Ahindra Nag

New utilization of vegetable oils

Energy crisis and growing fuel shortage is a global concern. This phenomenon is more conspicuous in the populous, developing countries. In order to look for alternatives and extenders to the conventional fuels, studies were performed on the seed oil of some relatively unknownPutranjiva roxburghii, a plant that is abundantly available in the Indian tropical subcontinent. In a prototype experiment, the physicochemical properties of theP. roxburghii seed oil were found to be suitable for blending with diesel up to 50% without any sacrifice in performance of an internal combustion engine. Another industrially useful material, factice (vulcanized oil), was also prepared from the same oil. It was found to be suitable for blending with rubber, improving its strength, hardness, viscosity, and scorch time, and also increased its degradation temperature. This oil is not commercially traded in the market and has not yet been recommended as edible; hence industrial exploitation will not affect consumer market directly. A few more preliminary experiments indicated that the by-product oilcake is a good plant nutrient and the oil exerts profound antifungal activity. These properties need to be investigated more extensively. This plant and its oilseed deserve further attention and investigation, particularly in the tropical, coastal developing countries.

Kinetics of solvent-free geranyl acetate synthesis by Rhizopus oligosporus NRRL 5905 lipase immobilized on to cross-linked silica

The objective of the present work was to study the kinetics of the solvent-free synthesis of geranyl acetate by a novel lipase (activity 60 U g−1) made by immobilization of lipase from Rhizopus oligosporous NRRL 5905 on to cross-linked silica gel. Transesterification was performed with vinyl acetate as the acyl donor. Vinyl acetate was used in large excess compared to geraniol, which made the reaction pseudo first order with respect to geraniol and the reaction rate followed Michaelis–Menten kinetics for a single substrate. To obtain the highest yield for geranyl acetate, various relevant physical parameters such as shaking speed, reaction time, enzyme concentration, initial water amount and reaction temperature that influence the activity of lipase were investigated. A maximum molar conversion of 67% was achieved after 48 h of reaction at 30°C, at an enzyme concentration of 25% w/v of reaction mixture. Substrate conversion remained constant for five successive cycles; thereafter the conversion dropped by only 11%. Using a pseudo first-order kinetic model for geranyl acetate synthesis in the absence of organic solvents, apparent Km and Vmax values were evaluated as 60 mM and 141 µmol g−1 h−1, respectively.

Selective Reduction of Conjugated Ethylenic Linkage in the Presence of Ion-Exchange Resin Bound Borohydride

Abstract The use of crosslinked polystyrene anion-exchange resin as a support for borohydride ions made it possible to reduce conjugated olefinic bonds selectively under very mild conditions. The isolation of the reduced products by a simple filtration and evaporation process is another interesting feature of this reaction.

Self-assembled cardanol azo derivatives as antifungal agent with chitin-binding ability

Cardanol is a non-isoprenoic phenolic lipid-mixture of distilled cashew nut shell liquid obtained from Anacardium occidentale. Herein, cardanol is purified from cashew nut shell liquid (CNSL) and synthesized to new compounds with different azo amphiphiles. These synthesized compounds are allowed to self-assembled in hydrophobic environment and checked antifungal activity against Candida albicans. Self-assembled structure of CABA showed higher antifungal activity (16μg/mL) and chitin-binding ability in comparison to CAP and CANB. Furthermore, the self-assembled azo amphiphiles are immobilized with silver ions to prepare hydrogel which showed eight folds enhanced antifungal activity. Toxicity is reduced by several folds of self-assembled or hydrogel structure in comparison to pure compounds. Thus, the self-assembled structure of amphiphiles and their hydrogels have been found to be new macromolecules of interest with potential use as antifungal drugs.

Utilization of Three Non-Edible Vegetable Oils for the Production of Biodiesel Catalysed by Enzyme

Enzymatic transesterification by using lipase as catalyst has become more attractive for the production of bio- diesel due to easy separation of products such as glycerol and fatty acid esters. Comparative studies of enzyme catalyzed transesterification of three less attended non edible oils (jatropha, karanja and putranjiva) have been discussed. The maximum yield has been obtained at 3:1 molar ratio of methanol and oil at 40°C and 8hrs reaction time. The percentage of conversion has been analyzed by Gas chromatography and 400 MHz 1 H NMR. It has been observed that degummed vegetable oil gives higher conversion in transesterification reaction than straight vegetable oil. Secondary alcohol gives better result than methanol for the production of biodiesel due to its higher miscibility nature in oil.

