This study validated the utilization of triacylglycerides (TAGs) by Pseudomonas mendocina CH50, a wild type strain, resulting in the production of novel mcl-PHAs with unique physical properties. A PHA yield of 58% dcw was obtained using 20g/L of coconut oil. Chemical and structural characterisation confirmed that the mcl-PHA produced was a terpolymer comprising of three different repeating monomer units, 3hydroxyoctanoate, 3-hydroxydecanoate and 3-hydroxydodecanoate or P(3HO-3HD-3HDD). Bearing in mind the potential of P(3HO-3HD-3HDD) in biomedical research, especially in neural tissue engineering, in vitro biocompatibility studies were carried out using NG108-15 (neuronal) cells. Cell viability data confirmed that P(3HO-3HD-3HDD) supported the attachment and proliferation of NG108-15 and was therefore, confirmed to be biocompatible in nature and suitable for neural regeneration.
Grafting of medium chain length polyhydroxyalkanoates (mcl-PHA) produced by Comamonas testosteroni onto carboxymethylchitosan (CMCH) using ceric ammonium nitrate (CAN) as an initiator was carried out under nitrogen atmosphere in aqueous medium. The grafting composition was 2 g CMCH, 0.2M CAN, and 0.5 g mcl-PHA. The reaction was carried out at 408C AE 18C for 4.5 h, and reaction product was extracted by acetone precipitation. The CMCH-g-mcl-PHA copolymers were characterized by Fourier transform infrared spectroscopy, Thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. The data obtained showed successful grafting of mcl-PHA onto CMCH polymer. TGA results indicated that the graft was stable up to 3808C, and the solubility studies revealed a high % grafting efficiency. Biodegradation studies of the graft in terms of microbial growth, extracellular protein concentration, and % weight loss in the graft were carried out for 30 days using a bacterial isolate Burkholderia cepacia 202 and a fungal isolate Aspergillus fumigatus 202. 93% weight loss of the graft was obtained in case of A. fumigatus 202, whereas B. cepacia 202 showed 76% loss in weight of the graft.
o-Lithio N-methyl benzamides (1a-f) upon alkylation with ethyl methyl ketone gave (±)-3-ethyl-3-methyl phthalides (2a-f),which upon treatment with concentrated H 2 SO 4 or anhydrous AlCl 3 furnished corresponding 3,3-dimethyl-3,4-dihydroisocoumarins (3a-f) and 3-methyl mellein (3g).J. Heterocyclic Chem., 39, 623 (2002).A number of phthalides and dihydroisocoumarins have interesting biological activities e.g. Cladosporin and its monoacetyl derivatives act as antifungal agents, Sclerotinin-A promotes growth of rice seedlings, 3-butylphthalide and 3-butyl-4,5-dihydrophthalide both are effective anticonvulsants, 7-hydroxy-3-butylidenephthalide possess cardiokinetic, antistenocardiacs, antiarrhythmics and coronary artery dilators activity [1][2][3][4][5].Recently, several workers [6][7][8] have studied the synthesis of 3-substituted phthalides and their transformation to 3-alkyl isocoumarins. The purpose of undertaking this work to explore the synthesis of 3,4-dimethyl dihydroisocoumarins as the natural product Oospalactone has this type of substitution pattern. However the phthalides (2a-f), surprisingly, were converted to 3,3-dimethyl-3,4-dihydroisocoumarins. Earlier 3,3-dimethyl-3,4-dihydroisocoumarins were prepared from β,β-dimethyl-2-carbostyrenes [9].In the present work (±)-3-ethyl-3-methyl phthalides (2a-f) were synthesized in a single step by alkylating o-litho N-methyl benzamides (1a-f) with 2-butanone in (40-50%) yield. These phthalides underwent smooth rearrangement with concenrrated H 2 SO 4 or anhydrous AlCl 3 to give dihydroisocoumarins (3a-g) in about (35-50%) yield (Scheme-I).The above conversion was successfully used to synthesize 3-methyl mellein. The structures of phthalides and dihydroisocoumarins are supported by analytical and spectral evidences. EXPERIMENTALAll melting and boiling points are uncorrected. Solid compounds were crystallised using ethyl acetate/n-hexane. 1 Hnmr spectra were recorded on Hitachi R-1500 (60 MHz) instrument using CDCl 3 as solvent. Chemical shifts are quoted in parts per million (δ) downfield from the internal tetramethylsilane reference and coupling constants (J) are given in Hz. The presence of exhangeable protons was confirmed by the use of deuterium oxide. 13 C-nmr spectra were recorded on Bruker DPX-200 (200 MHz) instrument with TMS as an internal standard. ir spectra were recorded in KBr on a Nicolett D-400 spectrophotometer. The progress of the reaction was monitered by thin layer chromatography. Iodine vapour was used for detection. Chromatographic separations were performed on silica gel column (60-120 mesh) (open bed chromatography) using gravity flow. Reagents, solvents and starting materials were purchased from standard sources and purified according to literature procedure.General Procedure for the Synthesis of (±)-3-Ethyl-3-methylisobenzofuran-1-ones (2a-f).To a well stirred solution of N-methyl benzamides (1a-f) (25.6 mmol) in 50 mL dry THF (freshly distilled over LiAlH 4 ), n-BuLi [(105 mmoles, prepared from lithium 2.57 g (370 mmoles) and nbutyl bromide...
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