大叶香茶菜抗肿瘤成分大叶庚的研究(Ⅱ)

鉴定了从大叶香茶菜Rabdosia macrophylla中分得的另外四种成分。三种为已知成分乌苏酸,香茶菜甲素(AmethystoidinA)及Enmenol。另一大叶庚为新的B-seco-ent-kaurene二萜,命名为RabdophyllinG,能延长荷艾氏腹永癌小鼠的生命并能抑制体外肝癌细胞的生长。     

毛叶香茶菜抗癌成分的研究——Ⅰ.毛叶香茶菜素A和B的结构

自毛叶香茶菜Rabdosia japonica(Burm.f)Hara的干叶中分离出四个二萜化合物,其中两个是新的二萜,命名为毛叶香茶菜素A和B。通过光谱分析和化学反应转变成已知化合物epinodosin 6和isodonal 8确定了毛叶香茶菜素A和B的结构分别为3和7。初步的抗癌试验表明,3和7都具有明显细胞毒作用。其它两个二萜成分证明为enmenol 4和epinodosinol 5。     

香茶菜甲素、大叶香茶菜丙及其衍生物的抗菌和细胞毒作用

通过对香茶菜属植物的两种二萜成分——香茶菜甲素、大叶香茶菜丙进行结构改造,观察它们的生物活性。结果表明,香茶菜甲素酰化物(Ⅱ)能显著提高抗菌作用,比原化合物提高2～3倍;大叶香茶菜丙水解物(Ⅴ)能显著提高细胞毒活性,比原化合物提高2.3倍。     

大萼香茶菜新二萜成分:大萼香茶菜甲素和乙素的结构

从大萼香茶菜Rabdosia macrocalyx(Dunn)Hara的干叶中得到三种成分,除乌苏酸外,其它两种为新二萜,分别命名为大萼香茶菜甲素(Macrocalin A)及乙素(Maerocalin B)。甲素及乙素对体外培养的Hela细胞有抑制作用,4μg/ml抑制率80%。用光谱法配合衍生物制备测定了它们的结构。     

长叶香茶菜化学成分的研究

从长叶香茶菜Rabdoisa stracheyi(Benth ex Hook.f)Hara的地上部分分离得到三种结晶性成分。其中两种为已知化合物6,7-dehydroroyleanone和β-谷甾醇,另一种为新的二萜醌类化合物。通过理化常数和光谱的分析以及衍生物的制备,测定其结构为16-acetoxy-7α-methoxyroyleanone(Ⅰ)。命名为长叶香茶菜甲素。     

瘿花香茶菜二萜成分的研究

从瘿花香茶菜Rabdosia rosthornii(Diels)Hara的叶和茎中分离出三种二萜类化合物。其中两种为已知化合物ponicidin和oridonin。另一种为新的二萜化合物。通过理化常数和光谱的分析以及衍生物的制备,测定了其结构,并命名为瘿花香茶菜甲素。     

显脉香茶菜素和毛叶香茶菜二萜的抗癌活性半经验MNDO研究

目的：解释显脉香茶菜素和毛叶香茶菜二萜的抗癌活性差别。方法：用MNDO的计算方法对显脉香茶菜素和毛叶香茶二萜的结构进行优化处理，计算结构参数和电子参数。结果：计算表明，显脉香茶菜素存在一个抗癌活性区，此区的活性明显高于毛叶香茶二萜的相应结构区。结论：量化计算较好地解释了显脉香茶菜素具有抗癌活性，而毛叶香茶二萜几乎没有抗癌活性。     

川藏香茶菜丁素和己素的结构确定

从川藏香茶菜中分离得到2个新化合物,经光谱解析和化学转换反应,确定川藏香茶菜丁素为3α,11β,13α-trihydroxy-entkaur-16-en-15-one(1),川藏香茶菜己素为11β,13α,15α-trihydroxy-entkaur-16-en-3α-β-D-glucoside(2)。     

