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Phytochemical Investigation of Trichilia emetica (Natal mahogany)

Usman, Abdullahi (2015) Phytochemical Investigation of Trichilia emetica (Natal mahogany). PhD thesis, Prifysgol Bangor University.

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Abstract

Trichilia emetica seeds have already been utilised for oil extraction. This project investigated the chemistry of by-products, especially water after boiling the seeds and the defatted residue. The first part of the study was to subject the seed oils to physicochemical analysis using standard methods of food analysis. The data obtained were acid (0.4±0.0 and 0.4±0.1 mg KOH/g), iodine (69.2±2.1 and 64.6±2.8 gI2/100g), peroxide (10.3±0.5 and 9.2±0.4 %) and saponifiable value (195.4±5.4 and 197.3±4.6) for T. emetica seeds from Ghana and Mozambique and were comparable to those of other edible oils. The fatty acid composition of the seeds and shell oils was determined using different analytical methods. The result obtained using 1H and 13C NMR and GC-MS of fatty acid methyl esters are 56-65% saturated (C14:0, C16:0, C18:0), 27-34% monounsaturated (C18:1, ω-9) and 4-10% polyunsaturated (C18:2 ω-6, 9 and C18:3 ω-6, 9, and 12) are in good agreement between the different methods of analysis for the proportion of individual fatty acids. Linolenic acid methyl ester was not detected in the seed oil. Phytochemical investigation of the unsaponifiable fraction of T. emetica seed oil resulted in the isolation of two sterols, β-sitosterol and stigmasterol. The second part of the study was the phytochemical examination of the boiled water extract of the seed. This resulted in the isolation of one new flavanol glycoside, catechin-3-O-α-L-rhamnopyranosyl (1→4) β-D-glucopyranoside and eight known compounds; catechin, epicatechin, taxifolin, elephantorrhizol, catechin 3-O-β-D-glucopyranoside, taxifolin 4’-O-β-D-glucopyranoside and eriodictyol 4’-O-β-D-glucopyranoside. Similarly, three known compounds Naringenin, Quercetin and Quercetin 3-O-β-D-glucopyranoside were isolated from the stem. To the best of our knowledge, this is the first report on the phenolic content of T. emetica. The third part of the study was the use of Azadirachta indica seeds and the seeds oil of Millettia pinnata as a model to check the various methods used in the unsuccessful attempt to isolate a limonoids from the seeds of T. emetica. These resulted in the isolation of two known limonoids and three furanoflavonoids: azadirachtin, nimbin, karanjin, pongapin and lanceolatin. The structures of these compounds were determined on the basis of spectroscopic methods and by comparison of the data obtained with literature. Some compounds were confirmed with X-ray crystallography.

Item Type: Thesis (PhD)
Subjects: Degree Thesis
Departments: College of Physical and Applied Sciences > School of Chemistry
Degree Thesis
Date Deposited: 25 Oct 2016 15:41
Last Modified: 18 May 2017 09:14
URI: http://e.bangor.ac.uk/id/eprint/8111
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