Free radical scavenging, enzyme inhibitory constituents from antidiabetic Ayurvedic medicinal plant Hydnocarpus wightiana Blume

Hydnocarpus wightiana is advocated in traditional Indian medicine to possess strong antidiabetic activity. In the course of identifying bioactive fractions from Indian medicinal plants we observed that acetone extract of the seed hulls of H. wightiana possess strong free radicals (DPPH and ABTS) scavenging, alpha-glucosidase and moderate N-acetyl-beta-D-glucosaminidase inhibitory activities. Further fractionation of the extract led to the isolation of hydnocarpin, luteolin and isohydnocarpin in substantial yields. All the compounds showed strong ABTS scavenging property. However, only luteolin could display strong DPPH scavenging activity. Furthermore, all the three compounds also showed varying degrees of alpha-glucosidase and N-acetyl-beta-D-glucosaminidase inhibitory activity, luteolin being the superior. The kinetics of alpha-glucosidase inhibition by these compounds showed that acetone extract inhibits the enzyme in competitive manner however, luteolin and isohydnocarpin showed mixed-type inhibition. This is the first report assigning hydnocarpin and isohydnocarpin free radical scavenging, alpha-glucosidase and N-acetyl-beta-D-glucosaminidase inhibitory properties and luteolin as N-acetyl-beta-D-glucosaminidase inhibitor. This study suggests that presence of amphiphilic antioxidant molecules along with enzyme inhibitory activities in the acetone extract of H. wightiana seed hulls may be responsible for the antidiabetic properties as advocated in traditional medicine.     

绿茶提取物对糖尿病大鼠糖耐量的影响及机制研究

目的　研究绿茶提取物对糖尿病大鼠糖耐量的影响及其机制。方法　给糖尿病大鼠口服蔗糖或淀粉和绿茶提取物后 ,观察绿茶提取物对糖尿病大鼠糖耐量的影响 ,并用比色法测定绿茶提取物对α-葡萄糖苷酶 (EC 3.2 .1.2 0 )和α -淀粉酶 (EC 3.2 .1.1)的抑制活性。结果　绿茶提取物可明显改善蔗糖或淀粉负荷糖尿病大鼠的血糖水平。在糖尿病相关酶的抑制试验中 ,绿茶提取物显示有较强的α -葡萄糖苷酶抑制活性 ,其α -葡萄糖苷酶的半抑制浓度(IC50 )值为 0 .13g/L ;绿茶提取物对α-淀粉酶的抑制活性则较弱 ,浓度为 1g/L时 ,其对α -淀粉酶的抑制率为 2 1%。结论　绿茶提取物能够降低糖尿病大鼠糖负荷血糖 ,可能由其对α -葡萄糖苷酶和α -淀粉酶的抑制作用所致     

A Comparative Study on the Inhibitory Effects of Different Parts and Chemical Constituents of Pomegranate on α‐Amylase and α‐Glucosidase

Pomegranate has been documented for the management of diabetes in Unani and Chinese medicine. This study compared the effects of the extracts of different pomegranate parts, including juice, peels, seeds and flowers, on carbohydrate digestive enzymes (α‐amylase and α‐glucosidase) in vitro. The methanolic flower extract inhibited α‐amylase and α‐glucosidase, while the methanolic peel extract inhibited α‐glucosidase selectively. The most active flower extract was subjected to water‐ethyl acetate partition. The ethyl acetate fraction was more potent than the water fraction in inhibiting both enzymes. Gallic acid and ellagic acid also showed selective inhibition against α‐glucosidase, and their presence in the ethyl acetate fraction was confirmed by HPLC‐DAD and HPLC‐HESI‐MS. Our findings suggest that the inhibition of carbohydrate digestive enzymes and their phenolic content may contribute to the anti‐hyperglycaemic effects of pomegranate flower and peel, and support their claims in diabetes. Copyright © 2012 John Wiley & Sons, Ltd.     

