Lathyrane diterpenes from Euphorbia prolifera and their inhibitory activities on LPS-induced NO production

A new lathyrane diterpene (1), an unreported spectroscopic data lathyrane diterpenene (2), and two known analaogues (3 and 4) have been isolated from Euphorbia prolifera. Their structures were elucidated as (12E,2S,3S,4R,5R,6S,9S,11S,15R)-3-butyryloxy-5,15-diacetoxy-6,17-epoxylathyra- 12-en-14-one (1), (12E,2S,3S,4R,5R,6S,9S,11S,15R)-3-propionyloxy-5,15-diacetoxy-6,17- epoxylathyra-12-en-14-one (2), (12E,2S,3S,4R,5R,6S,9S,11S,15R)-3-benzoyloxy-5,15-diacetoxy -6,17-epoxylathyra-12-en-14-one (3), and 15-O-acetyl-17-hydroxyjolkinol (4) by spectroscopic methods (IR, ESIMS, HR-ESIMS, NMR, and X-ray crystallography). The inhibitory activities on LPS-induced NO production of these diterpenes were evaluated and compounds 1, 3 and 4 showed inhibitory effects.     

鲜切马铃薯多酚氧化酶酶学特性及褐变抑制剂的研究

［目的］研究常用防腐、防褐抑制剂对切分马铃薯多酚氧化酶（PPO）的抑制效果及贮运品质的影响。［方法］以无公害马铃薯为试材,以邻苯二酚为底物,采用分光光度法和正交试验法,测定马铃薯中PPO的酶学特性及不同试剂作用下PPO的活性。［结果］马铃薯PPO的最适pH值为7.6,最适温度为32℃,短时高温处理能显著抑制PPO活性;PPO催化酶促褐变反应符合米氏方程,酶促反应的最大速率（Vmax）为0.2866U/（gFW·min）,米氏常数（Km）为0.032mol/L;NaHSO3、抗坏血酸能较好地抑制PPO活性,且随着浓度的升高,抑制效果增强;0.1%抗坏血酸、0.06%或0.10%CaCl2、0.08%苯甲酸钠、1.0%壳聚糖保鲜切分马铃薯丝在4℃下贮藏96h后褐变度仅为6.14%。［结论］马铃薯PPO活性受诸多因素影响,尤以pH值和温度影响最为显著;试验采用抗坏血酸等复合保鲜剂对切分马铃薯丝的褐变抑制进行了系统研究,关于不同试剂间多因素协同作用机理和抑制效应尚需做进一步研究。     

生防菌bio-2菌株对家禽病原菌的抑制作用

采用纸片药敏试验法,分别测定了不同稀释度生防菌bio-2菌株无菌滤液对分离自家禽的大肠杆菌、沙门氏菌和葡萄球菌等3种病原菌的抑菌作用。结果表明,生防菌bio-2菌株无菌滤液原液、1∶2、1∶4、1∶8、1∶16和1∶32倍稀释液对沙门氏菌、大肠杆菌和葡萄球菌均具有很好的抑菌作用,其中对沙门氏菌的抑菌效果最好(抑菌圈直径17.67~23.78 mm),对葡萄球菌的抑制效果次之(抑菌圈直径14.90~19.73 mm),对大肠杆菌的抑菌效果稍差(抑菌圈直径11.64~16.72 mm)。     

西瓜砧木体内汁液对枯萎病菌的影响

为了解西瓜砧木的抗病机理,提取4种砧木日本南瓜(RBNG)、黑籽南瓜(HZNG)、野生西瓜(YSXG)和瓢葫芦(PHL),以及西瓜品种为超甜花龙(CTHL)的芽期和苗期的体内汁液,测定其对西瓜枯萎病菌孢子萌发、菌丝生长的影响。结果表明,4种砧木芽期体内汁液都有较好的抑菌作用,且都高于超甜花龙;4种砧木苗期体内汁液的抑菌作用与超甜花龙之间的差异均不明显;4种砧木的抑菌作用之间均无显著差异。     

几种多糖对黄曲霉菌生长及产毒的抑制作用

研究了香菇多糖、海带多糖、石耳素等10余种多糖对黄曲霉生长及产毒的抑制作用,发现海带多糖、香菇纤维素、马铃薯直链淀粉、A型大豆多糖能够明显降低黄曲霉菌丝产量;同时海带多糖、香菇纤维素、马铃薯直链淀粉、香菇多糖、绿豆多糖抑制了黄曲霉菌产毒,其中海带多糖、马铃薯直链淀粉、香菇纤维素、香菇多糖能够明显降低黄曲霉菌菌丝产毒能力。     

Inhibitory effects of Schiff analogs of salicylidene aniline on phenoloxidase from Pieris rapae L. (Lepidoptera: Pieridae)

