Bio-assay guided isolation and identification of α-glucosidase inhibitors from the leaves of Aquilaria sinensis

Eight α-glucosidase inhibitors including four new compounds were isolated from the 70% aqueous ethanolic extract of leaves of Aquilaria sinensis (Lour.) Gilg by activity-directed fractionation and purification processes. The ethanolic extract was first separated into petroleum ether, ethyl acetate, n-butanol and water soluble fractions and screened for inhibitory activity against α-glucosidase. Further activity-directed investigation lead to the isolation of four new compounds with moderate inhibitory activity, viz, aquilarisinin (1), aquilarisin (2), hypolaetin 5-O-β-D-glucuronopyranoside (3) and aquilarixanthone (4) from the n-butanol fraction, and four known compounds showing potent activity including mangiferin (5), iriflophenone 2-O-α-L-rhamnopyranoside (6), iriflophenone 3-C-β-D-glucoside (7) and iriflophenone 3,5-C-β-D-diglucopyranoside (8) from the most potent ethyl acetate fraction. The structures of these compounds were determined by extensive spectroscopic analyses, including IR, UV, ESIMS, HRESIMS, 1D and 2D NMR.     

Partial purification and characterization of protein tyrosine kinases from normal tissues

Three membranous protein tyrosine kinases (PTKs) have been partially purified from human placenta and pig brain. The two placental enzymes (PTK-1 and -2) are distinct with respect to solubility in detergents, molecular weight, and enzymatic properties. The brain protein tyrosine kinase resembles placental PTK-1 with respect to molecular weight and some kinetic properties. However, stimulation of brain PTK is greater with Mn2+ than with Mg2+ whereas placental PTK-1 gives higher rates with Mg2+ than with Mn2+. All three enzymes are inhibited about 50% by 0.1 M NaCl. A monoclonal antibody raised in vitro against the brain enzyme inhibits brain PTK as well as placental PTK-2, but has no effect against PTK-1 or pp60src. It thus appears that these three enzymes are distinct entities that differ from each other both kinetically and immunologically. With synthetic tyrosine-glutamic acid polymers as a substrate, protein tyrosine kinase activity can be detected in crude extracts of membranes.     

Antioxidant potential of n-butanol fraction from extract of Jasminum mesnyi Hance leaves

Methanolic extract of Jasminum mesnyi Hance leaves having antidiabetic activity was subjected to fractionation to obtain antioxidant and antihyperglycemic rich fraction. Different concentrations of ethyl acetate and n-butanol fractions were subjected to antioxidant assay by DPPH method, nitric oxide scavenging activity and reducing power assay. The fractions showed dose dependent free radical scavenging property in all the models. IC50 values for ethyl acetate and n-butanol fractions were 153.45 +/- 6.65 and 6.22 +/- 0.25 microg/ml, respectively, as compared to L-ascorbic acid and rutin (as standards; IC50 values 6.54 +/- 0.24 and 5.43 +/- 0.21 microg/ml, respectively) in DPPH model. In nitric oxide scavenging activity, IC50 values were 141.54 +/- 9.95 microg/ml, 35.12 +/- 1.58 microg/ml, 21.06 +/- 0.95 microg/ml and 29.93 +/- 0.32 microg/ml for ethyl acetate, n-butanol fractions, L-ascorbic acid and rutin, respectively. n-Butanol fraction showed a good reducing potential and better free radical scavenging activity as compared to ethyl acetate fraction. Potent antioxidant n-butanol fraction showed better oral glucose tolerance test (antihyperglycemic) at par with metformin (standard drug), n-Butanol fraction contained secoiridoid glycosides which might be responsible for both antioxidant and antihyperglycemic activity.     

Enzyme inhibition and radical scavenging activities of aerial parts of Paeonia emodi Wall (Paeoniaceae)

The ethanolic extract derived from aerial parts of an indigenous medicinal plant Paeonia emodi was screened for enzyme inhibition activities against Urease (jack bean and Bacillus pasteurii) and alpha-Chymotrypsin. The extract was also investigated for its radical scavenging activity using DPPH assay. The crude extract was found to possess significant enzyme inhibition activities against jack bean (74%) and Bacillus pasteurii (80%) urease and a moderate activity (54%) against alpha-Chymotrypsin. The extract also displayed excellent (83%) radical scavenging activity. On the basis of these results, the crude extract was subsequently fractionated into n-hexane, chloroform, ethyl acetate, n-butanol and water fractions and tested independently for the aforesaid activities. Significant inhibitory activity against urease enzyme was observed for the ethyl acetate, n-butanol and water fractions while the n-hexane and chloroform fractions were devoid of any such activity. In the alpha-Chymotrypsin enzyme inhibition studies the activity was concentrated into the ethyl acetate fraction. All the fractions displayed potent radical scavenging activity. The crude extract and fractions thereof were also subjected to total phenolic content determination. A correlation between radical scavenging capacities of extracts and total phenolic content was observed in the majority of cases.     

