酶解法提取鸡血藤原儿茶酸的工艺研究

目的优化鸡血藤中原儿茶酸的提取工艺。方法在鸡血藤甲醇回流前,用果胶酶、纤维素酶分别处理,与未加酶组比较,得出最优酶。通过单因素实验,探讨最优酶的用量、时间、温度及酸碱度(pH)对原儿茶酸提取率的影响,并通过正交实验对其进行优化。结果果胶酶比纤维素酶的原儿茶酸提取率高,最优酶提取最佳条件为:加入pH 4.5果胶酶0.5%、50℃酶解1.5 h,70℃浸提2次,原儿茶酸提取率为2.88%。结论最佳条件下酶法能提高鸡血藤中原儿茶酸提取率。     

Decreased Phorbol Ester-Induced Inhibition of Inositol Trisphosphate Formation Mediated by Alpha1-Adrenoceptors in Myocytes of Spontaneously Hypertensive Rats

Alpha₁-adrenoceptors, norepinephrine(NE)-stimulated formation of inositol trisphosphate (IP3) and inhibitory effect on this formation by 12-o-tetradecanoyl phorbol 13-acetate (TPA) were studied in isolated myocytes of 8-week-old spontaneously hypertensive rat (SHR) and Wistar-Kyoto rat (WKY). The number of alpha₁-adrenoceptors in myocytes of SHR was significantly increased than that of WKY. No significant difference in maximum response or EC50 values of NE-stimulated IP3 formation was observed between the two strains. Both norepinephrine-stimulated and GTPyS-stimulated IP3 formation was inhibited by TPA. The inhibitory effect was less in SHR than in WKY. PA did not change the number and affinity of alphal-adrenoceptors. These results suggest that myocytes of SHR may have abnormality in G protein and/or phospholipase C and that activation of protein kinase C might inhibit IP3 formation less in SHR than in WKY, a step distal to alphal -adrenoceptors, probably at a step distal to alphal -adrenoceptors.     

Denervation supersensitivity of 5-HT-1c receptors in rat choroid plexus

Serotonin (5-HT)-stimulated phosphoinositide hydrolysis in the choroid plexus is mediated by the 5-HT-1c receptor. The current study demonstrates that treatment of rats with the serotonergic neurotoxin, 5,7-dihydroxytryptamine, caused a marked depletion of 5-HT and a supersensitive 5-HT-1c mediated phosphoinositide hydrolysis response. These data suggest that the 5-HT-1c site in choroid plexus receives tonic serotonergic input.     

Demethylation Kinetics of Aspartame and L-Phenylalanine Methyl Ester in Aqueous Solution

The kinetics of demethylation of aspartame and L-phenylalanine methyl ester were studied in aqueous solution at 25°C over the pH range 0.27–11.5. The pseudo-first-order rate constant for aspartame was resolved into individual contributions from methyl ester hydrolysis and diketopiperazine formation. pH – rate profiles were quantitatively described by chemically reasonable kinetic schemes. Aspartame is maximally stable at pH 4 (t ₉₀ = 53 days at 25°C); phe-nylalanine methyl ester, at pH 3. The potentiometrically measured pK _a values were pK _a1 3.19 and pK _a2 7.87 fr aspartame and pKa 7.11 for phenylalanine methyl ester.     

Tyrosine kinase inhibitors suppress prostaglandin F2α-induced phosphoinositide hydrolysis, Ca elevation and contraction in iris sphincter smooth muscle

We investigated the effects of the protein tyrosine kinase inhibitors, genistein, tyrphostin 47, and herbimycin on prostaglandin F_2α- and carbachol-induced inositol-1,4,5-trisphosphate (IP₃) production, [Ca²⁺]_i mobilization and contraction in cat iris sphincter smooth muscle. Prostaglandin F_2α and carbachol induced contraction in a concentration-dependent manner with EC₅₀ values of 0.92×10⁻⁹ and 1.75×10⁻⁸ M, respectively. The protein tyrosine kinase inhibitors blocked the stimulatory effects of prostaglandin F_2α, but not those evoked by carbachol, on IP₃ accumulation, [Ca²⁺]_i mobilization and contraction, suggesting involvement of protein tyrosine kinase activity in the physiological actions of the prostaglandin. Daidzein and tyrphostin A, inactive negative control compounds for genistein and tyrphostin 47, respectively, were without effect. Latanoprost, a prostaglandin F_2α analog used as an antiglaucoma drug, induced contraction and this effect was blocked by genistein. Genistein (10 μM) markedly reduced (by 67%) prostaglandin F_2α-stimulated increase in [Ca²⁺]_i but had little effect on that of carbachol in cat iris sphincter smooth muscle cells. Vanadate, a potent inhibitor of protein tyrosine phosphatase, induced a slow gradual muscle contraction in a concentration-dependent manner with an EC₅₀ of 82 μM and increased IP₃ generation in a concentration-dependent manner with an EC₅₀ of 90 μM. The effects of vanadate were abolished by genistein (10 μM). Wortmannin, a myosin light chain kinase inhibitor, reduced prostaglandin F_2α- and carbachol-induced contraction, suggesting that the involvement of protein tyrosine kinase activity may lie upstream of the increases in [Ca²⁺]_i evoked by prostaglandin F_2α. Further studies aimed at elucidating the role of protein tyrosine kinase activity in the coupling mechanism between prostaglandin F_2α receptor activation and increases in intracellular Ca²⁺ mobilization and identifying the tyrosine-phosphorylated substrates will provide important information about the role of protein tyrosine kinase in the mechanism of smooth muscle contraction, as well as about the mechanism of the intraocular pressure lowering effect of the prostaglandin in glaucoma patients.     

