Para-hydroxy Benzoate Research Articles

Simultaneous Estimation of Four Preservatives in Pharmaceutical Ointment by RP-HPLC

A simple, specific, precise and accurate reverse phase HPLC method has been developed for the simultaneous determination of preservatives (Methyl Para hydroxybenzoate, Ethyl para hydroxybenzoate, Propyl para hydroxybenzoate and Chlorocresol) in ointment. The chromatographic separation was achieved on Zorbax column, 150 mm × 4.6 mm, 5 µm, using PDA detector. The mobile phase was 50% Methanol (v:v), at a flow rate of 1.0 mL/min. All preservatives were detected at 230 nm, at 30oC temperature for column. The retention times were 2.15 min for Methyl para hydroxybenzoate, 2.70 min for Ethyl para hydroxybenzoate, 3.69 min for Propyl para hydroxybenzoate and 4.01 min for Chlorocresol, with incredibly good resolution between peaks. The method was validated according to the ICH guidelines with respect to specificity, linearity (r2 =0.999; 0.998; 0.999 and 0.998), accuracy (99 to 100.1%), precision (RSD<2%).

Development of nanofiltration PES membranes incorporated with hydrophilic para hydroxybenzoate alumoxane filler for high flux and antifouling property

The PES nanofiltration membranes incorporated with hydrophilic para hydroxybenzoate alumoxane (PHBA) filler were prepared with enhanced pure water flux, dye removal, and antifouling property. The fabricated membranes were characterized in terms of average pore radius, porosity, surface roughness, water contact angle, active layer thickness, and zeta potential. The surface roughness of the nanofiltration membranes decreased and the surface hydrophilicity of the nanofiltration membranes increased with the increase of the PHBA content. According to nanofiltration experiments, the highest pure water flux of the PES membranes incorporated with PHBA reached up to 80.47 kg/m2h under operation pressure of 0.4 MPa, which was nearly 5.8 times as much as that of the neat PES membrane. The PES membranes incorporated with PHBA filler also exhibited excellent antifouling performance and dye removal capability. In the best PHBA content with the P-PHBA 0.3 % membrane, the highest rejection of 99.21 and 98.53% were achieved for DR 16 and MB, respectively. Furthermore, the P-PHBA membranes exhibited good long-term operational pH stability for DR 16 rejection. P-PHBA 0.3 % membrane also exhibited the highest flux recovery ratio (98.50%) and the lowest irreversible fouling ration (1.50%). Moreover, the dominant fouling mechanism was determined using Hermia–"s model. This superior antifouling behavior and relatively high dye rejection combined with remarkable stability show the potential of the organic-inorganic fillers embedded nanofiltration membranes in sustainable water treatment technology.

Preparation and Evaluation of Polyherbal Facial Scrub

The main objective of present study was to prepare a polyherbal scrub incorporated into gel. Herbal cosmeceuticals usually contain the plant parts which possess antimicrobial, antioxidant and anti aging properties. Herbal cosmetics are the safest product to use routine with no side effects and cosmeceuticals are the product which influences the biological function of skin. In this preparation Green apple, cinnamon, Millet, Sandalwood, Neem , Turmeric, Arjuna, Fenugreek and honey is used as active ingredients and incorporated into the gel which is prepared with carbopol of different grades. Other ingredients like propylene glycol, Triethanolamine; methyl parahydroxy benzoate was added along with sodium lauryl sulfate into the gel. The prepared gel was evaluated for various parameters such as appearance, pH, viscosity, Spreadability, washability, irritability and found to be satisfied with all required characterizations. Thus, the developed formulation can be used as an effective scrub for using it to bear a healthy and glowing skin.

Structural, electrical and optical properties of gamma irradiated methyl para-hydroxy benzoate single crystals

