MPhil / PhD Theses

Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/213

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Start date: 1970Subject: search.filters.subject.Chemistry

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    Identification and estimation of the antioxidant activity of phenolic compounds in six medicinal oils
    (2010) Kotuwegedara, R.T.
    ABSTRACT: It is well known that constituents of many plants and herbs have been attracted a great deal of public and scientific interest because of their health-promoting effects as antioxidants and essential fatty acids sources. Six plants, Madhuca nerifolia (Mee), Sessamum indicum (Thala), Brassica juncea (Aba), Canarium zeylanicum (Kekuna), Calophyllum inophyllum (Domba) and Ricinus calamus ) (Endaru) were examined in order to determine their fatty acid compositions, phenolic compounds and antioxidant activities. In Sri Lanka medicinal seed oils are used only for limited number of applications in addition to their traditional medicinal purposes. Above medicinal plant oils are commonly used for traditional medicinal purposes. Mainly oils are extracted from the matured dry seeds by pressing. Traditionally, press works by applying pressure to seed paste to separate the oil and vegetation water from the solid material. The oil and vegetation water are then separated by standard decantation. The six medicinal oils contain a range of fatty acids including polyunsaturated fatty acids (PUFA) that are essential components in diet. The PUFA contents of five of the six investigated medicinal oil were significantly higher than those of palm oil, coconut oil and palm kernel oil. Among the tested six Sri Lankan medicinal oils, thala, mee and aba oils contain higher percentages of PUFA and EFA (Essential Fatty Acid) compared to the other expensive edible oils. According to the GLC analysis all the tested six medicinal oils contained, four common fatty acids Palmitic (C 16:0), Stearic (C 18:0), Oleic (C 18:1) and Linoleic (C 18:2) in different compositions. In addition to the above fatty acids kekuna oil contains capri lie acid (0.58%), capric acid (0.49%), lauric acid (4.10%) and myristic acid (1.63%) in small percentages. Linolenic acid (an omega-3 fatty acid) content of domba, kekuna, aba, mee and endaru oils are 0.21%, 19.09%, 24.37%, 0.06% and 1.87% respectively. Total polyphenol content (TPC) of medicinal oils was measured by using Folin - Denis method. According to the analysis of the tested six medicinal oils, the greatest TPC, 11 Img gallic acid equivalent (GE) per kilo gramme of oil, was detected in the domba seed oil extract, while the lowest TPC, 31 mg GE/kg, was observed in the Endaru seed oil extract. Methanol and water crude extracts from medicinal oils were investigated for their antioxidant activity in three different assays namely, oxidation of deoxyribose system, 1, l-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and the reducing power. Among the six oil extracts, the domba oil extract showed the most potent antioxidant activity in each assay, showing 39.8% (at 60 pg/ mL) oxidation of deoxyribose method, 68.5% in the DPPH radical scavenging method (at 60 pg/ mL) and 36.8 % (at 50pL extract) of reducing power. Positive correlations were found between total phenolic content in the oil extracts and their antioxidant activities. Therefore medicinal oils may have potential as natural antioxidants. RP-HPLC (Reversed phase) with UV detection was employed to distinguish phenolic compounds in above six medicinal oils. The phenolic substances were identified and quantified after comparison with reference standards. The tested oils contain, following one or more compounds like 3,4- dihydroxybenzoic acid, (+) - catechin hydrate, p- hydroxybenzoic acid, vannilic acid, caffeic acid, syringic acid, vannilin, ellagic acid and cinnamic acid as phenolic compounds in different concentrations. Medicinal oil blends were prepared by mixing with coconut oil. For that three seed oils were used, specifically aba, mee and thala while these oils contain higher amount of long chain polyunsaturated fatty acids and more compatible as edible oils compared to the other analyzed medicinal oils. Among the prepared blends, 40% aba, 60% mee and 50% thala oil blends are more favorable from the taste, color, texture and appearance than the other blends prepared with the same oils in different volume fractions. The tested thala (50%), mee (60%) and aba (40%) oil blends contain significant amount of EFA compared to the other expensive edible oils. The tested medicinal oil blends were further subjected to analysis their cholesterol lowering effect in vivo studies by using Wistar rats. By this method, total cholesterol level (HDL and LDL) and triglycerides level were tested during the period for 84 days in the blood serum of the Wistar rats. Most interestingly, tested aba oil blend (40%) showed the significant results than the other two-tested oil blends. However other tested two oil blends showed the excellent results compared to the commercial coconut oil. Total cholesterol level in the blood of Wistar rats when fed with aba, thala, mee oil blends and commercial coconut oil are 128 mg/ dL, 131 mg/ dL, 142 mg/ dL and 162 mg/ dL respectively. Significantly lower concentrations of blood serum triglycerides were found among the tested oil blends than the commercial coconut oil. Triglycerides level in the blood of Wistar rats when fed with aba, thala, mee oil blends and commercial coconut oil were found to be 96 mg/ dL, 109 mg/ dL, 136 mg/ dL and 152 mg/ dL respectively. These results suggest that the fatty acid unsaturation of medicinal oil blends were excellent source to reduce the cholesterol level and triglyceride level of the blood serum and provide more beneficial health effect to human beings.