In order to gain insight into the development of insecticides with novel modes of action, the effects of salicylidene aniline (a), salicylidene-4-chloroaniline (b), salicylidene-4-bromoaniline (c), and salicylidene-4-nitroaniline (d) on partially purified phenoloxidase (PO) from Pieris rapae L. were investigated. The results showed that the 4 compounds could inhibit PO activity, and the inhibitor concentrations leading to a loss of 50% activity (IC₅₀) were estimated to be 0.025 mmol L⁻¹, 0.732 mmol L⁻¹, 0.471 mmol L⁻¹, and 0.675 mmol L⁻¹, respectively. Meanwhile, all the inhibitors showed reversible competitive inhibition, except (d), which showed reversible mixed inhibition. The K_I values were determined as 0.106 mmol L⁻¹, 10.059 mmol L⁻¹, 8.390 mmol L⁻¹, and 20.198 mmol L⁻¹ for the four compounds, respectively. The UV-vis spectra of (a) and (d) in the presence of copper ions and the enzyme showed that (a) could directly chelate the copper ions of PO; however, (d) could neither chelate the additional copper ions nor the copper ions of PO.     

锡兰肉桂无水乙醇提取物的抑菌活性

采用菌丝生长速率法和组织测定法,测定锡兰肉桂无水乙醇提取物对胡椒瘟病菌、香蕉枯萎病菌、芒果炭疽病菌和芒果蒂腐病菌的抑菌活性以及20%锡兰肉桂微乳剂对胡椒瘟病的保护作用。结果表明,锡兰肉桂无水乙醇提取物对胡椒瘟病菌具有较好的抑菌活性,在浓度1.5 mg/mL时抑菌率为91.94%,EC50为0.687 5 mg/mL;对芒果炭疽病菌的抑菌率为63.75%,但对芒果蒂腐病菌无抑菌活性。20%锡兰肉桂微乳剂对胡椒瘟病表现出较好的保护效果,当稀释100倍和50倍时抑制率分别为72.79%和78.91%。     

禾豆间作氮素高效利用机理及农艺调控途径研究进展

为保障粮食安全,农业生产中化肥使用极为普遍,但过量使用,往往引起地下水污染、温室效应加剧、生物多样性降低等多种环境和生态问题。禾豆间作系统由于不同作物生物学特性和氮素利用存在差异,进行合理调控可充分发挥生物固氮优点,从而减少化肥投入,提高生产效益,是一种稳产、高产、高效可持续的种植体系。该系统中"氮转移"、"氮阻遏"消减和氮素时空分异是目前研究的热点,也是促进豆科作物固氮、减少化肥投入的有效途径,可实现禾、豆两种作物对氮素的高效利用。特别是该系统中作物品种、施氮制度、空间布局以及种植密度等农艺措施是对种间关系进行调控的必要手段,合理优化可有效促进禾/豆间作竞争与互补协同作用,增强氮素协调利用,从而挖掘两种作物对氮素高效利用的生物学潜力。为此,本文基于前人研究成果和农业可持续发展观点,重点综述了国内外有关禾豆间作氮素高效利用主要机理及相关农艺调控途径的研究现状,旨在为构建简易、高产、高效、氮肥节约型禾豆间作模式提供有力的科学依据和理论支撑。     

复合发酵液对致病疫霉的抑制机理

[目的]研究复合发酵液对致病疫霉[Phytophthora infestans （Mont.） de Bary）]的抑制机理。[方法]研究了白菜黑斑病菌和梨黑斑病菌的复合发酵液对致病疫霉的抑制作用机理。[结果]白菜黑斑病菌和梨黑斑病菌复合发酵液使致病疫霉菌丝形态发生畸变;对致病疫霉游动孢子释放和休止孢萌发的抑制率分别为95.93%和78.25%;经复合发酵液处理的致病疫霉病菌菌丝体中可溶性蛋白含量与对照相比有一定的下降,但与单一发酵液处理相比均无显著差异。[结论]该研究可为开发有效控制马铃薯晚疫病的高效、低成本复合型生物农药提供理论依据。     

Enzymatic dynamics of catechol oxidase from Gastrolina depressa

Properties of the phenoloxidase (PO) from adult of Gastrolina depressa Baly (Coleoptera: Chrysomelidae) as well as effects of some metal ions and inhibitors on the activity of PO purified by (NH₄)₂SO₄ were determined. The optimal pH and temperature of the enzyme for the oxidation of catechol were determined to be at pH 7.5 and at 40 °C, respectively. The kinetic parameters for the oxidation of L-DOPA and catechol by the PO were 15.01 and 9.17 mM, respectively. The PO activity was strongly inhibited by Zn²⁺ and Cu²⁺, different to Mg²⁺ slightly. Both ascorbic acid and cysteine exhibited competitive inhibition and the inhibitory constants (K_i) were determined to be 2.22 mM and 0.40 mM, respectively.