Semduramicin

The C-30 skeleton group accounts for about 60% of the polyethers for which stmctures have been deterrnined. Most of these contain a sugar moiety, usually 2,3,6-trideoxy-4-0-methyl-D-erythto pyranose [65104-53-2]. The single spiroketal subset is ikustrated by two closely related compounds, semduramicin (4, R = H, R =) and maduramicin alpha (4, R = CH3, R = ). Maduramicin is marketed as an anticoccidial and semduramicin is under development for the same appHcation. 

The absoqrtion profile of semduramicin is characterized by low levels in plasma, muscle, kidney, fat, and skin, but higher levels in the bile and liver (43). Liver constitutes the edible tissue with the highest total residues at all withdrawal times. Over a 5 day withdrawal period, total residues in each of liver, kidney, muscle, fat, and skin/fat tissues were depleted to 0.057, 0.022, 0.015, 0.011, and... 

Residues in liver of poultry sacrificed at 6 h after withdrawal, were comprised of unchanged semduramicin at a percentage of 45%, whereas an array of more polar, low-level ( 0.1 ppm) metabolites could be also detected. Using bile as a source of major semduramicin metabolites, the metabolism of semduramicin was spectrometrically determined to proceed by (9-demethylation of the methoxy groups in the A and G rings, as it has been also described for maduramicin (30, 31) and monensin (21, 44). 

LC-ISP-MS proved to be an attractive approach for the determination of semduramicin in chicken liver (120). Tandem MS using CID of the molecular ions could further enhance the specificity, providing structure elucidation and selective detection down to 30 ppb under SRM conditions. 

Ionophores, or polyether (PET) antibiotics, produced by various species of Streptomyces, possess broad spectrum anticoccidial activities. They are chemically characterized by several cyclic esters, a single terminal carboxylic acid group, and several hydroxyl groups. Representative members of this class include salinomycin (SAL), monensin (MON), lasalocid (LAS), narasin (NAR), maduramicin (MAD), and semduramicin (SEM). The main chemical properties of interest in the extraction methodology are their low polarities and instability under acidic conditions. They are able to form stable complexes with alkaline cations. All of these compounds, with the exception of LAS, bind monovalent cations (e.g., Na+ and K+). Lasalocid has a tendency to form dimers and can form complexes with divalent cations such as Mg2+ and Ca2+. The formation of metal complexes results in all of these compounds adopting a quasi-cyclic formation consequent to head-to-tail hydrogen bonding. No MRLs have yet been set by the EU for any of the carboxylic acid PETs (98). 

JF Ericson, A Calcagni, MJ Lynch. Determination of semduramicin sodium in poultry liver by liquid chromatography with vanillin postcolumn derivatization. J AOAC Int 77 577-582, 1994. 

Liquid chromatography-ionspray-mass spectrometry has been shown to be an attractive approach for the determination of semduramicin in chicken liver. Tandem MS using the CID of the molecular ions further enhanced the specificity providing strucmre elucidation and selective detection down to 30 ppb. Liquid chromatography-ionspray-mass spectrometry has also been successfully applied for the assay of 21 sulfonamides in salmon flesh. Coupling of LC with either ISP-MS or ISP-MS-MS has also been investigated as an attractive alternative for the determination of erythromycin A and its metabolites in salmon tissue. The combination of these methods permitted the identification of a number of degradation products and metabolites of erythromycin at the 10-50 ppb level. Tandem MS with CID has also been... 

RP Schneider, MJ Lynch, JF Ericson, HG Fouda. Electrospray ionization mass spectrometry of semduramicin and other polyether ionophores. Anal Chem 63 1789, 1991. 

Semduramicin (Figure 1) is a new potent monocarboxylic polyether antibiotic with antimicrobial and anticoccidial activity (5). It is comparable to several widely used polyether antibiotics (6)y including the commercialized anticoccidial feed additives monesin, salinomycin, lasalo-cid, narasin and maduramicin. The discovery of semduramicin arose from an effort to identify fermentation-derived products for the treatment of coccidiosis in poultry (5). It is obtained from a fermentation of a mutated strain of Actinomadura roseorufa (7),... 

