Displaying publications 1 - 20 of 36 in total

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  1. Ang HH
    Food Chem Toxicol, 2008 Jun;46(6):1969-75.
    PMID: 18328612 DOI: 10.1016/j.fct.2008.01.037
    The Drug Control Authority (DCA) of Malaysia implemented the phase three registration of traditional medicines on 1 January, 1992. A total of 100 products in various pharmaceutical dosage forms of a herbal preparation, containing Eugenia dyeriana, either single or combined preparations (more than one medicinal plant), were analyzed for the presence of lead contamination, using atomic absorption spectrophotometry. These samples were bought from different commercial sources in the Malaysian market, after performing a simple random sampling. Results showed that 22% of the above products failed to comply with the quality requirement for traditional medicines in Malaysia. Although this study showed that 78% of the products fully complied with the quality requirement for traditional medicines in Malaysia pertaining to lead, however, they cannot be assumed safe from lead contamination because of batch-to-batch inconsistency.
  2. Ang HH, Cheang HS
    Chemotherapy, 1999 Nov-Dec;45(6):446-51.
    PMID: 10567775
    Thirty clones were obtained from five Malaysian Plasmodium falciparum isolates using the limiting dilution method. These clones were then subjected to antimalarial testing using the modified in vitro microtechnique. The results showed that ST 85/B3, GC/C10 and ST 85/A2 clones decreased their susceptibilities to 19, 41 and 28% whilst ST 12/F8, ST 85/B3 and ST 85/B3 clones showed increases of 6, 43 and 21%, respectively, against chloroquine, mefloquine and quinine after cryopreservation. Further results also indicated that GC/B4, GC/B7, GC/C10, ST 85/A5, ST 85/D3, ST 148/F8 clones did not show any change (up to 2 decimal places) against chloroquine, ST 12/D5, ST 12/E8, ST 12/F8, ST 148/A5 clones against quinine after cryopreservation. They, however, maintained their original susceptibilities after cryopreservation.
  3. Ang HH, Lee KL
    Food Chem Toxicol, 2006 Aug;44(8):1245-50.
    PMID: 16567029 DOI: 10.1016/j.fct.2006.01.014
    The DCA (Drug Control Authority), Malaysia has implemented the phase three registration of traditional medicines on 1 January 1992. As such, a total of 100 products in various pharmaceutical dosage forms of a herbal preparation found in Malaysia, containing tongkat Ali hitam, either single or combined preparations, were analyzed for the presence of a heavy toxic metal, mercury, using atomic absorption spectrophotometer, after performing a simple random sampling to enable each sample an equal chance of being selected in an unbiased manner. Results showed that 26% of these products possessed 0.53-2.35 ppm of mercury, and therefore, do not comply with the quality requirement for traditional medicines in Malaysia. The quality requirement for traditional medicines in Malaysia is not exceeding 0.5 ppm for mercury. Out of these 26 products, four products have already registered with the DCA, Malaysia whilst the rest, however, have not registered with the DCA, Malaysia.
  4. Ang HH, Lee KL
    Fundam Clin Pharmacol, 2002 Dec;16(6):479-83.
    PMID: 12685506 DOI: 10.1046/j.1472-8206.2002.00106.x
    The effects of various fractions of Eurycoma longifolia Jack were studied on the orientation activities of the inbred, adult middle-aged Sprague-Dawley rats, 9 months old and retired breeders towards the receptive females (anogenital sniffing, licking, mounting), the environment (climbing, raring, exploration), themselves (nongenital grooming, genital grooming) and mobility (restricted, unrestricted) after treating these subjects twice daily for 10 days. Results showed that subjects treated with 800 mg/kg of E. longifolia Jack increased orientation activities towards the receptive females (anogenital sniffing, licking and mounting), increased genital grooming towards themselves and restricted movements to a particular area of the cage but decreased interest in the external environment (climbing, raring, exploration) as compared with the controls during the investigation period. In conclusion, this study gives further evidences that different fractions of E. longifolia Jack modified the orientation activities of the middle-aged male rats.
  5. Ang HH, Lee KL
    J Basic Clin Physiol Pharmacol, 2002;13(3):249-54.
