Author
Kirpal S. Bisht
Other affiliations: University of Massachusetts Lowell, University of Massachusetts Boston, Odense University ...read more
Bio: Kirpal S. Bisht is an academic researcher from University of South Florida. The author has contributed to research in topic(s): Lipase & Candida antarctica. The author has an hindex of 26, co-authored 137 publication(s) receiving 3360 citation(s). Previous affiliations of Kirpal S. Bisht include University of Massachusetts Lowell & University of Massachusetts Boston.
Papers published on a yearly basis
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TL;DR: The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed in this paper, where nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references.
Abstract: The secondary metabolites isolated from Piper species for the period 1907 to June 1996 have been reviewed. Nearly six hundred chemical constituents belonging to different classes of bioactive compounds are listed together with their source(s) and references. © 1997 Elsevier Science Ltd
802 citations
TL;DR: Comparison of % conversion vs time for bulk PDL polymerizations at 70 °C catalyzed by NI- and I-PS-30 showed that for short reaction times, the immobilized catalyst gave % conversions that were more than 10 times greater.
Abstract: Lipase-catalyzed ring-opening bulk polymerizations of ω-pentadecalactone (PDL) were investigated. Screening of selected commercial lipases as catalysts for PDL polymerization at 80 °C was carried out. The results of this work showed that polymerizations catalyzed by lipases PS-30, AK, Lipozyme-IM and Novozym-435 gave % PDL conversions ranging from 80 to 100% for 24 h reactions (Mn = 15 000−34 400). Lipase PS-30 both physically immobilized onto Celite-521 (I-PS-30) and in the crude powder or nonimmobilized form (NI-PS-30) was selected for further study. Comparison of % conversion vs time for bulk PDL polymerizations at 70 °C catalyzed by NI- and I-PS-30 showed that for short reaction times, the immobilized catalyst gave % conversions that were more than 10 times greater. In fact, the % monomer conversion to poly(PDL) was nearly quantitative (>98%) for 8 h polymerizations catalyzed by I-PS-30. Furthermore, for reactions conducted at 70 °C with careful removal of water, substantially greater poly(PDL) molecu...
170 citations
Abstract: This work was directed at extending the use of lipase-catalyzed ring-opening polymerizations to cyclic carbonate monomers. Of the seven lipases screened for bulk trimethylene carbonate (TMC) polymerization (70 °C, 120 h), Novozym-435 from Candida antarctica gave almost quantitative monomer conversion (97%) and poly(TMC) with a Mn = 15 000 (Mw/Mn = 2.2) with no apparent decarboxylation during propagation. The lipases from Pseudomonas species (AK and PS-30) and porcine pancreas (PPL) also exhibited high monomer conversions (>80%, 120 h) but gave lower molecular weight polymers with broad polydispersity. Analyses by 1H-NMR spectroscopy suggested that poly(TMC) prepared by Novozym-435-catalyzed polymerization had terminal −CH2OH functionalities at both chain ends. A monotonic increase in monomer conversion with time and the rapid increase in Mn as a function of monomer conversion for Novozym-435-catalyzed TMC bulk polymerization at 70 °C suggest that the polymerization has chain-type propagation kinetics. An ...
139 citations
TL;DR: In this article, taxonomically classified under the genus Taxus, a number of physiologically active compounds of different classes have been extracted from yew trees, including lignans, flavonoids, steroids and sugar derivatives.
Abstract: Yew trees, taxonomically classified under the genus Taxus, are sources of a number of physiologically active compounds of different classes. Taxane derivatives with various carbon skeletons, lignans, flavonoids, steroids and sugar derivatives have been isolated from different Taxus species. Compounds isolated from the genus Taxus between 1908 and December 1997 have been comprehensively reviewed.
126 citations
TL;DR: In this article, an enzyme-catalyzed ring-opening polymerization of a novel carbonate monomer, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one, was reported.
Abstract: Water-soluble polycarbonate having pendent carboxyl groups on the main-chain carbons is reported for the first time. This paper describes synthesis and enzyme-catalyzed ring-opening polymerization of a novel carbonate monomer, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (1). Various commercially available lipases were screened for their ability to polymerize 1 in bulk at 80 °C. Monomer conversion and molecular weight of the polymer were significantly influenced by the source of the enzyme. For example, of the seven lipases screened, lipase AK (from Pseudomonas fluorescens) gave the highest monomer conversion (97%) and molecular weight (Mn = 6100). In reactions carried out under identical experimental conditions, no polymerization was observed when thermally deactivated lipase AK was used. Debenzylation of 2 by catalytic hydrogenation led to the corresponding linear polycarbonate, 3, with pendent carboxyl groups. Presence of pendent carboxyl groups is expected to enhance the biodegradability of the polyc...
122 citations
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TL;DR: Privileged substructures are believed to achieve this through the mimicry of common protein surface elements that are responsible for binding, such as β- and gamma;-turns.
Abstract: Privileged substructures are of potentially great importance in medicinal chemistry. These scaffolds are characterized by their ability to promiscuously bind to a multitude of receptors through a variety of favorable characteristics. This may include presentation of their substituents in a spatially defined manner and perhaps also the ability to directly bind to the receptor itself, as well as exhibiting promising characteristics to aid bioavailability of the overall molecule. It is believed that some privileged substructures achieve this through the mimicry of common protein surface elements that are responsible for binding, such as β- and gamma;-turns. As a result, these structures represent a promising means by which new lead compounds may be identified.
2,434 citations
TL;DR: Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells.
Abstract: Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.
2,249 citations
TL;DR: This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field.
Abstract: Aliphatic polyesters prepared by ring-opening polymerization of lactones are now used worldwide as bioresorbabale devices in surgery (orthopaedic devices, sutures, stents, tissue engineering, and adhesion barriers) and in pharmacology (control drug delivery). This review presents the various methods of the synthesis of polyesters and tailoring the properties by proper control of molecular weight, composition, and architecture so as to meet the stringent requirements of devices in the medical field. The effect of structure on properties and degradation has been discussed. The applications of these polymers in the biomedical field are described in detail.
1,366 citations
TL;DR: This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems).
Abstract: Polycaprolactone (PCL) is an important polymer due to its mechanical properties, miscibility with a large range of other polymers and biodegradability. Two main pathways to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid: 6-hydroxyhexanoic acid, and the ring-opening polymerisation (ROP) of a lactone: e-caprolactone (e-CL). This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems). A surprising variety of catalytic systems have been studied, touching on virtually every section of the periodic table. A detailed list of reaction conditions and catalysts/initiators is given and reaction mechanisms are presented where known. Emphasis is put on the ROP pathway due to its prevalence in the literature and the superior polymer that is obtained. In addition, ineffective systems that have been tried to catalyse the production of PCL are included in the electronic supplementary information for completeness (141 references).
1,010 citations
Journal Article•
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TL;DR: Investigations compel the view that the ratio of the vital capacity to the body length, trunk length, chest circumference, surface area or weight or any combination of these measurements, is too variable to admit of any workable standard or normal value.
Abstract: These investigations and several others that have beenpublishedwithin recentyears compel us us to hold the view that the ratio of the vital capacity to the body length, trunk length, chest circumference,surfacearea or weight or any combination of thesemeasurements, is too variable to admit of any workable standardor normal value. On the other hand the vital capacity of each individual, after he had becomeaccustomedto the use of the spirometer,will be found to be subjectto but small variations as long as good health is maintained. Thereseems to beevidenceto show that a reductionin the vital capacityis ofen the first sign of a progressivedamageto the respiratorytissue.
976 citations