CO₂e per kg of substance produced but the accuracy of this data for 24-epibrassinolide is unknown.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C at pH 7 (mg l⁻¹)

3.8

at pH 4.5

Low

Solubility - In organic solvents at 20 °C (mg l⁻¹)

28700

Methanol

3.1

n-Heptane

5500

Ethyl acetate

18000

Acetone

Melting point (°C)

254.6

Boiling point (°C)

>400

Degradation point (°C)

>400

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

1.00 X 10⁰²

Calculated

Log P

2.0

at 30 °C

Low

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

No dissociation

Vapour pressure at 20 °C (mPa)

1.9 X 10^-12

Estimated

Low volatility

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

2.40 X 10^-13

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

pH 5.5: 205nm=183, 215nm=91.0
pH 0.6: 200nm=245
pH 13.4: 219nm=67

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Nor readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

34.4

Moderately persistent

DT₅₀ (lab at 20 °C)

34.4

Moderately persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier 2018: Dark aerobic conditions normalised Lab DT₅₀ range 22.17-69.55 days, Soils=3

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

Stable

Note

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

19.6

at 25 °C

Non-persistent

Note

pH sensitive: 24.1 days at pH 5, 16.4 days at pH 9, all at 25 °C

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

K_d (mL g⁻¹)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

K_foc (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)

> 5000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

300

Rat 90-day

Low

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary LC₅₀ (mg kg⁻¹ bw d⁻¹)

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹ dw soil)

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹ dw soil)

Soil micro-organisms

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

Seedling emergence ER₅₀ (g ha⁻¹)

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 10

Apis mellifera solubility limit

Moderate

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 92.2

Apis mellifera

Moderate

Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Chronic

Notes

Bumblebees (Bombus spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Mason bees (Osmia spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Other bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings)

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹, Std lab test

> 0.69

Aphidius rhopalosiphi

Moderate

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹, Std lab test

0.28

Typhlodromus pyri

Moderate

Beneficial insects (Ground beetles)

Beneficial insects (Butterflies)

Contact

Notes

Oral

Notes

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 5.0

Danio rerio

Moderate

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 2.86

Daphnia magna

Moderate

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic Plants (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹)

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹)

Algae - Chronic (growth rate, fresh; mg l⁻¹)

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

Regulatory Threshold Levels (RTLs)

Note: These RTLs have been calculated using the regulatory approach used in the European Union and based on ecotoxocity values in the PPDB.

Species group

RTL

Notes

Mammals

Worst case of acute and chronic mammals

Birds

No data

No data for acute and chronic birds

Soil organisms

No data

No data for acute and chronic earthworms

Terrestrial plants

No data

No data for non-target plants vegetative vigour and seedling emergence

Pollinators

0.2

Worst case of contact and oral honeybees

Arthropods

0.14

Worst case of parasitic wasps and predatory mites

Fish

No data

No data for temperate acute and chronic fish

Aquatic invertebrates

0.0286

Worst case of temperate acute and chronic aquatic invertebrates

Aquatic plants

No data

No data for free-floating plants, rooted plants, acute and chronic algae

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short Term Oral NOAEL (mg kg⁻¹ bw d⁻¹)

300

Rat 90-day

Low

Mammals - Long Term (Chronic) Oral NOAEL (mg kg⁻¹ bw d⁻¹)

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

> 2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 1.08

Rat 4 hr

Other Mammal toxicity endpoints

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

None allocated

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

None allocated

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

None allocated

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

None allocated

Dermal penetration studies (%)

0.01

Dangerous Substances Directive 76/464

Exposure Routes

Public

As the substance displays no biologically or toxicologically relevant hazard risks are consider negligible

Occupational

As the substance displays no biologically or toxicologically relevant hazard risks are consider negligible

Mammalian dose elimination route and rate

Rapidly distributed and excreted mainly via urine and faeces

Health issues

Specific human health issues (hazard-based)

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

No data found

General human health issues

Decrease in food consumption and loss of body weight may occur if ingested

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
Not expected to auto-ignite; Not highly flammable

CLP classification 2013

Environment: H413

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

24-epibrassinolide

French

German

Danish

Italian

Spanish

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	03/02/2026
Contact:	aeru@herts.ac.uk
Please cite as:	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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