Antibacterial and antifungal activities of andrachne cordifolia muell

The crude methanolic extract of Andrachne cordifolia Muell. (Euphorbiaceae) and its various fractions in different solvent systems (chloroform, ethyl acetate and n-butanol) were screened for antibacterial and antifungal activities. Crude extract and subsequent fractions demonstrated moderate to excellent antibacterial activities against the tested pathogens. Highest antibacterial activity was displayed by both chloroform and ethyl acetate fractions (100%) followed by the crude extract (68%) against Salmonella typhi. Similarly, crude extract and its subsequent fractions showed mild to excellent activities in antifungal bioassay with maximum (76%) antifungal activity against Microsporum canis by the chloroform fraction followed by the crude extract (65%).     

Antibacterial and antifungal activities of teucrium royleanum (Labiatea)

The crude methanolic extract and subsequent fractions of Teucrium royleanum (Labiatea) were screened for antibacterial and antifungal activities. Against tested pathogens, crude extract and subsequent fractions demonstrated moderate to excellent antibacterial activities. Highest antibacterial activity was displayed by the ethyl acetate fraction against S. typhi (100%), against E.coli (76.7%) and against P. aerugenosa (70.8%) followed by the chloroform fraction against S. typhi (85.7%). Similarly, the crude extract and its subsequent fractions showed mild to excellent activities in the antifungal bioassay with maximum antifungal activity against M. canis (87%) by the chloroform fraction followed by the ethyl acetate (71%) and n-butanol (70%) fractions.     

Enzyme inhibition and radical scavenging activities of aerial parts of Paeonia emodi Wall. (Paeoniaceae)

The ethanolic extract derived from aerial parts of an indigenous medicinal plant Paeonia emodi was screened for enzyme inhibition activities against Urease (jack bean and Bacillus pasteurii) and α-Chymotrypsin. The extract was also investigated for its radical scavenging activity using DPPH assay. The crude extract was found to possess significant enzyme inhibition activities against jack bean (74%) and Bacillus pasteurii (80%) urease and a moderate activity (54%) against α-Chymotrypsin. The extract also displayed excellent (83%) radical scavenging activity. On the basis of these results, the crude extract was subsequently fractionated into n-hexane, chloroform, ethyl acetate, n-butanol and water fractions and tested independently for the aforesaid activities. Significant inhibitory activity against urease enzyme was observed for the ethyl acetate, n-butanol and water fractions while the n-hexane and chloroform fractions were devoid of any such activity. In the α-Chymotrypsin enzyme inhibition studies the activity was concentrated into the ethyl acetate fraction. All the fractions displayed potent radical scavenging activity. The crude extract and fractions thereof were also subjected to total phenolic content determination. A correlation between radical scavenging capacities of extracts and total phenolic content was observed in the majority of cases.     

Enzyme inhibition activities of Teucrium royleanum

The crude methanolic extract and chloroform, ethyl acetate and n-butanol fractions of Teucrium royleanum were examined as inhibitors of actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease. A significant enzyme inhibition activity (52-83%) was shown by the crude methanolic extract and its fractions against acetylcholinesterase, while low to outstanding enzyme inhibitory activity was shown (19-93%) against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity against lipoxygenase and inactive against urease.     

怀山药醇提取物抗DPPH自由基活性研究

将怀山药乙醇提取物采用溶剂萃取的方法,分成极性不同的五个部分,并首次用DPPH(2,2-diphenyl-1-picrylhydrazyl)方法测定各部分的抗自由基活性,发现乙酸乙酯萃取部分活性最强,氯仿萃取部分次之,再其次是正丁醇和水溶性部分。乙酸乙酯和氯仿萃取部分较强的抗自由基活性主要归因于其中所含的多酚类成分。同时利用薄层层析(TLC)、紫外光谱(UV)、^13C核磁共振(NMR)技术及显色反应对酚性成分进行了定性检验,并用Folin-Denis法测定了各萃取部位中酚性成分含量,发现抗自由基活性与萃取物中多酚性成分含量有一定的相关性。因而在评价怀山药质量时,其中所含的酚性成分不应忽视。     