Phenolic‐Linked Biochemical Rationale for the Anti‐Diabetic Properties of Swertia chirayita (Roxb. ex Flem.) Karst.

The crude extract of Swertia chirayita, an important medicinal plant of Nepal, is locally used for many diseases including type 2 diabetes. In this study, crude aqueous and 12% ethanol solution extracts of S. chirayita collected from nine districts of Nepal were analyzed for anti‐diabetic‐linked anti‐hyperglycemia potential using in vitro biochemical assays. There was moderate‐to‐high positive correlation between antioxidant activity and total phenolic content of both extracts and moderate‐to‐high α‐glucosidase inhibitory activity. Although the anti‐diabetic property of S. chirayita is mainly attributed to the phytochemical swerchirin present in its hexane fraction, we propose that the crude extract of this plant used in local healing also has anti‐hyperglycemia potential. The crude extracts indicated the presence of three main phytochemicals mainly mangiferin, swertiamarin, and amarogentin and their derivatives. Among the standard compounds (mangiferin, swertiamarin, and amarogentin), mangiferin showed α‐glucosidase and 2,2‐diphenyl‐1‐picrylhydrazyl radical inhibitory activity indicating anti‐hyperglycemia potential. Copyright © 2012 John Wiley & Sons, Ltd.     

Medicinal Plants Traditionally Used for Treatment of Obesity and Diabetes Mellitus – Screening for Pancreatic Lipase and α‐Amylase Inhibition

In order to find new pancreatic lipase (PL) and α‐amylase inhibitors from natural sources for the treatment of obesity and related diseases as diabetes mellitus II, 23 medicinal plants with weight‐reducing, serum glucose‐reducing or related potential were investigated. Methanolic and water extracts of the plants were evaluated by using two in vitro test systems. Our findings have shown that the methanolic extract of Hibiscus sabdariffa L. (Malvaceae) showed high inhibitory activities to PL (IC₅₀: 35.8 ± 0.8 µg/mL) and α‐amylase (IC₅₀: 29.3 ± 0.5 µg/mL). Furthermore, the methanolic extract of Tamarindus indica L. (Leguminosae) showed a high anti‐lipase (IC₅₀: 152.0 ± 7.0 µg/mL) and the aqueous extract a high anti‐amylase (IC₅₀: 139.4 ± 9.0 µg/mL) activity. This work provides a priority list of interesting plants for further study with respect to the treatment of obesity and associated diseases. Copyright © 2015 John Wiley & Sons, Ltd.     

Triterpene acids isolated from Lagerstroemia speciosa leaves as α‐glucosidase inhibitors

The potential antidiabetic activity of ethyl acetate extract of the leaves of Lagerstroemia speciosa (LSL) was investigated by α‐amylase and α‐glucosidase inhibition assay. Six pentacyclic triterpenes (oleanolic acid, arjunolic acid, asiatic acid, maslinic acid, corosolic acid and 23‐hydroxyursolic acid) were isolated from LSL. Their structures were determined by spectroscopic analysis and their α‐glycosidase and α‐amylase inhibitory activities were investigated. They exhibited no or weak inhibitory activity against α‐amylase and middle α‐glucosidase inhibitory activities. Corosolic acid, which shows best bioactivity against α‐glucosidase (IC₅₀ = 3.53 µg/mL), contributes most to the α‐glucosidase inhibitory activity of EtOAc extract. The kinetics of inhibition of corosolic acid was also discussed. Results from this study might provide the scientific evidence for LSL for the treatment of diabetes in traditional medicine. Copyright © 2008 John Wiley & Sons, Ltd.     

