Recent Developments in Selected Sesquiterpenes: Molecular Rearrangements, Biosynthesis, and Structural Relationship among Congeners

Recent developments in selected sesquiterpenoids are reviewed for the past one decade (2005–2017) with special reference to Mechanisms of multistep molecular rearrangements of some sesquiterpenes or derivatives based on isotopic labeling studies and extensive spectroscopic analysis such as molecular rearrangement of acetyl cedrene to cedrene follower, acid catalyzed rearrangement of moreliane-based triketone, synthesis of (−)-isocomene and (−)-triquinane by acid-catalyzed rearrangement of (−)-modhephene, Total synthesis of (+)-cymbodiacetal, BF3 catalyzed molecular rearrangements of mono epoxides of α- and β-himachalenes, santonic acid: Zn-HCl-ether reduction. Insights into biosynthesis of albaflavenone, caryol-1(11)-ene-10-ol, (+)-koraiol, pogostol, patchouli alcohol and valerenadiene are discussed. Congeners for probing structure-biosynthetic relationship. This approach is discussed with the availability of very interesting results on the isolation of highly oxygenated secondary metabolites from endophytic fungi, Xylaria sp

BIOLEACHING OF COBALT AND ZINC FROM PYRITE ORE IN RELATION TO CALCITIC GANGUE CONTENT

Bioleaching of a pyrite ore containing high concentrations of cobalt (0.1%) and zinc (0.065%) was affected by small amounts of calcitic gangue (from 0.01 to 1.01%). Results from an air-lift percolator and from Erlenmeyer flask experiments show that a small percentage of calcite raises the pH and arrests the growth of the acidophilic bacterium Thiobacillus ferrooxidans. In percolator experiments, when calcite is completely removed by the continuous addition of small quantities of acid, and the pH of the liquor becomes acid, the micro-organism begins to grow and to bio-oxidize the pyrite ore. The growth of T. ferrooxidans shows different lag phase spans (from 13 to 190 days) depending on carbonate dissolution. The metals Fe, Zn and Co are released into the leaching solution together at different rates after a lag-time which depends on calcite concentrations in pyrite gangue. Metal ratios in the mineral bulk are different from those in the liquor, Zn dissolving 5 times more readily than Co. Bioleaching rates for metal removal from pyrite are higher in percolator (for Fe, from 5 to 15 mg/l/h) than in flask experiments (from 0.5 to 2 mg/l/h), but the lag phases are shorter (from 2 to 65 days). The differences between the two systems are related to calcite dissolution and gypsum precipitation

Integrated biological approach for the enhanced degradation of lindane

400-406Lindane is a persistent organic pollutant (POP) and its removal from various environmental compartments is a global priority. In the present study, three lindane degrading bacterial cultures, viz. Pseudoarthrobacter sp., Pseudomonas sp. and Klebsiella sp., were selected from among ten isolates obtained from lindane-exposed soils by enrichment culture technique. The cultures exhibited a maximum lindane degradation efficiency of ~50%, having little significance in bioremediation. However, in the presence of protozoa (ciliates) obtained from the same enrichment culture, lindane degradation efficiency of bacterial cultures increased to the tune of 90-92% with concomitant formation of 1,2,4-trichlorobenzene, a key degradation product. Lindane degradation by the bacterial cultures was also found to get enhanced by 10-15% in the presence of root exudates of lindane-tolerant plants, viz. corn, chili and coriander, even though these plants were unable to uptake any lindane and thus were unsuitable for phytoremediation per se. These data highlight the need for an intensive investigation on (a) bacteria-protozoa interactions for bioremediation of POPs and (b) use of POP-degrading bioinoculants in the rhizospheric soil of resistant plants as a possible alternative, in the absence of a viable conventional remedial option

Terpenoids-XXXVII: structure of α-elemene

On the basis of degradative and NMR studies, structure I is assigned to the hydrocarbon γ-elemene, the principal component obtained during acetic acid-perchloric acid dehydration of elemol (II)

Synthesis of olivacene, a constituent of <i>Archilejeunea olivacea</i>

2662-2664A simple synthesis of olivacene 1, a naturally occurring sesquiterpenoid hydrocarbon isolated from Archilejeunea olivacea has been described

Bioremediation of Metalliferous Wastes and Products using Inactivated Microbial Biomass

426-443In a developing country like India,. the rush for rapid industrial development coupled with lack of awareness about metal toxicity has become a serious concern to environmentalists. Some technologies, which are used in developed countries for detoxifying metals from industrial effluents, cannot be used in India due to economic constraints. Therefore, there is an urgent need for developing an economical and environment-friendly technology. At the same time, it is essential to prevent the loss of metals through the effluents. The 'Metal Biosorption' process provides a promising alternative method for economical recovery of metals

Terpenoids-XLVIII: structure and stereochemistry of hydroxyvaleranone and acetylhydroxyvaleranone

Two new sesquiterpenes, hydroxyvaleranone and its acetyl derivative, have been isolated from Indian valerian root oil (Valeriana wallichi). On the basis of NMR spectral results along with other spectroscopic, analytical and chemical data, structure I has been assigned to hydroxyvaleranone. ORD data and chemical evidences also indicate that it is represented by the stereoformula XXIII

Terpenoids-LVI: absolute configuration of elemol

The absolute configuration of elemol has been decided on the basis of its direct conversion to tetrahydrosaussurea-lactone. It is also shown that the lactone afforded by the formic acid treatment of the hydroxy acid obtained by ozonisation of dihydro elemon is a γ-lactone and not a δ-lactone as previously assumed