Effects of age and extraction solvent on phytochemical content and antioxidant activity of fresh Moringa oleifera L. leaves.

Antioxidant activity (AOA) and phytochemical content of Moringa oleifera Lam leaves were determined as a function of their age and extraction solvent. Fresh Moringa leaves aged 30, 45, and 60 days were harvested and extracted with three solvents; methanol, ethanol, and water. AOA of leaf extracts was measured using radical scavenging assays (DPPH, ABTS, antiperoxide activity [APA]) and reducing assays (FRAP and total antioxidant capacity [TAC]), and these were correlated with total polyphenols (TPC), total flavonoids (TFC), and chlorophyll contents of leaves. Significant variability (p < 0.05) in TPC and AOA of Moringa leaf extracts was observed with age and extraction solvent as well as their interaction. TPC and TFC increased with maturity, except in aqueous extract. The 60-day-old leaves showed highest TPC, TFC, and tocopherol contents with highest DPPH activity. On their part, 30-day-old leaves recorded better vitamin C, chlorophyll, and carotenoids with highest ABTS activity and APA. Methanol was best extraction solvent for TPC (4.6 g GAE/100 g DM) while ethanol was for flavonoids (1.8 g CE/100 g DM). Ethanol extracts exhibited the highest DPPH activity (53.3%-71.1%), while both ethanolic and methanolic extracts had similar and higher ABTS + activity (3.83-3.86 g AAE/100 g DM). Strong positive correlations (r ≥ 0.8; p < 0.05) were observed between chlorophyll content and DPPH, ABTS, and APA, suggesting that chlorophyll was the major contributor to AOA. TAC was highest in aqueous solvent. Free radical scavenging activity in Moringa leaves is positively correlated to chlorophyll, TFC, and TPC while reducing power is positively correlated to chlorophyll and TPC. AOA of fresh Moringa leaf extract is a function of its phytochemical content and is influenced by both the age of the leaves and the extraction solvent used. Methanolic and ethanolic extracts of 45-day-old Moringa leaves exhibited best antioxidant potentials.

Antioxidant activities of essential oil of Bidens pilosa (Linn. Var. Radita) used for the preservation of food qualities in North Cameroon.

This study aimed to determine the total antioxidant capacity of the essential oil (EO) of leaves of Bidens pilosa (Linn. Var. Radita) used as protectant of stored grains in Northern Cameroon. EO was characterized by GC-FID, antioxidant activity (AA) was determined by combining: evaluation of radical-scavenging activity, reducing power (RP) and co-oxidation of ß-carotene methods. Tests were carried out on crude and stored EO kept for two weeks at 31.48 ± 2.88°C and 58.56 ± 6.78% relative humidity. These conditions are the same as those of grain storage. GC analyses enabled the identification of 27 compounds, representing around 97.57% of the total oil contents. The major constituents of the EO were α-pinene (14.7%), ε-caryophyllene (13.5), and ß-ocimene (12.8%). The AA of the crude and stored EO are proportional to the concentrations and time of exposition. Exposed at the day light, this EO inhibit 77.4-18.69% for the DPPH system, 59.55-19.14% for RP method and 91.88-21.8% for ß-carotene-linoleate model system, respectively, from crude and 15 days storage EO at 20 mg L(-1). For the EC50 values, ß-carotene method is excellent and in the decreasing order of DPPH method, PR with 2.52 mg L(-1), 2.77 mg L(-1) and 4.13 mg L(-1), respectively, for the crude oil. The ET50 were 1.59 days for the RP method and 2.88 days DPPH system and ß-carotene-linoleate model system at 20 mg L(-1). These results showed that the EO of B. pilosa leaves exhibits AA that might be an added value for this EO preventing stored products from pest attacks.

Optimization of vegetable milk extraction from whole and dehulled Mucuna pruriens (Var Cochinchinensis) flours using central composite design.

