Optimization of microwave-assisted extraction of hydrophilic and lipophilic antioxidants from a surplus tomato crop by response surface methodology

Tomato is the second most important vegetable crop worldwide and a rich source of industrially interesting antioxidants. Hence, the microwave-assisted extraction of hydrophilic (H) and lipophilic (L) antioxidants from a surplus tomato crop was optimized using response surface methodology. The relevant independent variables were temperature (T), extraction time (t), ethanol concentration (Et) and solid/liquid ratio (S/L). The concentration-time response methods of crocin and β-carotene bleaching were applied, since they are suitable in vitro assays to evaluate the antioxidant activity of H and L matrices, respectively. The optimum operating conditions that maximized the extraction were as follows: t, 2.25 min; T, 149.2 ºC; Et, 99.1 %; and S/L, 45.0 g/L for H antioxidants; and t, 15.4 min; T, 60.0 ºC; Et, 33.0 %; and S/L, 15.0 g/L for L antioxidants. This industrial approach indicated that surplus tomatoes possess a high content of antioxidants, offering an alternative source for obtaining natural value-added compounds. Additionally, by testing the relationship between the polarity of the extraction solvent and the antioxidant activity of the extracts in H and L media (polarity-activity relationship), useful information for the study of complex natural extracts containing components with variable degrees of polarity was obtained.

Crocin and β-Carotene bleaching assays as analytical tools in the optimization of the extraction of hydrophilic and lipophilic antioxidants from tomato

Tomato (Lycopersicon esculentum Mill.) is the second most important vegetable crop worldwide and a rich source of hydrophilic (H) and lipophilic (L) antioxidants. The H fraction is constituted mainly by ascorbic acid and soluble phenolic compounds, while the L fraction contains carotenoids (mostly lycopene), tocopherols, sterols and lipophilic phenolics [1,2]. To obtain these antioxidants it is necessary to follow appropriate extraction methods and processing conditions. In this regard, this study aimed at determining the optimal extraction conditions for H and L antioxidants from a tomato surplus. A 5-level full factorial design with 4 factors (extraction time (I, 0-20 min), temperature (T, 60-180 •c), ethanol percentage (Et, 0-100%) and solid/liquid ratio (S/L, 5-45 g!L)) was implemented and the response surface methodology used for analysis. Extractions were carried out in a Biotage Initiator Microwave apparatus. The concentration-time response methods of crocin and P-carotene bleaching were applied (using 96-well microplates), since they are suitable in vitro assays to evaluate the antioxidant activity of H and L matrices, respectively [3]. Measurements were carried out at intervals of 3, 5 and 10 min (initiation, propagation and asymptotic phases), during a time frame of 200 min. The parameters Pm (maximum protected substrate) and V m (amount of protected substrate per g of extract) and the so called IC50 were used to quantify the response. The optimum extraction conditions were as follows: r~2.25 min, 7'=149.2 •c, Et=99.1 %and SIL=l5.0 giL for H antioxidants; and t=l5.4 min, 7'=60.0 •c, Et=33.0% and S/L~l5.0 g/L for L antioxidants. The proposed model was validated based on the high values of the adjusted coefficient of determination (R2.wi>0.91) and on the non-siguificant differences between predicted and experimental values. It was also found that the antioxidant capacity of the H fraction was much higher than the L one.

Dietary supplements based on borututu: wich is the most suitable choice for bioactive purposes?

Borututu ( Cochlospermum angolensis Welw.) is a widespread tree in Angola used since antiquity by traditional healers for the prevention and treatment of hepatic diseases and for the prophylaxis of malaria [1]. This plant is mostly consumed as infusions but is also available as dietary supplements, such as piiis, capsules, and syrups, among others. In the present study, the aim was to evaluate the proximate composition and energetic contribution of borututu as weii as its composition in hydrophilic (sugars and organic acids) and lipophilic (fatty acids and tocopherols) compounds, given the fact that this plant is directly introduced in some dietary supplements. Furthermore, the bioactivity (antioxidant, hepatoprotective and antimicrobial activities) of three different formulations of borututu (infusion, pills, and syrup) was assessed and compared, and since plant beneficial properties are often ascribed to phenolic compounds [2], the phenolic profile of the formulations was also analysed. Carbohydrates (88 g/100 g) and fat (2.5 g/100 g) were the major and tl1e minor components of the studied borututu dry barks, respectively, with an energetic contribution of 384 kcal/100 g. Fructose was the most abundant sugar (1.3 g/100 g), foilowed by sucrose, trehalose and glucose (1.1, 0.98 and 0.79 g/100 g, respectively). Oxalic (0.70 g/100 g), malic (0.63 g/100 g) and citric (0.57 g/100 g) acids were present in higher amounts but shikimic and fumaric acids were also detected. Among the fatty acids found in borututu, a prevalence of saturated fatty acids (SF A; 48.2%) was observed, whereas polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids were detected in relative percentages of 30.9% and 20.8%, respectively. P-tocopherol was the most abundant of the four isoforms found in the sample, foiiowed by o-, a- and y-tocopherol, present in concentrations of 597,43, 3.7 and 2.0 g/100 g, respectively. Borututu infusion revealed the highest antioxidant activity, with EC50 values ranging from 20 to 600 J.lg/mL and was the only formulation inhibiting the growth of an HepG2 ceii line, with a Gl5o value of 146 J.lg/mL. This formulation.also revealed the best antimicrobial capacity and proved to be able to inhibit the growth of Escherichia coli, E. coli ESBL, Staphylococcus aureus and Pseudomonas aeruginosa, with MIC values of 50, 6.2, 1.6 and 25 mg!mL, respectively. Pills revealed activity against some of the studied bacterial strains and the syrup did not reveal antimicrobial activity at the studied concentration. Eilagic acids, methyl ellagic acids, eucaglobulinlglobulusin B and (epi)gaiiocatechin-0-gallate were the compounds present in all the different formulations. The highest concentration of phenolic compounds was found in the infusion extract. Protocatechuic acid was the most abundant phenolic compound in the infusions, the only preparation where it was detected, whereas ( epi)gaiiocatechin- 0-gallate was the main phenolic in the pills and eucaglobulinlglobulusin in the syrup. In a general way, borututu proved to be a good source of phytochemicals such as phenolic compounds, with the infusions revealing the best bioactive properties.