Sweet potato storage root mucilage was extracted and purified by SDS and heating treatments. Total antioxidant activity, DPPH (1,1-diphenyl-2-picrylhydrazyl) staining, reducing power method, metal ion-dependent hydroxyl radical, FTC (ferric thiocyanate) method, and protection of calf thymus DNA against hydroxyl radical-induced damage were studied. Half-inhibition concentrations, IC50, were 0.08mg/ml and IC50>0.1mg/ml, respectively, for the crude and purified mucilage in the total antioxidant activity test. In the DPPH staining, the crude and purified mucilage appeared as white spots when they were diluted to 50 and 100μg per application, respectively. Like total antioxidant activity, reducing power, scavenging capacity against hydroxyl radical, FTC activity and protection of calf thymus DNA against hydroxyl radical-induced damage were found in the mucilage. It is suggested that the mucilage might contribute its antioxidant activities against both hydroxyl and peroxyl radicals.

The aim of this study was to examine possible antioxidant and antiproliferative activities of 95% ethanol or water extract from water spinach (Ipomoea aquatica Forsk) organs. DPPH staining, total phenolic compounds, total flavonoid content, DPPH radical, reducing power method, FTC method, and inhibition of cancer cell prolifera- tion were employed. Ethanol extract of stem demonstrated a positive effect in DPPH staining when it was diluted to 6.25 mg dry matter/mL while all other fractions showed no effect at the same dilution. This fraction also had the highest content of the total phenolic compounds, as well as the highest reducing power and FTC activity. Ethanol extract of leaf had the highest amount of flavonoids. Using DPPH colorimetric method, it was found that ethanol extract of stem had the highest radical-scavenging activity, followed by ethanol extract of leaf. The antiproliferative activities of water spinach extracts were studied in vitro using human lymphoma NB4 cells, and the following results were found: water extract of stem had the highest antiproliferative activity with an EC 50 of 661.40 ± 3.36 µg dry matter/mL, followed by ethanol extract of stem and ethanol extract of leaf. The water extract of leaf had the lowest antiproliferative activity (EC 50 >1000 µg dry matter/mL) under the experimental conditions.

Recombinant thioredoxin h (Trx2) overproduced in Escherichia coli (M15) was purified by Ni2+-chelated affinity chromatography. The molecular mass of Trx2 is approximately 1.4 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Total antioxidant status, 1,1-diphenyl-2-picrylhydrazyl (DPPH) staining, reducing power method, Fe2+-chelating ability, ferric thiocyanate (FTC) method, and protection of calf thymus DNA against hydroxyl radical-induced damage were studied. The thioredoxin h protein with a concentration of 12.5 mg/mL exhibited the highest activity (expressed as 0.37 +/- 0.012 mM ABTS* radical cation being cleared) in a total antioxidant status test. In the DPPH staining thioredoxin h appeared as white spots when it was diluted to 50 mg/mL (a final amount of 15 microg). Like the total antioxidant status, the reducing power, Fe2+-chelating ability, FTC activity, and protection against hydroxyl radical-induced calf thymus DNA damage were found with the thioredoxin h protein. It was suggested that thioredoxin h might contribute to its antioxidant activities against hydroxyl and peroxyl radicals.

The aim of this study is to examine possible antioxidant and antiproliferative activities of the different extracts from sweet potato (Ipomoea batatas (L.) Lam 'Tainong 57') organs. DPPH staining, total phenolic com- pounds and flavonoid content, DPPH radical, reducing power method, FTC method, and cell proliferation were all employed. In the DPPH staining, ethanol extract of vein had the highest radical-scavenging activity when it was diluted to 6.25 mg dry matter/mL. Among all the extracts, the highest amount of total phenolic and flavonoid com- pounds was found in the ethanol extract of vein. In the DPPH colorimetric method, it was found that ethanol extract of leaf had the highest radical-scavenging activity, followed by water extract of vein. In the reducing power activity assay, it was found that the water extract of leaf had the highest reducing power activity, followed by ethanol extract of vein. Like phenolic compounds, the highest FTC activity was found in the ethanol extract of vein. The antipro- liferative activities aof sweet potato were studied in vitro using human lymphoma NB4 cells, and the following re- sults were found: water extract of vein had the highest antiproliferative activity with an EC 50 of 449.6 ± 27.73 µg/mL, followed by water extract of storage root, water extract of leaf, ethanol extract of storage root, and ethanol extract of leaf. Although the ethanol extract of vein showed strong antioxidant activity, it had no antiproliferative activity under the experimental conditions tested.