ABSTRACTNonlinear optical materials (NLO) have been garnering attention due to their role in optical data storage, optical communication and laser technology. Organic crystals have emerged as an extremely important class of NLO materials, since their NLO properties compare very well with traditional inorganic NLO materials like KCl, LiNbO3, KDP (potassium dihydrogen phosphate), etc. They offer the additional advantage that they can be grown relatively inexpensively from solution close to room temperature, unlike the inorganic NLO materials which are grown from high temperature melts. In the present work, organic transparent single crystals of methyl para-hydroxy benzoate (MHB) were grown by slow evaporation solution growth technique (SEST) from aqueous solution at room temperature. The changes in structural, electrical and optical properties of gamma irradiated MHB single crystals were studied using X-ray diffraction (XRD), UV–Visible absorption spectroscopy, Photo-luminescence (PL), Fourier transform infrared (FTIR) spectroscopy and AC conductivity measurements at room temperature. The polished MHB single crystals were irradiated with gamma rays of doses 10 and 15 kilogray (kGy). From the XRD analysis, it was observed that gamma irradiation for these doses drastically decreases the crystallinity. The optical absorption constants were examined by UV-Visible absorption spectroscopy, measured over the wavelength range of 200–800 nm, at normal incidence. The optical band gap as estimated from the Tauc plot ((αhν)2 vs hν) was found to be reduced with increasing gamma irradiation doses. PL spectra showed emission at wavelengths of 361 nm (3.43 eV) and 452 nm (2.74 eV), with enhanced intensities for the irradiated crystals. FTIR spectroscopy was utilised to identify the functional groups of MHB and indicated the rupture of specific types of bonds with gamma irradiation. Apart from that, the enhancement of AC conductivity with gamma irradiation was also observed for the gamma irradiated crystals.

Preparation and evaluation of polyherbal facial scrub

The main objective of present study was to prepare a polyherbal scrub incorporated into gel. The use of natural ingredients to fight against acne, wrinkle and also to control secretion of oil is known as natural or herbal cosmetics. Herbal cosmeceuticals usually contain the plant parts which possess antimicrobial, antioxidant and anti aging properties. Herbal cosmetics are the safest product to use routine with no side effects and cosmeceuticals are the product which influences the biological function of skin. In this preparation Green apple , cinnamon, Millet, Sandalwood, Neem , Turmeric and honey is used as active ingredients and incorporated into the gel which is prepared with carbopol of different grades. Other ingredients like propylene glycol, Triethanolamine; methyl parahydroxy benzoate was added along with sodium lauryl sulfate into the gel. The prepared gel was evaluated for various parameters such as appearance, pH, viscosity, Spreadability, washability, irritability and found to be satisfied with all required characterizations. Thus, the developed formulation can be used as an effective scrub for using it to bear a healthy and glowing skin.&#x0D; Keywords: Polyherbal, Antioxidant, Anti Aging, Less Abrasive, Skin Exfoliate

The molecular basis for the intramolecular migration (NIH shift) of the carboxyl group during para-hydroxybenzoate catabolism.

The NIH shift is a chemical rearrangement in which a substituent on an aromatic ring undergoes an intramolecular migration, primarily during an enzymatic hydroxylation reaction. The molecular mechanism for the NIH shift of a carboxyl group has remained a mystery for 40 years. Here, we elucidate the molecular mechanism of the reaction in the conversion of para-hydroxybenzoate (PHB) to gentisate (GA, 2, 5-dihydroxybenzoate). Three genes (phgABC) from the PHB utilizer Brevibacillus laterosporus PHB-7a encode enzymes (p-hydroxybenzoyl-CoA ligase, p-hydroxybenzoyl-CoA hydroxylase and gentisyl-CoA thioesterase, respectively) catalyzing the conversion of PHB to GA via a route involving CoA thioester formation, hydroxylation concomitant with a 1, 2-shift of the acetyl CoA moiety and thioester hydrolysis. The shift of the carboxyl group was established rigorously by stable isotopic experiments with heterologously expressed phgABC, converting 2, 3, 5, 6-tetradeutero-PHB and [carboxyl-13 C]-PHB to 3, 4, 6-trideutero-GA and [carboxyl-13 C]-GA respectively. This is distinct from the NIH shifts of hydrogen and aceto substituents, where a single oxygenase catalyzes the reaction without the involvement of a thioester. The discovery of this three-step strategy for carboxyl group migration reveals a novel role of the CoA thioester in biochemistry and also illustrates the diversity and complexity of microbial catabolism in the carbon cycle.

A peculiar IclR family transcription factor regulates para-hydroxybenzoate catabolism in Streptomyces coelicolor.