    PMID: 12670032 DOI: 10.1515/jbcpp.2002.13.3.249
    The effect of increasing doses of various fractions of Eurycoma longifolia Jack extracts on libido was examined in middle-aged male rats. The results showed that a high dose (800 mg/kg) of all E. longifolia Jack extracts significantly increased mount frequency (MF) (P < 0.05) over that of untreated controls, but had no effect on the frequency of intromission or ejaculation. Methanol, chloroform, water, and butanol fractions exhibited MF of 2.5 +/- 0.1, 2.6 +/- 0.3, 2.5 +/- 0.1 and 2.6 +/- 0.2, respectively, in adult, middle-aged male rats, and retired breeders versus 2.3 +/- 0.1 in untreated controls. This translated to a minor increase in MF of 8.7%, 13.0%, 8.7%, and 13.0% for these fractions, respectively, during the 20-minute observation period. The results of this study show that E. longifolia Jack extracts can increase libido in middle-aged male rats.
  6. Ang HH, Cheang HS
    Jpn. J. Pharmacol., 1999 Apr;79(4):497-500.
    PMID: 10361892 DOI: 10.1254/jjp.79.497
    The anxiolytic effect of Eurycoma longifolia Jack in mice was examined. Fractions of E. longifolia Jack extract produced a significant increase in the number of squares crossed (controls= 118.2 +/- 10.2 squares), but significantly decreased both the immobility (controls = 39.4+/- 4.0 sec) and fecal pellets (controls= 12.3 +/-2.1 fecal pellets) when compared with control mice in the open-field test; they significantly increased the number of entries (controls=6.7+/-0.5 entries) and time spent (controls=42.9+/-0.1 sec) in the open arms, but decreased both the number of entries (controls= 13.2+/-0.7 entries) and time spent (controls= 193.4+/-0.7 sec) when compared with the control mice in the closed arms of the elevated plus-maze test. Furthermore, fractions of E. longifolia Jack extract decreased the fighting episodes significantly (controls= 18.0+/-0.4 fighting episodes) when compared with control mice. In addition, these results were found to be consistent with anxiolytic effect produced by diazepam. Hence, this study supports the medicinal use of this plant for anxiety therapy.
  7. Ang HH, Sim MK
    Biol Pharm Bull, 1998 Feb;21(2):153-5.
    PMID: 9514610 DOI: 10.1248/bpb.21.153
    The effects of Eurycoma longifolia JACK were studied on the orientation activities of sexually experienced male rats towards receptive females (mounting, licking, anogenital sniffing), environment (exploration, raring, climbing), themselves (genital grooming, non-genital grooming) and mobility (unrestricted, restricted) after dosing them with 200, 400 and 800 mg/kg body weight twice daily for 10 d prior to the test. The results showed that E. longifolia JACK modified the orientation activities of the treated male rats in that they significantly displayed more frequent and vigorous mounting, licking and anogenital sniffing towards the receptive females, and it further intensified self orientation as indicated by the increased grooming of the genitals compared to the controls (p<0.05). In addition, rats treated with 800 mg/kg of methanol, water and butanol extracts of E. longifolia JACK continued to show confinement to a particular area of the cage (around the female), thus showing restriction in movement as compared to the controls (p<0.05). However, the treated males possessed a lack of interest in the external environment as indicated by a reduction in exploration, raring and climbing on the cage wall. Hence, the present study further supports the folk use of E. longifolia JACK as an aphrodisiac.
  8. Ang HH, Sim MK
    Exp Anim, 1997 Oct;46(4):287-90.
    PMID: 9353636 DOI: 10.1538/expanim.46.287
    The effects of Eurycoma longifolia Jack were studied on the libido of sexually experienced male rats after dosing them with 200, 400 and 800 mg/kg body weight twice daily of different fractions of E. longifolia Jack for 10 days. Results showed that E. longifolia Jack produced a dose-dependent increase in mounting frequency of the treated animals with 400 mg/kg of chloroform, methanol, water and butanol fractions resulting in mounting frequencies of 5.3 +/- 1.2, 4.9 +/- 0.7, 4.8 +/- 0.7 and 5.2 +/- 0.1, and 800 mg/kg further increased them to 5.4 +/- 0.8, 5.4 +/- 0.8, 5.2 +/- 0.6 and 5.3 +/- 0.2 respectively but there were no erections, intromissions, ejaculations or seminal emissions during the 20-min observation period which allowed for the measurement of sexual arousal reflected by mounting frequency uninfluenced by other behavioural components. This study provides evidence that E. longifolia Jack is a potent stimulator of sexual arousal in sexually vigorous male rats in the absence of feedback from genital sensation.
  9. Ang HH, Ngai TH
    Fundam Clin Pharmacol, 2001 Aug;15(4):265-8.
