Tetronasin (Ref: ICI-139603)

Tetronasin (Ref: ICI-139603)	Last updated: 16/09/2025
(Also known as: antibiotic M139603; M-139603)

GENERAL INFORMATION

Description

An ionophore antibiotic compound that has activity against gram-positive bacteria

Examples of veterinary uses

Once used as a growth-promoter in farm animals

Examples of species treated

Pigs; Cattle

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Tetronasin exhibits complex stereoisomerism, primarily due to its structure as a polyether ionophore antibiotic. The molecule contains over 12 chiral centres distributed across its fused cyclic ether rings, including tetrahydrofuran, tetrahydropyran, and acyltetronic acid moieties, giving rise to multiple stereoisomers. However, the biologically active form of tetronasin is a single stereoisomer.

Chemical formula

C₃₅H₅₄O₈

Canonical SMILES

CC1CCCC(C1C(C)C(=C2C(=O)COC2=O)O)C=C(CO)C3C(CCC(O3)C=CC(C)C4C(CC(O4)C(C)OC)C)C

Isomeric SMILES

C[C@@H]1CCC[C@@H]([C@H]1[C@H](C)/C(=C\2/C(=O)COC2=O)/O)/C=C(\CO)/[C@H]3[C@@H](CC[C@H](O3)/C=C/[C@H](C)[C@H]4[C@H](C[C@@H](O4)[C@H](C)OC)C)C

International Chemical Identifier key (InChIKey)

XZJAKURZQBNKKX-QFQDJZPHSA-N

International Chemical Identifier (InChI)

InChI=1S/C35H54O8/c1-19-9-8-10-25(30(19)23(5)32(38)31-28(37)18-41-35(31)39)16-26(17-36)34-21(3)12-14-27(42-34)13-11-20(2)33-22(4)15-29(43-33)24(6)40-7/h11,13,16,19-25,27,29-30,33-34,36,38H,8-10,12,14-15,17-18H2,1-7H3/b13-11+,26-16+,32-31+/t19-,20+,21-,22+,23+,24+,25-,27-,29-,30-,33+,34-/m1/s1

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
tetronasin	-

General status

Veterinary substance type

Antibiotic, Growth promotor, Feed additive

Substance groups

Polyether (ionophore)

Minimum active substance purity

Known relevant impurities

Substance origin

Natural

Mode of action

Ruminal activity with a shift toward propionate and a decrease in dietary protein degradation

Molecular targets

[Intracellular protein transport, Blocker]

CAS RN

75139-06-9

EC number

CIPAC number

US EPA chemical code

PubChem CID

54688688

Therapeutic Class

Antiparasitic products, insecticides & repellents: Antiprotozoals

ATCvet Code

None assigned

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

602.80

PIN (Preferred Identification Name)

IUPAC name

CAS name

4-hydroxy-3-[(2S)-2-[(1S,2S,6R)-2-[(1E)-3-hydroxy-2-[(2R,3R,6S)-tetrahydro-3-methyl-6-[(1E,3S)-3-[(2R,3S,5R)-tetrahydro-5-[(1S)-1-methoxyethyl]-3-methyl-2-furanyl]-1-butenyl]-2H-pyran-2-yl]-1-propenyl]-6-methylcyclohexyl]-1-oxopropyl]-2(5H)-furanone

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

Commercial

Property

Value

Availability status

Considered obsolete but may be available in some countries

Introduction & key dates

Early 1980s, developed; 1987, patent filed; Late 1980s, commercial use starts; 2013, not approved UK

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

Coopers Animal Health

Example products using this active

Tetronasin

Formulation and application details

Usually supplied as a premix or feed additive

Commercial production

Tetronasin is produced through a microbial fermentation process using the actinomycete Streptomyces longisporoflavus. The production begins with cultivating this bacterium in nutrient-rich media under aerobic conditions, allowing it to biosynthesise tetronasin as a secondary metabolite. Key enzymatic steps include cyclisations, oxidations, and a rare inverse-electron-demand hetero-Diels–Alder-like [4+2] cyclisation, which forms the tetronate and polyether rings with precise stereochemistry. After fermentation, the compound is extracted from the culture broth using organic solvents, followed by purification through crystallisation or chromatography.

Impact on climate of production and use

As microbial-based products tend to use fermentation-based production processes rather than chemical synthesis, they typically have a lower fossil fuel input in formulation and active ingredient creation, and also have reduced downstream emissions due to biodegradability and minimal soil disruption, their life-cycle GHG emissions are expected to be low. Whilst hard and precise data is not available, broad estimates suggest that typically emissions are likely to be below 5 kg CO₂e/kg.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (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

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)

Refractive Index

Environmental release

Substance may enter the environment via the faeces of treated animals or by leaching from spilt medicated feed.

Degradation

Property

Value

Source; quality score; and other information

Interpretation

Soil degradation (days) (aerobic)

DT₅₀ (typical)

DT₅₀ (lab at 20 °C)

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

Note

Manure DT₅₀ (days)

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

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

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

Bio-concentration factor

BCF (l kg⁻¹)

CT₅₀ (days)

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

Mammals - Short term dietary NOEL

(mg kg⁻¹)

(ppm diet)

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

Birds - Acute LD₅₀ (mg kg⁻¹)

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

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

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)

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

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)

Beneficial insects (Predatory mites)

Beneficial insects (Ground beetles)

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)

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

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

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)

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

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

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

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

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

Dermal penetration studies (%)

Dangerous Substances Directive 76/464

Exposure Routes

Public

Occupational

Mammalian dose elimination route and rate

Eliminated via hepatic metabolism and biliary excretion

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

No data found

; ; ; ;

No data found

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

No data found

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

No information available

Handling issues

Property

Value and interpretation

General

No information available

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

tetronasin

French

tetronasine

German

Danish

Italian

Spanish

tetronasina

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	16/09/2025
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