Inhibition activities of Colchicum luteum baker on lipoxygenase and other enzymes

In vitro enzymes inhibition activities of the crude methanolic extract and various fractions of Colchicum luteum Baker (Liliaceae) including chloroform, ethyl acetate, n-butanol and aqueous were carried out against actylcholinesterase, butyrylcholinesterase, lipoxygenase and urease enzymes. A significant enzyme inhibition activity (89%) is shown by the crude methanolic extract and its fractions against lipoxygenase, while low to significant activity (32-75%) was evident against butyrylcholinesterase. The crude methanolic extract and its various fractions demonstrated low activity (29-61%) against acetylcholinesterase and no activity against urease.     

Antibacterial activity of extracts and neolignans from Piper regnellii (Miq.) C. DC. var. pallescens (C. DC.) Yunck

The evaluation of the activity of the aqueous and ethyl acetate extracts of the leaves of Piper regnellii was tested against gram-positive and gram-negative bacteria. The aqueous extract displayed a weak activity against Staphylococcus aureus and Bacillus subtilis with minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of 1000 micrograms/ml. The ethyl acetate extract presented a good activity against S. aureus and B. subtilis with MIC and MBC at 15.62 micrograms/ml. In contrast to the relative low MICs for gram-positive bacteria, gram-negative bacteria were not inhibited by the extracts at concentrations < or = 1000 mg/ml. The ethyl acetate extract was fractionated on silica gel into nine fractions. The hexane and chloroform fractions were active against S. aureus (MIC at 3.9 micrograms/ml) and B. subtilis (MIC at 3.9 and 7.8 micrograms/ml, respectively). Using bioactivity-directed fractionation, the hexane fraction was rechromatographed to yield the antimicrobial compounds 1, 2, 5, and 6 identified as eupomatenoid-6, eupomatenoid-5, eupomatenoid-3, and conocarpan, respectively. The pure compounds 1 and 2 showed a good activity against S. aureus with MIC of 1.56 micrograms/ml and 3.12 micrograms/ml, respectively. Both compounds presented MIC of 3.12 micrograms/ml against B. subtilis. The pure compound 6 named as conocarpan was quite active against S. aureus and B. subtilis with MIC of 6.25 micrograms/ml. The antibacterial properties of P. regnellii justify its use in traditional medicine for the treatment of wounds, contaminated through bacteria infections.     

Prediction of inhibitory activity of epidermal growth factor receptor inhibitors using grid search-projection pursuit regression method

The epidermal growth factor receptor (EGFR) protein tyrosine kinase (PTK) is an important protein target for anti-tumor drug discovery. To identify potential EGFR inhibitors, we conducted a quantitative structure-activity relationship (QSAR) study on the inhibitory activity of a series of quinazoline derivatives against EGFR tyrosine kinase. Two 2D-QSAR models were developed based on the best multi-linear regression (BMLR) and grid-search assisted projection pursuit regression (GS-PPR) methods. The results demonstrate that the inhibitory activity of quinazoline derivatives is strongly correlated with their polarizability, activation energy, mass distribution, connectivity, and branching information. Although the present investigation focused on EGFR, the approach provides a general avenue in the structure-based drug development of different protein receptor inhibitors.     

胡椒、芒果和黄皮的化感作用潜力

以胡椒、芒果和黄皮作为供体,玉米、黄豆、南瓜、花生、萝卜、稗草、马唐、柱花草为受体,通过种子萌发法和根生长法测定胡椒、芒果和黄皮的化感作用潜力.结果表明,玉米、黄豆、南瓜、稗草和马唐的萌发和根生长都受到3种供体水浸提液的影响,3种供体水浸提液在高浓度下抑制而在低浓度下则促进受体的萌发和根生长;胡椒和芒果根系周围的土壤对玉米萌发和根生长有促进作用而对花生的萌发和根生长则有抑制作用.3种供体的水浸提液通过乙酸乙酯、正丁醇萃取分离成不同极性的三相后分别对玉米、萝卜和柱花草进行处理.结果表明,胡椒和芒果浸提液的水相与正丁醇相对受体的抑制作用明显强于乙酸乙酯相,表明胡椒和芒果的化感物质具有较强的极性.     