香茶菜抗癌成分的研究

从香茶菜属植物香茶菜Rabdosia amethystoides(Benth) Hara中分得七种成分,其中之一香茶菜甲素为一新的四环二萜,有抗实验肿瘤及抑制金黄色葡萄球菌作用。用光谱法配合衍生物制备,确定甲素为7α,14β=羟基-20α羟甲基-16-贝壳杉烯-11,15=酮乙素为乌苏酸,丙素为β-谷甾醇,己素为硬脂酸,其余成分尚在研究中。     

假细锥香茶菜新二萜成分——假细锥甲素的结构

从假细锥香茶菜(Rabdosia coetsoides C.Y.Wu)叶分离得到新二萜成分,根据紫外光谱、红外光谱、质谱、核磁共振氢谱及碳谱等分析,推定了化学结构,并经X-射线衍射确证,命名为假细锥甲素。     

Bioactivation of 3-methylindole by isolated rabbit lung cells

3-Methylindole (3MI) is a pneumotoxin that causes selective lung lesions indicative of Clara cell and alveolar epithelial cell damage in ruminants and rodents. The present study examined the cytotoxicity of 3MI to isolated rabbit Clara cells, type II alveolar epithelial cells, and alveolar macrophages. 3MI produced a dose-dependent cytotoxicity to Clara cells detectable within 1 hr of incubation at 37 degrees C which reached a maximum at 3 hr. Concentrations of 0.25 and 0.5 mM 3MI were cytotoxic to Clara cells, while type II and alveolar macrophages required 1 mM 3MI before cytotoxicity was observed. The cytochrome P450 suicide substrate inhibitor, 1-aminobenzotriazole, inhibited 3MI-induced cytotoxicity in Clara cells, type II cells, and alveolar macrophages. These observations were consistent with a cytochrome P450-mediated bioactivation of 3MI to a toxic intermediate. Studies with a trideuteromethyl analog of 3MI demonstrated a much reduced cytotoxicity to Clara cells as well as to type II cells, and macrophages. The deuterium isotope effect suggested that C-H bond breakage at the 3-methyl group is a requisite oxidative transformation in the bioactivation of 3MI to a selective lung cell cytotoxin. The selectivity of cellular cytotoxicity is probably associated with higher rates of bioactivation by Clara cell cytochrome P450 monooxygenases compared to those of type II cells and macrophages. These studies demonstrate that 3MI is bioactivated in isolated pulmonary cells without the intervention of other organs and that bioactivation requires functional cytochrome P450 enzymes.     

Selective toxicity and type of cell death induced by various natural and synthetic compounds in oral squamous cell carcinoma

This article reviews the selective toxicity and type of cell death induced in oral squamous cell carcinoma (OSCC) by hundreds of natural and synthetic compounds. Flavonoids, coumarins, tannins, ketones and other synthetic compounds showed low to moderate tumor-specific cytotoxicity against human OSCC cell lines as compared with normal human oral cells (gingival fibroblast, pulp cell, periodontal ligament fibroblast), whereas anthracyclines, nocobactins and cyclic alpha, beta-unsaturated compounds showed much higher tumor-specific cytotoxicity. No strict relationship was found between the tumor-specific cytotoxicity and apoptosis induction. There was a considerable variation in drug-sensitivity among 5 OSCC cell lines. OSCC cell lines were generally resistant to apoptosis induction. The cytotoxic activity of antitumor agents is affected by various factors related to the compounds themselves, the cells and their environments. Systematization of the relationship between these factors and tumor-specificity may contribute in the quest for more active compounds.     