In Streptomyces coelicolor, we identified a para-hydroxybenzoate (PHB) hydroxylase, encoded by gene pobA (SCO3084), which is responsible for conversion of PHB into PCA (protocatechuic acid), a substrate of the β-ketoadipate pathway which yields intermediates of the Krebs cycle. We also found that the transcription of pobA is induced by PHB and is negatively regulated by the product of SCO3209, which we named PobR. The product of this gene is highly unusual in that it is the apparent fusion of two IclR family transcription factors. Bioinformatic analyses, in vivo transcriptional assays, electrophoretic mobility shift assays (EMSAs), DNase I footprinting, and isothermal calorimetry (ITC) were used to elucidate the regulatory mechanism of PobR. We found that PobR loses its high affinity for DNA (i.e., the pobA operator) in the presence of PHB, the inducer of pobA transcription. PHB binds to PobR with a KD of 5.8 μM. Size-exclusion chromatography revealed that PobR is a dimer in the absence of PHB and a monomer in the presence of PHB. The crystal structure of PobR in complex with PHB showed that only one of the two IclR ligand binding domains was occupied, and defined how the N-terminal ligand binding domain engages the effector ligand.

ECONOMIC ARTIFICIAL DIETS FOR REARING SPINY BOLLWORM, Earias insulana (BOISD.) (LEPIDOPTERA: NOCTUIDAE)

The present investigation was conducted to evaluate the use of four artificial diets that don’t contain agar and less expensive for mass rearing the spiny bollworm as compared to the agar – based artificial diet. These four diets A, B, C and D contained dried active yeast, ascorbic acid, sorbic acid, methyl parahydroxy benzoate, starch, liquid milk, vitamin mixture and formaldehyde 34 - 38%, except diet A not containing starch. In addition to the essential ingredient in diet A is kidney beans and wheat grated, diet B is kidney beans and soybeans flower , diet C is kidney beans and diet D is kidney beans and yellow lentils .The obtained results showed that the mean larval and pupal durations were affected significantly by diets A & B and non-significantly by diets C & D as compared with control diet .The longest larval and pupal periods were on control diet and shortest were on diet A .Weight of larvae and pupae reared on diets A, B, C and D were significantly higher than those of the larvae and pupae reared on control diet .The larval fed on the diet A gave the highest larval and pupal weights, while those fed on control diet gave the lowest weights .The highest larval and pupal mortality percentages were on control diet followed by diets C, B, D and A. The lowest pupation and emergence percentages were on control diet and the highest were on diet A .The highest number of deposited eggs and hatchability percentage were observed on diet A followed by diets B, D and C and the lowest were on control diet .The growth index and fitness index were highest on diet A and the lowest were on control diet. Moreover, the total cost of ingredients reduced by 5911 , 43.88 , 43.75 and 45.24% per 1000 g. diet of diets A, B, C and D, respectively as compared to the agar – based control diet.

Statistical investigation of lead removal with various functionalized carboxylate ferroxane nanoparticles

Four new types of carboxylate-ferroxane nanoparticles, namely; maleate ferroxane (MF), fumarateferroxane (FF), para-amino benzoate ferroxane (PABF) and para-hydroxy benzoate ferroxane (PHBF) were synthesized, characterized and used for lead removal from aqueous solutions. Lepidocrocite nanoparticles were also synthesized and characterized asa precursorforcarboxylate-ferroxanes. FTIR, SEM and DLS analysis characterized the synthesized samplesand final Pb(II) concentration were analysed using inductively coupled plasma atomic emission spectrometer. Performance evaluation of the nanoparticlesin adsorption process was achieved using Taguchi experimental design. Variables in adsorption process were initial pH, contact time, adsorbent dose, adsorbent typeand initial concentration of Pb2+ ions. The initial Pb(II) concentration was the most influential factor in the adsorption process among the five factors. Adsorption of lead was performed through two possible mechanisms; ion exchange and complex formation. Maleate ferroxane performed the best lead removal efficiency among the four types of ferroxane nanostructures studied. The adsorption kinetic data described well with a pseudo-second-order model and the equilibrium data fitted well to the Frendlich isotherm.

