变换波长HPLC法同时测定藿香鼻炎合剂中五种成分的含量

目的建立HPLC波长切换联合梯度洗脱法同时测定藿香鼻炎合剂中的广藿香酮、黄芩苷、汉黄芩苷、黄芩素和汉黄芩素含量的方法。方法采用Kromasil C_(18)(4.6 mm×250 mm,5μm)色谱柱;流动相A:乙腈,流动相B:0.4%磷酸溶液,进行梯度洗脱;流速:1.0 mL/min;柱温:30℃;检测波长分别规定为310 nm(广藿香酮)、280 nm(黄芩苷、汉黄芩苷、黄芩素和汉黄芩素)。结果广藿香酮、黄芩苷、汉黄芩苷、黄芩素和汉黄芩素的线性范围分别为4.300~86.00μg/mL(r=0.999 6)、15.87~317.4μg/mL(r=0.999 8)、6.920~138.4μg/mL(r=0.9999)、6.340~126.8μg/mL(r=0.999 4)、5.250~105.0μg/mL(r=0.999 8),平均加样回收率和RSD均符合中国药典规定。结论本文建立的HPLC波长切换联合梯度洗脱法同时测定广藿香酮、黄芩苷、汉黄芩苷、黄芩素和汉黄芩素5个成分,方法专属性强,重复性好,可作为藿香鼻炎合剂全面可靠的质量控制方法。     

黄芩素诱导乳腺癌细胞自噬

目的:考察黄芩素诱导乳腺癌细胞的自噬作用,并初步探讨其机制。方法:采用MTT实验考察黄芩素对乳腺癌MCF-7细胞和4T1细胞活力的影响,确定给药剂量。Western blot检测黄芩素(25、50和100μmol/L)及联合自噬抑制剂3-MA作用下,MCF-7细胞和4T1细胞中自噬特征蛋白LC3-Ⅱ和LC3-Ⅰ的表达水平,流式细胞术Annexin V/PI双染法观察3-MA对黄芩素诱导MCF-7细胞和4T1细胞凋亡的影响,确认黄芩素诱导自噬的作用。通过Western blot考察自噬信号通路相关蛋白p-mTOR、mTOR、p-AKT和AKT的蛋白水平,结合AKT-mTOR激活剂EGF明确AKT-mTOR通路在黄芩素诱导乳腺癌自噬中的作用。结果:50μmol/L及其以上剂量的黄芩素可显著抑制乳腺癌MCF-7细胞和4T1细胞的活力,其作用具有显著的时效和量效性。Western blot结果表明,50和100μmol/L黄芩素作用下MCF-7细胞和4T1细胞的LC3-Ⅱ/LC3-Ⅰ比例显著增强,3-MA加入后又明显降低。流式细胞术结果显示,相比黄芩素单用组,联合自噬抑制剂可促进MCF-7细胞的坏死和凋亡。通路蛋白研究表明mTOR和AKT总量不变,其活化蛋白水平在黄芩素作用下显著降低,而加入EGF后又再次增加。结论:黄芩素可通过抑制AKT-mTOR通路诱导乳腺癌MCF-7细胞和4T1细胞自噬。     

Effects of Baicalin on Oral Pharmacokinetics of Caffeine in Rats

Scutellaria baicalensis is one of the most widely used herbal medicines in East Asia. Because baicalein and baicalin are major components of this herb, it is important to understand the effects of these compounds on drug metabolizing enzymes, such as cytochrome P450 (CYP), for evaluating herb-drug interaction. The effects of baicalin and baicalein on activities of ethoxyresorufin O-deethylase (EROD), methoxyresorufin O-demethylase (MROD), benzyloxyresorufin O-debenzylase (BROD), p-nitrophenol hydroxylase and erythromycin N-demethylase were assessed in rat liver microsomes in the present study. In addition, the pharmacokinetics of caffeine and its three metabolites (i.e., paraxanthine, theobromine and theophylline) in baicalin-treated rats were compared with untreated control. As results, EROD, MROD and BROD activities were inhibited by both baicalin and baicalein. However, there were no significant differences in the pharmacokinetic parameters of oral caffeine and its three metabolites between control and baicalin-treated rats. When the plasma concentration of baicalin was determined, the maximum concentration of baicalin was below the estimated IC₅₀ values observed in vitro. In conclusion, baicalin had no effects on the pharmacokinetics of caffeine and its metabolites in vivo, following single oral administration in rats.     

黄芩素药代动力学研究进展

黄芩为中国药典收载的常用中药材,具有悠久的用药历史,含有多种黄酮类化合物,其中黄芩素为常用中药黄芩中的主要活性成分之一。笔者通过对黄芩素在体内的药动学研究进行总结,发现:黄芩素胃肠道吸收较好,主要分布在肝、肾、肺等组织器官中;黄芩素在大鼠体内代谢物主要是葡萄糖醛酸结合物,后者又可经胆汁和肠黏膜转运至肠腔,形成再吸收;黄芩素口服后血浆原型药物浓度极低。目前针对黄芩素的药动学行为研究主要是通过其代谢物黄芩苷的测定来间接实现,由此使得黄芩素替代黄芩苷进行口服制剂研究也成为可能。     

Fine tuning of a reported synthetic route for biologically active flavonoid,baicalein

A modified procedure of a previous synthetic route for baicalein was developed in order to obtain more than ten grams of baicalein for in vivo test. There were several difficulties in applying the published experimental procedures for a large scale of synthesis. The modified synthetic work was successfully accomplished by reducing amount of strong Lewis acid in Fries rearrangement and using tetrabutylammonium iodide as an additive to speed up the demethylation reaction in refluxing HBr into completion.     

