Talinum paniculatum (Jacq.) Gaertn. leaves - source of nutrients, antioxidant and antibacterial potentials.

BACKGROUND: The diet of most of the population is limited to a reduced number of plants, even in areas that have a varied and extensive diversity, such as Brazil. Unconventional Food Plants (UFPs) are plants considered exotic, native, and wild that grow naturally and can be used as food. Among these is Talinum paniculatum (Jacq.) Gaertn., which is widespread throughout Brazil and can be a potential source of nutrients. Due to the potential of utilization of UFPs in human food and the lack of studies regarding the composition of T. paniculatum, this study aimed to assess the nutritional value of T. paniculatum leaves, their antioxidant capacity, and their antimicrobial activity for possible use in food. METHODS: The characterization of the leaves of T. paniculatum was carried out through analyses of proximal composition, color, ascorbic acid, mineral profile, and antinutritional factors showing the presence of condensed and hydrolysable tannins and nitrates in low concentrations. Solvents of water, ethanol, ethanol/water, methanol, methanol/water, methanol/acetic acid and acetone/water/acetic acid were used to evaluate the extraction yield of phenolic compounds, antioxidant capacity, and antibacterial activity of the extracts. RESULTS: High contents of protein (18.61 g 100 g-1), insoluble dietary fiber (34.75 g 100 g-1), ascorbic acid (81.03 mg 100 g-1), magnesium, potassium, and calcium (649.600, 411.520 and 228.117 mg 100 g-1, respectively) were observed. Extraction using the mixture of solvents of methanol/acetic acid showed the highest yield of phenolic compounds (432.73 mg EAG 100 g-1) and antioxidant capacity using the DPPH assay (3144.92 mg 100 g-1). Bacillus cereus growth was inhibited by the T. paniculatum extracts. CONCLUSIONS: T. paniculatum leaves are a source of nutrients and their extracts have antioxidant and antibacterial potentials which can be used as supplements in food to improve one's health.

The effects of Curcuma longa L. leaf extracts on the prevention of oxidation in soybean oil.

BACKGROUND: The use of natural plant antioxidants has been an alternative approach to synthetic antioxidants for food applications. This study investigated the antioxidant properties of the leaves of Curcuma longa L. against the oxidation of soybean oil using leaf extracts obtained from seven different types of organic solvents and compared to the action of efficient synthetic antioxidants which are widely used and low cost but with toxicity risk. The application of natural alternatives from sources still little studied is a proposal and the extraction of compounds with high antioxidant capacity may vary according to the type of solvent, its mixture, its polarity and other factors that burden or harm the health of the consumer. METHODS: The leaf extracts were sanitized, dried, and obtained for solvent selection. The quantification of total phenolic compounds (TPC) and antioxidants was performed by using different combinations and proportions of solvents: water (100%), ethanol (100%), methanol (100%), ethanol/water (70%:30%), methanol/water (70%:30%), methanol/acetic acid (99.5%:0.5%), and acetone/water/acetic acid (70%:28:2%). The solvent selected was the one that extracted the highest content of phenolic and antioxidant compounds (using the free radical DPPH scavenging method and FRAP assay). It used an accelerated storage test and experimental design to assess oxidative stability (using peroxide index (PI), thiobarbituric acid reactive substances (TBARS), dienes (DC) and triple conjugates (TC) and statistical analysis). RESULTS: The ethanol/water solvent was efficient in the extraction of TPC (2422 mg GAE 100 g-1). The mixture of solvents extracted an average of 23.65% more TPC when compared to the single solvents. Regarding the antioxidant capacity, the ethanol/water solvent showed 1847 mg TE 100 g-1 using the DPPH and 217 µmol of FeSO4 100 g-1 using the FRAP assays. In addition, the oxidation of soybean oil was delayed by the accelerated storage test showing equivalent results to BHT at 0.02% for the values of PI, TBARS and DC/TC. CONCLUSIONS: The E/W extract showed the highest yield in the extraction of phenolic compounds and is a safe solvent for food. The addition of Curcuma longa L. leaf extract to soybean oil caused reductions in PI, TBARS, CD and CT values. The leaf extract of C. longa L. is considered to be a good alternative to synthetic antioxidants against the oxidative degradation of soybean oil.