PSP (I. batatas) cv. Ayamurasaki was purchased from the Xuzhou Sweet Potato Research Institute, Chinese Academy of Science (Xuzhou, Jiangsu Province, China). Macroporous AB-8 resin was purchased from Shanghai Lan-Ji Science Technology Development Co. Ltd. (China). All kits used for this study were purchased from Nanjing Jian-Cheng Bioengineering Institute (China). Streptozocin (STZ) was purchased from Sigma Chemical Co. (USA).

Fifty 3-wk-old male Kunming ablactation mice [18-22 g body weight (BW)] and 50 Specific Pathogen Free (SPF)-grade ICR mice (25 males and 25 females, 18-22 g BW) were purchased from the Experimental Animal Center of Soochow University (Suzhou, China). This study was approved by the Institute Review Board of Soochow University (IRB #12-02-0040).

PSPA was extracted as previously described [10] with some modification. PSPs were heated in a microwave oven for 15 min. The cooked potatoes (1 kg approximately) were crushed and suspended in acidic electrolyzed water (2 L, pH = 3.0). The suspension was cooled to 0℃ for 12 h without stirring. To remove the solid residue, the suspension was centrifuged at 12,000 rpm and 4℃ for 20 min on Avanti J-30I Centrifuge (Beckman, USA). Then the extracts were concentrated to remove water using a RE-5220 rotary evaporator (YaRong Biochemistry Instrument Factory, Shanghai, China). Through the Spray Dryer (Shanghai Trustech Co. Ltd., China) can transform into powder samples. The crude sample was dissolved in distilled water (1:5, W/V), and the solution loaded onto a solid phase extraction cartridge (AB-8 resin). The purified water was firstly eluted and the aqueous phase was discarded, 70% ethanolic water was secondly eluted and the ethanol-H₂O eluent was collected. The eluent was concentrated to remove ethanol using a RE-5220 rotary evaporator (YaRong Biochemistry Instrument Factory, Shanghai, China). The concentrated aqueous elute was lyophilized on vacuum freeze dryer (Thermo, USA) for further evaluation.

PSPs were heated in a microwave oven for 15 min. The cooked potatoes (1 kg approximately) were crushed and suspended in acidic electrolyzed water (2 L, pH = 3.0). The suspension was cooled to 0℃ for 12 h without stirring. To remove the solid residue, the suspension was centrifuged at 12,000 rpm and 4℃ for 20 min prior to application onto an Amberlite AB-8 column. The column was rinsed with water and the extracts were eluted with a solution of water/ethanol (7:3 v/v). The eluent was concentrated in vacuo, freeze-dried and referred to as the crude PSPA extracts.

The PSPA color was quantified using the spectrophotometric method previously described by Francis [11]. When the concentration of PSPA was 0.011% in aqueous solution, the ultraviolet (UV) spectrum was scanned from 200 to 600 nm in a 1-cm-thick absorption cell on U3000 Spectrophotometer (Hitachi Co. Ltd., Japan). Absorbance at the maximum absorption wavelength was measured. Color values for the PSPA extracts were calculated using the following equation:

in which $E_{1\mathrm{cm}}^{1\mathrm{\%}}$ is the color value for the 1% extract in the 1-cm colorimetric cell at the maximum absorption wavelength, A is the absorbance, and m is the amount (0.2-0.7 g) of sample analyzed.

Weighting 10.0 mg constant weight rutin standard (Beijing Aoke Biotechnology Co. Ltd., China), dissolving it use 98% ethanol, then constanting volume to 50 mL, so we have 200 µg/mL rutin standard solution. Accurately draw rutin standard solution 0, 10, 20, 30, 40, 50 µL in the absorption cell, and then followed by adding 70% ethanol solution 50, 40, 30, 20, 10, 0 µL. Numbered the absorption cells 0, 1, 2, 3, 4, 5. To each standard, a 10% sodium nitrite solution (National Medicine Group Chemical Reagent Co. Ltd., China) (10 µL) was added. The solutions were shaken and left standing for 6 min. Next, 10 µL of a 20% aluminum nitrate solution (National Medicine Group Chemical Reagent Co. Ltd., China) were added before the mixture was shaken, and 50 µL of a 2 mol/L NaOH solution were added. Finally, 200 µL of a 60% ethanol solution was added to each standard. The mixtures were shaken and left standing for 10-15 min. Using the blank ("0") as the reference, absorbance was measured at 510 nm to generate the rutin standard solution curve. Least squares regression was subsequently used to evaluate the relationship between the absorbance values and rutin standard concentration.

An UV spectrophotometric method was used to determine TF contents expressed as rutin equivalents [12]. The samples (10.0 mg each) were dissolved in 10 mL of 60% ethanol, and 1 mL of the solution was added to a test tube. Absorbance was measured at a wavelength of 510 nm on U3000 Spectrophotometer (Hitachi Co. Ltd., Japan), and TF concentrations were determined using the standard curve. The analyses were done in triplicate.

Gallic acid (National medicine group chemical reagent Co. Ltd.,China) (10.0 mg) was dried at 120℃ for 1h and dissolved in 100 mL water, to produce a 100 µg/mL gallic acid standard solution. Aliquots of the gallic acid standard solution (0.0, 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mL) were transferred to 10 mL graduated test tubes (Sangon Biotechnological Co. Ltd., Shanghai, China). Next, 5.0 mL of distilled water and 0.5 mL Folin-Ciocalteu phenol reagent (National Medicine Group Chemical Reagent Co. Ltd., China) were added. The solution was shaken for 1 min before 1.5 mL of a 20% Na₂CO₃ solution was added. The mixture was then incubated for 2 h at room temperature. Using the blank standard, absorbance was measured at 760 nm to generate the standard curve.

