Browsing by Author "Ameer, Farouk"
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Item Inhibition of oxidative stress and skin aging-related enzymes by prenylated chalcones and other flavonoids from helichrysum teretifolium(MDPI, 2015) Popoola, Olugbenga K.; Marnewick, Jeanine L.; Rautenbach, Fanie; Ameer, Farouk; Iwuoha, Emmanuel I.; Hussein, Ahmed A.Ten flavonoid-related structures viz. heliteretifolin (1), isoxanthohumol (2), 2',4',6'-trihydroxy-3'-prenylchalcone (3), isoglabranin (4), glabranin (5), 7-methoxyisoglabranin (6), quercetin (7), 4'-methoxyquercetin (8), 4'-methoxykaempferol (9) and mosloflavone (10) were isolated from a H. teretifolium methanolic extract and identified. One of them (compound 1) is reported for the first time from a natural source, while compounds 6, 8–10 were isolated for the first time from the genus Helichrysum. The total extract of H. teretifolium showed potent antioxidant activity. When tested for total antioxidant capacity compound 3 possesses moderate biological activity compared to 2, which displayed some of the highest TEAC values (4529.01 ± 2.44; 4170.66 ± 6.72) µM TE/g, respectively. Compounds 7 and 8 demonstrated the highest inhibitory activities on Fe2+-induced lipid peroxidation (IC50 = 2.931; 6.449 µg/mL); tyrosinase (8.092; 27.573) and elastase (43.342; 86.548). Additionally, the total antioxidant capacities measured as FRAP (4816.31 ± 7.42; 3584.17 ± 0.54) µM AAE/g, and ORAC for hydroxyl radical (7.265 ± 0.71; 6.779 ± 3.40) × 106 and peroxyl radical (17.836 ± 2.90; 12.545 ± 5.07) × 103 µM TE/g were also observed for compounds 7 and 8, respectively. In conclusion, H. teretifolium total extract represents a rich source of bioactive constituents with potent antioxidant and moderate anti-tyrosinase and anti-elastase activities that can help to avert accumulation of free radicals in the body, and could therefore be good candidates for the prevention and/or treatment of skin-related conditions, such as aging. This is the first scientific report on the chemical and biological profile of H. teretifolium.Item Low-Cost feedstock conversion to biodiesel via ultrasound technology(MDPI, 2009) Babajide, Omotola; Leslie, Petrik; Amigun, Bamikole; Ameer, FaroukBiodiesel has attracted increasing interest and has proved to be a good substitute for fossil-based fuels due to its environmental advantages and availability from renewable resources such as refined and waste vegetable oils. Several studies have shown that biodiesel is a better fuel than the fossil-derived diesel in terms of engine performance, emissions reduction, lubricity and environmental benefits. The increasing popularity of biodiesel has generated great demand for its commercial production methods, which in turn calls for the development of technically and economically sound process technologies. This paper explores the applicability of ultrasound in the optimization of low-cost feedstock – in this case waste cooking oil – in the transesterification conversion to biodiesel. It was found that the conversion efficiency of the waste oil using ultrasound was higher than with the mechanical stirring method. The optimized variables of 6:1 methanol/oil ratio at a reaction temperature of 30 °C and a reaction time of 30 min and 0.75% KOH (wt/wt) catalyst concentration was obtained for the transesterification of the waste oil via the use of ultrasound.Item Marrubiin(MDPI, 2013) Popoola, Olugbenga K.; Elbagory, Abdulrahman M.; Ameer, Farouk; Hussein, Ahmed A.The ethno-medicinal approach to drug discovery represents one of the most important sources of new and safe therapeutic agents to the challenges confronting modern medicine and daily life. Many of the traditionally important medicinal plants contain active molecules or ones that serve as precursors to biosynthesised secondary metabolites to which the biological activity could be attributed. Marrubiin is one such compound and is a potential valuable compound which exists in high concentrations in many traditionally important Lamiaceae species which have demonstrated excellent pharmacological properties with commendably high safety margins. Marrubiin's attributes include a low turnover, high stability and little catabolism, which are core characteristics required for therapeutic compounds and nutraceuticals of economic importance. In addition, marrubiin is considered a potential substrate for potent active compounds viz; marrubiinic