二苯胺棉酚中棉酚的含量测定

用紫外分光光度法测定二苯胺棉酚中棉酚的含量。方法回收率平均达 93.6 %以上 ,变异系数 ( CV )为1.2 %。该方法准确 ,重现性好 ,可作为二苯胺棉酚质量监控方法。     

Optical stability of gossypol

The optical stability of gossypol [1,1',6,6',7,7'-hexahydroxy-3,3'-dimetyl-5,5'-bis(1-methylethyl)-2,2'-binaphthalene-8,8'-dicarboxaldehyde], a natural product exhibiting profoundly enantiospecific antitumor and male antifertility action, was investigated by means of computational methods and thermal racemization experiments. The calculations on gossypol and several derivatives and model compounds were carried out using the MM2 force field; energies and geometries of minimum energy conformations, as well as structures along various inversion pathways, were calculated. According to the calculations, gossypol (the dialdehyde form) and its simple analogues are not thermally racemizable (energy barriers for rotational inversion above 50 kcal/mol). By contrast, the calculations suggest that the acetal tautomer of gossypol and its dehydration product (anhydrogossypol) are thermally racemizable, although the energy barriers are still relatively high (35–40 kcal/mol). Optically pure (+)-anhydrogossypol was prepared and characterized; its racemization became rapid only at high temperatures (180–200°C). When dehydration of gossypol was hindered (in aqueous solution), no racemization of gossypol was observed after prolonged heating at 90°C. © 1992 Wiley-Liss, Inc.     

The embryotoxicity of gossypol

In utero development was analyzed in pregnancies that resulted from matings between gossypol-treated male rats and untreated female rats and in pregnancies in which gossypol was administered to the pregnant rat only. Gossypol treatment of males had no effect on the outcome of pregnancy. There was no significant effect on resorption, fetal growth, or malformation rate. Similarly, gossypol administered to pregnant dams at stages during organogenesis had no observable effect on pregnancy. Under the conditions of this experiment, gossypol administered to either the breeding male rat or the pregnant female rat had no demonstrable adverse effect on development in utero.     

Acute hypokalemic effect of gossypol

Clinical trials had demonstrated that chronic ingestion of gossypol induced infertility in males. Hypokalemia of various severities were reported in volunteers taking gossypol. The purpose of this study is to investigate the effects of acute gossypol infusion into alkalotic rats. Plasma potassium concentration decreased from 4.08 to 2.87 mM after gossypol infusion with minimal change in urinary potassium excretion. The hypokalemic effect of gossypol was also observed in nephretomized rats. Some of the factors that are known to affect potassium distribution between the extracellular and intracellular fluid compartment have been investigated in these rats. Plasma glucose concentration was not significantly altered. Gossypol induced hypokalemia was not blocked in rats treated with propranolol. It is therefore believed that the acute hypokalemic effect of gossypol is a direct shifting of potassium into cells.     

Effect of elicitors on the production of gossypol and methylated gossypol in cotton hairy roots

The effect of two chemical elicitors, salicylic acid and methyl jasmonate, on the production of gossypol, 6-methoxygossypol, and 6,6′-dimethoxygossypol in Gossypium barbadense hairy roots was examined. Methyl jasmonate, but not salicylic acid, was found to increase the production of gossypol and its methylated forms, but with a concomitant reduction in culture growth. The optimal methyl jasmonate dose was between 100 and 300 μM for hairy roots harvested 7 days after elicitation. After 20 d of induction with 100 μM methyl jasmonate, an eightfold increase in the level of gossypol was observed in elicited cultures compared with control cultures, double the highest gossypol levels previously reported for any cotton tissue. A two to threefold increase in the level of 6-methoxygossypol and a slight increase in the levels of 6,6′-dimethoxygossypol were also observed. Although methyl jasmonate stimulated the production of both optical forms of gossypol, the distribution of the enantiomers was different between elicited and control cultures.     

Preparation of enantiomeric gossypol by crystallization

Large enantiomorphic crystals of gossypol-acetone (1:3) were grown from acetone solutions of rac-gossypol-acetic acid (1:1) at 4 degrees C. By controlling the initial gossypol concentration, crystallization time, and solution volume, single crystals were grown that weighed >50 mg, equivalent to >37 mg of enantiomeric gossypol. Even larger crystals were possible, but it was difficult to produce these reliably without contamination of the antipode. Essentially all of the acetone within the crystal form was removed by storing the crystals under vacuum for 3-4 days. By employing these techniques, gram quantities of enantiomeric gossypol were prepared in high chemical and optical purity. Based on measured and reported optical rotations, the optical purity of samples prepared by crystallization was greater than the optical purity of samples prepared by chromatographic separation of gossypol-amine diastereomers. The principal limitation of crystallization as a preparative method is the need to determine the chirality and purity of each product crystal. Nevertheless, the method competes favorably with preparative-scale chromatographic procedures.     

Renal transport of gossypol in the rabbit

The present work was carried out to investigate the transport characteristics of gossypol, a toxic weak organic acid (pK = 7.2) contained in cottonseed, into the rabbit renal cortical slice. The uptake of gossypol increased linearly during a 2-hr incubation after which it leveled off with the average slice-to-medium concentration ratio (S/M) slightly above 20. In the presence of metabolic inhibitors, the S/M gossypol leveled off at about 9, suggesting an extensive binding of gossypol to tissue proteins. The uptake of gossypol was significantly inhibited by p-aminohippurate (PAH), probenecid, ouabain, and DIDS, all of which are known inhibitors of renal organic anion transport. However, the gossypol uptake was not affected by tetraethylammonium (TEA), a prototypical organic cation. Kinetic studies indicated that the apparent Km for gossypol transport is 0.28 mM, and also that probenecid inhibits gossypol transport in a competitive manner. It is concluded that gossypol is transported by the renal tubule through the classic organic anion system.     

