大黄化学成分及抗氧化、酶抑制特性研究进展

大黄始载于汉·《神农本草经》,具有泻下攻积、凉血解毒、利湿退黄之功效。现代药理学研究证实大黄具有显著的抗氧化活性,且能竞争性抑制α-葡萄糖苷酶和酪氨酸酶的活性。本文将对大黄中化学成分、抗氧化活性(清除DPPH·、ABTS·+、OH·自由基及对油脂的抗氧化作用)、酶抑制特性(抑制酪氨酸酶、α-葡萄糖苷酶的活性)作一小结,以期能为大黄的药效物质研究及整体开发与利用提供理论依据。

Characteristics of CO_2 Exchange and Chlorophyll Fluorescence of Transgenic Rice with C_4 Genes

The responses of photosynthesis of phosphoenopyruvate carboxylase (PEPC), pyrurate dikinase (PPDK), NADP-malic enzyme (NADP-ME) and PPDK+PEPC transgenic rice (Oryza saltiva L.) plant to light, temperature, CO 2 and the characteristics of chlorophyll fluorescence under photoinhibition conditions were studied. The results were as follows: 1. The light-saturated photosynthetic rates of transgenic rice plants were higher than that of wild type, in which the light-saturated point of PEPC and PPDK+PEPC transgenic rice plants was 200 μmol·m -2·s -1 higher than that of untransformed rice and the light-saturated photosynthetic rates were 51.6% and 58.5% respectively. The carboxylation efficiency of PEPC transgenic rice plant increased by 49.3% and the CO 2 compensation point decreased by 26.2% than that of untransformed rice. Under high temperature (35 ℃), the photosynthetic rate of PEPC transgenic rice plant was higher over 17.5% than that of untransformed rice. 2. On the 8th day after photoinhibition treatment, the PSⅡ photochemical efficiency (F v/F m) and photochemical quenching (qP) of PEPC and PPDK+PEPC transgenic rice plants decreased by about 20%-30% while the non-photochemical quenching (qN) increased by approximately 30%. But F v/F m and qP of untransformed rice decreased by over 50% while qN increased by less than 10%. The result suggested that transgenic rice plants were more tolerant to photoinhibition.

Flk-1 specific kinase inhibitor SU5416 blocked angiogenesis of Lewis carcinoma in mouse and prolonged the survival

Objective: To reveal the mechanism and effect of SU5416 in the treatment of mouse Lewis cancer in vivo. Methods: Lewis cell was transplanted into groin of C57/B6 mouse by subcutaneous injection, then SU5416 was administrated intraperitoneally to investigate the impact of SU5416 on tumor angiogenesis and growth in vivo. 32 mice were treated with SU5416 at two different doses every day until the end-point. As a control, 8 mice received no treatment and 8 mice were treated with vehicle (DMSO) only after implantation. Results: Median survival in the treated group was statistically longer compared to that in the control groups (P < 0.05) and no significant systemic adverse was observed. Histological analysis of the treated tumors showed an increase in necroses and reduced in angiogenesis compared to the control tumors. Furthermore, the percent of apoptotic cells increased in the treated tumors by FCM, the expressions of VEGF and KDR had no change after SU5416 administration by western blot. Conclusion: SU5416 may be useful therapeutics drug that specifically inhibits the enzymatic activity of KDR kinase and could down regulate the tumor angiogenesis.

Effects of transgenic poplar clone 741 with insect resistance on structure and diversity of arthropod community

Arthropod community structure and diversity were investigated in transgenic insect-resistant hybrid poplar 741 field trial plots, which had five isogenic clones with two genes （Bt. toxin [Cry IAc] and arrowhead proteinase inhibitor [API]） in comparison to control plots. Transgenic poplar clones were investigated according to their insect resistance （high and medium resistant clones）, being systematically probed into varying levels with feeding tests before. Investigations were carded out during three years （2002, 2003 and 2005）. The results indicated that among the basal species, transgenic plants in general had lower amounts of phytophagous insects, and an increased quantity of neutral arthropods such as saprophytic and strolling species. Among the top and intermediate species in transgenic variants, the quantity of predatory natural enemies was increased, while the amount of parasitoid ones was slightly reduced. The arthropod community characteristic indices were analyzed from different aspects in the three variants. It was discovered that, not only the characteristic indices of the whole arthropod community, but also the characteristic indices of the sub-communities （such as natural enemy, pest and neutral arthropods） and the functional groups categorized by their feeding patterns, showed a higher diversity and evenness and a lower dominancy concentration indices in the high-resistant and medium-resistant plots compared with the control. Transgenic poplar 741 showed improved ecological effects both in partial and total aspects. It could be concluded that composition and structure of the arthropod community in plots with transgenic insect-resistant poplar were turned to be more reasonable and itsdiversity and stability was enhanced.

Stability and cytotoxicity of angiotensin-I-converting enzyme inhibitory peptides derived from bovine casein

This study investigated the effect of heat treatment combined with acid and alkali on the angiotensin-I- converting enzyme （ACE） inhibitory activity of peptides derived from bovine casein. The free amino group content, color, and cytotoxicity of the peptides were measured under different conditions. When heated at 100 ℃ in the pH range from 9.0 to 12.0, ACE inhibitory activity was reduced and the appearance of the peptides was significantly darkened. After thermal treatment in the presence of acid and alkali, the free amino group content of ACE inhibitory peptides decreased markedly. High temperature and prolonged heating also resulted in the loss of ACE inhibitory activity, the loss of free amino groups, and the darker coloration of bovine casein-derived peptides. However, ACE inhibitory peptides, within a concentration range of from 0.01 to 0.2 mg/ml, showed no cytotoxicity to Caco-2 and ECV-304 cell lines after heat treatment. This indicated that high temperature and alkaline heat treatment impaired the stability of bovine casein-derived ACE inhibitory peptides.