acid, and marrubenol. The contribution of marrubiin to drug discovery thus needs to be put into prospective due to its ready availability, high potential applications and ease of modification. In this short review we highlight the most important chemical and pharmacological aspects reported on marrubiin since it was discovered.Item Novel zeolite Na-X synthesized from fly ash as a heterogeneous catalyst in biodiesel production(Elsevier, 2012) Babajide, Omotola; Petrik, Leslie; Musyoka, Nicholas; Ameer, FaroukSeveral studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to demonstrate the prospect of utilizing South African class F fly ash as a raw material for zeolite synthesis subsequently applied as a solid base catalyst in the production of biodiesel. A novel faujasite zeolite material synthesized from South African class F fly ash and denoted as FA/Na-X was ion exchanged with potassium to obtain the South African class F fly ash based zeolite FA/K-X. This heterogeneous catalyst was used in the conversion of sunflower oil with methanol to yield fatty acid methyl esters. Different characterization techniques were employed to give more information about this zeolite material. The FA/Na-X and the ion exchanged FA/K-X were applied as catalysts in biodiesel synthesis via transesterification reactions. A high quality biodiesel with a yield of 83.53% was obtained at reaction conditions of methanol:oil ratio of 6:1, catalyst amount of 3% (w/w) of oil and reaction temperature of 65 ◦C after 8 h.Item Optimisation of biodiesel production via different catalytic and process systems(University of the Western Cape, 2011) Babajide, Omotola Oluwafunmilayo; Petrik, Leslie; Ameer, Farouk; Amigun, Bamikole; Dept. of ChemistryThe production of biodiesel (methyl esters) from vegetable oils represents analternative means of producing liquid fuels from biomass, and one which is growing rapidly in commercial importance and relevance due to increase in petroleum prices and the environmental advantages the process offers. Commercially, biodiesel is produced from vegetable oils, as well as from waste cooking oils and animal fats. These oils are typically composed of C14-C20 fatty acid triglycerides. In order to produce a fuel that is suitable for use in diesel engines, these triglycerides are usually converted into the respective mono alkyl esters by base-catalyzed transesterification with short chain alcohol, usually methanol. In the first part of this study, the transesterification reactions of three different vegetable oils; sunflower (SFO), soybean (SBO) and waste cooking oil (WCO) with methanol was studied using potassium hydroxide as catalyst in a conventional batch process. The production of biodiesel from waste cooking oil was also studied via continuous operation systems (employing the use of low frequency ultrasonic technology and the jet loop reactor). The characterisation of the feedstock used and the methyl ester products were determined by different analytical techniques such as gas chromatography (GC), high performance liquid chromatography (HPLC) and thin layer chromatography (TLC). The effects of different reaction parameters (catalyst amount, methanol to oil ratio, reaction temperature, reaction time) on methyl ester/FAME yield were studied and the optimum reaction conditions of the different process systems were determined. The optimum reaction conditions for production of methyl esters via the batch process with the fresh oil samples (SFO and SBO) were established as follows: a reaction time of 60 min at 60 ºC with a methanol: oil ratio of 6:1 and 1.0 KOH % wt/wt of oil; while the optimum reaction conditions for the used oil (WCO) was observed at a reaction time of 90 min at 60 ºC, methanol: oil ratio of 6:1 and 1.5% KOH wt/wt of oil. The optimum reaction conditions for the transesterification of the WCO via ultrasound technology applied in a continuous system in this study were: a reaction time of 30 min, 30 ºC, 6:1 methanol/oil ratio and a 0.75 wt% (KOH) catalyst concentration. The ultrasound assisted transesterification reactions performed at optimum conditions on the different oil samples led to higher yields of methyl esters (96.8, 98.32 and 97.65 % for WCO, SFO and SBO respectively) compared to methyl esters yields (90, 95 and 96 % for WCO, SFO and SBO respectively) obtained when using conventional batch procedures. A considerable increase in yields of the methyl esters in the