Screening of some medicinal plants from cameroon for beta-lactamase inhibitory activity

In efforts to find new bioactive beta-lactamase inhibitors, this study investigated 16 Cameroonian plants belonging to 10 families which were evaluated for anti-beta-lactamase activity. The investigation showed that extracts 2, 6, 3 and 5 of the 16 plants investigated presented interesting in vitro beta-lactamase inhibition (over 90%), respectively, of the beta-lactamases TEM-1, OXA-10, IMP-1 and P99. These extracts were from Mammea africana (all beta-lactamases), Garcinia lucida, G. kola (OXA-10, IMP-1 and P99), Bridelia micrantha (OXA-10, P99), Ochna afzelii (OXA-10, P99), Prunus africana (IMP-1) and Adenia lobata (TEM-1). After elimination of tannins (according to the European Pharmacopoeia) the extracts from B. micrantha, G. lucida and M. africana were tested further for their anti-beta-lactamase activity. The extracts from B. micrantha and G. lucida exhibited potent inhibitory activity, respectively, of beta-lactamase OXA-10 (IC(50) = 0.02 mg/mL) and P99 (IC(50) = 0.01 mg/mL). The anti-beta-lactamase activity of M. africana extract was weak. The isolation and the structural elucidation of the active constituents of G. lucida and B. micrantha will provide useful leads in the development of beta-lactamase inhibitors.     

Anticancer activity of limonoid from Khaya senegalensis

Two limonoids were isolated from the methanol extract of Khaya senegalensis (Meliaceae), and their structures were identified as 3alpha,7alpha-dideacetylkhivorin (1) and 1-O-acetylkhayanolide B (2) on the basis of MS and NMR spectral data. Complete assignments of (1)H and (13)C chemical shifts for compounds 1 and 2 were achieved by means of 1D and 2D NMR including DEPT, (1)H-(1)H COSY, HMQC, HMBC experiments. Compound 1 showed significant growth inhibitory activities against MCF-7, SiHa and Caco-2 cells with IC(50) values in the range of 0.07-0.14 microm (35-69 ppm) while compound 2 did not.     

Rat lens aldose reductase inhibitory constituents of Nelumbo nucifera stamens

Aldose reductase, the principal enzyme of the polyol pathway, has been shown to play an important role in the complications associated with diabetes. A methanol extract of the stamens of Nelumbo nucifera Gaertn. was shown to exert an inhibitory effect on rat lens aldose reductase (RLAR), and thus was fractionated using several organic solvents, including dichloromethane, ethyl acetate and n-butanol. The ethyl acetate-soluble fraction, which manifested potent RLAR-inhibitory properties, was then purified further via repeated measures of silica gel and Sephadex LH-20 column chromatography. Thirteen flavonoids: kaempferol (1) and seven of its glycosides (2-9), myricetin 3',5'-dimethylether 3-O-beta-d-glucopyranoside (10), quercetin 3-O-beta-d-glucopyranoside (11) and two isorhamnetin glycosides (12, 13) were isolated from N. nucifera, as well as four non-flavonoid compounds: adenine (14), myo-inositol (15), arbutin (16) and beta-sitosterol glucopyranoside (17). These compounds were all assessed with regard to their RLAR-inhibitory properties. Among the isolated flavonoids, those harboring 3-O-alpha-l-rhamnopyranosyl-(1-->6)-beta-d-glucopyranoside groups in their C rings, including kaempferol 3-O-alpha-l-rhamnopyranosyl-(1-->6)-beta-d-glucopyranoside (5) and isorhamnetin 3-O-alpha-l-rhamnopyranosyl-(1-->6)-beta-d-glucopyranoside (13), were determined to exhibit the highest degree of rat lens aldose reductase inhibitory activity in vitro, evidencing IC(50) values (concentration required for a 50% inhibition of enzyme activity) of 5.6 and 9.0 microm, respectively.     

