Displaying publications 21 - 40 of 107 in total

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  1. Fulltext Editorial: Developing medicinal plant extracts commercially: The importance of extraction and fractionation
    Brendler T, Chua LS, Abdullah LC, Yam MF
    Front Pharmacol, 2023;14:1140783.
    PMID: 36755954 DOI: 10.3389/fphar.2023.1140783
  2. Inhibitory effects of Cinnamomum burmannii Blume stem bark extract and trans-cinnamaldehyde on nasopharyngeal carcinoma cells; synergism with cisplatin
    Daker M, Lin VY, Akowuah GA, Yam MF, Ahmad M
    Exp Ther Med, 2013 Jun;5(6):1701-1709.
    PMID: 23837058
    Nasopharyngeal carcinoma (NPC) is a malignancy that occurs in the epithelium of the nasopharynx. The standard treatment of NPC patients with locoregionally advanced stages is problematic and is often associated with toxicities. Therefore, it is essential to screen for naturally occurring compounds with strong apoptosis-inducing activity and minimal toxicity. This study investigated the effects of the standardized methanol extract of Cinnamomum burmannii Blume stem bark and its main constituent, trans-cinnamaldehyde (TCA), on human NPC cell lines. The content of TCA in C. burmannii methanol extract was standardized to be 13.61% w/w by means of gas chromatography-mass spectrometry (GC-MS). NPC cell proliferation was clearly inhibited within 24 h of treatment, with TCA exhibiting greater activity than the methanol extract. TCA was more active against NPC cells compared with cisplatin. There was a pronounced downregulation of the proliferation markers, Ki67 and proliferating cell nuclear antigen (PCNA) in the TCA-treated cells; while morphological observation indicated the induction of apoptosis. Caspase activation and prominent DNA damage, which are markers of apoptosis induction were detected. TCA demonstrated the ability to scavenge nitric oxide. The simultaneous combination of TCA and cisplatin produced synergistic anti-proliferative effects. Collectively, these data indicate the potential use of TCA for the treatment of NPC.
  3. Discovery of trans-3,4,4'-trihydroxystilbene as new lead vasorelaxant agent for antihypertensive drug development
    Loh YC, Chan SY, Oo CW, Yam MF
    Life Sci, 2021 Aug 01;278:119560.
    PMID: 33915131 DOI: 10.1016/j.lfs.2021.119560
    AIMS: The structure-vasorelaxant activity relationships (SARs) assessment in previous study has found that trans-3,4,4'-trihydroxystilbene (344OH) could potentially act as a vasorelaxing agent with demonstration of over 2-fold maximal relaxation (Rmax) compared to its analogue, resveratrol. The present study focuses on the mechanism of actions and pathways employed by 344OH and compared to its analogue to further speculate the SAR of stilbenoids towards vasorelaxation.

    MATERIALS AND METHODS: The 344OH employed in present study was synthesized based on the protocol in previous study. The vascular responses towards the cumulative addition of 344OH were evaluated using in vitro rat aortic rings assays.

    KEY FINDINGS: The pEC50 and Rmax values were found to be 4.33 ± 0.05 and 106 ± 3.99%, respectively. Results showed that the vasorelaxation of 344OH were predominated by G-protein-coupled muscarinic- (M3) and β2-adrenergic receptors, followed by PGI2/AC/cAMP- and NO/sGC/cGMP-dependent pathways. It was also identified that 344OH employed voltage-activated- (Kv), calcium-activated- (Kca) and inwardly-rectifying (Kir) potassium channels and act as an antagonist for both VOCC and IP3R while regulating the action potential in the vasculature.

    SIGNIFICANCE: The different position of hydroxyl substituent located in A-ring of the stilbenoid backbone in 344OH compared to resveratrol resulted in a significant difference in mechanistic actions that lead to 344OH's fast-acting and less time-dependent vasorelaxation behaviour. This has substantially increased the potential of 344OH to be developed as an effective antihypertensive drug in future. Present findings further strengthen our inferences where the SARs study approach should be carried out as the mainstream methodology in future drug development research.

