Browsing by Author "Haris, Parvez I."
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- Mechanism of action and the biological activities of Nigella sativa oil componentsPublication . Silva, André Filipe C.; Haris, Parvez I.; Serralheiro, Maria Luisa; Pacheco, RitaNigella sativa seeds oil is consumed because of its health benefits. Although the oil has been studied for its properties and composition, these effects are often associated with its major compound thymoquinone, and less has been reported about the other components' contributions to the pharmacological properties and mechanism of action. The present study aimed to evaluate the oil compounds' antioxidant and anti-tumour activities, and its effect on molecular targets associated with the claimed health effects. A wide a range of biochemical and biophysical techniques were used to understand the biological activities of the oil components. Compounds such as thymoquinone and volatile monoterpenes such as alpha-thujene, alpha-pynene, sabinene and 3-carene were identified by using GC-MS. Similar high antioxidant activities were obtained for the oil and its non-volatile (NV) fraction, with enzymes inhibition and cytotoxic activity against MCF-7 and A375 cells the oil showed a strong effect but not its NV fraction. Analysis of A375 cells' proteome in contact with the oil showed increased expression of proteins POTEF and HSP 90-b suggesting that the oil's antitumor effect was due to apoptosis and cellular stress. FT-IR studies in two model proteins in contact with the oil allowed oil compounds-protein interactions to be recognized and also showed that volatiles stabilized proteins. Therefore, not only thymoquinone but also the volatile monoterpenes were important for the diversity of properties, and therefore modifications in the chemical composition of the oil, as an outcome of storage or even food preparation, may affect its biological activity.
- Serum albumin modulates the bioactivity of rosmarinic acidPublication . Brito, Elsa; Silva, André; Fale, Pedro; Pacheco, Rita; Serralheiro, António; Haris, Parvez I.; Ascensão, Lia; Serralheiro, Maria LuisaRosmarinic acid (RA) is a phenolic compound with biological activity. The objective of the present study was to investigate whether this compound kept its biological activity in the presence of proteins. For this purpose, bovine serum albumin (BSA) was used as a model protein, and the capacity of the RA to inhibit acetylcholinesterase (AChE) and affect antioxidant activity was evaluated in the absence and presence of BSA. A mixture of phenolic compounds containing RA, obtained from a medicinal plant was added to this study. The AChE inhibitory activity of RA was reduced by *57% in the presence of BSA, while the antioxidant activity increased. These results lead to the investigation of the effect of RA on the BSA structure using Fourier transform infrared spectroscopy (FTIR). At 37 C and higher temperatures, RA caused a decrease in the temperature modifications onthe proteinstructure. Furthermore, FTIR and native-gel analysis revealed that protein aggregation/ precipitation, induced bytemperature, wasreduced in thepresence of RA. The novelty of the present work resides in thestudy of the enzyme inhibitory activity and antioxidant capacity of polyphenols, such as RA, in the presence of a protein. The findings highlight the need to consider the presence of proteins when assessing biological activities of polyphenols in vitro and that enzyme inhibitory activity may be decreased, while the antioxidant capacity remains or even increases.
- Substrate interaction with recombinant amidase from Pseudomonas aeruginosa during biocatalysisPublication . Pacheco, Rita; Karmali, Amin; Serralheiro, Maria Luísa M.; Haris, Parvez I.The interaction of a variety of substrates with Pseudomonas aeruginosa native amidase (E.C. 3.5.1.4), overproduced in an Escherichia coli strain, was investigated using difference FTIR spectroscopy. The amides used as substrates showed an increase in hydrogen bonding upon association in multimers, which was not seen with esters. Evidence for an overall reduction or weakening of hydrogen bonding while amide and ester substrates are interacting with the enzyme is presented. The results describe a spectroscopic approach for analysis of substrate-amidase interaction and in situ monitoring of the hydrolysis and transferase reaction when amides or esters are used as substrates.