Pharmacokinetics of baicalein,baicalin and wogonin after oral administration of a standardized extract of<Emphasis Type="Italic">Scutellaria baicalensis</Emphasis>, PF-2405 in rats

The pharmacokinetics of active components such as baicalein, wogonin and oroxylin A were evaluated after oral administration of a purified extract of Scutellaria baicalensis GEORGI (PF-2405) containing the high contents of baicalein, wogonin and oroxylin A to rats. Following oral administration of PF-2405 at 10, 20 and 40 mg/kg dose (equivalent to 4.5, 9.0 and 18 mg/kg baicalein), a major constituent baicalein and its active metabolite baicalin showed dose-linear pharmacokinetics as evidenced by unaltered dose-normalized AUC, dose-normalized Cmax, Ae(0-30h) and GI(30h) values. Following oral administration of PF-2405 at three doses (equivalent to 0.4, 0.8 and 1.6 mg/kg wogonin), dose-normalized Cmax and dose-normalized AUC were comparable between the 20 and 40 mg/kg PF2405 doses, but plasma concentrations of wogonin at 10 mg/kg of PF-2405 were not measurable as they were below limit of quantitation (LOQ; 18 pmol/mL). Following oral administration of PF-2405 at the three doses (equivalent to 1.5, 3.0 and 6.0 mg/kg oroxylin A), the concentrations of oroxylin A in plasma, urine and gastrointestine samples were below the assay LOQ (18 pmol/mL). Significant differences in AUCs, Ae(0-30h) and GI(30h) values for baicalein and baicalin were observed after oral administration of pure baicalein (18 mg/kg) and PF-2405 (40 mg/kg). The increases in AUCs of baicalein and baicalin after oral administration of PF-2405 may have been due to the significant decrease in GO(30h) values for baicalein.     

Effect of baicalein from Scutellaria baicalensis on prevention of noise-induced hearing loss

Noise-induced hearing loss (NIHL) has been thought to primarily involve damage to the sensory hair cells of the cochlea via mechanical and metabolic mechanisms. This study examined the effects of baicalin, baicalein, and Scutellaria baicalensis (SB) extract against NIHL in a mouse model. Mice received oral treatment with SB, baicalin, baicalein beginning 30 min prior to noise exposure and continuing once daily throughout the study. Hearing threshold shift was assessed by auditory brain stem responses for 35 days following noise exposure. Central auditory function was evaluated by auditory middle latency responses. Cochlear function was determined based on transient evoked otoacoustic emissions. SB significantly reduced threshold shift, central auditory function damage, and cochlear function deficits, suggesting that SB may protect auditory function in NIHL and that the active constituent may be a flavonoid, baicalein.     

In vitro and in situ evaluation of herb-drug interactions during intestinal metabolism and absorption of baicalein

Ethnopharmacological relevance

Baicalein (B), a bioactive flavone isolated from the root of a traditional Chinese medicinal herb Scutellaria baicalensis Georgi, was found to undergo extensive intestinal Phase II metabolism during its absorption process. Compounds sharing the same metabolic pathways with B or being inhibitors of enzymes UGT and SULT are expected to interfere with the metabolism of B leading to alteration of the absorption of B. The present study aims to identify potential intestinal absorption and metabolism interactions between B and four selected compounds, namely acetaminophen (APAP), (−)-epicatechin (EC), piperine (PIP) and curcumin (CUR) using in vitro and in situ models.

Materials and methods

Three in vitro and one in situ methods were employed to investigate the effect of selected compounds on the metabolism and absorption on B. Incubation studies using rat intestinal s9 and Caco-2 cell lysate were used to study the effect of selected compounds on glucuronidation and sulfation of B. Sigmoidal dose–response curves were plotted and IC₅₀ values were estimated. Apical to basolateral absorption study using Caco-2 cell monolayer model was also employed to study the effect of selected compounds on absorption of B. The most potent inhibitor identified was selected to further investigate its potential herb–drug interaction with B using in situ rat intestinal perfusion model. LC/MS/MS was used for the analysis of B and its metabolites in collected samples.

Results

It was found that all the four selected compounds could produce a dose-dependent inhibition on the glucuronidation and sulfation of B. Moreover, the presence of CUR and high-dose EC demonstrated a subsequent increase in the absorption of B. In general, the order of potency on glucuronidation inhibition is: CUR > PIP > EC > APAP; while the potency order on sulfation inhibition is: CUR > EC > PIP > APAP. CUR was selected to further study its in vivo effect on B using in situ rat intestinal perfusion model. It was found that CUR could significantly increase the absorption of B via the inhibition on formation of its metabolites.

Conclusions

Our findings indicated that the intestinal metabolism of B could be inhibited by all the selected compounds with CUR being the most potent inhibitor, which could result in subsequent increase of absorption of B. The current study had significant implications for further investigation on the in vivo evaluations of the herb–drug and herb–herb interactions between B and selected compounds, especially CUR.