Targeted delivery and enhanced cytotoxicity of cetuximab-saporin by photochemical internalization in EGFR-positive cancer cells

Photochemical internalization (PCI) is a novel technology of macromolecular delivery. By PCI, endocytosed membrane-impermeable therapeutic drugs are photochemically released from entrapment in endo-lysosomal compartments to the cytosol of target cells. In the present report, we describe the in vitro proof-of-concept for PCI of cetuximab-saporin, an immunotoxin targeting EGFR-expressing cells. This immunotoxin consists of the chimeric murine-human IgG1 monoclonal antibody cetuximab (C225 or Erbitux) bound to the type I ribosome-inactivating protein toxin saporin by a biotin-streptavidin linkage. The photochemical treatment enhanced the cytotoxicity of the immunotoxin in a synergistic manner in three different EGFR-expressing carcinoma cell lines derived from different tumor tissues (colorectal, HCT-116; prostate, DU-145; and epidermis, A-431). Both cytotoxicity of cetuximab-saporin and epifluorescence of Alexa488-cetuximab were evaluated by competition with cetuximab demonstrating specific binding and uptake of cetuximab-saporin in EGFR positive cells. In the EGFR-negative uterine sarcoma cell line MES-SA, neither binding nor preferential accumulation of Alexa488-cetuximab was detected. In addition, PCI enhanced the cytotoxicity of cetuximab-saporin to the same extent as streptavidin-saporin in the MES-SA cells. In conclusion, PCI enhances selectivity of the cytotoxicity of the immunotoxin cetuximab-saporin in EGFR-expressing cells.     

Cytotoxicity of nickel oxide particles in rat alveolar macrophages cultured in vitro.

The cytotoxicity of two types of nickel oxide particles was investigated in rat alveolar macrophages cultured in vitro. The trypan blue dye exclusion test and the release of lactate dehydrogenase into culture medium were used as cytotoxic indices. Although both types of nickel oxide particles were produced by the same manufacturer and were commercially sold under the same name of "nickel oxide", one type of the nickel oxide particles which had black color was much more cytotoxic than the other type of green color. The black nickel oxide particles were more soluble in various kinds of solutions than the green nickel oxide particles. Therefore, it appears that the difference in the cytotoxicity of the black and green nickel oxide particles may be attributable to the difference in the solubility of the particles.     

Cytotoxicity of gelonin conjugated to targeting molecules: effects of weak amines, monensin, adenovirus, and adenoviral capsid proteins penton, hexon, and fiber

It has been reported previously that ammonium chloride, chloroquine, monensin, and adenovirus-2 potentiate the cytotoxicity of several protein toxins conjugated with various targeting molecules. We have tested whether these agents, and protein components of adenovirus-2, would enhance the cytotoxicity of conjugates of gelonin with J5, an antibody directed against common acute lymphoblastic leukemia-associated antigen, with 5E9, an antibody directed against human transferrin receptor, or with ricin B-chain. We found that none of these agents affected the cytotoxicity of gelonin conjugates to any significant extent. For example, monensin moderately (3-fold) enhanced the cytotoxicity of 5E9-gelonin for Namalwa cells but showed no effect when 5E9-gelonin was tested on HeLa cells. The potentiating effects of these agents for the cytotoxicity of free gelonin varied from marked to nonexistent, depending on the type of cells. In particular, adenovirus-2 potentiated the cytotoxicity of gelonin for HeLa cells but not for Namalwa cells. The three major adenoviral capsid proteins, penton, hexon, and fiber, were isolated. It was shown that penton potentiated the cytotoxicity of gelonin for HeLa cells and that hexon and fiber had no measurable effect on the cytotoxicity of gelonin. However, like the whole virus, penton was not able to affect the cytotoxicity of gelonin conjugates.     

