Cell viability is lowered by emmemectin benzoate (MK-244; 2.5–40 μM; 12 and 24 hours) in a dose- and time-dependent way [1]. 16HBE cells are exposed to 2.5–20 μM of emmemactin benzoate for 24 hours, which causes DNA damage and ROS generation [1]. Emamectin Benzoate (2.5 – 20 μM; 12 hours) raises the levels of cleaved-PARP, Bax/Bcl-2, caspase-3, caspase-9, and cytochrome c [1]. With an IC50 of 3.72 μM, emamectin benzoate (2.5, 5, 10, 15 μM; 72 hours) decreases the viability of Trichopodia exigua Tn5B1-4 cells. Condensates and cytochromes undergo nuclear staining when exposed to emamectin benzoate [2]. Examine[1]

In liver tissue, emamectin benzoate (MK-244; sidewall; 25–100 mg/kg/day; for 14 days) dramatically increases oxidative damage [3].

Cell Viability Assay[1]
Cell Types: Human normal bronchial epithelial cell line 16HBE
Tested Concentrations: 2.5, 5, 7.5, 10, 15, 20, 40 μM
Incubation Duration: 12 and 24 hrs (hours)
Experimental Results: Cell viability diminished in a time- and dose-dependent manner at 12 hrs (hours) The IC50 values within 24 hrs (hours) were 11.88 μM and 9.67 μM, respectively.

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Apoptosis analysis [1]
Cell Types: Human normal bronchial epithelial cell line 16HBE
Tested Concentrations: 2.5, 5, 10, 20 μM
Incubation Duration: 24 hrs (hours)
Experimental Results: Induced cell apoptosis and caused chromatin shrinkage and nuclear fragmentation.

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Western Blot Analysis [1]
Cell Types: Human normal bronchial epithelial cell line 16HBE
Tested Concentrations: 2.5, 5, 10, 20 μM
Incubation Duration: 12 hrs (hours)
Experimental Results: Cytochrome-c, caspase-3, and cas-pase-9 levels increased, Cleavage-PARP, Bax/Bcl-2.

Animal/Disease Models: 10weeks old Swiss albino male mice (25-30 g) [3]
Doses: 25, 50, 100 mg/kg
Route of Administration: oral; daily; lasting for 14 days
Experimental Results: Lead to significant induction of oxidation in liver tissue injury, as evidenced by increased TBARS levels and diminished GSH levels.

