A. Seenivasan

Bio: A. Seenivasan is an academic researcher from Department of Biotechnology. The author has contributed to research in topics: Monascus purpureus & Lovastatin. The author has an hindex of 5, co-authored 10 publications receiving 103 citations. Previous affiliations of A. Seenivasan include National Institute of Technology, Raipur & Annamalai University.

Microbial Production and Biomedical Applications of Lovastatin

Abstract: Lovastatin is a potent hypercholesterolemic drug used for lowering blood cholesterol. Lovastatin acts by competitively inhibiting the enzyme, 3-hydroxy-3-methylglutaryl coenzyme A reductase involved in the biosynthesis of cholesterol. Commercially lovastatin is produced by a variety of filamentous fungi including Penicillium species, Monascus ruber and Aspergillus terreus as a secondary metabolite. Production of lovastatin by fermentation decreases the production cost compared to costs of chemical synthesis. In recent years, lovastatin has also been reported as a potential therapeutic agent for the treatment of various types of tumors and also play a tremendous role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. This review deals with the structure, biosynthesis, various modes of fermentation and applications of lovastatin.

Characterization of Terephthalic Acid Monomer Recycled from Post-Consumer PET Polymer Bottles

Abstract: Summary The idea of recycling of PET to obtain terephthalic acid (TPH) monomer is fast gaining traction; therefore it has become imperative to develop standard characterization methods to assess the purity of terephthalic acid using reliable and easily available laboratory equipment/techniques. Experimental studies on recycling of post-consumer PET waste were conducted in a batch reactor. The PET was subjected to a de-esterification reaction to break down the ester bonds via alkali decomposition in ethylene glycol at 155 °C under the influence of ultrasound. The end product, terephthalic acid, was characterized for the functional purity using UV-Visible spectrophotometry, FT-IR, and thermal methods. The terephthalic acid was ascertained by the characteristic peak at 240 nm using UV-Visible spectrophotometer and was quantified using a commercially available standard sample of terephthalic acid. The purity of end product was confirmed using FT-IR and thermogravimetric and differential thermal analysis.

Lovastatin Nanoparticle Synthesis and Characterization for Better Drug Delivery

Abstract: Nano drug delivery system is the latest technology employed in various medicinal applications. This technol- ogy can be adapted to the conventional drug administration due to its site-specific targeting phenomena. The oral lipo- philic drug administration has its drawbacks due to poor solubility and bioavailability. Lipid-based carrier systems are now widely popular due to improved efficiency, especially for lovastatin delivery. Lovastatin is an important drug which arrests the rate-limiting step of the cholesterol cascade. This drug has short half-lives, poor oral-administered bioavailabil- ity, poor solubility, and is rapidly metabolizable. Based on the composition, the drug delivery carriers are classified into solid lipid nanoparticles (SLNs), lipid emulsions (LEs), and nanostructured lipid carriers (NLCs). Among them, NLCs are a smarter generation of drug delivery carriers for lovastatin. The selection of various lipid systems and their formulation are discussed in this paper. Moreover, the characterization of these carrier systems to achieve the optimal characteristic features is discussed in a concise manner.

Quantification of Lovastatin Produced by Monascus purpureus

Abstract: Development of a novel method for the quantification of lovastatin is an interesting problem in the analytical field. In the literature, many reports use spectrophotometric method for the quantification of lovastatin. However, the analysis of fermentation broth containing lovastatin appears to be inaccurate using spectrophotometric method. Hence, the estimation of lovastatin produced by Monascus purpureus and pure lovastatin was attempted by UV-visible spectrophotometer as well as HPLC. It was observed that the analogues and/or intermediates of lovastatin synthesized in the fermentation broth and the products of fermentation caused superimposition effect on the absorption spectrum. Phosphate is a medium constituent for the production of lovastatin by the organism which contributed significantly to the superimposition of absorption spectrum. On the other hand, HPLC analysis consistently gave reliable results for the estimation of lovastatin under all the experimental conditions studied.

Characterization, Modes of Synthesis, and Pleiotropic Effects of Hypocholesterolemic Compounds – A Review

Abstract: Studies on the various cholesterol-lowering agents is one of the important areas in clinical research. Identifica- tion and characterization of potential molecules from various sources have been carried out in the past and their relation- ship with the enzymes which are involved in the cholesterol cascade is gaining interest. In this review, we have high- lighted various inhibitors involved in the cholesterol cascade as well as cholesterol-lowering agents, viz., tocotrienol, flavonoids, phytosterols, phytostanols, statins, DADS, and synthetic compounds. The mechanism of action and characteri- zation of these hypocholesterolemic compounds are discussed in this communication. Major natural sources as well as synthetic and biological routes of synthesis of these compounds are reviewed in a concise manner. Especially, various HMG-CoA analogues including statins have been reviewed specifically. In this respect, researchers have identified 2,3- oxidosqualene cyclase-lanosterol synthase (lanosterol syn- thase, oxidosqualene-lanosterol cyclase, lanosterol synthase, 2,3-oxidosqualene-lanosterol cyclase, human lanosterol syn- thase (EC 5.4.99.7)) having a molecular weight of 83 kDa, catalyzing the highly selective cyclization reaction from the substrate 2,3-oxidosqualene (squalene 2,3-epoxide, squalene 2,3-oxide, (S)-squalene-2,3-epoxide, 2,3-epoxisqualene, oxidosqualene) into lanosterol, as an appropriate step for the inhibition of cholesterol biosynthesis (3). Oxidosqualene cyclase inhibitors (OSCI) arrest the downstream of 2,3- oxidosqualene which helps to stimulate epoxysterols to