An UV spectrophotometric method was used to determine the TP contents as gallic acid equivalents [13]. The samples (10.0 mg each) were dissolved in 10 mL of distilled water and 1 mL of the solution was transferred to a test tube. Absorbance was measured at wavelength of 760 nm on U3000 Spectrophotometer and TP concentration was calculated according to the standard curve.

Twelve-mo-old male Kunming mice (50.36 ± 3.76 g BW) were obtained. The animals were randomly divided into five groups: the control group treated with 0.4 mL physiological saline, a positive group treated with 100 mg/kg BW of vitamin C or E (National Medicine Group Chemical Reagent Co. Ltd., China); three PSPA groups treated with low, medium, or high doses (100, 500 and 1,000 mg/kg BW, respectively) of PSPA; and a 5-month-old control group treated with 0.4 mL physiological saline. All the groups were treated for 30 d, and blood was collected from the eyeballs on 31th day. The serum was obtained at 4000 rpm for 20 min on the centrifuge (Beckman Coulter, Inc., USA). The total antioxidation capacity (T-AOC) as well as the levels of superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione peroxidase (GSH-PX) in the serum were measured using the appropriate commercial kits. The assays were performed in triplicate. The data are expressed as the mean values and standard deviation (SD).

Fifty 3-wk-old male Kunming ablactation mice (18-22 g BW) were maintained under controlled conditions (18-25℃, 50-80% humidity, and a 12-h light/dark cycle) with free access to rodent food (Suzhou Experimental Animal Food Co. Ltd., Suzhou, China) and tap water. The mice were divided into five groups. The control group (I) was treated with rodent food. The PSPA ig group (II) was treated with normal forage and 1.0 g PSPA/kg BW in 0.5 mL water was poured into the stomach daily by using special syringe (Sangon Biotechnological Co. Ltd., Shanghai, China). The PSPA po group (III) was treated with normal forage mixed with PSP extract (10 g/kg) as previously described [7]. Group IV was treated with a high-saturated fat, high-sugar diet (18% lard, 20% sugar, 3% egg yolk, and 59% basal) and PSPA. Finally, group V was treated with a high-saturated fat, high-sugar diet. All mice were fed for 4 wk according to their treatment group and BW was recorded weekly. After 4 wk, each mouse was weighed, injected with STZ (100 mg/kg BW), and then returned to their feeding regimen for another week. At the end of the feeding period, all the animals were fasted for 12 h. Blood samples were then collected by amputating the tail, blood glucose concentrations were measured using commercially available kits (BIOSINO Biotechnology and Science INC, China), and BW was recorded. Finally, all mice were anesthetized with pentobarbital sodium (National Medicine Group Chemical Reagent Co. Ltd., China) (35 mg/kg) and euthanized by cervical decapitation, and their hearts, livers, kidneys, and pancreas were excised and weighed. The organ index was calculated using the following formula:

Pancreas and islet tissues were fixed at 10% buffered formalin overnight and then immersed in 70% ethanol for storage at room temperature. The tissues were embedded in paraffin. Sections were cut at 5µm on positively charged slides. The section were stained with hematoxylin and eosin (National Medicine Group Chemical Reagent Co. Ltd., China) (HE) using conventional methods.

The food intake and water intake are obtained through the offered amount minus the surplus amount every day.

Fifty SPF-grade ICR mice (25 males and 25 females, 18-22 g BW) were acquired from the Experimental Animal Center of Soochow University. The mice that were implanted with mice S180 anal sarcoma cells were provided by Nanjing Kai-Ji Biotechnology Development Co. Ltd (Nanjing, China). All animals were randomly assigned to five groups (n = 10 per group): a blank control (treated with 0.4 mL normal saline), negative control (implanted with tumor cells), and three treatment groups (implanted with tumor cells) given 100, 500, or 1,000 mg/kg BW PSPA.

During the experimental period, all animals had free access to five kinds of food (Table 4) and tap water. BW was recorded daily along with the numbers and sizes of sarcomas observed. The day after two successive weeks of treatments, the BW of each group was measured and blood was collected by removing the eyeballs. Entire sarcomas were removed from each mouse to measure tumor inhibition rates calculated with the following formula:

in which C is the average tumor weight for the negative control group (g) and T is the average tumor weight for the treatment group (g).

The rate of BW changes was evaluated with the following formula:

in which W is BW 2 wk after inoculation with the tumor cells (g) and W₀ is the BW before inoculation with the tumor cells.

SOD, MDA, and GSH-PX levels were measured with the appropriate commercial kits.

The experimental data were evaluated with Anova. Results are presented as the mean ± standard deviation for the indicated number of independently performed experiments.

PSPA extracts had strong absorption between 269 and 360 nm (Fig. 1) due to the characteristics of the acyl-anthocyanin structure. In the visible region (528 nm), the highest absorbance value was 0.335. The calculated color value of the sample was 30.15.

In the present study, rutin and gallic acid were used as reference standards to determine TF and TP contents, respectively, in the extracts. Two standard curves are quantities of rutin and gallic acid as abscissae and their absorbance values at 510 and 760 nm as ordinates, respectively, with the following regression equations: y = 0.01297x + 0.00429 and y = 0.01389x + 0.03654. The rutin or gallic acid concentrations and the absorbance values had a positive linear relationship. Using the linear regression equations, TF and TP concentrations were calculated as 932.5 mg/g and 140.789 mg/g, respectively. Based on these results, it appeared that anthocyanin extracted from PSP contained high TF and TP levels.