Chemoenzymatic synthesis of antiinflammatory drugs in enantiomerically pure form

A novel chemoenzymatic route to chiral antiinflammatory drugs in enantiomerically pure form is described.

Selectivity in enzyme catalysed reaction : preferential hydrolysis of saturated methyl ester over the corresponding unsaturated ester by pig liver esterase

SummarySaturated methyl ester is preferentially hydrolysed in presence of corresponding α,β-unsaturated ester by Pig Liver Esterasse. This selectivity is known for aliphatic, aromatic and heterocyclic esters.Chemo, regio and stereoselective transformations are an important goal towards synthetic efficiency (Bartman and Trost, 1984). Among the various methods that are employed to achieve such reactions, enzymatic transformations are in the forefront of current research activities (Jones, 1986) because of several advantages over the chemical methods. These include extremely high degree of selectivity, easier isolation of products, specially with immobilized enzymes and their reusability. In the past decade this class of biocatalysts has provided a plathora of valuable selective transformations (Boland et.al, 1991). Pig Liver Esterase (PLE) is one such enzyme which has been thoroughly studied and used for asymmetric (Zhu and Tedford, 1990) and regioselective (Adachi et.al, 1986) hydrolysis of esters. Several chiral building blocks for the synthesis of complex natural products (Imori et.al., 1983) have been synthesized through PLE. In this communication, we report the preferential hydrolysis of a saturated ester over its unsaturated counterpart. The preference is total and works well for aliphatic, aromatic as well as heterocyclic systems.

Enzymatic synthesis and analytical monitoring of terpene ester by 1H NMR spectroscopy

Terpene esters of fatty acids have potential applications in food, cosmetic, and pharmaceutical industries. The present study focuses on the synthesis of terpene esters of long chain fatty acids catalyzed by Candida antarctica lipase B. Different parameters like temperature, solvent, and enzyme concentration for the esterification of terpene alcohols (geraniol and citronellol) with oleic acid were studied. Maximum conversion (98 %) was found for both terpene esters at 60°C in 2,2,4-trimethylpentane as well as in dry hexane and around 95–97 % in other tested solvents. The reaction was also carried out using stearic and linoleic acid in hexane to study the effects of unsaturation in the substrate in which stearic acid showed the maximum conversion. The reaction was monitored by 1H nuclear magnetic resonance spectroscopy. Using the peak integration values of methylene protons of terpene and terpene ester of δ = 3.6 and 4.0 for citronellol and δ = 4.2 and 4.6 for geraniol, respectively, percentage conversions of each of the esters were calculated.

Selectivity in enzyme catalysed reactions: Preferential hydrolysis of a phenolic acetate in the presence of an aromatic methyl ester by pig liver esterase

INTRODUCTION : Synthesis of CcxnPlex natural products often requires chemo. reglo or stereoselective transformations. some of which can be accompllshed by various synthetic reagents(Bartman and Trost, 1984). For example chemoselective hydrolysis of t-butyl ester in presence of a benzyl ester can be carried out with trifluoroacetic acid (Bryan et.al.1977) while the benzy I ester is removed preferentially by hydrogenolysls (Stelakatos et.al, 1966) or by Na/llould NH9 (EIaldwln,1981). However the success of purely chemical methods In chemoselective reactlons Is only limited. The alternate biocatalytlc approach (Tramper et.al. 1984; Davies, 1989) has much wider apollcatlon compared to the chemical methods. Pig Liver Esterase (PLE) a hydrolytic enzyme has been frequently used for the preparation of enantlomerlcally pure chlral building blocks (Zhu and Tedford, 1990; Santaniello, 1992). However ,PLE has been rarely used for carrying out chemoselectlve transformations. Recently (Basak et.al.1993). PLE has been used to hydrolyse a saturated methyl ester preferentially over Its unsaturated counterpart. In thls communication we report the selective hydrolysis of a phenolic ester, namely the acetate,over an aromatic methyl ester, both functlonallties being present in the same molecule(Scheme-1)

CSJ acting as a versatile highly efficient greener resource for organic transformations

Simple, new, greener and efficient alternatives to the existing protocols have been developed for the reduction of aromatic aldehydes to their corresponding alcohols, decarboxylation of substituted benzoic acids (C6–C1) and substituted cinnamic acids (C6–C3) with a hydroxyl group at the para position with respect to the acid group to corresponding phenolic compounds and vinyl phenols respectively by using a natural feedstock, cucumber juice (CSJ), which acts as a greener solvent system, performing a substrate-selective reaction. Additionally, the hydrolysis of the acetyl as well as the benzoyl group of aromatic compounds has been carried out to afford excellent yield by CSJ.