Azizah Osman

Antioxidative activity of extracts from Mengkudu (Morinda citrifolia L.) root, fruit and leaf

This study was conducted to evaluate the antioxidative activity of extracts from different parts of Mengkudu (Morinda citrifolia L.), including leaf, fruit and root. Methanol and ethyl acetate were used as solvents and antioxidative effects measured by a ferric thiocyanate method (FTC) and thiobarbituric acid test (TBA). The methanol extract of Mengkudu root exhibited high antioxidative activity that was not significantly (P<0.05) different from α-tocopherol or butylated hydroxyl toluene (BHT), while the methanol extracts of fruit and leaf showed negligible activities. On the other hand, the ethyl acetate extract of all parts of Mengkudu exhibited significant antioxidative activity, which is comparable to that of both α-tocopherol and BHT. Similar trends of antioxidant activity were observed using either the FTC or TBA methods. Roots showed the highest activity of the parts tested. The results suggest that several compounds contribute to antioxidative activity of different parts of Mengkudu. Activity in the roots may be due to both polar and non-polar compounds but, in the leaf and fruit, only to non-polar compounds.

Effect of Freeze-Drying on the Antioxidant Compounds and Antioxidant Activity of Selected Tropical Fruits

The effects of freeze-drying on antioxidant compounds and antioxidant activity of five tropical fruits, namely starfruit (Averrhoa carambola L.), mango (Mangifera indica L.), papaya (Carica papaya L.), muskmelon (Cucumis melo L.), and watermelon Citruluss lanatus (Thunb.) were investigated. Significant (p < 0.05) differences, for the amounts of total phenolic compounds (TPC), were found between the fresh and freeze-dried fruit samples, except muskmelon. There was no significant (p > 0.05) change, however, observed in the ascorbic acid content of the fresh and freeze-dried fruits. Similarly, freeze-drying did not exert any considerable effect on β-carotene concentration of fruits, except for mango and watermelon, where significantly (p < 0.05) higher levels were detected in the fresh samples. The results of DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging and reducing power assays revealed that fresh samples of starfruit and mango had relatively higher antioxidant activity. In case of linoleic acid peroxidation inhibition measurement, a significant (p < 0.05) but random variation was recorded between the fresh and freeze-dried fruits. Overall, in comparison to β-carotene and ascorbic acid, a good correlation was established between the result of TPC and antioxidant assays, indicating that phenolics might have been the dominant compounds contributing towards the antioxidant activity of the fruits tested.

Changes in quality of sugar-cane juice upon delayed extraction and storage.

Abstract The quality of sugar-cane juice extracted from stored canes, as well as changes in quality of fresh juice stored at different temperatures, were studied. Cane stems were stored at 10±1°C, 85–88% relative humidity (RH) and 27±1°C, 55–85% RH, while fresh juice was stored at 5±1°C, 61–84% RH and 27±1°C, 55–85% RH. The physicochemical parameters evaluated were juice yield, juice colour, total soluble solids, sugar content (sucrose, fructose, glucose), titratable acidity, pH, chlorophyll content and sensory evaluation for colour and flavour. Viscosity and total microbial count on stored cane juice were also determined. Results showed that low temperature storage (10°C) of canes was able to maintain the quality of juice for up to 9 days while low temperature storage (5°C) of juice could last for only 4 days. During storage, sucrose contents decreased while fructose, glucose and titratable acidity increased in both types of samples. The colour changes in juice extracted from stored canes was inconspicuous until day 9. Deterioration of cane stored at 27±1°C occurred faster than that stored at 10±1°C. Fresh sugar-cane juice became spoiled after 4 days when stored at 5±1°C and 1 day when stored at 27±1°C. Microbial count, especially lactic acid bacteria count, increased during storage of cane juice.

Ascorbate oxidase from starfruit (Averrhoa carambola): preparation and its application in the determination of ascorbic acid from fruit juices

Abstract A study was conducted to utilize ascorbate oxidase (AAO) from very immature starfruit for the enzymatic determination of ascorbic acid (AsA) in colored samples. The enzyme preparation was carried out by a combination of (NH 4 ) 2 SO 4 fractionation, DEAE-Toyopearl 650 M and ultrafiltration. A calibration curve for AsA was constructed by plotting the amount of AsA oxidized by the enzyme at a specified reaction time against the absorbance. The curve showed a linear relationship in the range of 0–100 μg ml −1 AsA used. Using the plot, the values of AsA in juice samples were determined and compared with the conventional 2,6-dichloroindophenol method.

Isolation and Identification of Antioxidative Compound from Fruit of Mengkudu (Morinda citrifolia L.)

This study was conducted to isolate and identify the antioxidative compound from fruit extracts of Mengkudu (Morinda citrifolia L.). The extract was fractionated on a Sephadex LH-20 column chromatography using ethanol as eluate. Six major fractions were isolated according to UV absorption intensity of phenolic contents at 725 nm. Antioxidative activity of these fractions was evaluated in a ferric thiocyanate method (FTC) and thiobarbituric acid test (TBA). The antioxidative activities were then compared to that of α-tocopherol (natural antioxidant) and butylated hydroxytoulene or BHT (synthetic antioxidant). Results showed that all isolated fractions demonstrated high antioxidative activity compared to either BHT or α-tocopherol. Further separation of these fractions on a high-performance liquid chromatography (HPLC) procedure based on water-methanol gradient with trifluoreacetic acid (TFA) for simultaneous analysis of flavonoids, indicated that they contain several active compounds. The major flavonoids that have been detected in M. citrifolia are catechin and epicatechin.