Dolichandroside A,a new α‐glucosidase inhibitor and DPPH free‐radical Scavenger from Dolichandrone falcata seem

A new phenylpropanoid glycoside, dolichandroside‐A, together with seven known compounds α‐lapachone, lapachol, aloesaponarin II, 8‐hydroxydehydroiso‐α‐lapachone, β‐sitosterol, 3,8‐dihydroxydehydroiso‐α‐lapachone and verbascoside were isolated from the active ethyl acetate soluble extract of heartwood of Dolichandrone falcata. All except for dolichandroside‐A are known compounds, but have been isolated for the first time from this plant. The structure of all these compounds was determined on the basis of 1D‐ and 2D‐NMR spectral data. All the isolates were tested for α‐glucosidase inhibitory and DPPH radical scavenging activity. This is the first report identifying DPPH scavenging activity and α‐glucosidase inhibitory activity in D. falcata. Furthermore, along with a new compound, dolichandroside‐A, this study also assigns for the first time α‐glucosidase inhibitory activity to verbascoside and aloe saponarin‐II. Copyright © 2008 John Wiley & Sons, Ltd.     

应用α-葡萄糖苷酶抑制剂高通量筛选模型筛选降血糖中药

 目的建立筛选α-葡萄糖苷酶抑制剂的体外高通量筛选模型,并对30味常用清热解表中药进行筛选。方法应用大鼠小肠上段提取的α-葡萄糖苷酶,以蔗糖作为底物,通过测定反应体系中葡萄糖的生成量来检测α-葡萄糖苷酶的活性。通过优化酶促反应条件,建立检测α-葡萄糖苷酶活性的比色测定法及其抑制剂体外筛选的方法,并对30味中药共72个样品进行高通量筛选。结果阿卡波糖对α-葡萄糖苷酶的抑制活性与文献报道相近;筛选发现鸭跖草、山慈菇和桑叶等3味中药的不同极性提取物对α-葡萄糖苷酶有可重复的抑制作用。结论应用比色法建立的筛选模型可进行α-葡萄糖苷酶抑制剂的高通量筛选及中药相关活性物质的发现。     

刺五加果实及种子内源萌发抑制物质活性的研究

目的 :通过对刺五加果实及种子内源萌发抑制物质的研究 ,探讨了刺五加种子休眠的原因。方法 :制备刺五加果实的各部分及种子的粗提物 ,并测定其活性 ;制备刺五加中果皮的乙醚提取液并进行纸层析 ,然后测定各区段的活性。结果和结论 :首次证明了刺五加果实及其外果皮、中果皮、种子中均含有一定活性的内源抑制物质。外果皮、中果皮、种子中所含的内源抑制物质对白菜种子萌发的抑制活性高于对白菜幼根生长抑制活性 ,刺五加中果皮乙醚提取物纸层析在Rf 0.l区段对白菜种子萌发和白菜幼根生长有最强抑制 ,刺五加果实粗提物能抑制小麦种子萌发过程中α-淀粉酶活性 ,且在一定浓度范围内对小麦种子萌发及幼苗生长也有明显抑制作用 ,随粗提物浓度增大抑制活性明显增强。刺五加果实和种子中活性较高的内源抑制物质与刺五加种子的深沉休眠特性密切相关。     

Antioxidant and anticholinesterase constituents from the petroleum ether and chloroform extracts of Iris suaveolens

The aim of this study was to investigate the phytochemical, antioxidant and anticholinesterase activities of Iris suaveolens. After determining total phenolic and flavonoid contents of the petroleum ether, chloroform and methanol extracts prepared from the rhizomes, the antioxidant capacity of the extracts was established using β‐carotene–linoleic acid and CUPRAC methods. The chloroform extract which was rich in phenolic content exhibited the highest inhibition of lipid peroxidation in the β‐carotene–linoleic acid system, and the best cupric reducing antioxidant capacity among the tested extracts. The petroleum ether extract indicated moderate anticholinesterase activity while the chloroform extract revealed significant butyrylcholinesterase inhibitory activity (75.03 ± 1.29%). Spectroscopic methods were used for the structural elucidation of the compounds (1–13) isolated from the petroleum ether and chloroform extracts. Coniferaldehyde (6), having the highest antioxidant activity in the β‐carotene–linoleic acid assay at 25 and 50 µg/mL, demonstrated also the best effect in the CUPRAC method among the tested compounds (1–12). 3‐Hydroxyirisquinone (10) showed the best anticholinesterase activity among the tested compounds (1–4, 6–12), and coniferaldehyde exhibited almost the same butyrylcholinesterase inhibitory activity (82.60 ± 2.33%) as galantamine (86.26 ± 0.66%). Copyright © 2010 John Wiley & Sons, Ltd.     

