Efrotomycin (Ref: FR-02A)

Efrotomycin (Ref: FR-02A)	Last updated: 08/09/2025
(Also known as: Antibiotic FR 02A; mocimycin; MK 621)

GENERAL INFORMATION

Description

Efrotomycin is produced by Streptomyces lactamodurans NRRL 3802 and used in veterinary medicine as a narrow-spectrum antibiotic

Examples of veterinary uses

Mainly used as a growth promoter

Examples of species treated

Pigs

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Efrotomycin exhibits geometric (cis-trans) and stereoisomerism, which are crucial to its biological activity. As a complex macrolide antibiotic derived from Streptomyces lactamodurans, its molecular structure includes multiple double bonds with defined E/Z (trans/cis) configurations, as well as several chiral centres that contribute to its isomeric diversity.

Chemical formula

C₅₉H₈₈N₂O₂₀

Canonical SMILES

CCC(C(=O)NCC=CC=C(C)C(C(C)C1C(C(C(O1)C=CC=CC=C(C)C(=C2C(=O)C=CN(C2=O)C)O)O)O)OC)C3(C(C(C(C(O3)C=CC=CC)(C)C)OC4C(C(C(C(O4)C)OC5C(C(C(C(O5)C)OC)O)OC)OC)O)O)O

Isomeric SMILES

CCC(C(=O)NC/C=C/C=C(\C)/C(C(C)C1C(C(C(O1)/C=C/C=C/C=C(\C)/C(=C\2/C(=O)C=CN(C2=O)C)/O)O)O)OC)C3(C(C(C(C(O3)/C=C/C=C/C)(C)C)OC4C(C(C(C(O4)C)OC5C(C(C(C(O5)C)OC)O)OC)OC)O)O)O

International Chemical Identifier key (InChIKey)

ZLECMEJICSWJLT-LIWMBINXSA-N

International Chemical Identifier (InChI)

InChI=1S/C59H88N2O20/c1-15-17-19-27-39-58(8,9)53(80-56-45(67)50(74-13)49(35(7)76-56)79-57-51(75-14)44(66)48(73-12)34(6)77-57)52(68)59(71,81-39)36(16-2)54(69)60-29-23-22-25-32(4)46(72-11)33(5)47-43(65)42(64)38(78-47)26-21-18-20-24-31(3)41(63)40-37(62)28-30-61(10)55(40)70/h15,17-28,30,33-36,38-39,42-53,56-57,63-68,71H,16,29H2,1-14H3,(H,60,69)/b17-15+,20-18+,23-22+,26-21+,27-19+,31-24+,32-25+,41-40+

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Antibiotic, Antibacterial, Growth promoter

Substance groups

Unclassified substance

Minimum active substance purity

Known relevant impurities

Substance origin

Natural

Mode of action

Inhibits bacterial protein synthesis

Molecular targets

[50S ribosomal protein L10, Antagonist]

CAS RN

56592-32-6

EC number

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

ATCvet Code

None allocated

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

1145.33

PIN (Preferred Identification Name)

IUPAC name

2-[2,3-dihydroxy-4-[3-hydroxy-5-(4-hydroxy-3,5-dimethoxy-6-methyloxan-2-yl)oxy-4-methoxy-6-methyloxan-2-yl]oxy-5,5-dimethyl-6-[(1E,3E)-penta-1,3-dienyl]oxan-2-yl]-N-[(2E,4E)-7-[3,4-dihydroxy-5-[(1E,3E,5E)-7-(2-hydroxy-1-methyl-4-oxopyridin-3-yl)-6-methyl-7-oxohepta-1,3,5-trienyl]oxolan-2-yl]-6-methoxy-5-methylocta-2,4-dienyl]butanamide

CAS name

31-O-[6-deoxy-4-O-(6-deoxy-2,4-di-O-methyl-a-L-mannopyranosyl)-3-O-methyl-b-D-allopyranosyl]-1-methylmocimycin

Forever chemical

Other status information

Evidence of use in third world countries

Relevant Environmental Water Quality Standards

Physical state

Pale yellow solid

Commercial

Property

Value

Availability status

Largely obsolete but may be available in some countries

Introduction & key dates

Late 1970s, first synthesised; Early 1980s, introduced into vet medicine; Late 1990s, start of phase-out

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

Boehringer Ingelheim
Merial

Example products using this active

Producil

Formulation and application details

It was exclusively marketed as a feed additive

Commercial production

Efrotomycin is produced through a microbial fermentation process using Nocardia lactamdurans, a soil-dwelling actinomycete. The organism is cultivated in a chemically defined or complex medium, often containing sources like monosodium glutamate and glycerol, which enhance yield when paired with sulphuric acid pH control. The fermentation is typically carried out in shaker flasks or fermentors, where temperature, nutrient feed rate, and sterilisation conditions are tightly regulated to optimise biosynthesis. Efrotomycin is a secondary metabolite, so its production peaks during the stationary phase of microbial growth. After fermentation, the compound is extracted, commonly using solvents like methanol or acetone-water-ammonia mixtures, and purified through filtration and 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)

1000

Moderate

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

Neutral media: 232nm, 327nm

Surface tension (mN m⁻¹)

Refractive Index

Environmental release

Environmental exposure possible via the faeces and urine of treated livestock

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)

11.5

5% faeces in soil mix 20°C

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)

92.8

Non-mobile

K_foc (mL g⁻¹)

5262

¹/_n

0.93

Notes and range

USEPA data K_f range 8.34-294 mL g⁻¹, K_foc range 575.5-11017 mL g⁻¹, ¹/_n range 0.787-1.05, Soils=4

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 soil and groundwater metabolites

None

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

efrotomycin B

Pig (Stomach)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 7500

Rat

Low

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)

> 1000

Low

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)

> 100

Salmo gairdneri

Low

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)

180

Daphnia magna

Low

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

Daphnia magna

Low

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)

> 7500

Rat

Low

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Subcutaneous LD₅₀ > 2000 mg kg⁻¹

Mouse

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

Largely metabolised and excreted via urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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

May cause diarrhoea

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

efrotomycin

French

efrotomycine

German

Danish

Italian

Spanish

efrotomicina

Greek

Polish

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	08/09/2025
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