    PMID: 11564133 DOI: 10.1046/j.1472-8206.2001.00038.x
    The aphrodisiac effect of Eurycoma longifolia Jack (0.5 g/kg) was evaluated in noncopulator male rats using an electrical cage. Fractions of E. longifolia Jack decreased the hesitation time of noncopulator male rats, throughout the investigation period. Furthermore, it possessed a transient increase in the percentage of the male rats responding to the right choice, more than 50% of the male rats scored "right choice" after 3 weeks post-treatment and the effect became more prominent after 8 weeks post-treatment (only 40-50% of the control male rats responded to the right choice) using the electrical copulation cage. Hence, this study lends further support to the use of the plant by indigenous populations as a traditional medicine for its aphrodisiac property.
  10. Ang HH, Sim MK
    Arch Pharm Res, 1997 Dec;20(6):656-8.
    PMID: 18982276 DOI: 10.1007/BF02975228
    The effects ofEurycoma longifolia Jack were studied on the sexual behaviour of male rats. Sexually normal male rats were treated twice daily with 500 mg kg(-1) of different fractions ofE. longifolia Jack for 10 days prior to test and were then observed for their copulatory behaviour with a receptive female in a copulation cage. Results showed that was a significant increase (p<0.05) in EL-1, EL-2, EL-3 but significant decrease (p<0.05) in both PEI-1 and PEI-2 in treated male rats as compared to the control male rats indicating thatE. longifolia Jack increased the sexual performance of the treated male rats by extending the duration of coitus and decreasing the refractory period between the different series of copulation. Hence, this preliminary work supports the folk use of this plant as having aphrodisiac property.
  11. Ang HH, Cheang HS
    Arch Pharm Res, 2001 Oct;24(5):437-40.
    PMID: 11693547 DOI: 10.1007/BF02975191
    It has been reported that Eurycoma longifolia Jack commonly known as Tongkat Ali has gained notoreity as a symbol of man's ego and strength by the Malaysian men because it increases male virility and sexual prowess during sexual activities. As such, the effects of 200, 400 and 800 mg/kg of butanol, methanol, water and chloroform fractions of E. longifolia Jack were studied on the laevator ani muscle in both uncastrated and testosterone-stimulated castrated intact male rats after dosing them for 12 consecutive weeks. Results showed that 800 mg/kg of butanol, methanol, water and chloroform fractions of E. longifolia Jack significantly increased (p<0.05) the leavator ani muscle to 58.56+/-1.22, 58.23+/-0.31, 60.21 +/-0.86 and 62.35 +/-0.98 mg/100 g body weight, respectively, when compared with the control (untreated) in the uncastrated intact male rats and 49.23+/-0.82, 52.23+/-0.36, 50.21+/-0.66 and 52.35+/-0.58 mg/100 g body weight, respectively, when compared to control (untreated) in the testosterone-stimulated castrated intact male rats. Hence, the pro-androgenic effect as shown by this study further supported the traditional use of this plant as an aphrodisiac.
  12. Ang HH, Sim MK
    Arch Pharm Res, 1998 Dec;21(6):779-81.
    PMID: 9868556 DOI: 10.1007/BF02976776
    The aim of this study is to provide evidence on the aphrodisiac property of Eurycoma longifolia Jack. An electric grid was used as an obstruction in the electrical copulation cage in order to determine how much an aversive stimulus the sexually naive male rat for both the treated with E. longifolia Jack and control groups were willing to overcome to reach the estrous receptive female in the goal cage. The intensity of the grid current was maintained at 0.12 mA and this was the intensity in which the male rats in the control group failed to crossover to reach the goal cage. Results showed that E. longifolia Jack continued to enhance and also maintain a high level of both the total number of successful crossovers, mountings, intromissions and ejaculations during the 9-12th week observation period. In conclusion, these results further enhanced and strengthened the aphrodisiac property of E. longifolia Jack.
  13. Ang HH, Lee KL
    Int J Toxicol, 2007 Sep-Oct;26(5):433-9.
    PMID: 17963130 DOI: 10.1080/10915810701583036
    The DCA (Drug Control Authority) of Malaysia implemented phase 3 registration of traditional medicines in January 1992 with special emphasis on the quality, efficacy, and safety of all dosage forms of these medicines. For this reason, a total of 100 herbal products containing Smilax myosotiflora were purchased in the Malaysian market and analyzed for mercury content, as mercury is a recognized reproductive toxicant. The products were analyzed using cold vapor atomic absorption spectrophotometry. It was found that 89% of the above products do not exceed 0.5 ppm of mercury. Heavy metal poisoning such as mercury has been associated with traditional medicines. Therefore, it is important that doctors and health care practitioners are aware of these risks and finding ways to minimize them, including questions pertaining to the use of these remedies during the routine taking of a patient's history.