ultrasound assisted reaction process were obtained at room temperature, in a remarkably short time span (completed in 30 min) and with a lower amount of catalyst (0.75 wt % KOH) while the results from the continuous jet loop process system showed even better results, at an optimum reaction condition of 25 min of reaction, a methanol: oil ratio of 4:1 and a catalyst amount of 0.5 wt%. This new jet loop process allowed an added advantage of intense agitation for an efficient separation and adequate purification of the methyl esters phase at a reduced time of 30 min. The use of homogeneous catalysts in conventional processes poses many disadvantages; heterogeneous catalysts on the other hand are attractive on the basis that their use could enable the biodiesel production to be more readily performed as a continuous process resulting in low production costs. Consequently, a solid base catalyst (KNO3/FA) prepared from fly ash (obtained from Arnot coal power station, South Africa) and a new zeolite, FA/Na-X synthesized from the same fly ash were used as solid base catalysts in the transesterification reactions in the conversion of a variety of oil feedstock with methanol to methyl esters. Since fly ash is a waste product generated from the combustion of coal for power generation, its utilization in this manner would allow for its beneficiation (as a catalytic support material and raw material for zeolite synthesis) in an environmentally friendly way aimed at making the transesterification process reasonably viable. Arnot fly ash (AFA) was loaded with potassium (using potassium nitrate as precursor) via a wet impregnation method while the synthesized zeolite FA/Na-X was ion exchanged with potassium (using potassium acetate as precursor) to obtain the KNO3/FA and FA/K-X catalysts respectively. Several analytical techniques were applied for characterization purposes. The results of the XRD and XRF showed that the AFA predominantly contained some mineral phases such as quartz, mullite, calcite and lime. The high concentration of CaO in AFA was apparent to be beneficial for the use of fresh fly ash as a support material in the heterogeneous catalysed transesterification reactions. XRD characterisation of KNO3/FA results indicated that the structure of KNO3/FA gradually changed with the increase in KNO3 loading. The catalyst function was retained until the loading of KNO3 was over 10 %. IR spectra showed that the KNO3 was decomposed to K2O on the fly ash support during preparation at a calcination temperature of 500 ºC. The CO2-TPD of the KNO3/FA catalysts showed that two basic catalytic sites were generated which were responsible for high catalytic abilities observed in the transesterification reactions of sunflower oil to methyl esters. On the other hand, XRD results for the as- received zeolite synthesized from AFA showed typical diffraction peaks of zeolite NaX. SEM images of the FA /NaX showed nano platelets unique morphology different from well known pyramidal octahedral shaped crystal formation of faujasite zeolites and the morphology of the FA /KX zeolite did not show any significant difference after ion exchange. The fly ash derived zeolite NaX (FA /NaX) exhibited a high surface area of 320 m2/g. The application of the KNO3/FA catalysts in the conversion reactions to produce methyl esters (biodiesel) via transesterification reactions revealed methyl ester yield of 87.5 % with 10 wt% KNO3 at optimum reaction conditions of methanol: oil ratio of 15:1, 5 h reaction time, catalyst amount of 15 g and reaction temperature 160 °C, while with the use of the zeolite FA/K-X catalyst, a FAME yield of 83.53 % was obtained for 8 h using the ion exchanged Arnot fly ash zeolite NaX catalyst (FA/KX) at reaction conditions of methanol: oil ratio of 6:1, catalyst amount of 3 % wt/wt of oil and reaction temperature of 65 ºC. Several studies have been carried out on the production of biodiesel using different heterogeneous catalysts but this study has been able to uniquely demonstrate the utilization of South African Class F AFA both as a catalyst support and as a raw material for zeolite synthesis; these catalyst materials subsequently applied sucessfully as solid base catalysts in the production of biodiesel.Item Phytochemical screening and biological activity studies of five South African indigenous medicinal plants(Academic Journals, 2010) Babajide, Jelili Olalekan; Mabusela, Wilfred