This paper attempts to examine the real values of Malaysian herbal products in the aspects of quality, safety and efficacy as curing agents. In so doing it will also determine the driving force behind the intense public interest for herbal medicine as alternative or complementary to conventional medicine. Most herbal products in the Malaysian market are not sufficiently provided with information on their ingredients, indications, dosage, pharmacology, contraindications and possible side-effects. Most published information on the products on evidence of safety and efficacy is not supported with scientific evidence. The present practice of traditional medicine still depend heavily on information obtained through ethnopharmacological experiences. However, the herbal product market is experiencing a tremendous growth and there is an increased trend of incorporating herbal therapy into modern medical practice by many mainstream health professionals. Unfortunately, the popularity of herbal products is more associated with consumer attitudes and the ability of the herbalists to influence rather than their true quality as medicinal agents. Many people are exploited due to ignorance on the real value of herbals as therapeutic agents. It is especially disappointing when popular media, promotional literature and talk shows by individuals promoting quackery are given much publicity. Even worse, many individuals trained in the health sciences are promoting quackery. This has often left the consumers with the perception that the authority condones the improper use of herbal products. Thus, it is important for pharmacists and physicians to be trained in traditional herbal medicine so that they can educate the public on the benefits, quality, safety and proper use of herbal products.
This paper outlines the past five decades of scientific interests and advances in medicinal plant research in Malaysia. Initially the prime interest of research programmes has been on phytochemical studies leading to the discovery of biologically active compounds as chemical templates to produce new drug candidates. As the Malaysian herbal medicine market experiences an extraordinary growth, the research approaches taken have recently included activities to develop herbal medicines into quality, efficacious and safe products for human consumption. Advances in chromatographic and spectroscopic techniques have had a tremendous impact on the isolation and structure elucidation of the constituents of medicinal plants. The development of a series of bioassay methodologies and utilization of bioassay-guided isolation techniques have contributed significantly to the progress of medicinal plant research in Malaysia. Research work on some medicinal plants carried out by the local scientists will be illustrated as examples.
Introduction: Inhibition of the cholinesterase’s function leads to paralysis and death. This mechanism is served as a common mode of action of insecticide. The three tropical seaweeds, namely Bryopsis pennata, Padina australis and Sargassum binderi were reported for its potential mosquito larvicidal effect. In the present study, these seaweeds were evaluated for their potential as a cholinesterase inhibitor in the mechanism of larvicidal action. Methods: Ace- tylcholinsterase (AChE) inhibition assay was carried out based on the colorimetric method using a microplate reader. Phytochemical content of the seaweed extracts was screened by using liquid chromatography-mass spectroscopy (LC-MS). Results: Green seaweed B. pennata showed the strongest inhibition effect towards in vitro AChE by using
tissue homogenates of Aedes aegypti (IC50 value = 0.84 mg mL ) and Aedes albopictus as the enzyme source (IC
-1
value = 0.92 mg mL-1). The pattern of Lineweaver-Burk plots revealed that B. pennata was a mixed type inhibitor of
AChE, as the readings of Km, Vmax, Ki and Ki’, indicates that it had a strong inhibition ability with high binding affin- ity towards both free enzyme and enzyme-substrate complex. Conclusion: These findings suggest the compound(s) in
B. pennata extract serves as a promising source that could be developed into a mosquito larvicidal agent with AChE inhibition effect.
The leaf and bark oils of Cinnamomum verum J.S. Presl. were examined for their antifungal activity against 6 dermatophytes (Trichophyton rubrum, T. mentagrophytes, T. tonsurans, Microsporum canis, M. gypseum and M. audouini), one filamentous fungi (Aspergillus fumigatus) and 5 strains of yeasts (Candida albicans, Ca. glabrata, Ca. tropicalis, Ca. parapsilosis and Crytococcus neoformans) by using the broth microdilution method. The antifungal activities of 4 standard compounds (cinnamaldehyde, eugenol, linalool and a-terpineol) which were major constituents in the oils were also investigated in an effort to correlate the effectiveness of the oils with those of the components of the oils. The combined antifungal effect of the oils against M. canis, M. gypseum and Cr. neoformans was investigated by the checkerboard assay. Isobolograms were constructed and Fractional Inhibitory Concentrations Index (FICI) were calculated to determine the combination effects between the oils. The chemical composition of the oils was analyzed by gas chromatography (GC) and gas chromatography- mass spectrometry (GC-MS). The oils showed strong activity against all the tested fungi with Minimum Inhibition Concentration (MIC) values ranging from 0.04 to 0.31 mg/ml. Cinnamaldehyde which was the most abundant component of the bark oil of C. verum showed the strongest activity against all the fungi studied. Based on the results of the assay on standard samples, it may be that the high levels of cinnamaldehyde and eugenol in the oils and in combination with the minor components could be responsible for the high antifungal activity of the oils. The antifungal effect of the leaf and bark oils of C. verum in combination against the tested fungi was not synergistic. However, the effect was additive against M. gypseum and antagonistic against Cr. neoformans and M. canis.
