The objectives of this study were to determine phenolic content and antioxidant activity of methanolic extracts from different parts of cantaloupe (leaf, stem, skin, seed and flesh). The flesh extract afforded the highest yield (89.6 ± 0.3%) whilst the lowest yield was obtained from the seed (13.7 ± 0.5%) (p < 0.05). The leaf extract showed the highest total phenolic content (26.4 ± 0.3 mg GAE/g extract) and total flavonoid content (69.7 ± 3.37 μg RE/g extract) accompanied with best antioxidant activity through all antioxidant assays (p < 0.05). In addition, the stem extract also exhibited good antioxidant activity. Thus, these results suggest that methanolic extracts of cantaloupe leaf and stem may serve as a potential source of natural antioxidant for food and nutraceutical application.

a b s t r a c tThe antioxidant activities of crude methanolic extract (CME) and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black cumin seedcake were investigated. DPPH radical scavenging activity, b-carotene-linoleate bleaching, and inhibition of corn oil oxidation were used to evaluate the antioxidant capacity. The total phenolics were found to be 78.8, 27.8, 32.1 and 12.1 mg gallic acid equivalents (GAE)/g in EAF, CME, WF and HF, respectively. The CME and EAF exhibited the highest DPPH followed by WF and HF. The extract/fractions showed high effect on reducing the oxidation of b-carotene. The effect of extract/fractions on the oxidative stability of corn oil at 70°C was tested in the dark and compared with butylated hydroxyanisole (BHA). The oil peroxide and anisidine values were generally lower with addition of PRFs in comparison to a control. The predominant phenolic compounds identified by HPLC-DAD in CME and WF of black cumin seedcake were hydroxybenzoic, syringic and p-cumaric acids.

The proximate analysis of seeds and physicochemical properties of oils extracted from six Sudanese cucurbit seeds Cucumis mello var. agrestis, Cucumis melo var. flexuosus, Cucumis sativus, Citrullus lanatus var. colocynthoides, Cucumis prophetarum, and Luffa echinata were examined by established methods. For each variety, the proximate analysis showed ranges for moisture, protein, and carbohydrates as 3.70-6.87, 14.50-17.50, and 15.62-28.89% on a dry matter basis, respectively. The oils were extracted by Soxhlet using petroleum ether, with yields that ranged from 10.9 to 27.10% (wt/wt). The obtained extracted oils were subjected to phyiscochemical, fatty acid, and tocopherol analysis. The physicochemical characterization of the oil revealed that the refractive indices and relative densities of the oils fell within the narrow ranges of 1.334-1.442 and 0.874-0.920 g/cm 3 , respectively. Unsaponifiable matters ranged between 0.8 and 1.2 mg KOH/g, whilst peroxide values (PV) ranged from 2.3 to 4.1 meq/kg. The ranges of the values for free fatty acid (FFA %) were 1.2-4.0%. The predominant fatty acids were 16:0, 18:0, 18:1, and 18:2 with ranges of 8.9-14.2, 6.0-9.4, 14.6-32.1, and 43.6-65.5%, respectively. c-Tocopherol was the predominant tocopherol in all samples ranging from 0.8 to 43.2% of the total tocopherols, followed by d-tocopherol and a-tocopherol.

Three unusual oils, obtained from Sclerocarya birrea (Marula), Aspongopus viduatus (melon bug) and Agonoscelis pubescens (sorghum bug), collected in Sudan from Abu Gibaiha, Ghibaish and Rahad agricultural areas, respectively, were investigated. In addition to the oil content, the fatty acid as well as sterol composition was determined by capillary gas chromatography and the tocopherols were evaluated by high-performance liquid chromatography. Oxidative stability of the oils was investigated by the Rancimat method. The oil content of seeds from S. birrea amounted to 53.5%, whereas bugs of A. viduatus and A. pubescens came to 45 and 60%, respectively. The oils contained 67.2, 46.5 and 40.9% oleic acid, 5.9, 3.4 and 34.5% linoleic acid, 14.1, 44.2 and 12.1% palmitic acid and traces of linolenic acid, respectively. The tocopherol content of these oils amounted to 13.7, 0.3 and 34.0 mg/100 g oil, respectively. Gammatocopherol was the predominant tocopherol in the oil of S. birrea and A. pubescens . The total content of sterols in the three oils was 287, 17 and 450 mg/100 g oil, respectively, whereas b -sitosterol was determined as the main compound in all oils with about 60% of the total sterols. In the oil of S. birrea higher amounts of 5-avenasterol (4.8 mg/100 g) were found. The oxidative stability of the oils, as measured by the Rancimat test at 120C, was 43, 38 and 5.1 h, respectively.

Two kenaf varieties QP3 and V36 were used to obtain protein concentrates. Proximate analysis, foaming, water and oil absorption properties were studied. Significant (P<0.05) differences were observed among the two varieties only in their content in oil and carbohydrates. The protein concentrate yield was 13.04% and 10.56%, respectively. The two varieties showed significantly different (P<0.05) water and oil absorption capacities. QP3 showed higher foaming capacity than did V38, and it was increased with increasing salt and sugar concentration. Albumin was the main fraction representing 59.6% and 66.1% in QP3 and V36 varieties, respectively, followed by globulin, which represented 22.6% and 19.1%, respectively. The ratios of albumin, globulin, glutelin and prolamin were significantly different. Based on the data obtained from sodium dodecyl sulphate polyacrylamide gel electrophoresis, the main kenaf seed proteins present in the concentrates were five proteins with molecular weights ranging from 10 to 66. kDa. From differential scanning calorimetry data, QP3 and V36 protein concentrates had similar denaturation temperatures (82.6 and 81.8°C, respectively).

No abstract

The antioxidant activities of phenolic rich fractions (PRFs) from crude methanolic extract (CME), and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black mahlab (Monechma ciliatum) and white mahlab (Prunus mahaleb) seedcakes were investigated. The total phenolic compounds were found to be higher in white mahlab than black mahlab seedcakes. The antioxidant activity determined by the DPPH method revealed that black mahlab PRFs had the highest antioxidant activity, compared to white mahlab fractions. The presence of antioxidants in the two mahlab PRFs reduced the oxidation of βcarotene by hydroperoxides from these extracts/fractions. The effect of the two mahlab PRFs on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The CME performed better antioxidant activity in inhibiting the formation of both primary and secondary oxidation products. The qualitative and quantitative characterisation of phenolic compounds was carried out by HPLC/DAD.

This study suggests that the essential oils from Cinnamomum pubescens Kochummen and Etlingera elatior could be potentially used as a new source of natural antioxidant and antibacterial in the food and pharmaceutical industries.