Purification and characterization of membrane-bound polyphenoloxidase (mPPO) from Snake fruit [Salacca zalacca (Gaertn.) Voss].

Membrane-bound polyphenoloxidase (mPPO) an oxidative enzyme which is responsible for the undesirable browning reaction in Snake fruit (Salacca zalacca (Gaertn.) Voss) was investigated. The enzyme was extracted using a non-ionic detergent (Triton X-114), followed by temperature-induced phase partitioning technique which resulted in two separate layers (detergent-poor phase at the upper layer and detergent-rich phase at the lower layer). The upper detergent-poor phase extract was subsequently fractionated by 40-80% ammonium sulfate and chromatographed on HiTrap Phenyl Sepharose and Superdex 200 HR 10/30. The mPPO was purified to 14.1 folds with a recovery of 12.35%. A single prominent protein band appeared on native-PAGE and SDS-PAGE implying that the mPPO is a monomeric protein with estimated molecular weight of 38kDa. Characterization study showed that mPPO from Snake fruit was optimally active at pH 6.5, temperature 30°C and active towards diphenols as substrates. The K(m) and V(max) values were calculated to be 5.46 mM and 0.98 U/ml/min, respectively, when catechol was used as substrate. Among the chemical inhibitors tested, l-cysteine showed the best inhibitory effect, with an IC(50) of 1.3 ± 0.002 mM followed by ascorbic acid (1.5 ± 0.06 mM), glutathione (1.5 ± 0.07 mM), EDTA (100 ± 0.02 mM) and citric acid (186 ± 0.16 mM).

Antioxidant Activity of Different Extracts of Red Pitaya (Hylocereus polyrhizus) Seed

Antioxidant activity of three different extracts (ethanolic, chloroformic, and hexanic) of red flesh pitaya (Hylocereus polyrhizus) seed using free radical scavenging assay, linoleic acid model system, and ferric thiocyanate (FTC) method was determined. Ethanolic extract inhibit 74.76% of free radicals at 1000 μg/mL, while chloroformic extract gave the highest inhibition using linoleic acid model system (98.90% at 100 μg/mL) and FTC (96.34%) method. Total phenolic and ascorbic acid contents of the seed were 13.56 ± 2.04 and 0.36 ± 0.01 mg/g, respectively, while catechin was the major flavonoid detected. In conclusion, the study showed that both polar and non-polar compounds contribute to the antioxidative activity measured.

Physico-chemical changes in sugarcane (Saccharum officinarum var yellow cane) and the extracted juice at different portions of the stem during development and maturation

A study was conducted to determine the physicochemical differences between portions (top, middle, and bottom) of sugarcane at different maturation stages (between 3 and 10 months from planting). The variety used was Saccharum officinarum var. Yellow cane. The parameters analysed were weight, diameter, yield, total soluble solids (TSS), pH, titratable acidity, sugar content (sucrose, glucose, fructose). The weight, diameter, total soluble solids (TSS) and sucrose content increased significantly (P<0.01) in all portions (top, middle and bottom) up to the end of maturity. On the other hand, titratable acidity (TA), pH, juice yield, glucose and fructose contents decreased significantly (P<0.01) during maturation. However, significant differences were also detected in weight, diameter, TSS, sugar content, pH, TA and juice yield between the different portions during maturation. Sucrose content, juice yield and TSS were found to be the most suitable indicators of maturity, while TA, glucose and fructose contents were found to be poor maturity indicators. A suitable harvesting stage was found to be between 7 and 8 months after planting. Copyright

Inhibitory effect of Morinda citrifolia L. on lipoprotein lipase activity.

Efficacy of Morinda citrifolia L. leaf (MLE) and fruit extracts (MFE) in inhibiting lipoprotein lipase (LPL) was determined in vitro. The result of the study showed that the highest inhibition on the LPL activity was exhibited by MLE (66%+/- 2.1%), which is significantly higher than that demonstrated by MFE (54.5%+/- 2.5%), green tea extract (GTE) (54.5%+/- 2.6%), and catechin (43.6%+/- 6.1%). Percent of LPL inhibition increase with concentration of the extracts. Quantitative analysis of the extracts revealed the presence of high levels of (+)-catechin at 63.5 +/- 17 and 53.7 +/- 5.7 mg/g in MLE and MFE, respectively, although not as high as that found in GTE (530.6 +/- 42 mg/g). Appreciable amount of epicatechin was found in all extracts tested, while rutin was only found in MLE and MFE. The study suggested that both leaf and fruit of M. citrifolia may be used as antiobesity agents in body weight management.

Optimization of Osmotic Dehydration of Seedless Guava (Psidium guajava L.) in Sucrose Solution using Response Surface Methodology

Abstract In this study, osmotic dehydration of seedless guava was studied through response surface methodology. Seedless guava cubes were dehydrated in sucrose solution at different concentration (30–50% w/w), temperature (30–50°C) and immersion time (15–240 min) with respect to weight reduction, solid gain and water loss. A Box–Behnken design was used to determine the optimum processing conditions that yield maximum weight reduction, water loss and minimum solid gain. The models developed for all responses were significant (p<0.05). The response surface plots were constructed to show the interaction of process variables. Optimum process conditions were found to be sucrose concentration of 33.79% w/w, temperature of 30.00°C and immersion time of 240 min through desirability function method. At these optimum points, weight reduction, solid gain and water loss were found to be 0.189 (gg−1), 0.050 (gg−1) and 0.237 (gg−1), respectively.