Absorption, Distribution and Excretion
There were 2 dosing groups, each consisting of 2 male beagles. Group 1 received 0.5 mg/kg of (3)H-MK-0243 benzoate (1 mL/kg in 5% ethanol ... 0.239 mCi/mg; 98.8% radiochemically pure) on day 1 and 0.5 mg/kg of (3)H-MK-0243 HCl (1 mL/kg in deionized water ... 0.229 mCi/mg; 98.7% radiochemically pure) on day 15. Dosing was reversed for Group 2. Body weights were determined before each dose. 2 mL of blood was withdrawn for drug level determinations following each dose at 0.5, 1, 2, 4, 6, 8, 24, 48, 96 and 168 hr. Urine and feces were collected for drug level analysis at 0 to 24 and 72 to 96 hr. There was no evidence of drug effects. The mean plasma half lives for the benzoate and HCl salts were 35.7 +/- 3.4 hr and 35.5 +/- 4.4 hr, respectively. The mean plasma approximate area under the curve (AUC) for the benzoate and HCl salts was 4479 +/- 1476 and 4574 +/- 1514 ng/g plasma/7days. The mean peak plasma MAB1a (the major component of MK-0243 at 90 to 95%) levels were ~100 ng equivalents/g plasma, occurring at ~6 hr for either salt. Combined fecal and urine recoveries during the 1st and 4th days were ~40% and 0.01% of the dose, respectively. It is concluded that the 2 salts are bioequivalent in male beagle dogs.
The dermal absorption of the experimental avermectin insecticide emamectin benzoate was studied in the Rhesus monkey. Dermal absorption was calculated by comparing radioactivity levels in excreta following dermal application of the compound with those following administration of an equivalent intravenous dose. After iv administration of 300 ug (3)H-MAB1a (prepared as a 1:1 solution of propylene glycol:saline) to three monkeys, plasma levels decreased biphasically with a rapid decline in radioactivity during the first 15 min followed by a slower decline to background. By 7 days post-dose, approximately 90% and 5% of the administered radioactivity was recovered in the feces and urine, respectively. After a washout period, 300 micrograms [(3)H]MAB1a (dissolved in emulsifiable concentrate) was applied topically to the shaved forearm of the same monkeys. Following a 10-hr exposure period, approximately 90% of the radioactivity was recovered in a soap and water wash of the exposed forearms. Although plasma radioactivity levels generally remained below background levels, approximately 1.5% of the applied dose was recovered in the excreta. Dermal absorption of [()3H]emamectin benzoate was calculated as 1.6%. The low dermal penetration of emamectin benzoate indicates that minimal actual exposure of agricultural workers to this compound will occur.
The aims of this study were to investigate the content of emamectin in blood, mucus and muscle following field administration of the recommended dose, and correlation with sea lice infection on the same fish (elimination study). The tissue distribution of tritiated emamectin benzoate after a single oral dose in Atlantic salmon was also investigated by means of whole-body autoradiography and scintillation counting (distribution study). In the elimination study, concentrations of emamectin benzoate reached maximum levels of 128, 105 and 68 ng/g (p.p.b.) for blood, mucus and muscle respectively, on day 7, the last day of administration. From day 7, the concentration in the blood declined until concentration was less than the limit of detection on day 77. The concentration was higher in mucus compared with plasma (P < 0.05) except on days 7 and 21. The concentration of emamectin benzoate decreased gradually from the end of treatment (day 7) to day 70 with half-lives of 9.2, 10.0 and 11.3 days in muscle, plasma and mucus respectively. The distribution study demonstrated a high quantity of radioactivity in mucous membranes (gastrointestinal tract, gills) throughout the observation period (56 days). Activity was high in the epiphysis, hypophysis and olfactory rosette throughout the study. The highest activity was observed in the bile, indicating this to be an important route for excretion. The distribution study confirmed the results from the elimination study with respect to concentrations in blood, skin mucous and muscle.
Atlantic salmon (approximately 1.3 kg) maintained in tanks of seawater at 5 +/- 1 degrees C were dosed with 3H-emamectin B1 benzoate in feed at a nominal rate of 50 ug of emamectin benzoate/kg/day for 7 consecutive days. Tissues, blood, and bile were collected from 10 fish each at 3 and 12 hr and at 1, 3, 7, 15, 30, 45, 60, and 90 days post final dose. Feces were collected daily from the tanks beginning just prior to dosing to 90 days post final dose. The total radioactive residues (TRR) of the daily feces samples during dosing were 0.25 ppm maximal, and >97% of the TRR in pooled feces covering the dosing period was emamectin B1a. Feces TRR then rapidly declined to approximately 0.05 ppm by 1 day post final dose. The ranges of mean TRR for tissues over the 90 days post dose period were as follows: kidney, 1.4-3 ppm; liver, 1.0-2.3 ppm; skin, 0.04-0.09 ppm; muscle, 0.02-0.06 ppm; and bone, <0.01 ppm. The residue components of liver, kidney, muscle, and skin samples pooled by post dose interval were emamectin B1a (81-100% TRR) and desmethylemamectin B1a (0-17% TRR) with N-formylemamectin B1a seen in trace amounts (<2%) in some muscle samples. The marker residue selected for regulatory surveillance of emamectin residues was emamectin B1a. The emamectin B1a level was quantified in individual samples of skin and muscle using HPLC-fluorometry and was below 85 ppb in all samples analyzed (3 hr to 30 days post dose).
For more Absorption, Distribution and Excretion (Complete) data for EMAMECTIN (8 total), please visit the HSDB record page.