Isolation of linoleic and alpha-linolenic acids as COX-1 and -2 inhibitors in rose hip

Rose hip has previously shown clinical efficacy in the treatment of osteoarthritis, and organic solvent extracts of rose hip have showed inhibition of cyclooxygenase-1 and -2. A petroleum ether extract of rose hip was fractioned by VLC on silica; on a C-18 column and by HPLC. Each step was COX-1/2 activity-guided. The bioassay-guided fractionation led to the isolation of linoleic acid (the IC50 for COX-1 was 85 microm and 0.6 microM for COX-2) and alpha-linolenic acid (the IC50 for COX-1 was 52 microM and 12 microM for COX-2). The COX-2/COX-1 ratio was 0.007 for linoleic acid and 0.2 for alpha-linolenic acid. Linoleic acid and alpha-linolenic acid contribute to the COX-1 and -2 inhibitory activity of rose hip.     

Effect of Natural β‐Glucosidase Inhibitors in Reducing Toxicity of Amygdalin in Persicae Semen

Amygdalin can be decomposed into hydrocyanic acid, which is the primary source of Persicae Semen toxicity, by gut flora. Here, the inhibitory activity of β‐glucosidase for test herb extracts was first determined and compared. In turn, optimization of the ratio of substrate and inhibitor in vitro and LD₅₀ values of extracts, serum and liver contents of amygdalin in vivo was measured. Lycii Cortex was found to be the best inhibitory activity for β‐glucosidase. The ratio of amygdalin‐to‐Lycii Cortex extract of 7.19:8.18 (mmol L^?1/mg mL^?1) can be relatively suitable for inhibiting β‐glucosidase activity in test in vitro reaction system. After mixed with Lycii Cortex extract, the toxicity of Persicae Semen ethanol extract in mice is significantly reduced and more amygdalin can be absorbed into the bloodstream. The study provides useful information for reducing toxicity of Persicae Semen and suggests how to better use these natural β‐glucosidase inhibitors in the utilization of glycosides and aglycones. Copyright © 2017 John Wiley & Sons, Ltd.     

Screening of various plant extracts used in ayurvedic medicine for inhibitory effects on human immunodeficiency virus type 1 (HIV-1) protease

To identify substances with anti-human immunodeficiency virus (HIV) activity in traditional medicines, water and methanol extracts of crude drugs used in Indian traditional medicine (Ayurveda) were subjected to screening for their inhibitory effects on HIV type 1 protease (PR). The enzyme activity was determined by HPLC and of the 39 crude drugs tested, the extracts of the seeds of Areca catechu, the bark of Eugenia jambolana, the bark of Saraca indica and the stem bark of Terminalia arjuna inhibited the HIV-1 PR activity by more than 70% at a concentration of 0.2 mg/mL. The most potent inhibition was shown by the A. catechu extract, from which some procyanidins were isolated. One of them, arecatannin B1 showed significant HIV-1-PR inhibitory activity.     

Evaluation of the antioxidant and free radical scavenging properties of Secamone afzelii Rhoem

The antioxidant activity of a methanol extract of Secamone afzelii stems was tested using the DPPH assay and the active compound was identified as alpha-tocopherol. HPLC determination showed that 0.12% w/w alpha-tocopherol was present in the plant. The total extract also showed effective free radical scavenging activity in the assay for non-enzymatic lipid peroxidation in liposomes with an IC50 value of 90 microg/mL, with alpha-tocopherol isolated from the plant having an IC50 of 15 microg/mL in the same system, thus demonstrating the presence of other antioxidants.     

