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|Title:||Study of extraction processes and their impact on bioactivity of botanicals||Authors:||CHEAH LI CHIN, EMILY||Keywords:||Magnolia officinalis, SFE, PLE, milling, Mycobacterium smegmatis, FIC||Issue Date:||3-Aug-2009||Citation:||CHEAH LI CHIN, EMILY (2009-08-03). Study of extraction processes and their impact on bioactivity of botanicals. ScholarBank@NUS Repository.||Abstract:||Eight botanicals, namely Persicaria hydropiper, Murraya koenigii, Arachis hypogaea, Houttuynia cordata, Epipremnum pinnatum, Typhonium flagelliform, Magnolia officinalis (Magnolia) bark, and Imperata cylindrica were screened for antimicrobial and antioxidant properties. Extracts of Magnolia bark obtained by boiling in water and maceration in ethanol resulted in promising activity against Mycobacterium smegmatis. Thus, Magnolia bark was chosen as the model botanical material for further investigation.
Different milling methods were investigated. In comparison to cut and impact milling, conical screen milling enabled higher throughput of material with significant reduction in dust and fines generation and narrower particle size distribution of milled product. The grater-bore screen was crucial in fracturing the highly tensile bark material. One of the most attractive features of the conical screen mill was its robustness under choke feeding conditions, which enabled it to handle large loads at a time. The performance of impact and cut milling methods, on the other hand, was highly dependent on the feed weight used. The application of conical screen milling to botanical material has not been reported in literature. Conical screen milling was found to be superior to cut and impact milling in this study.
Modern extraction processes employing high diffusion fluids, i.e. pressurized liquid extraction (PLE) and supercritical fluid extraction (SFE), were compared against Soxhlet extraction (SXE) for the preparation of Magnolia bark extracts. Pressure and temperature were found to exert the strongest influence on SFE of honokiol and magnolol from Magnolia bark. Particle size exerted minimal influence on the SFE process, attesting to the high diffusivity of the supercritical fluid. On the contrary, PLE was strongly dependent on the particle size of the botanical matrix as well as the temperature of extraction. In general, extracts obtained by SFE had greater proportions of the bioactive compounds compared to those obtained by PLE and SXE. Pressurized liquid extraction resulted in comparable yields to SXE but at shorter extraction time and marked reduction in solvent consumption. Polar solvent possessing the hydroxyl group was found to increase the yields obtained by high diffusion fluid extraction systems.
SFE crude extracts of Magnolia bark were found to produce comparable or greater activity than streptomycin against Mycobacterium smegmatis. The MIC and FIC of the extract were obtained using a microdilution method developed. This method is suitable than the conventional macrodilution method for situations where the test materials are limited. The MIC of SFE extracts was found to be 0.460 - 0.930 mcg/ml, which was greater than that of rifampicin (1.00 - 1.25 mcg/ml) or honokiol (1.50 - 2.00 mcg/ml) and magnolol (1.00 - 1.50 mcg/ml) alone. Synergism was also observed between honokiol and magnolol, which is not reported in the literature. Additionally, a novel finding was the ability of the SFE extract to act as an adjuvant to streptomycin and rifampicin in antimycobacterial therapy, as indicated by the FIC indices of 0.45 and below.
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