天山云杉针叶水提取物自毒效应及自毒物质的分离鉴定

天山云杉(Picea schrenkiana)是亚洲中部山地的特有物种, 在中国仅见于新疆, 主要分布在天山南北坡和昆仑山西部北坡, 对天山山地的水源涵养、水土保持和林业生产具有不可或缺的重要性。云杉天然林自然更新不良或障碍和生产力下降等问题的出现已成为长期困惑林业工作者的一大难题。该文从植物间的化感与自毒作用研究着手, 分析云杉针叶水提液的乙醚、乙酸乙酯、正丁醇萃取物对自身种子萌发和幼苗生长影响实验。以种子发芽率、发芽势和发芽指数作为种子萌发参数, 以胚根、胚芽长度和实生苗干湿重的变化作为幼苗生长参数。研究结果表明: 种子萌发实验中乙醚萃取物具有最强的抑制效应(IC₅₀ = 5.84 mg·ml^-1), 而正丁醇萃取物的抑制效应最弱(IC₅₀> 10.00 mg·ml^-1); 幼苗生长实验中, 1.25 mg·ml^-1乙醚萃取物对幼苗生长具有显著抑制作用(p<0.05), 1.25 mg·ml^-1正丁醇萃取物能够促进其幼苗生长, 大于2.5 mg·ml^-1的正丁醇萃取物对幼苗生长具有显著抑制效应(p<0.05)。采用GC-MS-MS和NMR技术分析3种有机萃取物的化学组成, 鉴定并定量分析出了包括酚酸、长链脂肪酸、单宁酸和吲哚类物质在内的17种化合物。乙醚萃取物中存在的2-keto-4a-methyl-8-methoxy-2, 3, 4, 4a, 5, 6, 11, 12-ocahydrochrysene (在该文中, 将其命名为云杉酮)为一新的化感物质。该研究证明了天山云杉针叶中存在的化感与自毒物质是导致其种群天然更新障碍的一个最主要原因, 同时揭示了自毒作用发生的化学物质基础。     

Phagodeterrence and insecticidal activity of Hyptis suaveolens (Poit.) against four important lepidopteran pests

This study was carried out to evaluate the antifeedant and larvicidal activities of Hyptis suaveolens Poit. (Lamiaceae) leaves crude extracts and their fractions against four lepidopteran pests namely Helicoverpa armigera (Hbn.), Spodoptera litura (Fab.), Earias vittella (Fab.) and Leucinodes orbonalis (G.). Hexane, chloroform and ethyl acetate extracts were tested by leaf disc and fruit disc no-choice methods at 1% and 1,000?ppm concentrations for crude and fractions, respectively. Ethyl acetate extract of H. suaveolens exhibited the maximum antifeedant and insecticidal activity at 1% concentration against all the tested insects. It was subjected to fractionation using silica column chromatography with different combinations of hexane and ethyl acetate used as mobile phase. Among the 15 fractions obtained, fraction 2 showed the maximum antifeedant and insecticidal activity against all tested insects at 1000?ppm concentration. Preliminary phytochemical analysis of fraction 2 showed the presence of terpenoids and alkaloids. H. suaveolens could be considered as a safe and eco-friendly insecticide for lepidopteron pest management.     

Antioxidant activity of the phenol rich fractions of leaves of Chukrasia tabularis A. Juss

The present study was designed to explore the antioxidant potential of chloroform, ethyl acetate, n-butanol and water fractions of 80% methanol extract of leaves Chukrasia tabularis by 2,2'-diphenyl-1-picrylhydrazyl (DPPH), deoxyribose degradation (non-site specific and site specific), reducing power and DNA nicking assays. The different fractions showed significant activities in all the free radical scavenging tests and these findings have also shown direct relationship between antioxidant activity and phenolic content. Among the fractions, ethyl acetate fraction exhibited highest inhibition of 93.14%, 89.99%, 87.04% in DPPH, non-site specific and site specific deoxyribose degradation assays, respectively and 91.20% reduction of ferricyanide to give Prussian blue coloured complex in reducing power assay at maximum concentration tested. This preliminary study indicates the antioxidant activity of the leaves of Chukrasia tabularis, and moreover the results showed correlation with the amount of phenolic content present in different fractions.     

