Browsing by Author "Canelo, Laura Isabel Nave"
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- Caraterização Química de Produtos Naturais de Plantas Medicinais de AngolaPublication . Canelo, Laura Isabel Nave; Mendonça, Dina Isabel Malheiros Dinis deNeste trabalho foram estudadas as seguintes plantas medicinais angolanas: a raiz da Piliostigma thonningii (Schum.) Milne-Redh, a raiz da Phragmanthera glaucocarpa (Peyr.) Balle, recolhidas no Uíge, a parte aérea da Croton gratissimus Buch., recolhida na Quiita, a raiz da Peltophorum africanum Sond. e ramos da Gymnosporia senegalensis (Lam.) Loes., recolhidas na Humpata. O material vegetal foi macerado e exaustivamente extraído a frio com metanol. Posteriormente, procedeu-se ao fracionamento do extrato de metanol em fração de hexano, clorofórmio e acetato de etilo. Por fracionamento destas frações, com misturas de vários solventes de polaridades crescentes, foram isolados diversos tipos de compostos. Na raiz da Piliostigma thonningii foram isolados o β–sitosterol, ácido benzóico, ácido 3-O-β-D-fucopiranosilquinóvico, ácido 3-O-α-L-ramnopiranosilquinóvico e a vincosamida. Todos estes compostos, exceto o β–sitosterol, são pela primeira vez isolados no género Bauhinia e na Piliostigma thonningii. A raiz da Phragmanthera glaucocarpa foi estudada, embora não tenham sido isolados quaisquer compostos. Na parte aérea da Croton gratissimus foram isolados o 1β-metoxicariolan-9β-ol, o 7δ-metoxiopposit-4(15)-en-1β-ol, 6α-metoxieudesm-4(15)-en-1β-ol, ácido cis-ózico, germacra-4(15),5,10(14)-trien-1β-ol, ent-kaur-16-en-19-ol, ácido 15-metoxi-neo-clerodan-3,13-dien-15,16-olida-18-óico, sacarose e o trans-4-hidroxi-N-metilprolina pela primeira vez no género Croton. Foram ainda isolados o óxido de cariofileno, ácido ent-kaur-16-en-19-óico, espatulenol, β-sitosterol e lupeol, já isolados no género Croton e alguns nas folhas da Croton gratissimus. Na raiz da Peltophorum africanum foram isolados dois compostos, o lupeol e o mallanósido A, que nunca foram isolados no género Peltophorum. Nos ramos da Gymnosporia senegalensis foram isolados dois compostos, que nunca foram isolados no género Gymnosporia o 3β-hidroxi-30-nor-lup-20-ona e o 3-epi-gloquidiol. O β-sitosterol e o 3β-hidroxi-lup-20(29)-en-30-al foram também isolados, sendo que o segundo é pela primeira vez isolado na G. senegalensis.
- In Vitro Antioxidant Activity and Total Phenolic Content of Root Extracts from Phragmanthera glaucocarpa (Peyr.) BallePublication . Fernandes, Nélson; Canelo, Laura Isabel Nave; Mata, Rosalina da Conceição dos Santos; Mendonca, Dina; Mendonça, AntónioBackground: Africa has a rich diversity of plant species, which can be considered important sources of new chemical compounds that can be used in the development of novel therapeutic drugs. Objectives: The present study aimed at investigating the antioxidant activity and total phenolic content of extracts obtained from the roots of Phragmanthera glaucocarpa (Peyr.) Balle, a plant used in Angola folk medicine. Methods: The prepared extracts were tested for their antioxidant activity using ABTS (2,2’-azinobis-(3-ethyl-benzothiazoline-6-sulfonic acid), DPPH (1’,1’-diphenyl-2-picrylhydrazyl), and peroxide value methods. Total phenolics were evaluated by the FolinCiocalteu method. Results: For ABTS, the best EC50 result was obtained with the ethyl acetate fraction (1.06 ± 0.30 mg/mL). For the DPPH method, the methanol extract and aqueous fraction presented the best EC50 results, 0.10 ± 0.01 mg/mL and 0.10 ± 0.00 mg/mL, respectively. The ethyl acetate fraction had the highest phenolic content (280.42 ± 0.15 mg G.A.E. /g of dry extract). The best result for the peroxide reduction value on the eighth day of sunflower oil oxidation was obtained for the aqueous fraction, with 131.40 ± 1.05 meq O2 /g of lipid sample. Conclusions: The results of the present study demonstrate that the roots of the medicinal plant Phragmanthera glaucocarpa (Peyr.) Balle represent a promising source of natural phenolic compounds with antioxidant activity.
- Utilização de bagaço de uva na remoção da cor em soluções aquosasPublication . Canelo, Laura Isabel NaveGrape bagasse generated in wine production can be used as a potential biosorbent for colour removal. Batch experiments were carried out for kinetic studies of textile dyes Acid Orange 7 (AO7) and Direct Red 80 (DR80) onto dried grape bagasse, at pH of 7-7.5. For dye AO7 the influence of initial dye concentration (from 20 to 100 mg/), temperature (20, 37 and 50ºC) and contact time was evaluated. A maximum efficiency rate (ca. 89%) was found for 2.5g of biosorbent in tests with a 20 ml solution /g biosorbent. Kinetic studies show that, at 50ºC, experimental data are well described by a pseudo second order model. However, the rate-limiting step of the process at 37ºC appears to be the internal diffusion. At 20ºC both processes are determinant. The equilibrium data were fitted to the Langmuir, Freundlich and Langmuir-Freundlich isotherms. Langmuir and Langmuir-Freundlich were considered as those that better describe the equilibrium results. The adsorption capacities ranged from 2,7 a 3,5 mg de AO7/g biosorbent. Dye DR80 displayed a lower efficient colour removal rate (ca. 43%) than AO7 in similar test conditions, which could be due to the type of solute-sorbent interactions, since DR80 is a linear molecule with a higher hydrophilic character. Results show that grape bagasse could be employed as a low-cost adsorbent on colour removal.