  4. Fulltext Microencapsulation Curcuminoids for Effective Delivery in Pharmaceutical Application
    Ang LF, Darwis Y, Por LY, Yam MF
    Pharmaceutics, 2019 Sep 02;11(9).
    PMID: 31480767 DOI: 10.3390/pharmaceutics11090451
    Curcuminoids have been long proven to possess antioxidant, anti-inflammatory and antibacterial properties which are crucial in their role as a pharmacological active agent. However, its poor solubility, high oxidative degradation, light sensitivity and poor bioavailability have been huge hurdles that need to be overcome for it to be administered as an oral or even a topical medication. In this present study, a complex coacervation microencapsulation approach was used to encapsulate the curcuminoids using both gelatin B and chitosan (at the optimum ratio of 30:1% w/w) for a more efficient drug delivery system. Curcuminoids microcapsules (CPM) were developed to be spherical in shape, discrete and free flowing with a reduced color staining effect. The thick wall of the CPM contributes directly to its integrity and stability. Cross-linking increases the density of polymers' wall network, hence, further increasing the decomposition temperature of curcuminoids microcapsules. Microencapsulation demonstrated an increment in curcuminoids solubility, while chemical cross-linking allowed for sustained release of the drug from the microcapsules by lowering the swelling rate of the available polymer networks. Thus, the microcapsules complied with the zero order release kinetics with super case-II transport mechanism. On the basis of all that was discussed above, it can be safely concluded that CPM should be incorporated in delivery system of curcuminoid, especially in its topical delivery for controlled drug release purposes, for not only a more efficient drug delivery system design but also a more efficacious optimization of the pharmacological benefits of curcuminoids.
  5. Vasorelaxant effect of 5,7,4'- Trihydroxyflavanone (Naringenin) via endothelium dependent, potassium and calcium channels in Sprague Dawley rats: Aortic ring model
    Tan CS, Tew WY, Jingying C, Yam MF
    Chem Biol Interact, 2021 Oct 01;348:109620.
    PMID: 34411564 DOI: 10.1016/j.cbi.2021.109620
    Naringenin is a naturally occurring flavanone (flavonoid) known to have bioactive effects on human health. It has been reported to show cardiovascular effects. This study aimed to investigate the possible vasorelaxant effect of naringenin and the mechanism behind it by using a Sprague Dawley rat aortic ring assay model. Naringenin caused significant vasorelaxation of endothelium-intact aortic rings precontracted with phenylephrine (pD2 = 4.27 ± 0.05; Rmax = 121.70 ± 4.04%) or potassium chloride (pD2 = 4.00 ± 0.04; Rmax = 103.40 ± 3.82%). The vasorelaxant effect decreased in the absence of an endothelium (pD2 = 3.34 ± 0.10; Rmax = 62.29 ± 2.73%). The mechanisms of the vasorelaxant effect of naringenin in the presence of antagonists were also investigated. Indomethacin, 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, atropine, 4-aminopyridine, Nω-nitro-l-arginine methyl ester, glibenclamide and propranolol significantly reduced the relaxation stimulated by naringenin in the presence of endothelium. Besides that, the effect of naringenin on the voltage-operated calcium channel (VOCC) in the endothelium-intact aortic ring was studied, as was intracellular Ca2+ release from the sarcoplasmic reticulum (SR) in the endothelium-denuded aortic ring. The results showed that naringenin also significantly blocked the entry of Ca2+ via the VOCC, SERCA/SOCC and suppressed the release of Ca2+ from the SR. Thus, the vasorelaxant effect shown by naringenin mostly involve the COX pathway, the endothelium-dependent pathway via NO/sGC/prostaglandin, calcium and potassium channels.
  6. Fulltext Impact of gentamicin coadministration along with high fructose feeding on progression of renal failure and metabolic syndrome in Sprague-Dawley rats
    Ibraheem ZO, Basir R, Aljobory AKh, Ibrahim OE, Alsumaidaee A, Yam MF
    Biomed Res Int, 2014;2014:823879.