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Metabolism / Metabolites
Atlantic salmon (approximately 1.3 kg) maintained in tanks of seawater at 5 +/- 1 degrees C were dosed with [(3)H]emamectin B1 benzoate in feed at a nominal rate of 50 ug of emamectin benzoate/kg/day for 7 consecutive days. Tissues, blood, and bile were collected from 10 fish each at 3 and 12 hr and at 1, 3, 7, 15, 30, 45, 60, and 90 days post final dose. Feces were collected daily from the tanks beginning just prior to dosing to 90 days post final dose. The total radioactive residues (TRR) of the daily feces samples during dosing were 0.25 ppm maximal, and >97% of the TRR in pooled feces covering the dosing period was emamectin B1a. Feces TRR then rapidly declined to approximately 0.05 ppm by 1 day post final dose. The ranges of mean TRR for tissues over the 90 days post dose period were as follows: kidney, 1.4-3 ppm; liver, 1.0-2.3 ppm; skin, 0.04-0.09 ppm; muscle, 0.02-0.06 ppm; and bone, <0.01 ppm. The residue components of liver, kidney, muscle, and skin samples pooled by post dose interval were emamectin B1a (81-100% TRR) and desmethylemamectin B1a (0-17% TRR) with N-formylemamectin B1a seen in trace amounts (<2%) in some muscle samples. The marker residue selected for regulatory surveillance of emamectin residues was emamectin B1a. The emamectin B1a level was quantified in individual samples of skin and muscle using HPLC-fluorometry and was below 85 ppb in all samples analyzed (3 hr to 30 days post dose).
...a single mammalian metabolite has been identified. This metabolite is characterized as an N-demethylation byproduct of emamectin.
The metabolism of (3)H/(14)C-labeled 4"-deoxy-4"-epimethylaminoavermectin B1a (MAB1a) benzoate, the major homologue (>/=90%) of the avermectin insecticide emamectin benzoate, was studied in laying chickens. Ten Leghorn hens (Gallus domesticus) were orally dosed once daily for 7 days (1 mg/kg of body weight/day). Eggs and excreta were collected daily, and eggs were subsequently separated into whites and yolks. Chickens were euthanized within 20 hr after the last dose, and liver, kidney, heart, muscle, fat, ovaries, gizzard, gastrointestinal tract and contents, and carcass were collected. Approximately 70 and 6% of the total administered dose were recovered in the excreta plus gastrointestinal tract and contents and in the tissues plus eggs, respectively. Two novel metabolites, i.e. the 24-hydroxymethyl derivative of the parent compound (24-hydroxymethyl-4"-deoxy-4"-epimethylaminoavermectin B1a) and the N-demethylated derivative of 24-hydroxymethyl-4"-deoxy-4"-epimethylaminoavermectin B1a (24-hydroxymethyl-4"-deoxy-4"-epiaminoavermectin B1a), were identified. In addition, eight fatty acid conjugates of each of these two metabolites, comprising 8-75% of total radioactive residues in tissues and eggs, were isolated and identified. Although this represents some of the most extensive in vivo fatty acid conjugation to a xenobiotic reported to date, potential human exposure to MAB1a residues from consumption of chicken would be extremely low, because the dosage level in this study was approximately 1000-fold greater than the MAB1a residue levels seen in crops and because the majority of the applied dose was recovered in the excreta. Based on these findings, the avian biotransformation of MAB1a differs substantially from the mammalian biotransformation.
While emamectin benzoate is not extensively metabolized in mammals, the limited information on the metabolites of emamectin benzoate suggests that metabolism does not result in the detoxification of emamectin benzoate. One plant metabolite of emamectin benzoate is somewhat more toxic than emamectin benzoate itself.

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Biological Half-Life
Emamectin benzoate was rapidly cleared from plasma /of rats/ with half-lives ranging from about 15 to 28 hours after oral or intravenous dosing.
Emamectin benzoate is a relatively large molecule (actually a mixture of four closely related molecules) which is not completely absorbed on oral administration, is poorly absorbed by the dermal administration, and rapidly eliminated in the feces with whole-body half-lives of about 1.5 days.
The tissue distribution of tritiated emamectin benzoate after a single oral dose in Atlantic salmon was also investigated by means of whole-body autoradiography and scintillation counting (distribution study). The concentration of emamectin benzoate decreased gradually from the end of treatment (day 7) to day 70 with half-lives of 9.2, 10.0 and 11.3 days in muscle, plasma and mucus respectively.

Toxicity Summary
It has low solubility in water and extensive non-specific binding. It opens GABA-insensitive chloride channels, reducing membrane resistance and increasing conductance inward. (T10)