Like previous consumer safety studies with polyether antibiotics, the work reported here was undertaken to determine the tissue distribution, metabolic fate and depletion of residues of 14C-semduramicin sodium in broilers and to characterize the depletion of residues of the drug in poultry dosed under commercial use conditions. 

Instruments. The HPLC system for analysis of unchanged semduramicin was modeled after an LC-post column reaction system described earlier for salinomycin sodium in feeds (15-16). The mobile phase consisting of ethyl acetate, iso-octane, glacial acetic acid, triethylamine, methanol (650 + 350 + 44-2 + 1) was used in conjunction with a Dupont Zorbax silica 4.6 mm X 25 cm analytical column. NMR spectra were recorded on a Bruker WM-250 spectrometer (modified to incorporate a pulse programmer and Aspect-3000 data system) and a Bruker AM-500 spectrometer, using 50 mg samples dissolved in CDCI3. The 13C and IH chemical shifts for semduramicin were assigned as reported elsewhere (17). FAB (fast atom bombardment) mass spectra were obtained on a VG 70/250 S spectrometer at 1000 resolution. 

Labeled Compound. l4C-Semduramicin was prepared with a specific activity of 2.34 mCi/mmole by biosynthesis from sodium [2-l4C]acetate in... 

Animal Feeding and Dosing with Semduramicin Sodium. A group of 48 chicks (24 per sex) was fed ad libitum a ration containing 25 ppm semduramicin sodium, the recommended use concentration, for 44 days from the day of hatch. Livers were collected from 3 males and 3 females randomly selected at 6,12,18, 24, 36 and 48 hours following withdrawal of the medication. For the identification of metabolites in bile, 35-day-old male broilers were housed in groups of 15 to 24 in 6 pens. They were provided ad libitum access to non-medicated water and to feed medicated with 25 ppm semduramicin sodium for 14 days, then sacrificed and bile collected from the gall bladders of 93 birds. ... 

Extraction of Residues in Bile for HPLC Profiling. Bile recovered from poultry dosed with l4C-semduramicin sodium was diluted with distilled water, extracted with chloroform and the extract was concentrated to dryness. The residue was reconstituted in ethyl acetate/ isooctane (8 2), and aliquots of this solution were analyzed by HPLC with liquid scintillation counting of fractions to derive the chromatographic profile of radioactivity. 

Isolation of Metabolites from Poultry Bile for Spectral Identification. Pooled samples of bile from poultry receiving feed medicated at 25 ppm semduramicin sodium for 7 days were extracted with ethyl acetate followed by chloroform. Abundant metabolites were isolated by collection of fractions from repeated injections on a normal phase silica HPLC column. The recovered fractions were analyzed by Fast Atom Bombardment Mass Spectrometry and proton NMR spectroscopy. 

The total amount of semduramicin sodium recovered from the HPLC was determined by reference to a standard calibration curve that related the peak area ratio of semduramicin sodium to the internal standard. The radioactivity recovered from the HPLC was corrected for the recovery of cold semduramicin sodium. In this procedure the dynamic range of the calibration curve for the nonlabeled semduramicin sodium extended from 1-40 pg/mL, and the dynamic range for tissue fortified with l4C-semdura-... 

TABLE I. 13C and IH NMR Chemical Shift Data for Semduramicin Sodium in CDCI3 Including Sites ( ) for Incorporation (13C +) of [2-l3C]acetate... 

Radiotracer Studies in Poultry. The radiotracer study characterized the depletion of total residues in edible tissues of 37-day old broiler chickens that received 7-day s ad libitum access to feed medicated with 25 ppm l4C-semduramicin sodium. Residues in edible tissues were determined at 6,12,24,48 and 120 hours after treatment. The tissue containing the highest total residues at all withdrawal times was liver. Liver residues were 1.8 or more times higher than residues in the next highest tissues, fat or skin. Total residues in liver were depleted from a mean value of 0.273 pg/g at 6 hours to 0.058 pg/g at 24 hours, and eventually to 0.018 pg/g at 120 hours (Table II). 

TOTAL CARBON-14 RADIOACTIVITY UNCHANGED C-14 SEMDURAMICIN SODIUM... 

Figure 4. Radiometric determination of the decline of total and unchanged residues in livers of poultry fed carbon-14 labeled semduramicin sodium at 25 ppm for 7 days.

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