    PMID: 25045706 DOI: 10.1155/2014/823879
    The current study evaluates the impact of high fructose feeding in rat model of gentamicin induced nephrotoxicity. Sprague-Dawley rats weighing 180-200 g were randomized into four groups; (C) received standard rodents chow with free access to ad libitum drinking water for 8 weeks and was considered as control, (F) received standard rodents chow with free access to drinking water supplemented with 20% (W/V) fructose for the same abovementioned period, (FG) was fed as group F and was given 80 mg/kg (body weight)/day gentamicin sulphate intraperitoneally during the last 20 days of the feeding period, and (G) was given gentamicin as above and fed as group C. Renal function was assessed at the end of the treatment period through measuring serum creatinine, uric acid and albumin, creatinine clearance, absolute and fractional excretion of both sodium and potassium, twenty-four-hour urinary excretion of albumin, and renal histology. For metabolic syndrome assessment, fasting plasma glucose and insulin were measured and oral glucose tolerance test was performed throughout the treatment period. Results showed that gentamicin enhances progression of fructose induced metabolic syndrome. On the other hand, fructose pretreatment before gentamicin injection produced a comparable degree of renal dysfunction to those which were given fructose-free water but the picture of nephrotoxicity was somewhat altered as it was characterized by higher extent of glomerular congestion and protein urea. Overall, more vigilance is required when nephrotoxic drugs are prescribed for patients with fructose induced metabolic syndrome.
  7. Fulltext Effects of extracts and fractions of Gynura procumbens on rat atrial contraction
    Abrika OS, Yam MF, Asmawi MZ, Sadikun A, Dieng H, Hussain EA
    J Acupunct Meridian Stud, 2013 Aug;6(4):199-207.
    PMID: 23972242 DOI: 10.1016/j.jams.2013.01.020
    There is currently a great deal of research interest in utilizing plant compounds against human diseases, including hypertension. The present study investigated the effects of different extracts and fractions from leaves of Gynura procumbens Merr. on rat atrial contraction in vitro. Isolated left and right atria, mounted in a 20-ml organ bath, were allowed to equilibrate for 15 min before the application of the extracts or fractions. The extracts (petroleum-ether extract (PE) and methanol extract (ME)) and the fractions (chloroform fraction (CHL), ethyl-acetate fraction (EA), n-butanol fraction (NB) and water fraction (WA) of the methanol extract) were tested at three concentrations (0.25, 0.5 and 1.0 mg/ml), with a β-adrenergic agonist (isoprenaline) as a control. All data on contraction responses were log-transformed and analyzed. When exposed to the different extracts, both atria tended to exhibit greater contractive responses with the NB whereas cardiac contractions had a tendency to be reduced with most other extracts. For a given extract, the contraction responses were particularly greater at 0.5 mg/ml for the right atrium and at 1 mg/ml for the left atrium. Further analysis focusing on the NB fraction revealed that positive inotropism was greater in left atria exposed to highly-concentrated F2 and F3 sub-fractions. Taken together, our results suggest that NB extracts and fractions from the G. procumbens-leaf methanol extract have positive inotropic activities and, hence, can be considered as an alternative/traditional medicine against increased blood pressure in humans or can be used in strategies aimed at finding antihypertensive biomolecules from an accessible source.
  8. Antioxidant versus anti-diabetic properties of leaves from Vernonia amygdalina Del. growing in Malaysia
    Atangwho IJ, Egbung GE, Ahmad M, Yam MF, Asmawi MZ
    Food Chem, 2013 Dec 15;141(4):3428-34.
    PMID: 23993503 DOI: 10.1016/j.foodchem.2013.06.047
    The antioxidant and anti-diabetic properties of the sequential extracts of Vernonia amygdalina based on the chemical composition of the most effective anti-diabetic extract were studied. Using DPPH and ABTS radical scavenging as well as FRAP assays, the extracts showed a consistent dose-dependent trend of potent antioxidant activity in the following solvents: water extract>methanol extract>chloroform extract>and petroleum ether extracts. In the oral glucose tolerance test, the chloroform extract exerted the highest response (33.3%), similar to metformin (27.2%), after 2h compared to the control (50.8%, P<0.05). After a 14-day administration in diabetic rats, the chloroform extract recorded the highest blood (23.5%) and serum (21.4%) glucose-lowering effects (P<0.05). GC-MS analysis of the chloroform extract revealed high levels of linoleic acid (4.72%), α-linolenic acid (10.8%) and phytols (12.0%), as well as other compounds.
