Browsing by Author "Govender, Hogantharanni."

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A comparative study of solvent extraction, Soxhlet extraction, steam distillation, headspace analysis and headspace solid phase microextraction for the extraction of volatile terpenoid compounds in the curry leaf plant (Murraya koenigii).
(2010) Govender, Hogantharanni.; Martincigh, Bice Susan.; Kindness, Andrew.
A comparative study was undertaken of different extraction methods for the isolation of volatile organic compounds from Murraya koenigii (curry leaf plant). The techniques studied included the traditional methods of extraction, namely, Soxhlet and solvent extraction as well as steam distillation. The solvent–free extraction techniques of headspace analysis and headspace solid phase micro-extraction (HS-SPME) were also investigated. In the evaluation of SPME, two different fibre coatings, poly(dimethylsiloxane) and poly(acrylate), were compared. Preliminary work to determine the effect of extraction parameters, such as extraction time, was carried out. The volatile oils in the fresh leaves of Murraya koenigii were isolated by the above-mentioned extraction methods and analysed by gas chromatography-mass spectrometry. The main aroma contributing compounds were identified by comparison of their retention times with those of standards and their mass spectra with those of known compounds contained in the National Institute of Science and Technology Standard Reference Database 1A (NIST 98). The essential oil contained mainly terpenes: monoterpene and sesquiterpene hydrocarbons. The constituents were identified and only the five selected analytes of interest, a-pinene, β-pinene, a-phellandrene, β-caryophyllene and a-caryophyllene were quantified in three of the methods, namely solvent extraction, soxhlet extraction and steam distillation. From the quantitative determination of the compounds of interest, steam distillation favoured the extraction of β-caryophyllene. The solvent and Soxhlet extractions showed no significant differences between the quantities obtained for a- and β- caryophyllene. The steam distillation and Soxhlet methods showed similar quantities of a-caryophyllene extracted. The extraction of the monoterpenes, a-pinene, β-pinene, and a-phellandrene, was favoured by the Soxhlet method of extraction. Quantification was difficult with HS-SPME and headspace analysis. Headspace analysis proved effective in the detection of the very volatile analytes. Headspace-SPME combined with GC-MS was found to be suitable for the identification of both monoterpenes and sesquiterpenes of M. koenigii. From this study, solvent extraction and Soxhlet extraction were found to be superior to the other methods studied for the characterisation and quantitation of the volatile organic compounds in essential oils of Murraya koenigii.
Synthesis and biological activity of quinoline derivatives.
(2018) Govender, Hogantharanni.; Koorbanally, Neil Anthony.
A total of 42 compounds, which include 12 quinoline-3-carboxamides (A5a-l), 15 quinolone thiosemicarbazones (B5a-o) and 15 tetrazoloquinoline phenylhydrazones (C5a-o) were successfully synthesized and characterised. Of these 42 compounds, 36 have been prepared for the first time in this work, with 4 thiosemicarbazones and 2 phenylhydrazones being previously reported. The 2-chloroquinoline-3-carbaldehyde intermediate was the basic scaffold on which the three types of quinoline hybrids were based on. Various substituents were placed at C-6 on this substituent to create small libraries of compounds. This key intermediate was prepared using the Vilsmeier-Haack reaction, which resulted in a quinoline with a carbaldehyde at C-3. In the case of the quinoline-3-carboxamides, the aldehyde at position 3 was oxidized to the acid functionality via the Pinnick Oxidation. This was followed by the preparation of carboxamides using a coupling reaction with different substituted anilines and using the coupling reagents EDC∙HCl and HOBt in the presence of triethylamine used as a base. The thiosemicarbazones were prepared by condensing the 2-quinolone carbaldehydes with thiosemicarbazides and the tetrazolophenylhydrazones prepared by first forming a tetrazolo ring with sodium azide on the quinoline and then forming phenylhydrazones from the carbaldehyde moiety and phenylhydrazines. The quinoline scaffold was varied at C-6 with Cl, F, Br and CH3 groups and the various hybrids were varied again using different anilines, thiosemicarbazides and phenylhydrazines. The structures of the synthesised compounds were elucidated using 1D and 2D NMR spectroscopy. The synthesised compounds were tested for their antibacterial activity against two Gram positive (Staphylococcus aureus and S. aureus Rosenbach (MRSA)) and four Gram negative species, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Salmonella typhimurium. Although compounds in all three classes of hybrids showed antibacterial activity, these were not as good as current drugs being used as antibiotics. The synthesised compounds showed antibacterial activity in the range of 0.80 to 36.49 mM.