Monascus secondary metabolites: production and biological activity

Abstract: The genus Monascus, comprising nine species, can reproduce either vegetatively with filaments and conidia or sexually by the formation of ascospores. The most well-known species of genus Monascus, namely, M. purpureus, M. ruber and M. pilosus, are often used for rice fermentation to produce red yeast rice, a special product used either for food coloring or as a food supplement with positive effects on human health. The colored appearance (red, orange or yellow) of Monascus-fermented substrates is produced by a mixture of oligoketide pigments that are synthesized by a combination of polyketide and fatty acid synthases. The major pigments consist of pairs of yellow (ankaflavin and monascin), orange (rubropunctatin and monascorubrin) and red (rubropunctamine and monascorubramine) compounds; however, more than 20 other colored products have recently been isolated from fermented rice or culture media. In addition to pigments, a group of monacolin substances and the mycotoxin citrinin can be produced by Monascus. Various non-specific biological activities (antimicrobial, antitumor, immunomodulative and others) of these pigmented compounds are, at least partly, ascribed to their reaction with amino group-containing compounds, i.e. amino acids, proteins or nucleic acids. Monacolins, in the form of β-hydroxy acids, inhibit hydroxymethylglutaryl-coenzyme A reductase, a key enzyme in cholesterol biosynthesis in animals and humans.

Funnels, Pathways and the Energy Landscape of Protein Folding: A Synthesis

Abstract: The understanding, and even the description of protein folding is impeded by the complexity of the process. Much of this complexity can be described and understood by taking a statistical approach to the energetics of protein conformation, that is, to the energy landscape. The statistical energy landscape approach explains when and why unique behaviors, such as specific folding pathways, occur in some proteins and more generally explains the distinction between folding processes common to all sequences and those peculiar to individual sequences. This approach also gives new, quantitative insights into the interpretation of experiments and simulations of protein folding thermodynamics and kinetics. Specifically, the picture provides simple explanations for folding as a two-state first-order phase transition, for the origin of metastable collapsed unfolded states and for the curved Arrhenius plots observed in both laboratory experiments and discrete lattice simulations. The relation of these quantitative ideas to folding pathways, to uni-exponential {\em vs.} multi-exponential behavior in protein folding experiments and to the effect of mutations on folding is also discussed. The success of energy landscape ideas in protein structure prediction is also described. The use of the energy landscape approach for analyzing data is illustrated with a quantitative analysis of some recent simulations, and a qualitative analysis of experiments on the folding of three proteins. The work unifies several previously proposed ideas concerning the mechanism protein folding and delimits the regions of validity of these ideas under different thermodynamic conditions.

Biotechnological production and applications of statins.

Abstract: Statins are a group of extremely successful drugs that lower cholesterol levels in blood; decreasing the risk of heath attack or stroke. In recent years, statins have also been reported to have other biological activities and numerous potential therapeutic uses. Natural statins are lovastatin and compactin, while pravastatin is derived from the latter by biotransformation. Simvastatin, the second leading statin in the market, is a lovastatin semisynthetic derivative. Lovastatin is mainly produced by Aspergillus terreus strains, and compactin by Penicillium citrinum. Lovastatin and compactin are produced industrially by liquid submerged fermentation, but can also be produced by the emerging technology of solid-state fermentation, that displays some advantages. Advances in the biochemistry and genetics of lovastatin have allowed the development of new methods for the production of simvastatin. This lovastatin derivative can be efficiently synthesized from monacolin J (lovastatin without the side chain) by a process that uses the Aspergillus terreus enzyme acyltransferase LovD. In a different approach, A. terreus was engineered, using combinational biosynthesis on gene lovF, so that the resulting hybrid polyketide synthase is able to in vivo synthesize 2,2-dimethylbutyrate (the side chain of simvastatin). The resulting transformant strains can produce simvastatin (instead of lovastatin) by direct fermentation.

Zerumbone-loaded nanostructured lipid carriers: preparation, characterization, and antileukemic effect.

Abstract: Zerumbone, a natural dietary lipophilic compound with low water solubility (1.296 mg/L at 25°C) was used in this investigation. The zerumbone was loaded into nanostructured lipid carriers using a hot, high-pressure homogenization technique. The physicochemical properties of the zerumbone-loaded nanostructured lipid carriers (ZER-NLC) were determined. The ZER-NLC particles had an average size of 52.68 ± 0.1 nm and a polydispersity index of 0.29 ± 0.004 μm. Transmission electron microscopy showed that the particles were spherical in shape. The zeta potential of the ZER-NLC was −25.03 ± 1.24 mV, entrapment efficiency was 99.03%, and drug loading was 7.92%. In vitro drug release of zerumbone from ZER-NLC was 46.7%, and for a pure zerumbone dispersion was 90.5% over 48 hours, following a zero equation. Using the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay in human T-cell acute lymphoblastic leukemia (Jurkat) cells, the half maximal inhibitory concentration (IC50) of ZER-NLC was 5.64 ± 0.38 μg/mL, and for free zerumbone was 5.39 ± 0.43 μg/mL after 72 hours of treatment. This study strongly suggests that ZER-NLC have potential as a sustained-release drug carrier system for the treatment of leukemia.