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- Total antioxidant capacity of plant infusions: Assessment using electrochemical DNA-based biosensor and spectrophotometric methodsPublication . Barroso, M. Fátima; Ramalhosa, Maria João; Alves, Rita C.; Dias, Alexandra; Soares, Cristina M. D.; Oliva-Teles, M. Teresa; Delerue-Matos, CristinaNine plant infusions were assessed in terms of their polyphenolic compounds and antioxidant capacity properties by performing a “battery” of assays. Bioactive compounds (total phenolic and flavonoid content) were measured using spectrophotometric procedures and the total antioxidant capacity was determined by DPPHradical dot-RSA, FRAP and DNA-based biosensor against the reactive oxygen species: HOradical dot and H2O2. Although the optical methods are based on the donation of hydrogen or electrons between antioxidants and radicals, the DNA-based biosensor intends to simulate an in vivo assay by exposing DNA layer to biological ROS and antioxidants. In general, green and black tea showed higher polyphenolic content and antioxidant capacity evaluated by the described methods. All the analysed plant beverages showed to be a good source of bioactive compounds, particularly the green and black tea, peppermint and senna.
- Angolan cymbopogon citratus used for therapeutic benefits: nutritional composition and influence of solvents in phytochemicals content and antioxidant activity of leaf extractsPublication . Soares, Marta O.; Alves, Rita C.; Pires, Pedro C.; Oliveira, M. Beatriz P. P.; Vinha, Ana F.Folk medicine is a relevant and effective part of indigenous healthcare systems which are, in practice, totally dependent on traditional healers. An outstanding coincidence between indigenous medicinal plant uses and scientifically proved pharmacological properties of several phytochemicals has been observed along the years. This work focused on the leaves of a medicinal plant traditionally used for therapeutic benefits (Angolan Cymbopogon citratus), in order to evaluate their nutritional value. The bioactive phytochemical composition and antioxidant activity of leaf extracts prepared with different solvents (water, methanol and ethanol) were also evaluated. The plant leaves contained ~60% of carbohydrates, protein (~20%), fat (~5%), ash (~4%) and moisture (~9%). The phytochemicals screening revealed the presence of tannins, flavonoids, and terpenoids in all extracts. Methanolic extracts also contained alkaloids and steroids. Several methods were used to evaluate total antioxidant capacity of the different extracts (DPPH; NO; and H2O2 scavenging assays, reducing power, and FRAP). Ethanolic extracts presented a significantly higher antioxidant activity (p < 0.05) except for FRAP, in which the best results were achieved by the aqueous extracts. Methanolic extracts showed the lowest radical scavenging activities for both DPPH; and NO; radicals.
- Optimization of antioxidants extraction from coffee silverskin, aroasting by-product, having in view a sustainable processPublication . Costa, Anabela; Alves, Rita C.; Vinha, Ana F.; Barreira, Sérgio V. P.; Nunes, Maria A.; Cunha, Luís M.; Oliveira, M. Beatriz P. P.Coffee silverskin is a major roasting by-product that could be valued as a source of antioxidant compounds. The effect of the major variables (solvent polarity, temperature and extraction time) affecting the extraction yields of bioactive compounds and antioxidant activity of silverskin extracts was evaluated. The extracts composition varied significantly with the extraction conditions used. A factorial experimental design showed that the use of a hydroalcoholic solvent (50%:50%) at 40 °C for 60 min is a sustainable option to maximize the extraction yield of bioactive compounds and the antioxidant capacity of extracts. Using this set of conditions it was possible to obtain extracts containing total phenolics (302.5 ± 7.1 mg GAE/L), tannins (0.43 ± 0.06 mg TAE/L), and flavonoids (83.0 ± 1.4 mg ECE/L), exhibiting DPPHradical dot scavenging activity (326.0 ± 5.7 mg TE/L) and ferric reducing antioxidant power (1791.9 ± 126.3 mg SFE/L). These conditions allowed, in comparison with other “more effective” for some individual parameters, a cost reduction, saving time and energy.
- Improving bioactive compounds extractability of Amorphophallus paeoniifolius (Dennst.) NicolsonPublication . Costa, Anabela S. G.; Barreira, João C. M.; Ruas, Adilson; Vinha, Ana F.; Pimentel, Filipa B.; Alves, Rita C.; Ferreira, Isabel C. F. R.; Oliveira, M. Beatriz P. P.Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is an underground, unbranched deciduous plant that produces a large tubercle (rhizome) with recognized health effects. In this study, the influence of solvent nature (water, water/etanol (1:1) and absolute ethanol) and processing type (fresh, lyophilized and boiled) on the antioxidant activity and bioactive compounds extractability of elephant foot yam was evaluated. Extracts were compared for their contents in total phenolics, flavonoids and tannins. Moreover, their antioxidant capacity was assessed by the ferric reducing antioxidant power (FRAP) and the 2,2-diphenyl-1-picrylhydrazyl radical (DPPHradical dot) scavenging capacity assays. Phenolics (154 mg GAE/L) and tannins (109 mg GAE/L) were maximized in lyophilized samples extracted with the hydroalcoholic solvent, which attained also the highest FRAP value (711 mg FSE/L). In turn, flavonoids reached the highest yields in lyophilized samples (95 mg ECE/L) extracted with pure ethanol, as well as the highest DPPHradical dot scavenging activity. These findings might have practical applications to define the best processing methodology regarding the enhancement of elephant foot yam, either for prompt consumption, as well as to develop food supplements or pharmaceutical related products.