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Interactions
House flies, Musca domestica L., are important pests of dairy operations worldwide, with the ability to adapt wide range of environmental conditions. There are a number of insecticides used for their management, but development of resistance is a serious problem. Insecticide mixtures could enhance the toxicity of insecticides in resistant insect pests, thus resulting as a potential resistance management tool. The toxicity of bifenthrin, cypermethrin, deltamethrin, chlorpyrifos, profenofos, emamectin benzoate and fipronil were assessed separately, and in mixtures against house flies. A field-collected population was significantly resistant to all the insecticides under investigation when compared with a laboratory susceptible strain. Most of the insecticide mixtures like one pyrethroid with other compounds evaluated under two conditions (1?1-"A" and LC50: LC50-"B") significantly increased the toxicity of pyrethroids in the field population. Under both conditions, the combination indices of pyrethroids with other compounds, in most of the cases, were significantly below 1, suggesting synergism. The enzyme inhibitors, PBO and DEF, when used in combination with insecticides against the resistant population, toxicities of bifenthrin, cypermethrin, deltamethrin and emamectin were significantly increased, suggesting esterase and monooxygenase based resistance mechanism. The toxicities of bifenthrin, cypermethrin and deltamethrin in the resistant population of house flies could be enhanced by the combination with chlorpyrifos, profenofos, emamectin and fipronil. The findings of the present study might have practical significance for resistance management in house flies.

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Non-Human Toxicity Values
LD50 Mouse (female) oral (gavage) 165 mg/kg /Benzoate-methyl t-butyletherate (MBTE) solvates of emamectin, 96.4% pure/
LD50 Mouse (female) oral (gavage) 141 mg/kg /Benzoate monohydrate solvates of emamectin, 99.1% pure/
LD50 Rat (female) oral (gavage) 53 mg/kg /Benzoate-methyl t-butyletherate (MBTE) solvates of emamectin, 96.4% pure/
LD50 Rat (female) oral (gavage) 58 mg/kg /Benzoate monohydrate solvates of emamectin, 99.1% pure/
LD50 Mouse oral (gavage) 107 mg/kg

[1]. Chenguang Niu, et al. Toxic effects of the Emamectin Benzoate exposure on cultured human bronchial epithelial (16HBE) cells. Environ Pollut. 2020 Feb;257:113618.
[2]. Shaorong Luan, et al. Emamectin benzoate induces ROS-mediated DNA damage and apoptosis in Trichoplusia Tn5B1-4 cells. Chem Biol Interact. 2017 Aug 1;273:90-98.
[3]. Özge Temiz, et al. Biopesticide emamectin benzoate in the liver of male mice: evaluation of oxidative toxicity with stress protein, DNA oxidation, and apoptosis biomarkers. Environ Sci Pollut Res Int. 2020 Jun;27(18):23199-23205.

Emamectin B1a is a member of emamectins.
The avermectins are a series of macrocyclic lactone derivatives with potent anthelmintic properties. A commonly used therapy in recent times has been based on oral or parenteral administration of avermectins, which are macrocyclic lactones produced by fermentation of various, carefully prepared laboratory broths using the soil micro-organism Streptomyces avermitilis. They show activity against a broad range of nematodes and arthropod parasites of domestic animals at dose rates of 300 microgram/kg or less. Unlike the macrolide or polyene antibiotics, they lack significant antibacterial or antifungal activity. (L829)

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Mechanism of Action
Emamectin benzoate is the 4'-deoxy-4'-epi-methyl-amino benzoate salt of avermectin B1 (abamectin), which is similar structurally to natural fermentation products of Streptomyces avermitilis. Emamectin benzoate is being developed as a newer broad-spectrum insecticide for vegetables and has a very low application rate. The mechanism of action involves stimulation of high-affinity GABA receptors and a consequent increase in membrane chloride ion permeability.
Overexpression of P-glycoproteins (Pgps) is assumed to be a principal mechanism of resistance of nematodes and arthropods to macrocyclic lactones. Quantitative RT-PCR (Q-RT-PCR) was used to demonstrate changes in transcription levels of two putative P-glycoprotein genes, designated here as SL0525 and SL-Pgp1, in sea lice (Lepeophtheirus salmonis) following exposure to emamectin benzoate (EMB). Pre-adult L. salmonis were challenged in an EMB bioassay for 24 hr and gene expression was studied from lice surviving EMB concentrations of 0, 10, and 30 ppb. Gene expression was measured using Q-RT-PCR with elongation factor 1 (eEF1alpha) as an internal reference gene. The results show that both target genes, SL0525 and SL-Pgp1, had significantly increased levels of expression with exposure to 10ppb EMB (p=0.11 and p=0.17, respectively) whereas the group exposed to 30 ppb was on the verge of being significant (p=0.053) only in the expression of SL-Pgp1. Gene expression for SL0525 and SL-Pgp1 were increased over five-fold at 10 ppb EMB. Therefore, the upregulation of these target genes may offer protection by increasing Pgp expression when lice are exposed to EMB. Optimized Q-RT-PCR can be used to determine if over-expression of these genes could be the basis for development of resistance in sea lice and thus allow suitable alternative chemotherapeutic options to be assessed.
Macrocyclic lactones, including avermectins and milbemycins, are novel parasiticides and insecticides that are produced through fermentation by soil-dwelling microorganisms. Although various macrocyclic lactones may differ in their potency and safety, all of them are believed to share common pharmacologic/toxicologic mechanisms, i.e. leading to paralysis and death of parasites and other target organisms via the activation of a glutamate-gated chloride channel in the invertebrate nerve and muscle cells and/or through the effect on gamma-aminobutyric acid (GABA) receptors. Ivermectin is the first macrocyclic lactone that was released for use in both animals and humans, and has demonstrated both excellent efficacy and high tolerability in the treatment of parasite infestations. Other macrocyclic lactones, such as abamectin, emamectin, and moxidectin were subsequently commercialized and have been used as insecticides and acaricides for crop protection or parasiticides for animal health.