  9. Fulltext Anti-hyperglycaemic activity of swietenia macrophylla king (meliaceae) seed extracts in normoglycaemic rats undergoing glucose tolerance tests
    Hashim MA, Yam MF, Hor SY, Lim CP, Asmawi MZ, Sadikun A
    Chin Med, 2013;8(1):11.
    PMID: 23684219 DOI: 10.1186/1749-8546-8-11
    Swietenia macrophylla King (Meliaceae) is used to treat diabetes mellitus in Malaysia. This study aims to evaluate the anti-hyperglycaemic potential of petroleum ether (PE), chloroform (CE) and methanol (ME) extracts of S. macrophylla seeds, in normoglycaemic and streptozotocin (STZ)-induced diabetic rats.
  10. Orthosiphon stamineus: traditional uses, phytochemistry, pharmacology, and toxicology
    Ameer OZ, Salman IM, Asmawi MZ, Ibraheem ZO, Yam MF
    J Med Food, 2012 Aug;15(8):678-90.
    PMID: 22846075 DOI: 10.1089/jmf.2011.1973
    Orthosiphon stamineus Benth. (Lambiaceae) is an important plant in traditional folk medicine. This review is a comprehensive summary of the currently available chemical, pharmacological, and toxicological investigations as well as the traditional and therapeutic uses of this plant. Different in vitro and in vivo models have been addressed along with a survey of all phytochemicals identified in this plant, including flavonoids, terpenoids, and essential oils. Previous studies revealed that O. stamineus possesses several pharmacological activities, which are attributed to its phytochemical content. It was found that O. stamineus exhibits diuretic, hypouricemic, renal protective, antioxidant, anti-inflammatory, hepatoprotective, gastroprotective, antihypertensive, antidiabetic, antihyperlipidemic, antimicrobial, and anorexic activities. In conclusion, O. stamineus has wide traditional and pharmacological uses in various pathophysiological conditions. Therefore, it is an attractive subject for further experimental and clinical investigations.
  11. Fulltext Bioactivity-guided isolation of ethyl-p-methoxycinnamate, an anti-inflammatory constituent, from Kaempferia galanga L. extracts
    Umar MI, Asmawi MZ, Sadikun A, Atangwho IJ, Yam MF, Altaf R, et al.
    Molecules, 2012 Jul 23;17(7):8720-34.
    PMID: 22825623 DOI: 10.3390/molecules17078720
    This study evaluated the anti-inflammatory effect of Kaempferia galanga (KG) using an activity-guided approach. KG rhizomes were serially extracted with petroleum ether, chloroform, methanol and water. These extracts (2 g/kg each) were tested for their ability to inhibit carrageenan-induced rat paw edema. The chloroform extract was found to exert the highest inhibition (42.9%) compared to control (p < 0.001), hence it was further fractionated by washing serially with hexane, hexane-chloroform (1:1) and chloroform. The chloroform fraction (1 g/kg) showed the highest inhibitory effect (51.9%, (p < 0.001), on carrageenan-induced edema. This chloroform fraction was further fractionated with hexane-chloroform (1:3) and chloroform, and of the two fractions, the hexane-chloroform sub-fraction was the most effective in inhibiting edema (53.7%, p < 0.001). GC-MS analysis of the active sub-fraction identified ethyl-p-methoxycinnamate (EPMC) as the major component, which was re-crystallized. EPMC dose-dependently inhibited carrageenan-induced edema with an MIC of 100 mg/kg. Moreover, in an in vitro study, EPMC non-selectively inhibited the activities of cyclooxygenases 1 and 2, with IC₅₀ values of 1.12 µM and 0.83 µM respectively. These results validate the anti-inflammatory activity of KG which may be exerted by the inhibition of cyclooxygenases 1 and 2. EPMC isolated from this plant may be the active anti-inflammatory agent.