  14. Ang HH, Lee KL, Kiyoshi M
    Int J Environ Health Res, 2004 Aug;14(4):261-72.
    PMID: 15369991
    The DCA (Drug Control Authority), Malaysia implemented the phase 3 registration of traditional medicines on 1 January 1992 with special emphasis on the quality, efficacy and safety (including the presence of heavy metals) in all pharmaceutical dosage forms of traditional medicinal preparations. As such, a total of 100 traditional medicinal preparations, containing Smilax myosotiflora, in various pharmaceutical dosage forms, which were bought in the Malaysian market, were analysed for lead content using atomic absorption spectrophotometry. Results showed that 15% of the products analysed possessed 10.23-23.05 ppm of lead, and therefore, do not comply with the quality requirement for traditional medicines in Malaysia. The quality requirement for traditional medicines in Malaysia is that they should not exceed 10 ppm of lead. Out of these 15 products, five products exhibited 10.23-23.05 ppm of lead, in fact they have already been registered with the DCA Malaysia. However, the rest of the products, which possessed 12.24-20.72 ppm of lead, have still not been registered with the DCA Malaysia. Although this study successfully showed that only 85% of the products complied with the quality requirement for traditional medicines in Malaysia pertaining to lead, they cannot, however, be assumed to be safe from lead contamination because of batch-to-batch inconsistency.
  15. Ang HH, Cheang HS, Mak JW
    Chemotherapy, 2005 Oct;51(6):377-80.
    PMID: 16227695
    Exposure of Plasmodium falciparum to increasing sublethal drug concentrations followed by drug treatment led to the development of many resistant parasites. Therefore, the susceptibility of these clones to the type II antifolate drugs, cycloguanil and pyrimethamine, before and after subculturing them in vitro for a period of 3 years, was studied.
  16. Ang HH, Chan KL, Mak JW
    Folia Parasitol., 1998;45(3):196-8.
    PMID: 9805783
    Five Malaysian isolates of the protozoan Plasmodium falciparum Welch were cultured in vitro following the method of Trager and Jensen (1976, 1977) and subsequently cloned using the limiting dilution method of Rosario (1981). Thirty clones were obtained and were later characterized against schizontocidal drugs, chloroquine, mefloquine and quinine, using the modified in vitro microtechnique. Results showed that these local isolates were heterogeneous and most of the clones exhibited similar pattern of susceptibility as their parent isolate except for ST 168 clone and two ST 195 clones that were sensitive but two ST 165 clones, two ST 168 clones and five ST 195 clones were resistant against quinine, respectively. Results also indicated that they were pure clones compared to their parent isolate because their drug susceptibility studies were significantly different (p < 0.05).
  17. Ang HH, Chan KL, Mak JW
    Folia Parasitol., 1997;44(2):128-30.
    PMID: 9269721
    Six clones were obtained from each Plasmodium falciparum (Welch, 1897) isolate from different geographical areas, Gombak A (Malaysian), Gombak C (Malaysian), ST 9 (Malaysian, ST 12 (Malaysian), ST 85 (Malaysian, ST 148 (Malaysian), Gambian (African) and TGR (Thailand) isolates using the limiting dilution method (Rosario 1981). Forty-eight clones were obtained and were characterized by an electrophoresis isoenzyme analysis of PEPE (Peptidase E) (EC. 3.4.11 or 13). Results showed that they were pure clones as they were monovariant with regards to this enzyme unlike their parent isolates which were divariant.
  18. Ang HH, Chan KL, Mak JW
    Med Trop (Mars), 1996;56(4):349-51.
    PMID: 9112620
    Six clones were derived from each of five isolates of Malaysian Plasmodium falciparum and characterized with regard to susceptibility to schizontocidal drugs, chloroquine, mefloquine, and quinine. The 5 isolates were found to be resistant to chloroquine and sensitive to mefloquine and quinine. Most of the clones displayed susceptibility patterns similar to those of their parent isolate, except ST9/D8 clone which became sensitive to chloroquine, C/C10 and ST148/A5 clones which became resistant to mefloquine and to quinine respectively. This diversity in susceptibility to schizontocidal drugs would likely have been overlooked by assessment of natural uncloned isolates against antimalarial drugs.
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