Morphology and production mechanism of the functionalized carboxylate alumoxane micro and nanostructures

Four types of carboxylate alumoxanes, namely, para hydroxybenzoate alumoxane (PHBA), salicylate alumoxane, para aminobenzoate alumoxane (PABA) and fumarate alumoxane were successfully synthesized from boehmite nanoparticles and the corresponding carboxylic acids and characterized, two of which (salicylate and fumarate-alumoxanes) have not been reported in the literature so far. Boehmite nanoparticles were used as the starting material. The structures were characterized, using FTIR, SEM, TEM and TG-DTA. Mechanisms were proposed for the formation of the synthesized structures. TEM micrographs of salicylate alumoxane confirmed the morphologies such as nano-sheets, nanorods and nanoribbons. Nanothreads were observed in the TEM micrographs of fumarate alumoxane. Cubic agglomerates of fumarate alumoxane were detected. PHBA with structures similar to hexagonal prism were detected. Mechanisms were proposed for the formation of these products. Microstructure analysis explained well the experimental parameters obtained from thermal analysis.

Degradation of 4-chlorobiphenyl and 4-chlorobenzoic acid by the strain Rhodococcus ruber P25

The strain Rhodococcus ruber P25 utilizes 4-chlorobiphenyl (4CB) and 4-chlorobenzoic acid (4CBA) as sole carbon and energy sources. 4CB degradation by washed cells of strain P25 was accompanied by transient formation of 4CBA, followed by its utilization and release of equimolar amounts of chloride ions into the medium. The strain R. ruber P25 possessed active enzyme systems providing 4CBA degradation via the stages of formation of intermediates, para-hydroxybenzoate (PHBA) and protocatechuic acid (PCA), to compounds of the basic metabolism. The involvement of protocatechuate 4,5-dioxygenase in 4CBA degradation by rhodococci was revealed. It was established that the initial stage of 4CBA degradation (dehalogenation) in the strain R. ruber P25 was controlled by the fcbA and fcbB genes encoding 4-CBA-CoA ligase and 4-CBA-CoA dehalogenase, respectively. The genes encoding 4CBA dehalogenase components have not been previously detected and characterized in bacteria of the genus Rhodococcus.

Genetics of Primary CoQ10 Deficiency

Coenzyme Q10 (CoQ10) is a lipophilic component of the mitochondrial respiratory enzyme chain, which transfers electrons to complex III (cytochrome bc1 complex) from complex I (NADH-CoQ reductase), complex II (succinate dehydrogenase), and from the oxidation of fatty acids and branched-chain amino acids via flavin-linked dehydrogenases. Additional cellular functions of CoQ10 have been described. Deficiency of CoQ10 in muscle has been identified in patients with a spectrum of encephalomyopathies ranging from predominant cerebellar ataxia to pure myopathy. In a family with two children affected by infantile-onset encephalomyopathy and nephropathy, the first mutation in a CoQ biosynthetic gene, COQ2, was identified, thus proving the existence of primary CoQ10 deficiency. This article reviews the current state-of-knowledge regarding biochemical and molecular genetic features of inherited CoQ10 deficiency. Keywords: para-hydroxybenzoate (PHB), S. cerevisiae, C. elegans, nuclear DNA (nDNA), ataxia oculomotor apraxia 1 (AOA1)

Miscibility study on blend of thermotropic liquid crystalline polymers and polyester

AbstractThe miscibility of thermotropic liquid crystalline polymers (TLCPs) and polyester blends was investigated with thermal and morphological analyses, as well as transesterification. TLCPs composed of 80 mol % para‐hydroxybenzoate (PHB) and 20 mol % poly(ethylene terephthalate) (PET) or 60 mol % PHB and 40 mol % PET, and polyesters such as PET and poly(ethylene 2,6‐naphthalate) (PEN) were melt blended in an internal mixer. DSC analyses were performed to investigate the thermal transition behavior and to obtain thermodynamic parameters. All the blends showed only a single glass‐transition temperature, which means they are partially miscible in the molten state. The Flory–Huggins interaction parameter was calculated employing the Nishi–Wang approach, and negative values were obtained except for the P(HB8‐ET2)/PEN blends. Transesterification was investigated using 1H‐NMR, and the change of chemical shift compared to pure PET or P(HB‐ET)s was observed in the P(HB‐ET)/PET blends. An intermediate chemical shift value (4.83 ppm) was observed in the P(HB6‐ET4)/PEN blends, which indicates transesterification occurred. The fractured surface morphology of scanning electron micrographs showed that the interfaces between the LC droplets and matrix were not distinct. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1842–1851, 2003

Ubiquinone. Biosynthesis of quinone ring and its isoprenoid side chain. Intracellular localization.