Extraction conditions for maximum values of protein yield, protein content, sugar content and dry matter of vegetable milk extracts from dehulled Mucuna cochinchinensis bean flour and whole Mucuna cochinchinensis bean flour were investigated using response surface methodology. A Central Composite Design (CCFD) with three factors: temperature (25 to 95 °C); extraction time (6 to 74 min.) and water to flour ratio (6 to 24 mL/g) were used. Data analysis showed that all the factors significantly (p < 0.05) affected the responses variables. The optimal conditions determined for extraction were temperature 63-66 °C, water to flour ratio 12-13 mL/g and extraction time of 57-67 min. At these optimum points the protein and sugar contents, extraction yield of protein and dry matter were respectively 14.0 g/100 mL, 4.8 g/100 mL, 53.8 g/100 g, 12.1 g/100 g for vegetable milk produced from dehulled M. cochinchinensis bean flour and 6.4 g/100 mL, 3.5 g/100 mL, 50.0 g/100 g and 8.0 g/100 g for vegetable milk extracted from whole M. cochinchinensis bean flour milk. The optimal condition was verified at the optimum points for model validation and the response values were not significantly different from the predicted values.

Mucilage chemical profile and antioxidant properties of giant swamp taro tubers.

The yellow (YP) and white (WP) sections of giant swamp taro (GST) contain 40.0 g/kg and 51.5 g/kg (dry wt) respectively of pure mucilage made up of D-glucose (44.95-78.85 %), D-galactose (8.70-25.35 %), D-mannose (3.20-10.45 %), D-arabinose (2.45-5.20 %) and small amounts of glucuronic acid and rhamnose. Arabinogalactan-proteins (5.30-8.83 g/kg) contain mainly arabinose and galactose (in a 1:1 proportion) and also significant amounts of rhamnose, xylose, glucuronic acid and mannose. Antioxidant activity of YP was higher than those of WP while chelating ability and reducing power increased with mucilages content. Generally YP and WP showed better reducing power (1.06 ± 0.35 at 5 mg/mL) than ascorbic acid (0.89 ± 0.22). WP and YP chelated ferrous ions by 20.0-76.0 % and 16.4-71.0 % respectively. Effective concentrations (EC50) of mucilages (WP 1.28 ± 0.05 mg/mL; YP 1.42 ± 0.04 mg/mL) were lower than those of citric acid (1.58 ± 0.04 mg/mL). Generally mucilage from the WP and YP sections are excellent sources of chelating agents.

Chemical composition, functional and sensory characteristics of wheat-taro composite flours and biscuits.

The physicochemical, alveographic and sensory characteristics of precooked taro-wheat composite flours and their biscuits were investigated. A 2x7 factorial design consisting of two varieties of taro flour (Red Ibo Ngaoundere, RIN, and egg-like varieties) and 7 levels of wheat substitutions (0, 5, 10, 15, 20, 25 and 30 %) was used for this purpose. It was observed that water absorption capacity (range 95-152 g/100 g), water solubility index (range 18.8-29.5 g/100 g) and swelling capacity (range 125.4-204.6 mL/100 g) of composite flours significantly (p < 0.05) increased with increase in taro level. Conversely the dough elasticity index (range 59.8-0 %), extensibility (78-22 mm) and strength (range 281-139 × 10(-4) joules) significantly (p < 0.05) diminished with increase in wheat substitution. Up to 10 % substitution with RIN taro flour and 15 % with egg-like taro flour, the composite taro-wheat dough exhibited elasticity indices acceptable for the production of baking products, whereas at all levels of taro substitution, the composite biscuits samples were either acceptable as or better (5-10 % substitution with RIN flour) than 100 % wheat biscuit.

Compositional, spectroscopic and rheological analyses of mucilage isolated from taro (Colocasia esculenta L. Schott) corms.

Tropical roots and tubers generally contain mucilage. These mucilages exhibit unique rheological properties with considerable potential as a food thickener and stabilizer. A one-step extraction procedure was used to isolate starch free mucilage and associated proteins from a number of taro (Colocasia esculenta) varieties. The monosaccharide and amino acid composition, the structural and flow properties were investigated. The results showed that yield of mucilage fraction varied from 30 to 190 g.kg(-1). A negative correlation (r = -0.87; p < 0.05) was observed between the crude protein level and the yield. The monosaccharide profiles revealed that galactose, mannose and arabinose were the main monosaccharides in the hydrolysate of the mucilage. From the 17 amino acids analyzed, aspartic acid/asparagine (14.4-17.2%) and glutamic acid/glutamine (10.3-13.6%) were prominent in the mucilage as well as the flour. No significant differences were observed in the FT-IR spectra and in the viscosity behavior of the mucilage dispersions. The greatest difference in the mucilage is based on its monosaccharide profile while the protein composition, which reflects that of the flour, is relatively stable.