  12. Screening of stepping forces in an arthritic rat model using a novel analgesic meter and data acquisition system
    Yam MF, Ahmad M, Por LY, Ang LF, Basir R, Asmawi MZ
    Sensors (Basel), 2012;12(7):9603-12.
    PMID: 23012561
    The stepping forces of normal and Freund Complete Adjuvant (FCA)-induced arthritic rats were studied in vivo using a proposed novel analgesic meter. An infrared charge-coupled device (CCD) camera and a data acquisition system were incorporated into the analgesic meter to determine and measure the weight of loads on the right hind paw before and after induction of arthritis by FCA injection into the paw cavity. FCA injection resulted in a significant reduction in the stepping force of the affected hind paw. The stepping force decreased to the minimum level on day 4 after the injection and then gradually increased up to day 25. Oral administration of prednisolone significantly increased the stepping forces of FCA-induced arthritic rats on days 14 and 21. These results suggest that the novel device is an effective tool for measuring the arthritic pain in in vivo studies even though walking is a dynamic condition.
  13. Acute and subchronic oral toxicity of Coriolus versicolor standardized water extract in Sprague-Dawley rats
    Hor SY, Ahmad M, Farsi E, Lim CP, Asmawi MZ, Yam MF
    J Ethnopharmacol, 2011 Oct 11;137(3):1067-76.
    PMID: 21767625 DOI: 10.1016/j.jep.2011.07.007
    Coriolus versicolor, which is known as Yun Zhi, is one of the commonly used Chinese medicinal herbs. Recent studies have demonstrated its antitumor activities on cancer cells which led to its widespread use in cancer patient. However, little toxicological information is available regarding its safety. The present study evaluated the potential toxicity of Coriolus versicolor standardized water extract after acute and subchronic administration in rats.
  14. Fulltext Antihyperglycemic effect of orthosiphon stamineus benth leaves extract and its bioassay-guided fractions
    Mohamed EA, Mohamed AJ, Asmawi MZ, Sadikun A, Ebrika OS, Yam MF
    Molecules, 2011 May 04;16(5):3787-801.
    PMID: 21544041 DOI: 10.3390/molecules16053787
    Preliminary investigations were carried out to evaluate the antidiabetic effects of the leaves of O. stamineus extracted serially with solvents of increasing polarity (petroleum ether, chloroform, methanol and water); bioassay-guided purification of plant extracts using the subcutaneous glucose tolerance test (SbGTT) was also carried out. Only the chloroform extract, given at 1 g/kg body weight (b.w.), significantly reduced (P < 0.05) the blood glucose level of rats loaded subcutaneously with 150 mg/kg (b.w.) glucose. The active chloroform extract of O. stamineus was separated into five fractions using a dry flash column chromatography method. Out of the five fractions tested, only chloroform fraction 2 (Cƒ2), at the dose of 1 g/kg (b.w.) significantly inhibited (P < 0.05) blood glucose levels in SbGTT. Active Cƒ2 was split into two sub-fractions Cƒ2-A and Cƒ2-B, using a dry flash column chromatography method. The activities Cƒ2-A and Cƒ2-B were investigated using SbGTT, and the active sub-fraction was then further studied for anti-diabetic effects in a streptozotocin-induced diabetic rat model. The results clearly indicate that Cƒ2-B fraction exhibited a blood glucose lowering effect in fasted treated normal rats after glucose-loading of 150 mg/kg (b.w.). In the acute streptozotocin-induced diabetic rat model, Cƒ2-B did not exhibit a hypoglycemic effect on blood glucose levels up to 7 hours after treatment. Thus, it appears that Cƒ2-B functions similarly to metformin, which has no hypoglycemic effect but demonstrates an antihyperglycemic effect only in normogycemic models. The effect of Cƒ2-B may have no direct stimulatory effects on insulin secretion or on blood glucose levels in diabetic animal models. Verification of the active compound(s) within the active fraction (Cƒ2-B) indicated the presence of terpenoids and, flavonoids, including sinensitin.