Ubiquinone, known as coenzyme Q, was shown to be the part of the metabolic pathways by Crane et al. in 1957. Its function as a component of the mitochondrial respiratory chain is well established. However, ubiquinone has recently attracted increasing attention with regard to its function, in the reduced form, as an antioxidant. In ubiquinone synthesis the para-hydroxybenzoate ring (which is the derivative of tyrosine or phenylalanine) is condensed with a hydrophobic polyisoprenoid side chain, whose length varies from 6 to 10 isoprene units depending on the organism. para-Hydroxybenzoate (PHB) polyprenyltransferase that catalyzes the condensation of PHB with polyprenyl diphosphate has a broad substrate specificity. Most of the genes encoding (all-E)-prenyltransferases which synthesize polyisoprenoid chains, have been cloned. Their structure is either homo- or heterodimeric. Genes that encode prenyltransferases catalysing the transfer of the isoprenoid chain to para-hydroxybenzoate were also cloned in bacteria and yeast. To form ubiquinone, prenylated PHB undergoes several modifications such as hydroxylations, O-methylations, methylations and decarboxylation. In eukaryotes ubiquinones were found in the inner mitochondrial membrane and in other membranes such as the endoplasmic reticulum, Golgi vesicles, lysosomes and peroxisomes. Still, the subcellular site of their biosynthesis remains unclear. Considering the diversity of functions of ubiquinones, and their multistep biosynthesis, identification of factors regulating their cellular level remains an elusive task.

An evaluation of carbon and nitrogen assimilatory patterns for taxonomic differentiation of Penicillium species

A series of standardized medium formulations differing in carbon and nitrogen sources was evaluated for use in taxonomic differentiation of Penicillium species. Two media containing glucose as the carbon source and either nitrate or ammonium as the nitrogen source yielded optimal growth for most Penicillium species, and were, therefore, selected as reference media for evaluating growth parameters on other medium formulations. The nitrogen status of the medium was altered either by the addition of phosphinothricin, a potent inhibitor of ammonium assimilation via the glutamine synthetase pathway, or by using urea, phenylalanine, proline, creatine, glycinebetaine, choline, or bovine serum albumin as a substituted nitrogen source. Sucrose, sorbitol, mannitol, cellobiose, cellulose, palmitic acid, and para hydroxybenzoate were used as substitutes for glucose. The examination of colony area, hyphal density and changes in the color of pH indicators on day 7 yielded a set of 64 characters with a high degree of variation among Penicillium strains. The ability to assimilate various carbon and nitrogen sources appears to follow taxonomic lines in Penicillium. Furthermore, the acidification of the growth medium on a given nutrient source is a strong taxonomic trait in Penicillium. A sorting protocol has been developed to allow a broadly based discontinuous separation of taxa by segregating growth and acidification ratings into four broad categories, assigning an alphabetical coding to each category, and a staggered grouping of categories into two group with intermediate ratings included in both. The resolution power of the sorting scheme is demonstrated by the separation of 222 strains belonging to six test species P. atramentosum, P. citreonigrum, P. commune, P. corylophilum, P. oxalicum, and P. spinulosum from a dataset of 1860 Penicillium strains, including 1472 isolates from house dust samples, 199 isolates isolates from outdoor habitats, 121 ex-type strains and 68 named strains from various culture collections. For each species, only a fraction of character groups included in the sorting protocol was required for separating matching isolates. In addition a total of 180 strains were found to match one of the six test species except for a single character difference. These results support the use of physiological media both for species and for infraspecific differentiation of Penicillium taxa. The biochemical basis of species differentiation on the given physiological media is discussed.

Possibility of waveguide formation on organic nonlinear crystal methyl para-hydroxy benzoate using high energy ion irradiation

Organic nonlinear optical single crystals of Methyl para-Hydroxy Benzoate (MHB) have been grown using gel-solution technique. These crystals are cut along z-axis and are bombarded with Ag 14+ ions of energy 100 MeV. The results show an increase in refractive index at the ion irradiated region. The dielectric constant of the irradiated crystal is increased more than 15 times compared to that of a nonirradiated crystal. The result of these changes and comparative study of second harmonic generation (SHG) efficiency before and after irradiation is discussed.