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    Breeding structure of dengue vector, Aedes albopictus in areas at risk of epidemics using DNA markers
    (2010) Mapa, M.M.S.T.
    ABSTRACT: Dengue fever is currently considered to be the most serious vector-bom disease in Sri Lanka. Aedes aegypti, and Aedes albopictus have been implicated to be the most important vectors of dengue transmission. To understand the transmission of the disease, knowledge of the population (breeding) structure and magnitude of dispersal (gene flow) among Aedes mosquito populations is essential, as it directly influences dengue virus transmission. Random amplified polymorphic DNA (RAPD) analysis was undertaken to examine breeding structure in 19 A. albopictus populations from three worst affected districts in Sri Lanka, namely Colombo, Gampaha and Kandy, with a distance range extending —100 km. The data were used to determine the genetic diversity, differentiation, magnitude of gene flow among A. albopictus populations at the macro (different districts) and micro (different sites in a district) geographical levels. Allele and genotype frequencies were measured on 62 RAPD loci. Allele frequencies were estimated assuming that RAPD alleles segregate as dominant markers and the genotype frequencies at those loci are in Hardy-Weinberg equilibrium. The investigation showed that A. albopictus appears to be the dominant mosquito species of the sampled areas of each district. Nei’s mean gene diversity, He, in each district ranged from 0.2722 - 0.3173. High levels of population differentiation (structuring) was found in both among three districts (Gst = 0.2969; Nm = 1.1841; 9 = 0.1915) and among different cities of each district (Gst =0.1558-3343). The intra population polymorphism, Hs, in each district is also high and ranged from 0.2009-0.2637. The level of gene flow among A. albopictus populations within Colombo district is moderate (Nm = 1.6711 mosquitoes per generation). Highest values of gene flow were observed in Gampaha district (Nm = 2.7096) with lowest values observed from Kandy district (Nm = 0.9955). Cluster analysis based on Nei’s genetic distance, indicate that populations from neighboring areas in each district are clustered according to their geographical origin. The result indicate significant population differentiation and structuring of A. albopictus mosquitoes in Sri Lanka, which may be attributed to dynamic equilibrium between factors that favor differentiation and homogenizing factors in recently established populations.
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    Comparison of fatty acid composition and antioxidant properties of virgin coconut oil and traditional coconut oil
    (2010) Hapuarachchi, C.D.
    ABSTRACT: The major quality parameters (peroxide value, acid value, iodine value and saponification value) of coconut oil were determined using reported methods. Both traditional coconut oils (TCO1, TCO2 and TCO3) and virgin coconut oils (VC01, VC02 and VC03) gave different results for quality parameters (Acid value and peroxide value) which were prepared using different endosperm components. The peroxide value of TCO 3 was found to have the lowest value compared to other oils and the lowest acid value was observed in VCO 2. Individual fatty acid analyses of traditional coconut oil, virgin coconut oil and commercial coconut (CCO) were done using gas chromatography. The phenolic composition and antioxidant potential were determined and compared in TCO, VCO and CCO. The objective of this study was to investigate how processing method, temperature and components of the endosperm of coconut affected the yields of phenolic substances and the antioxidant capacity of coconut oil. Total phenolic content of TCO and VCO was determined by the Folin-Denis procedure and expressed as acid equivalents. The total phenol content in TCO varied from 66 - 305 mg/kg and in VCO the above value varied from 62 - 66 mg/kg . In addition, antioxidant activities were tested by using 2,2-diphenyl-l-picryhydrazyl (DPPH) free radical scavenging assay, deoxyribose assay and ferric-reducing antioxidant power. Polyphenol fraction from TCO was found to have the highest inhibitory effect on radical scavenging activity and reducing power compared to that from the other two oils. Individual phenolic compounds present in the nonsaponifiable fraction of coconut oils were identified and quantified by Reverse Phase HPLC with UV detection. The phenolic compounds were identified comparing the retention time of authentic standards. Then the phenolic compounds were quantified by using calibration curves Effect of polyphenol fraction isolated from TCO, VCO and CCO were tested for the ability to maintain physiological antioxidant levels. Coconut oil mixed meals were fed to Wistar rats for 84 days and after the experimental period, Trolox Equivalent Antioxidant Capacity (TEAC) of erum of rats were compared. TEAC value was determined by the ABTS [2,2/-azinobis (3-ethylbenzothiazoneline-6-sulfonic acid)] assay using the Trolox as a standard compound. The results of the experiment showed that the diet containing TCO, had the highest level of TEAC value and the value significantly increased and stabilized with the time. Phenolic compounds and antioxidant activity of coconut cake (poonac) was also investigated. TCO shows excellent antioxidant properties due to the rich phenolic fraction of TCO. The nutritional quality of other coconut oil cans also improved by incorporation of phenolic substances in to coconut oil from coconut cake. The study indicated better antioxidant activities of coconut cake extracts compared to BHT. Enriched coconut oil was prepared using coconut cake and copra oil and this oil effectively enhanced the total antioxidant capacity of the blood serum of Wistar rats. The total phenol contents in coconut oils significantly correlated with TEAC values.
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