Chin-Feng Chan

Dramatic synergistic anticancer effect of clinically achievable doses of lovastatin and troglitazone

Lovastatin (an HMG‐CoA reductase inhibitor) and troglitazone (a PPAR‐γ agonist) have been intensively studied prospectively for their application in cancer treatment. However, clinical trials of lovastatin or troglitazone in cancer treatment resulted in only limited responses. To improve their efficacy, lovastatin and troglitazone have, respectively, been tried to combine with other anticancer agents with varied outcomes. In our study, we found a dramatic synergism between lovastatin and troglitazone in anticancer at clinically achievable concentrations. This synergism was found in far majority of cell lines tested including DBTRG 05 MG (glioblastoma) and CL1‐0 (lung). This amazing synergism was accompanied by synergistic modulation of E2F‐1 and p27Kip1, which were reported to mediate the anticancer activities of lovastatin and troglitazone, respectively, and other cell cycle regulating proteins such as CDK2, cyclin A and RB phosphorylation status. With this dramatic combination effect of lovastatin and troglitazone, a promising regimen of cancer therapy may be materialized in the future.

Activation of transcription factors of nuclear factor kappa B, activator protein-1 and octamer factors in hyperalgesia.

Involvement of c-fos and neuronal nitric oxide synthase (nNOS) in the hyperalgesia induced by complete Freund adjuvant (CFA) has been reported. In this paper, we attempted to investigate whether the transcription factors regulating the gene expression of c-fos and nNOS, including activator protein-1 (AP-1), nuclear factor kappa B (NF-kappa B), and octamer factors (Oct), are activated by CFA during the development of hyperalgesia. The electrophoretic mobility shift assay (EMSA) was used to determine whether there were changes in the transcription factors in the lumbar spinal cord of adult rats following subcutaneous injection of CFA in one hindpaw of the rats. Maximum binding of AP-1, NF-kappa B and Oct was found at 0.5, 1 and 2 h after CFA injection, respectively. These findings suggest that the activation of these transcription factors is pivotal for the expression of c-Fos and nNOS proteins, which reached a peak at 3 and 48 h after CFA injection, respectively. The behavioral testing of hyperalgesia demonstrated that CFA reduced the thresholds for mechanical and thermal algesia, reaching a minimum at 6 h. The thresholds had only partially recovered after 96 h. Based on these findings, we conclude that AP-1, NF-kappa B and Oct are crucial for the expression of c-Fos proteins at an early stage (at 3 h) and for the expression of nNOS at a late stage of hyperalgesia (48 h post-injection) induced by CFA.

Antioxidative activity of water extract of sweet potato leaves in Taiwan

This study reports the preparation of four varieties of water extract from sweet potato leaves from Taiwan, including TNG10, TNG57, TNG66 and YSP, and evaluates their antioxidative activity. The EC50 values (scavenging DPPH radicals) of TNG10, TNG57, TNG66 and YSP were 0.27±0.01, 0.19±0.01, 0.41±0.02, and 0.31±0.02mg/ml, respectively, on a freeze-dry weight basis. The total phenolic contents of these water extracts were in the order: TNG57>TNG10>TNG66>YSP. The TNG10 and TNG57 extracts exhibited better reducing power and scavenging effects of superoxide radicals than did TNG66 and YSP. At a concentration of 1mg/ml, TNG10 and TNG57 significantly protected HaCaT cells from H2O2-induced cytotoxicity. The water extracts of YSP had more flavonoids than had those of TNG66 which may have contributed to their higher activity in many antioxidative assays. These results suggest that the water extracts of all four varieties of sweet potato leaves, and especially TNG10 and TNG57, display potent antioxidative effects.

Suramin prevents cerebellar granule cell-death induced by dequalinium.

In this study, we demonstrated that an anticancer drug, dequalinium, a bisquaternary ammonium compound, is a potent neurotoxicant with IC(50) of 0.46 microM on the cultured cerebellar granule neurons. Its selective neurotoxicity revealed by 100-fold more toxic than the other two analogs, pancuronium and vecuronium. The mechanisms underlying dequalinium (DQ)-induced neurotoxicity were explored and found to be associated with decreased mitochondrial membrane potential, increased free radical production and ATP depletion. Suramin (a nonselective purinergic P(2) receptor antagonist and an anticancer drug) but not the glutamate receptor antagonists, MK-801, NBQX (1,2,3,4 tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium), and DNQX (6,7-dinitroquinoxaline-2,3-dione) significantly prevents the DQ-induced neurotoxicity. By means of microfluorometric image-processing technique using the fluorescent probes, fluorescein diacetate/propidium iodide and Hoechst 33258, respectively, we showed that 1 microM DQ for 24 h induced about 53.5% of apoptosis and 37.5% of necrosis. All of these effects of DQ can be completely prevented by suramin. From these results, we conclude that DQ-induced neurotoxicity was not mediated by glutamate receptor, but by increasing free radical productions and cell energy depletion. Suramin with its beneficial antagonistic effects on DQ-induced neurotoxicity may provide an effective approach for neurodegeneration.

Changes in sugar composition during baking and their effects on sensory attributes of baked sweet potatoes

The objective of this study was to evaluate the influence of sugar composition on the sensory attributes of seven baked sweet potatoes. The sugar composition was analyzed using high performance liquid chromatography. Results showed that the total sugar content of baked sweet potatoes increased significantly because of the formation of maltose. The maltose content dramatically increased after baking, and became the major sugar component of baked sweet potatoes. On the other hand, baked sweet potatoes were evaluated on a 7-point hedonic scale for sensory analysis. Overall acceptability results showed that the panelists preferred baked CYY95-26 and TNG66 over the other baked varieties. Because the correlation between overall acceptability and sweetness was the highest (r = 0.69, p < 0.01), sweetness was determined as the most important factor determining the overall acceptability of baked sweet potatoes. Although sugar composition changed on baking, the overall acceptability of baked sweet potatoes was highly associated with the sucrose content.