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Therapeutic Uses
Therapeutic category (veterinary): antiparasitic

C56H81NO15

1008.2401

885.523

155569-91-8

11549937

White to off-white powder
Off-white crystalline powder

141-146ºC

4.628

3

14

9

63

1750

20

O1C([H])([H])C2=C([H])C([H])=C([H])[C@]([H])(C([H])([H])[H])[C@@]([H])(C(C([H])([H])[H])=C([H])C([H])([H])[C@]3([H])C([H])([H])[C@@]([H])(C([H])([H])[C@]4(C([H])=C([H])[C@]([H])(C([H])([H])[H])[C@@]([H])([C@@]([H])(C([H])([H])[H])C([H])([H])C([H])([H])[H])O4)O3)OC([C@]3([H])C([H])=C(C([H])([H])[H])[C@]([H])([C@]1([H])[C@]32O[H])O[H])=O)O[C@@]1([H])C([H])([H])[C@@]([H])([C@]([H])([C@]([H])(C([H])([H])[H])O1)O[C@@]1([H])C([H])([H])[C@@]([H])([C@]([H])([C@]([H])(C([H])([H])[H])O1)[N+]([H])([H])C([H])([H])[H])OC([H])([H])[H])OC([H])([H])[H].[O-]C(C1C([H])=C([H])C([H])=C([H])C=1[H])=O |c:8,23,t:4|

CXEGAUYXQAKHKJ-NSBHKLITSA-N

InChI=1S/C49H75NO13/c1-12-26(2)44-29(5)18-19-48(63-44)24-35-21-34(62-48)17-16-28(4)43(27(3)14-13-15-33-25-56-46-42(51)30(6)20-36(47(52)59-35)49(33,46)53)60-40-23-38(55-11)45(32(8)58-40)61-39-22-37(54-10)41(50-9)31(7)57-39/h13-16,18-20,26-27,29,31-32,34-46,50-51,53H,12,17,21-25H2,1-11H3/b14-13+,28-16+,33-15+/t26-,27-,29-,31-,32-,34+,35-,36-,37-,38-,39-,40-,41-,42+,43-,44+,45-,46+,48+,49+/m0/s1

(1'R,2R,3S,4'S,6S,8'R,10'E,12'S,13'S,14'E,16'E,20'R,21'R,24'S)-2-[(2S)-butan-2-yl]-21',24'-dihydroxy-12'-[(2R,4S,5S,6S)-4-methoxy-5-[(2S,4S,5S,6S)-4-methoxy-6-methyl-5-(methylamino)oxan-2-yl]oxy-6-methyloxan-2-yl]oxy-3,11',13',22'-tetramethylspiro[2,3-dihydropyran-6,6'-3,7,19-trioxatetracyclo[15.6.1.14,8.020,24]pentacosa-10,14,16,22-tetraene]-2'-one

Emamectin benzoate; Avermectin b1, 4''-deoxy-4''-(methylamino)-, (4''R)-, benzoate

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Note: Please store this product in a sealed and protected environment, avoid exposure to moisture.

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ≥ 31 mg/mL

Solubility in Formulation 1: ≥ 2.08 mg/mL (Infinity mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.08 mg/mL (Infinity mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.08 mg/mL (Infinity mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 20.8 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)