T.; Green, Ivan; Ameer, Farouk; Weitz, Frans; Iwuoha, Emmanuel I.Different extracts and fractions of five selected indigenous South African medicinal plants, namely, Cissampelos capensis, Geranium incanum and three Gethyllis species, were subjected to phytochemical screening and testing for cytotoxicity using the brine shrimp lethality bioassay, and antimicrobial activity assays against nine microbes, which included three fungal species, three Gram negative and three Gram positive bacteria.The majority of the extracts tested positive for the presence of tannins, phenolics and flavonoids, while in selected cases, phytochemical tests suggested the presence of essential oils, glycosides or alkaloids. The methanol extract of Gethyllis gregoriana displayed the highest cytotoxicity levels. Generally, the highest levels of biological activity were shown to reside in the methanolic extracts, while hexane extracts revealed very low to zero activity. The total tertiary alkaloid (TTA) of C. capensis was mostly active against Bacillus subtilis, a Gram +ve bacteria. The trends observed for the cytotoxicity assay were in agreement with those observed for the antimicrobial assay.Item The synthesis of prodrugs and novel analogues of Beta-sympathomimetic bronchodilators(University of the Western Cape, 1998) Adams, Mortimer Hilary; Ameer, Farouk; Green, Ivan R.Prodrugs are reversible derivatives of active drugs destined to undergo chemical or enzymatic transformation to the active drug after administration in order that the active drug may subsequently elicit the desired pharmacological response . In synthesizing a prodrug, the physico chemical properties of a drug are altered by suitable functionalisation of an appropriate appendage of the drug molecule such that some barrier or problem may be circumvented or obviated in totality. Prodrugs of bronchodilators have been prod used with the aim of reducing enzymatic degradation, improving their bio-availability and, displaying a marked separation between their desirable bronchodilator and undesirable cardiovascular activities. Chlorphentermine (II), a lung accurnulating arnine, was used as a carrier molecule in novel prodrugs which potentially possess these attributes. Model prodrugs viz. CPE (20) and CPETA (t4), consisting of chlorpltentennine (ll) connected through a propionic ester link to ethanol and etafedrine (13), respectively, were synthesized by reacting the alcohols with acryloyl chloride and the resultant acrylates subsequently reacted with chlorphentennine (II). CPA (21), the prodmg hydrolysis product of CPE (20), was also synthesized. Closely related analoEres of CPETA (t4) narnely PETA (15) and CPAP' (16) were then synthesized. PETA (15) was synthesized by the condensation of methylamino- I -phenylpropane (phentenrtine) and etaf-edrine ( I 3).Item Use of coal fly ash as a catalyst in the production of biodiesel(Slovnaft VÚRUP, 2010) Babajide, Omotola; Petrik, Leslie; Musyoka, Nicholas; Amigun, Bamikole; Ameer, FaroukSouth Africa is largely dependent on the combustion of coal for electricity production; Eskom’s coalfired power stations consume approximately 109 million tons of coal per annum, producing around 25 million tons of ash, to supply the bulk (93%) of South Africa’s electricity. The management of this fly ash has been a concern with various approaches for its beneficial use being investigated. This work presents the results of transesterification reaction using sunflower oil as feedstock with methanol and class F fly ash catalyst derived from a coal fly ash dump in South Africa to produce methyl esters (biodiesel). The fly ash based catalyst was prepared using the wet impregnation procedure with different loadings of potassium. This was characterized by powder X-ray diffraction (XRD), FTIR spectroscopy. The XRD patterns obtained indicated that the structure of the support gradually deformed with an increase in the loading and the extent of decomposition of KNO3 varied with the amount of loading. The influence of various reactions parameters such as loading amount of active components, methanol: oil ratio, reaction time, temperature and catalyst deactivation was investigated. The fly ash based catalyst loaded with 5% wt KNO3 at a reaction temperature of 160ºC exhibited maximum oil conversion (86.13%). The biodiesel synthesized was tested and important fuel properties of the methyl esters (Biodiesel) compared well with ASTM biodiesel standard