COQ2 is a candidate for the structural gene encoding para-hydroxybenzoate:polyprenyltransferase.

Coenzyme Q functions as a lipid-soluble electron carrier in eukaryotes. In Saccharomyces cerevisiae, the enzymes responsible for the assembly of the polyisoprenoid side chain and subsequent transfer to para-hydroxybenzoate (PHB) are encoded by the nuclear genes COQ1 and COQ2, respectively. Yeast mutants defective in coenzyme Q biosynthesis are respiratory defective and provide a useful tool to study this non-sterol branch of the isoprenoid biosynthetic pathway. We isolated a 5.5-kilobase genomic DNA fragment that was able to functionally complement a coq2 strain. Additional complementation analyses located the COQ2 gene within a 2.1-kilobase HindIII-BglII restriction fragment. Sequence analyses revealed the presence of a 1,116-base pair open reading frame coding for a predicted protein of 372 amino acids and a molecular mass of 41,001 daltons. The amino acid sequence exhibits a typical amino-terminal mitochondrial leader sequence and six potential membrane-spanning domains. Primer extension and Northern analyses indicate the gene is transcriptionally active. Transformation of a coq2 strain with the 2.1-kilobase HindIII-BglII genomic restriction fragment on a multicopy plasmid restores PHB:polyprenyltransferase activity to wild-type levels. Disruption of the chromosomal COQ2 gene indicates the gene is not essential for viability, yet is required for PHB:polyprenyltransferase activity and respiratory function. In addition, the deduced amino acid sequence of PHB:polyprenyltransferase contains a putative allylic polyprenyl diphosphate-binding site. The presence of this aspartate-rich domain in a number of functionally distinct proteins which utilize polyprenyl diphosphate substrates is reported.

Effect of flow history on the morphology of thermotropic liquid crystalline copolyesters

AbstractMorphological studies have been carried out on a thermotropic liquid crystalline copolyester based on poly(ethylene terephthalate) (PET) and para hydroxybenzoate (PHB) that has been subjected to different types of flow histories. Wide angle X‐ray scattering investigations and chemical etching (n‐propylamine is the etchant) in conjunction with electron microscopy studies conducted on end gated injection molded plaques of the 60 percent PHB and 80 percent PHB copolyesters indicate that a highly oriented skin region and a less oriented core region is present. Chemical etching studies performed on microtomed layers of end gated and center gated plaques show that the etching is less pronounced in the skin region and is more pronounced in the core. The microtomed layers of the end gated injection molded plaques when analyzed by ESCA indicate the presence of a “PHB rich” skin region and a “PET” rich core region. Biaxial orientation, as denoted by WAXS measurements, is observed when the 60 percent PHB copolyester is squeezed between lubricated parallel plates.

The Nutritional Requirements of Termites in Axenic Cultures. 2. Studies on the Effectiveness of Antibiotics in the Sterilization of Workers of Reliculitermes flavipes12

In an effort to obtain sterile third- and fifth-instar workers of Retkulitermes flavipes (Kollar) for nutritional studies, antifungal and antibacterial agents were incorporated into the diet. Methyl para-hydroxy benzoate proved adequate as a fungicide at levels as low as 0.015 molar, but none of the antibiotics tested singly or in combination killed all of the termite-associated bacteria. A number of factors were investigated for their influence on the potency of the antibiotics, but changes made in materials and techniques as a result of these studies were not effective in increasing the activity of the bactericides.

The Solubility and Complexing Properties of Oxytetracycline and Tetracycline I. Interaction in Aqueous Solution

Oxytetracycline dihydrate and tetracycline trihydrate form soluble complexes with sodium salicylate, sodium parahydroxy benzoate, sodium saccharin, sodium p -amino benzoate, caffeine, and N-methyl pyrrolidone in aqueous solution. In all cases the tetracycline interactions were greater than those with oxytetracycline. With the exception of sodium salicylate at concentrations below 0.5 M, the solubilizing activities of these compounds are roughly in the order listed above. Logarithmic plots show a linear relationship in dilute solution and the slope values of these curves reveal that an increase in solubility of the tetracyclines is concomitant with an increase in the complexing agent dependency. The solubilization may be due, in part, to the presence of strong electronegative centers within the agents used. Two recrystallization procedures for the preparation of oxytetracycline and tetracycline hydrates are described.