Naproxen 1-Alkylazacycloalkan-2-one esters as dermal prodrugs: in vitro evaluation

1-Alkylazacycloalkan-2-one esters of naproxen were synthesized and assayed to determine their stability in phosphate buffer and isopropyl myristate, susceptibility to undergoing in vitro enzymatic hydrolysis and flux through excised human skin. 1-Methylazacycloalkan-2-one esters of naproxen (I–IV) proved poorly stable both in aqueous media and isopropylmyristate while 1-ethylazacycloalkan-2-one esters (V–VIII) were much more stable. Esters V–VIII were readily hydrolyzed in vitro by porcine esterase and esters V–VI penetrated excised human skin better than the parent drug from aqueous suspensions. On the basis of the results obtained, 1-ethylpyrrolidone and 1-ethylvalerolactam appear to be suitable promoieties for obtaining naproxen dermal prodrugs.     

Potent inhibitory action of chlorethylclonidine on the positive inotropic effect and phosphoinositide hydrolysis mediated via myocardial alpha1-adrenoceptors in the rabbit ventricular myocardium

Summary The influence of the alpha_lb-adrenoceptor-selective antagonist chlorethylclonidine on the alpha₁-adrenergic positive inotropic effect and the phosphoinositide hydrolysis induced by phenylephrine was investigated in the rabbit ventricular myocardium. Pretreatment of membrane fractions derived from the rabbit ventricular muscle with 10^–5 mol/l chlorethylclonidine decreased the specific binding of [³H]prazosin (at a saturating concentration of 10^–9 mol/l) from the control value of 11.27±0.48 to 4.18±1.87 fmol/mg protein. The inhibition by adrenaline of the binding of [³H]prazosin (slope factor and affinity) was not affected by chlorethylclonidine. The positive inotropic effect of phenylephrine (in the presence of 3 × 10^–7 mol/l bupranolol) was inhibited by chlorethylclonidine in a concentration-dependent manner (10^–7–10^–5 mol/l) and abolished by 10^–5 mol/l chlorethylclonidine. The concentration of chlorethylclonidine to inhibit the phenylephrine-induced maximum response to 50% was 2.4 × 10^–6 mol/l. The accumulation of [³H]inositol monophosphate and [³H]inositol trisphosphate induced by 10^–5 mol/l phenylephrine was inhibited by chlorethylclonidine in the same concentration range. These findings indicate that the myocardial alpha₁-adrenoceptors mediating a positive inotropic effect in the rabbit ventricular myocardium may belong to the chlorethylclonidine-sensitive alpha_1b-subtype, and that the subcellular mechanism of action involve phosphoinositide hydrolysis. Send offprint requests to M. Endoh at the above address     

ELIMINATION OF DIFLUNISAL AS ITS ACYL GLUCURONIDE, PHENOLIC GLUCURONIDE AND SULFATE CONJUGATES IN BILE-EXTERIORIZED AND INTACT RATS

1. The disposition of diflunisal (DF) was investigated in both bile-exteriorized and intact rats given 10 and 100 mg/kg doses intravenously (i.v.). 2. In addition to the phenolic glucuronide (DPG) and acyl glucuronide (DAG) conjugates, the sulfate conjugate (DS) was found to be a major metabolite. The glucuronides were excreted preferentially in bile, whereas DS was excreted almost exclusively in urine. 3. In bile-exteriorized animals, recoveries of DPG, DAG and DS in bile were 12.2%, 23.8%, 0.4%, respectively, and in urine, 10.3%, 5.6% and 15.2%, respectively, at the 10 mg/kg dose; and in bile, 11.3%, 41.6% and 1.0% respectively, and urine 2.9%, 1.1% and 17.0%, respectively, at the 100 mg/kg dose. 4. Total plasma clearance of DF and formation clearance of DF to DPG were reduced at the higher dose, suggesting saturation of this glucuronidation pathway. Formation clearances of DF to DAG and DS were little affected by the dose change. 5. Considerable enterohepatic recirculation of DF was apparent from the prolongation of DF and its conjugates in plasma of rats with an intact bile flow into the gut. The net metabolic effect of such cycling was enhancement of overall DS formation, from 15.6% and 18.0% of the 10 and 100 mg/kg doses, respectively, in bile-exteriorized rats to 28.5% and 42.1% of the doses respectively, in the intact animals.     

Rapid hydrolysis of proteins and peptides by means of microwave technology and its application to amino acid analysis

A rapid heating method of hydrolysis by the use of microwave oven has been applied to amino acid analysis of proteins and peptides. This convenient method has been compared with the conventional 6 n HCl hydrolysis at 110° for 24 h. The advantages of this new method are its expedition and the accurate and comparable results as compared to the tedious conventional technique. The method provides a rapid processing of multiple samples within minutes instead of days and inexpensive access to the important data of amino acid compositions of proteins by the commonly used microwave oven. The necessary change in the design of hydrolysis vials and the safety precautions accompanying this novel use of microwave acid-digestion method are also described.     

综合利用河虾加工下脚料的工艺研究

本文测定了河虾加工下脚料的成分,研究了蛋白酶对河虾加工下脚料作用的最适条件,分析了采用酶法回收的蛋白质提取物的组成及性质,提出了采用酶法和化学法相结合的综合利用河虾加工下脚料的工艺路线。