Xanthine oxidase (XO) is an enzyme that catalyzes the metabolism of hypoxanthine and xanthine into uric acid. XO also serves as an important biological source of free radicals that contribute to oxidative damage involved in many pathological processes. Antioxidant effects of several Primulaceae species have been reported but their XO inhibitory activity has not been investigated. Thus, this study was conducted to determine the XO inhibitory and free radical scavenging activities of Primulaceae species and to correlate these activities with their total phenolic contents (TPC). A total of 129 extracts of different plant parts of twelve Primulaceae species were assayed for XO inhibition spectrophotometrically at 290 nm using allopurinol as a positive control. The antioxidant activity was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and TPC of the extracts were determined by the Folin-Ciocalteau method. The Pearson correlation analysis indicated that the TPC of the extracts showed moderate positive correlations with XO inhibition (r=0.31, p<0.05) and DPPH antioxidant activity (r=0.31, p<0.05) for all of the dichloromethane extracts. Amongst the extracts tested, the dichloromethane extract of the roots of Labisia pumila var. alata showed the strongest inhibitory effects for XO (IC50 4.8 μg/mL) and DPPH free radical capacity (IC50 1.7 μg/mL). The results suggested that Primulaceae species, particularly the dichloromethane extract of L. pumila var. alata roots, are the potential source of useful leads for the development of XO inhibitors.
The water decoction of Labisia pumila var. alata is used traditionally in childbirth, as well as for the treatment of flatulence, dysentery, dysmenorrhoea and join pains. This study was carried out to determine the best method and optimum parameters of aqueous axtraction of the leaves and roots of this species. The laboratory methos esed were maceration, ddecoction, reflux and Saxhlet, whereas the parameters studied were temperature, duration and pH of axtraction. The yields and thin layer chromatographic profiles of the freeze-dried extracts were analysed. The study showed that in general the percentage yields of the water soluble extracts were higher for the roots than the leaves, as well as the extracts obtained from heating than those obtained at room temperature. The most effective extraction parameters for L. pumila var. alata were as follows:maceration (25 C, at least 6 hr), decoction (60 C, not exceeding 10 min) and reflux (100 C, not exceeding 4 hr). Saxhlet method was found to be the least effective. The pH analysis had shown the possibility of degradation of some of the phytochemicals at extreme pH values of 1,2 and 14.
The chemical compositions of the leaf and bark oils of Xylopia caudata were examined by co-chromatography with authentic samples on a polar capillary column (PEG 20M) and a non polar capillary column (SE-30), GC/MS and further comparison with Kovats Retention Index. The essential oils were mainly made up of monoterpenoids. The major components in both oils were β-pinene, α-pinene, limonene and a-terpineol which collectively represented 90% and 69% of the leaf and bark oils respectively.
Kandungan kimia minyak pati daun dan kulit kayu Xylopia caudata telah dikaji secara ko-kromatografi dengan sampel tulen di atas turus rerambut polar (PEG 20M) dan turus rerambut kurang polar (SE-30), KG/SJ dan perbandingan dengan Indeks Penahanan Kovats. Sebahagian besar minyak pati tersebut terdiri daripada sebatian monoterpenoid. Komponen utama yang terdapat dalam kedua-dua minyak pati tersebut adalah β-pinena, α-pinena, limonena dan a-terpineol yang mewakili 90% dan 69% daripada minyak pati daun dan kulit kayu masing-masing.