Susceptibility of some clinical isolates of <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> to fractions from the aerial parts of <Emphasis Type="Italic">Leuzea carthamoides</Emphasis>

The antimicrobial activity of the dichloromethane extract from aerial parts of Leuzea carthamoides DC. was tested in vitro against 19 Staphylococcus aureus strains (ATCC 25923, CNCTC Mau 43/60, clinical isolates). The extract was fractionated by column chromatography on silica gel into six fractions (petroleum ether, toluene, dichloromethane, ethyl acetate, methanol and water). The minimum inhibitory concentrations (MICs) of the fractions ranged from 64 to 1024 μg/mL. An ethyl acetate fraction (EA 1) with the widest range of activity inhibited all of the strains with MIC in the range 128–512 μg/mL. This fraction exhibited potent activity against strains which showed associated resistance to oxacillin, ciprofloxacin and erythromycin.     

竹叶提取物的体外抑菌及抗氧化活性的研究

本文用水提取竹叶有效成分,将提取液浓缩至含生药量约1.0 g/mL,经醇沉后取清液浓缩,再经石油醚、三氯甲烷、乙酸乙酯、正丁醇分步萃取,得不同极性的各部分提取物。以金黄色葡萄球菌和大肠杆菌为供试菌,采用抑菌圈法(琼脂扩散法)和最低抑菌浓度(MIC)法测定其抑菌效果。结果显示,石油醚、三氯甲烷、乙酸乙酯部分均表现抑菌活性。各供试样对两种菌的抑菌圈直径达9.8～18.4 mm,最低抑菌浓度分别为1.25 mg/mL2,.50 mg/mL和5.00 mg/mL。最后采用亚硝基红盐-Co2+褪色法研究了竹叶提取物对.OH的清除作用,结果表明三氯甲烷和乙酸乙酯部分萃取物的抗氧化性明显优于水提物,其中乙酸乙酯部分萃取物的IC50值为1.06 mg/mL。     

New natural urease inhibitors from Ranunculus repens

Phytochemical investigations on the chloroform and ethyl acetate soluble fractions of the roots of Ranunculus repens led to the isolation of methyl 3,4,5-trihydroxybenzoate 1, R(+)- 4-methoxydalbergione 2 and R(+)-dalbergiophenol 3. The structures of these compounds were established through spectral studies including 1D and 2D NMR experiments and by comparison with literature data. These compounds showed potent inhibitory activity against urease.     

In vitro efficacy of bioactive extracts of 15 medicinal plants against ESbetaL-producing multidrug-resistant enteric bacteria

Alcoholic crude extracts and some fractions from 15 traditionally used Indian medicinal plants were investigated for their ability to inhibit the growth of extended spectrum beta-lactamases (ESbetaL)-producing multidrug-resistant enteric bacteria. The test bacteria Eschrichia coli and Shigella were resistant to 16-23 antibiotics with intermediate or resistance to beta-lactams (minimum inhibitory concentration (MIC) value range 16-1024 microg/ml). The crude plant extracts demonstrated zone of inhibition in the range of 11-29 mm against one or more test bacteria. On the basis of promising activity, 12 plants were selected to determine their efficacy in terms of MIC, which ranged from 0.64 mg/ml to 10.24 mg/ml. The extracts of Acorus calamus, Hemidesmus indicus, Holarrhena antidysenterica and Plumbago zeylanica demonstrated relatively high activity as compared to other plant extracts and were fractionated into acetone, ethyl acetate and methanol. Acetone fraction in most of the cases exhibited higher potency (low MIC value) as compared to ethyl acetate and methanol fraction. However, in Plumbago zeylanica, ethyl acetate fraction was most active. Synergistic interactions among crude extracts were demonstrated in the 12 different combinations against ESbetaL-producing E. coli (ESbetaL-02). Certain combinations exhibited significant synergy with enlargement of combined inhibition zone size by 5 mm. Interaction of crude extracts with five antibiotics (Tetracycline, ciprofloxacin, nalidixic acid, chloramphenicol and streptomycin) demonstrated synergistic interaction with tetracycline and ciprofloxacin by 10 and 3 plant extracts respectively. Phytochemical analysis and thin layer chromatography (TLC) bioautography of crude extracts showed the presence of alkaloids, phenols and flavonoids as active phytoconstituents. Most active fractions of four plants were subjected to Infrared spectroscopy and the major groups of compounds were detected. The plant extracts were further tested for their in vitro haemolytic activity to sheep erythrocytes and demonstrated no haemolysis at recommended doses. Further activity-guided fractionation of active fractions is needed to isolate and characterize the active principle in order to establish the mode of action against the ESbetaL-producing multidrug-resistant enteric bacteria and the mechanism of synergy.