Ultrasound-Assisted Anthocyanin Extraction of Purple Sweet Potato Variety TNG73, Ipomoea batatas, L

The acidic-ethanol anthocyanin extraction process of TNG73 sweet potatoes was improved with introducing the sonication treatment. The linear terms of sonication time and extraction temperature were determined to be significant factors. Response surface methodology (RSM) models were successfully established to perform the extraction study and energy requirement analysis. After calculating the required energy for collected anthocyanins (J/µg), the process with higher extraction temperature became less effective. Based on the combined results of extraction study and energy requirement analysis, the recommended operating condition of anthocyanin extraction process was at 25°C with 22 min sonication.

Kinetics of Mushroom Tyrosinase and Melanogenesis Inhibition by N-Acetyl-pentapeptides

We investigated the kinetics of 4N-acetyl-pentapeptides, Ac-P1, Ac-P2, Ac-P3, and Ac-P4, regarding inhibition of mushroom tyrosinase activity. The peptides sequences of Ac-P1, Ac-P2, Ac-P3, and Ac-P4 were Ac-RSRFK, Ac-KSRFR, Ac-KSSFR, and Ac-RSRFS, respectively. The 4N-acetyl-pentapeptides were able to reduce the oxidation of l-DOPA by tyrosinase in a dose-dependent manner. Of the 4N-acetyl-pentapeptides, only Ac-P4 exhibited lag time (80 s) at a concentration of 0.5 mg/mL. The tyrosinase inhibitory effects of Ac-P4 (IC50 0.29 mg/mL) were more effective than those of Ac-P1, Ac-P2, and Ac-P3, in which IC50s were 0.75 mg/mL, 0.78 mg/mL, and 0.81 mg/mL, respectively. Kinetic analysis demonstrated that all 4N-acetyl-pentapeptides were mixed-type tyrosinase inhibitors. Furthermore, 0.1 mg/mL of Ac-P4 exhibited significant melanogenesis inhibition on B16F10 melanoma cells and was more effective than kojic acid. The melanogenesis inhibition of Ac-P4 was dose-dependent and did not induce any cytotoxicity on B16F10 melanoma cells.

Studies of Carotene Extraction from Sweet Potato Variety CYY95-26, Ipomoea batatas, L

The goal of this study was to extract β-carotene from CYY95-26 sweet potatoes. Acetone was used as the solvent to successfully extract β-carotene. To achieve better extraction results, acetone concentration was required to be higher than 75%. Two extraction parameters, including acetone concentration and extraction time, were evaluated with the response surface methodology. The process was optimized, and optimal extraction conditions were determined to be 91.1% of acetone and 19.6 min extraction. Acetone concentration was a significant factor of the β-carotene extraction. The multiple extraction improved the extraction performance. After the third extraction, 278.1 mg/kg of β-carotene was extracted. The major carotene of CYY95-26 sweet potatoes was all-trans-β-carotene. CYY95-26 also contained small amount of 9-cis-β-carotene and 13-cis-β-carotene which were carotene isomers.

Extraction Parameter Studies for Anthocyanin Extraction from Purple Sweet Potato Variety TNG73, Ipomoea Batatas, L

Anthocyanins were successfully extracted from TNG73 purple sweet potatoes (PSP), which were provided by Agricultural Research Institute (ARI), Chia-Yi Agricultural Experiment Station, Taiwan. An acidic-ethanol extraction method was used, and the extraction parameters were carefully evaluated. The experimental design and process data for anthocyanin extraction were analyzed by statistical software. The HCl concentration, extraction time, and extraction temperature were significant factors in the extraction of anthocyanins from PSP. Using 15% HCl (1.5N HCl in ethanol) with a 9 g/100mL PSP solid/solvent ratio at 25°C for 30 min was adequate for PSP anthocyanin extraction. The extraction performance was increased 15~25% by running a second extraction. Under the same process conditions, the performance was improved about 80% when sonication was applied. The difference caused by the sonication treatment was more significant for the high solid/solvent ratio system. Ultrasound-assisted extraction was a useful tool for PSP anthocyanin extraction. The goals of this study were to collect detailed process data for further process scaling-up and to develop an ultrasound-assisted anthocyanin extraction process.

Site of action of suramin and reactive blue 2 in preventing neuronal death induced by dequalinium

Dequalinium (DQ, an anticancer drug) is a potent neurotoxicant in the cultured developing cerebellar granule neurons (CGNs) with an IC50 of 1.31 · M after 24 hr incubation. By utilizing fluorometric technique, we found that DQ initially induced apoptosis and then necrosis associated with a marked decrease in ATP contents. The purinergic P2 receptor antagonists (suramin, and reactive blue 2) prevented DQ‐cytotoxicity, although glutamate ionotropic receptor antagonists (MK 801 and NBQX) could not. Furthermore, we quantitatively determined a reduction of mitochondrial membrane potential and an increase of free radical production induced by DQ. Suramin abolished these detrimental events of DQ. This suggests that neuronal death induced by DQ is mediated, at least in part, through a signaling pathway of free radical production‐mitochondrial dysfunction. Further evidence supporting this contention is that CGN progressively became more sensitive to both DQ‐induced cytotoxicity and reduced mitochondrial membrane potential. This implies that neuronal mitochondria are apparently one of the target sites for DQ and suramin and directly or indirectly induce neurotoxicity and neuroprotection respectively. The alteration in mitochondrial membrane potential during neuronal maturation may be one of the determinants accounting for the increased susceptibility to neurotoxicants such as DQ. J. Neurosci. Res. 62:692–699, 2000.