Narasin

Narasin	Last updated: 16/09/2025
(Also known as: (4S)-4-methyl-salinomycin; compound 79891; antibiotic A 28086A )

GENERAL INFORMATION

Description

A veterinary ionophone coccidiostat and antibacterial agent

Examples of veterinary uses

Mainly used to prevention of coccidiosis, as a performance and growth enhancer

Examples of species treated

Chickens; Cattle

Approval status

VMR 2013/2033 approval status (GB/UK)

Not approved

EU Regulatory approval status

Not approved

Chemical structure

Isomerism

Narasin exhibits stereoisomerism, specifically diastereomerism, due to its complex polyether structure with multiple chiral centres. As a derivative of salinomycin, narasin contains a spiroketal framework and several tetrahydropyran and tetrahydrofuran rings, each contributing to its stereochemical complexity. The molecule has numerous asymmetric carbon atoms, leading to the possibility of multiple. In practice, narasin is produced as a mixture of closely related isomers—primarily Narasin A (about 96%) along with minor components like Narasin B, D, and I.

Chemical formula

C₄₃H₇₂O₁₁

Canonical SMILES

CCC(C1C(CC(C(O1)C(C)C(C(C)C(=O)C(CC)C2C(CC(C3(O2)C=CC(C4(O3)CCC(O4)(C)C5CCC(C(O5)C)(CC)O)O)C)C)O)C)C)C(=O)O

Isomeric SMILES

CC[C@H]([C@H]1[C@H](C[C@@H]([C@@H](O1)[C@@H](C)[C@@H]([C@H](C)C(=O)[C@H](CC)[C@@H]2[C@H](C[C@H]([C@]3(O2)C=C[C@H]([C@@]4(O3)CC[C@@](O4)(C)[C@H]5CC[C@@]([C@@H](O5)C)(CC)O)O)C)C)O)C)C)C(=O)O

International Chemical Identifier key (InChIKey)

VHKXXVVRRDYCIK-CWCPJSEDSA-N

International Chemical Identifier (InChI)

InChI=1S/C43H72O11/c1-12-30(35(46)27(8)34(45)28(9)36-23(4)21-24(5)37(51-36)31(13-2)39(47)48)38-25(6)22-26(7)42(52-38)18-15-32(44)43(54-42)20-19-40(11,53-43)33-16-17-41(49,14-3)29(10)50-33/h15,18,23-34,36-38,44-45,49H,12-14,16-17,19-22H2,1-11H3,(H,47,48)/t23-,24-,25-,26+,27-,28-,29-,30-,31+,32+,33+,34+,36+,37+,38-,40-,41+,42-,43-/m0/s1

2D structure diagram/image available?

Yes

General status

Veterinary substance type

Coccidiostat, Antiobiotic, Antibacterial, Antiparasitic, Growth stimulant, Feed additive

Substance groups

Ionophore

Minimum active substance purity

Known relevant impurities

Substance origin

Synthetic

Mode of action

Dissociates the calcium fluxes in muscle fibers

Molecular targets

[NF-κB signaling, Inhibition], [IκBα phosphorylation, Antagonist]

CAS RN

55134-13-9

EC number

CIPAC number

US EPA chemical code

PubChem CID

Therapeutic Class

Antiparasitic products, insecticides & repellents: Antiprotozoals

ATCvet Code

QP51AH04

Controlled Drug?

Regulation 37/2010 MRL Classification

Molecular mass

765.03

PIN (Preferred Identification Name)

IUPAC name

(2R)-2-[(2R,3S,5S,6R)-6-[(1S,2S,3S,5R)-5- [(2S,5S,7R,9S,10S,12R,15R)-2-[(2R,5R,6S)-5-ethyl-5-hydroxy-6-methyl-2-tetrahydropyranyl]-15-hydroxy-2,10,12-trimethyl-1,6,8-trioxadispiro[4.1.57.35]pentadec-13-en-9-yl]-2-hydroxy-1,3-dimethyl-4-oxoheptyl]-3,5-dimethyl-2-tetrahydropyranyl]butanoic acid

CAS name

Forever chemical

Other status information

Relevant Environmental Water Quality Standards

Physical state

White to off-white, crystalline powder

Related substances & organisms

nicarbazin

Commercial

Property

Value

Availability status

Introduction & key dates

1977, discovered; 1978, first scientific publication; 1984, European patent

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

Elanco Animal Health

Example products using this active

Maxiban G160
Monteban

Formulation and application details

Usually supplied as a feed additive

Commercial production

The production of narasin is achieved through a microbiological fermentation process. It begins with cultivating a specific strain of Streptomyces aureofaciens, notably NRRL 5758 or NRRL 8092, in a submerged aerobic fermentation medium rich in carbohydrates, nitrogen sources, and inorganic salts. Under carefully controlled conditions of temperature, pH, and aeration, the microorganism synthesises narasin over several days. Once fermentation is complete, the broth is filtered to remove biomass, and narasin is extracted using organic solvents. The crude product is then purified, typically via crystallisation or chromatography, to isolate Narasin A, the major active isomer.

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)

102

Moderate

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

Melting point (°C)

resolidifies remelts at 198

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

217

Flashpoint (°C)

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

7.08 X 10⁰⁴

Calculated

Log P

4.85

High

Fat solubility of residues

Solubility

Data type

Density (g ml⁻¹)

Dissociation constant pKa) at 25 °C

7.9

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

Ethanol: 285nm

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)

8.8

Non-persistent

DT₅₀ (lab at 20 °C)

Moderately persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

116

Persistent

DT₉₀ (field)

Note

USEPA data: DT₅₀ range 21-49 days, DT₉₀ 69-162 days

Manure DT₅₀ (days)

Aqueous photolysis DT₅₀ (days) at pH 7

Value

1.5

Moderately fast

Note

Susceptible to photolysis

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

Value

Stable

Note

Stable pH 7 and 9, DT₅₀ 3.5 days at pH 5

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)

Slightly mobile

K_oc (mL g⁻¹)

1619

Notes and range

USEPA data K_d range 7.1 to 108 mL g⁻¹, K_oc range 507-3670 mL g⁻¹, Soils=5

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

1.22

Calculated

Low leachability

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

dihydroxynarasin

Animal (Liver)

9-keto-trihydroxynarasin

Animal (Liver)

hydroxynarasin

Animal (Liver)

trihydroxynarasin

Animal (Liver)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

21.2

Rat

High

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)

75.57

Colinus virginianus

High

Birds - Short term dietary (LC₅₀/LD₅₀)

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

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

> 20

Lumbricus terrestris

Moderate

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

0.5

Moderate

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)

> 3.27

Lepomis macrochirus

Moderate

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

0.033

Lepomis macrochirus

Moderate

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

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

> 7.72

Daphnia magna

Moderate

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

0.077

Daphnia magna

Moderate

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)

21.2

Rat

High

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

Mammals - Inhalation LC₅₀ (mg l⁻¹)

Other Mammal toxicity endpoints

Intravenous LD₅₀ = 1.96 mg kg⁻¹

Rat

Intraperitoneal LD₅₀ = 7.0 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

Rapidly metabolised in liver and eliminated in faeces

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

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

May cause behavioural and gastrointestinal problems

Handling issues

Property

Value and interpretation

General

IMDG Transport Hazard Class 9

CLP classification 2013

WHO Classification

Not listed (Not listed)

UN Number

UN2811

Waste disposal & packaging

Packaging Group II (moderate danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

narasin

French

narasine

German

Danish

Italian

Spanish

narasino

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