Membrane actions of male contraceptive gossypol tautomers

The role of different gossypol tautomers in the interaction of this molecule with membranes has been investigated using the isolated hemiacetal moiety of gossypol and the pH dependency of the keto-enol tautomeric equilibrium. Our results indicate that: the actions of the hemiacetal tautomer cannot explain the effects of gossypol on mitochondrial oxidative phosphorylation, lipid membrane interfacial potentials, and proton conductance of lipid bilayers; the enolate forms of gossypol are the species that bind to the membrane interface and decrease the electrostatic interfacial potential; and the uncharged (keto and/or enol) species in equilibrium with the enolate forms of gossypol give the molecule the ability to carry protons across biological membranes.     

Inhibition of DNA polymerase alpha by gossypol

Our earlier studies have shown that gossypol is a specific inhibitor of DNA synthesis in cultured cells at low doses. In an attempt to determine the mechanism for the inhibition of DNA synthesis by gossypol we observed that gossypol does not interact with DNA per se but may affect some of the enzymes involved in DNA replication. These studies indicated that gossypol inhibits both in vivo and in vitro the activity of DNA polymerase alpha (EC 2.7.7.7), a major enzyme involved in DNA replication, in a time- and dose-dependent manner. Kinetic analysis revealed that gossypol acts as a noncompetitive inhibitor of DNA polymerase alpha with respect to all four deoxynucleotide triphosphates and to the activated DNA template. Inhibition of DNA polymerase alpha does not appear to be due to either metal chelation or reduction of sulfhydryl groups on the enzyme. Gossypol also inhibited HeLa DNA polymerase beta in a dose-dependent manner, but had no effect on DNA polymerase gamma. These results suggest that inhibition of DNA polymerase alpha may account in part for the inhibition of DNA synthesis and the S-phase block caused by gossypol. The data also raise the possibility that gossypol may interfere with DNA repair processes as well.     

Inactivation of intestinal brush-border enzymes by gossypol

Gossypol, a pigment found in cottonseed that has recently been shown to have antifertility properties, inhibited the activity of 3 intestinal brush border enzymes in a concentration-dependent manner. Suspensions of rat intestinal mucosa were incubated with various concentrations of gossypol for 45 minutes and then washed. At a concentration of 6 mg per gm mucosa, gossypol inhibited the activities of alkaline phosphatase, maltase, and sucrase by 57, 73, and 77%, respectively. Gossypol is a bifunctional agent, capable of cross-linking amino acid side chains, and its action on brush-border enzymes may be due to this mechanism. Recent investigations have demonstrated that rats fed a diet of 10-15 mg of gossypol/day/kg of body weight exhibit reduced fertility. This study suggests that a partial inhibition of brush-border enzymes may occur at doses used to cause infertility. Such a side effect should be considered in studies and treatments utilizing a gossypol diet.     

Apoptotic effect of gossypol on human lymphocytes

The overall objective of this study was to determine the effect of gossypol on human lymphocytes. Blood samples were taken from healthy donors and lymphocytes were cultured with various concentrations of gossypol (25-150 microM). The percentage of apoptotic cells was determined by assessing DNA fragmentation by agarose gel electrophoresis; morphological features of apoptosis were assessed by light microscopy. The concentrations of gossypol required to induce apoptosis in human lymphocytes without causing necrosis through cytotoxic effects were between 25-50 microM.     

Glucoamylase immobilization on silochrome using gossypol

The paper is concerned with conditions of glucoamylase binding with silanized silochrome using gossypol, dialdehyde isolated from cotton-plant. Kinetic properties of the immobilized enzyme are studied. The enzyme pH optimum does not change with immobilization and the temperature optimum is shifted from 50 degrees to 60 degrees C; a certain increase of the seeming Km is also observed. A high yield of the enzyme activity in immobilization evidences for the possibility of using gossypol as a binding agent in glucoamylase immobilization.     

Synthesis and antiviral activities of novel gossypol derivatives

In this study, a series of novel gossypol derivatives were synthesized and screened in vitro for their anti-HIV-1 and anti-H(5)N(1) activities, respectively. Replacing the aldehyde groups of gossypol with some amino acids not only reduced the cytotoxicity but also enhanced the activities against HIV-1 and H(5)N(1). Compounds 13-17 showed more potent activities against HIV-1 and H(5)N(1) than the other gossypol derivatives. Meanwhile, these compounds also exhibited more potent activities against H(5)N(1) than 1-adamantylamine. The absence of the COONa group in gossypol derivatives resulted in a loss of anti-HIV-1 activity, suggesting that this group might play an important role in mediating the antiviral activity. Time-of-addition assays indicated that compounds 13-17 had the similar mechanism of anti-HIV-1 action with T20. Molecular modeling analysis demonstrated that compounds 13-17 could fit inside the gp41 hydrophobic pocket through hydrogen bonding network, hydrophobic contacts and strong electrostatic interactions.