6-N-Acyltriciribine analogues: structure-activity relationship between acyl carbon chain length and activity against HIV-1

Triciribine (TCN) and triciribine-5'-monophosphate (TCN-P) are active against HIV-1 at submicromolar concentrations. In an effort to improve and better understand this activity, we have conducted a structure-activity relationship study to explore the tolerance of TCN to structural modifications at the 6-position. A number of 6-N-acyltriciribine analogues were synthesized and evaluated for antiviral activity and cytotoxicity. The cytotoxicity of these compounds was minimal in three human cell lines (KB, CEM-SS cells, and human foreskin fibroblasts (HFF)). The compounds were marginally active or inactive against herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV). In contrast, most of the compounds exhibited moderate to high activity against human immunodeficiency virus type 1 (HIV-1), IC(50)'s = 0.03 to 1 microM. This structure-activity relationship study identified the N-heptanoyl group as having the optimal carbon chain length. This compound was as active against HIV-1 as TCN and TCN-P. Reverse phase HPLC of extracts from uninfected cells treated with 6-N-acyltriciribines detected sufficient TCN-P to account for anti-HIV activity thereby suggesting a prodrug effect. Studies in an adenosine kinase deficient cell line showed that the 6-N-acyl derivative was not phosphorylated directly but first was metabolized to triciribine which then was converted to TCN-P.     

蓖麻毒素的毒性作用机制及其在肿瘤治疗中的应用

蓖麻毒素对哺乳动物细胞具有很强的毒性,属于Ⅱ型核糖体失活蛋白。其A链是活性链,可使核糖体失活,从而使蛋白质合成受阻,细胞死亡。基于蓖麻毒素的细胞毒性,人们将蓖麻毒素及其A链应用于肿瘤治疗领域,目的在于特异性杀伤肿瘤细胞,并减小对正常细胞的毒性。本文就蓖麻毒素的分子结构、毒性机制以及近年来在肿瘤治疗领域的研究进展作一综述。     

Pokeweed Antiviral Protein: Its Cytotoxicity Mechanism and Applications in Plant Disease Resistance

Pokeweed antiviral protein (PAP) is a 29 kDa type I ribosome inactivating protein (RIP) found in pokeweed plants. Pokeweed produces different forms of PAP. This review focuses on the spring form of PAP isolated from Phytolacca americana leaves. PAP exerts its cytotoxicity by removing a specific adenine from the α-sarcin/ricin loop of the large ribosomal RNA. Besides depurination of the rRNA, PAP has additional activities that contribute to its cytotoxicity. The mechanism of PAP cytotoxicity is summarized based on evidence from the analysis of transgenic plants and the yeast model system. PAP was initially found to be anti-viral when it was co-inoculated with plant viruses onto plants. Transgenic plants expressing PAP and non-toxic PAP mutants have displayed broad-spectrum resistance to both viral and fungal infection. The mechanism of PAP-induced disease resistance in transgenic plants is summarized.     

Comparison of the cytotoxic and mutagenic potential of liquid smoke food flavourings, cigarette smoke condensate and wood smoke condensate.

Although products of pyrolysis are often cytotoxic and mutagenic, the relationship between the type of material pyrolysed and the toxicity of the resulting pyrolysis products is poorly understood. The objective of this study was to evaluate and compare the cytotoxicity and mutagenicity of several types of common pyrolysis products. The cytotoxicity and mutagenicity of these products were assessed by using neutral red uptake and Ames mutagenicity assays, respectively. The biological activities of four liquid smoke food flavourings (LSF) were compared with two other pyrolysis-derived materials; cigarette smoke condensate (CSC) and a wood smoke condensate (WSC). Results indicated all of the mixtures exhibited a concentration-dependent cytotoxic response. The CSC and WSC were less cytotoxic than three of the LSFs, but more cytotoxic than one of the brands. The CSC was mutagenic in two Salmonella strains; however, none of the LSFs or WSC was mutagenic using TA98, and only three of the LSFs were positive with TA100. The six pyrolysis-derived materials evaluated in this study showed differing patterns and magnitudes of cytotoxicity and mutagenicity. These results indicate that the cytotoxicity and mutagenicity of complex mixtures derived from pyrolysis products are affected by the type of material pyrolysed and/or the method used to prepare the mixture. The cytotoxic potential of some commercial smoke flavourings is greater than cigarette smoke condensate and several of the food flavourings are mutagenic in one Salmonella strain.