  15. Anti-inflammatory and analgesic effects of ketoprofen in palm oil esters nanoemulsion
    Sakeena MH, Yam MF, Elrashid SM, Munavvar AS, Azmin MN
    J Oleo Sci, 2010;59(12):667-71.
    PMID: 21099145
    Ketoprofen is a potent non-steroidal anti-inflammatory drug has been used in the treatment of various kinds of pains, inflammation and arthritis. However, oral administration of ketoprofen produces serious gastrointestinal adverse effects. One of the promising methods to overcome these adverse effects is to administer the drug through the skin. The aim of the present work is to evaluate the anti-inflammatory and analgesic effects from topically applied ketoprofen entrapped palm oil esters (POEs) based nanoemulsion and to compare with market ketoprofen product, Fastum(®) gel. The novelty of this study is, use of POEs for the oil phase of nanoemulsion. The anti-inflammatory and analgesic studies were performed on rats by carrageenan-induced rat hind paw edema test and carrageenan-induced hyperalgesia pain threshold test to compare the ketoprofen entrapped POEs based nanoemulsion formulation and market formulation. Results indicated that there are no significant different between ketoprofen entrapped POEs nanoemulsion and market formulation in carrageenan-induced rat hind paw edema study and carrageenan-induced hyperalgesia pain threshold study. However, it shows a significant different between POEs nanoemulsion formulation and control group in these studies at p<0.05. From these results it was concluded that the developed nanoemulsion have great potential for topical application of ketoprofen.
  16. Fulltext Anti-inflammatory and analgesic effects of Elephantopus tomentosus ethanolic extract
    Yam MF, Ang LF, Ameer OZ, Salman IM, Aziz HA, Asmawi MZ
    J Acupunct Meridian Stud, 2009 Dec;2(4):280-7.
    PMID: 20633503 DOI: 10.1016/S2005-2901(09)60069-8
    Elephantopus tomentosus is widely used in Asia, especially in Malaysia, for the treatment of pain and inflammation. In the present study, the analgesic and anti-inflammatory effects of a 95% ethanol extract of E. tomentosus were investigated in different experimental models. In the anti-inflammation study, 1000 mg/kg of extract significantly reduced carrageenan-induced hind paw edema (p < 0.05) and inhibited abdominal permeability compared with control (p < 0.01). The analgesic activity was assayed in several experimental models in mice: (1) hot plate, (2) tail flick, (3) writhing test; and rats: carrageenan-induced hyperalgesia pain threshold test. However, at the doses tested, no significant activity was found in the hot plate test and the tail flick test. E. tomentosus ethanol extract at 1000 mg/kg significantly (p < 0.05) increased hyperalgesia pain threshold and inhibited writhing activity. The results suggest that E. tomentosus ethanol extract at 1000 mg/kg dose is effective in anti-inflammatory and non-steroidal anti-inflammatory drug type anti-nociception activities.
  17. Toxicity evaluation of a standardised 50% ethanol extract of Orthosiphon stamineus
    Mohamed EA, Lim CP, Ebrika OS, Asmawi MZ, Sadikun A, Yam MF
    J Ethnopharmacol, 2011 Jan 27;133(2):358-63.
    PMID: 20937371 DOI: 10.1016/j.jep.2010.10.008
    The present investigation was carried out to evaluate the safety of standardised 50% ethanol extract of Orthosiphon stamineus plant by determining its potential toxicity after acute and subchronic administration in rats.
  18. Evaluation of the anti-pyretic potential of Orthosiphon stamineus Benth standardized extract
    Yam MF, Ang LF, Basir R, Salman IM, Ameer OZ, Asmawi MZ
    Inflammopharmacology, 2009 Feb;17(1):50-4.