Antiinflammatory activity of methanol extract isolated from stem bark of Magnolia kobus

The present study reports the antiinflammatory activity of a methanol extract isolated from the stem bark of Magnolia kobus (MK). MK potently inhibited lipopolysaccharide (LPS)-induced production of nitric oxide and interleukin-1beta (IL-1beta) in RAW 264.7 cells, a murine macrophage-like cell line. The secretion of tumor necrosis factor-alpha (TNF-alpha) was also suppressed in LPS-stimulated RAW 264.7 cells although the magnitude of inhibition was weaker than that of nitric oxide and IL-1beta. The mRNA expressions of inducible nitric oxide synthase (iNOS), IL-1beta and TNF-alpha were also suppressed by MK in LPS-stimulated RAW 264.7 cells. Further study demonstrated that LPS-induced DNA binding of AP-1 and phosphorylation of c-jun N-terminal kinase (JNK) were inhibited by MK treatment in RAW 264.7 cells, whereas phosphorylation of p38 mitogen-activated protein kinase was unaffected. Moreover, topical application of MK suppressed ear swelling in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation model. Collectively, these results suggest that MK exerts antiinflammatory effects in vitro and in vivo and this might be mediated, at least in part, by blocking AP-1 and JNK activation.     

Anti-obesity action of Salix matsudana leaves (Part 2). Isolation of anti-obesity effectors from polyphenol fractions of Salix matsudana

Previously, it was reported that polyphenol fractions prepared from the leaves of Salix matsudana reduced the elevation of the rat plasma triacylglycerol level at 3 and 4 h after oral administration of a lipid emulsion containing corn oil, at a dose of 570 mg/kg. Moreover, body weights at 2-9 weeks and the fi nal parametrial adipose tissue weights were significantly lower in mice fed the high-fat diet with 5% polyphenol fractions of S. matsudana leaves than in those fed the high-fat diet alone. The polyphenol fractions of S. matsudana leaves also significantly reduced the hepatic total cholesterol content, which was elevated in mice fed the high-fat diet alone. In addition, the polyphenol fractions of S. matsudana leaves inhibited palmitic acid uptake into brush border membrane vesicles prepared from rat jejunum and alpha-amylase activity, and their fractions enhanced norepinephrine-induced lipolysis in fat cells. To clarify the active substances inhibiting the palmitic acid uptake into small intestinal brush border membrane, the alpha-amylase activity or enhancing the norepinephrine-induced lipolyis in fat cells, the isolation of the active substances from polyphenol fraction was attempted using the above three assay systems. Compounds 1, 2 and 3 were isolated from the polyphenol fractions and identified as apigenin-7-O-d-glucoside, luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside, respectively. Among three flavonoids, apigenin-7-O-d-glucoside inhibited alpha-amylase activity, and luteolin-7-O-d-glucoside and chrysoeriol-7-O-d-glucoside inhibited palmitic acid uptake into small intestinal brush border membrane. Furthermore, three flavonoid glucosides enhanced norepinephrine-induced lipolysis in fat cells.     

Screening of Chinese and Mongolian herbal drugs for anti-human immunodeficiency virus type 1 (HIV-1) activity

Water and methanol extracts of 30 Chinese and Mongolian medicinal plants were tested for their human immunodeficiency virus type-1 (HIV-1) inhibitory activity. Of the 60 extracts, 23 showed anti-HIV activity. Bioassay-guided fractionation of one of the most active extracts, the methanol extract of the root tuber of Stephania cepharantha, led to the isolation of two alkaloids, aromoline and FK-3000 as potent inhibitory substances. They completely inhibited the cytopathic effects of HIV-1 on MT-4 cells at 31.3 and 7.8 microg/mL, respectively.