    PMID: 19127348 DOI: 10.1007/s10787-008-8038-3
    The anti-pyretic activity of a standardized methanol/water (50/50) extract of Orthosiphon stamineus Benth. (SEOS) was investigated for its effect on normal body temperature and yeast-induced pyrexia in Sprague Dawley (SD) rats. The SEOS showed no effect on normal body temperature. Doses of 500 and 1000 mg/kg body weight of SEOS significantly reduced the yeast-induced elevation in body temperature. This effect persisted up to 4 h following the administration of the extract. The anti-pyretic effect of SEOS was comparable with that of paracetamol (acetaminophen in U.S) (150 mg/kg p.o.), a standard anti-pyretic agent. HPLC study revealed that rosmarinic acid, sinensetin, eupatorin and tetramethoxyflavone were present in SEOS in the amounts of 7.58%, 0.2%, 0.34% and 0.24% respectively. The LD(50) of the extract in rats was higher than 5000 mg/kg body weight. Therefore, the present study ascertained that SEOS possesses a significant anti-pyretic activity.
  19. Fulltext Antidiabetic properties and mechanism of action of Orthosiphon stamineus Benth bioactive sub-fraction in streptozotocin-induced diabetic rats
    Mohamed EA, Yam MF, Ang LF, Mohamed AJ, Asmawi MZ
    J Acupunct Meridian Stud, 2013 Feb;6(1):31-40.
    PMID: 23433053 DOI: 10.1016/j.jams.2013.01.005
    Orthosiphon stamineus is a popular folk medicine widely used to treat many diseases including diabetes. Previous studies have shown that the sub-fraction of chloroform extract was able to inhibit the rise of blood glucose levels in a glucose tolerance test. This study was carried out to evaluate the chronic effect and possible mechanism of action of the bioactive chloroform sub-fraction of O. stamineus using streptozotocin-induced diabetic rats and in vitro methods. Administration of the chloroform extract sub-fraction 2 (Cƒ2-b) at a dose of 1 g/kg twice daily on diabetic rats for 14 days showed a significant lowering (p < 0.05) of the final blood glucose level compared to the pretreatment level. However, there were no significant differences in the plasma insulin levels post-treatment compared to the pretreatment levels for all doses of Cƒ2-b. Conversely, Cƒ2-b at a concentration of 2 mg/mL significantly increased (p < 0.001) the glucose uptake by the rat diaphragm muscle. The increase in glucose uptake was also shown when the muscle was incubated in a solution containing 1 IU/mL of insulin or 1 mg/mL of metformin. Furthermore, the effect of this sub-fraction on glucose absorption in the everted rat jejunum showed that Cƒ2-b at concentrations of 0.5 mg/mL, 1 mg/mL and, 2 mg/mL significantly reduced the glucose absorption of the jejunum (p < 0.05-0.001). Similarly, the absorption of glucose was also inhibited by 1 mg/mL and 2 mg/mL of metformin (p < 0.001). These results suggest that the effect of Cƒ2-b may be due to extra-pancreatic mechanisms. There was no evidence that the plant extract stimulated the release of insulin in order to lower the blood glucose level.
  20. Fulltext Overview of Antagonists Used for Determining the Mechanisms of Action Employed by Potential Vasodilators with Their Suggested Signaling Pathways
    Loh YC, Tan CS, Ch'ng YS, Ahmad M, Asmawi MZ, Yam MF
    Molecules, 2016 Apr 15;21(4):495.
    PMID: 27092479 DOI: 10.3390/molecules21040495
    This paper is a review on the types of antagonists and the signaling mechanism pathways that have been used to determine the mechanisms of action employed for vasodilation by test compounds. Thus, we exhaustively reviewed and analyzed reports related to this topic published in PubMed between the years of 2010 till 2015. The aim of this paperis to suggest the most appropriate type of antagonists that correspond to receptors that would be involved during the mechanistic studies, as well as the latest signaling pathways trends that are being studied in order to determine the route(s) that atest compound employs for inducing vasodilation. The methods to perform the mechanism studies were included. Fundamentally, the affinity, specificity and selectivity of the antagonists to their receptors or enzymes were clearly elaborated as well as the solubility and reversibility. All the signaling pathways on the mechanisms of action involved in the vascular tone regulation have been well described in previous review articles. However, the most appropriate antagonists that should be utilized have never been suggested and elaborated before, hence the reason for this review.
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