Sanan Subhadhirasakul

Studies on the indole alkaloids of gelsem1um elegans (thailand): structure elucidation and proposal of biogenetic route

Abstract Chemical investigation of the roots of Gelsemium elegans collected in Thailand resulted in the isolation of the new indole alkaloids, 16-epi-voacarpine, 19-hydroxydihydrogelsevirine, and 19-(Z)-taberpsychine, along with eight known bases. Among them, the structure of “akuammidine” and koumidine were revised to have 19-(Z) ethylidene configuration. From the seeds of G. elegans 14-hydroxygelsedine was obtained. Furthermore, three new alkaloids, koumine N-oxide, gelsemine N-oxide, and 19-oxo-gelsenicine, were found from the leaves of G. elegans . A new and plausible biogenetic route of gelsemium alkaloids is proposed.

Antifungal activities of extracts from Thai medicinal plants against opportunistic fungal pathogens associated with AIDS patients

In this study, 36 extracts derived from 10 plant species were selected to screen for their antifungal activity against clinical isolates of Candida albicans, Cryptococcus neoformans and Microsporum gypseum. Selection was based on their use by traditional Thai healers or their reported antimicrobial activities in an attempt to find bioactive medicines for use in the treatment of opportunistic fungal infections in AIDS patients. The disc diffusion and hyphal extension–inhibition assays were primarily used to test for inhibition of growth. Minimum inhibitory concentration was determined by dilution methods. The chloroform extracts of Alpinia galanga and Boesenbergia pandurata had pronounced antifungal activity against C. neoformans and M. gypseum, but exhibited weak activity against C. albicans. Alpinia galanga and B. pandurata are excellent candidates for the development of a remedy for opportunistic fungal infections in AIDS patients.

Cassane diterpenoids from the stem of Caesalpinia pulcherrima.

Cassane diterpenoids: pulcherrin A, pulcherrin B, pulcherrin C, neocaesalpin P, neocaesalpin Q and neocaesalpin R, together with eight known compounds: isovouacapenol C, 6beta-cinnamoyl-7beta-hydroxy-vouacapen-5alpha-ol, pulcherrimin E, pulcherrimin C, alpha-cadinol, 7-hydroxycadalene, teucladiol and bonducellin were isolated from the stem of Caesalpinia pulcherrima. The chemical structures were elucidated by analysis of their spectroscopic data.

Evaluation of Antibacterial Activities of Medicinal Plants Widely Used Among AIDS Patients in Thailand

Abstract Antibacterial activity of 12 selected Thai medicinal plants used as self-medication by HIV/AIDS patients in Thailand was studied. Thirty-nine chloroform, methanol, and aqueous extracts from these plants were investigated for their antibacterial activity against important pathogenic bacteria commonly associated with AIDS infection. These included Staphylococcus aureus., methicillin-resistant Staphylococcus aureus. (MRSA), Streptococcus mutans., and Salmonella typhi.. Inhibition of growth was tested using paper disk agar diffusion method. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by agar microdilution method and agar dilution method in Petri dishes with millipore filters. The Gram-positive bacteria were proved to be susceptible to the chloroform extracts of Alpinia galanga. (L.) Willd., Boesenbergia rotunda. Mansf. (L.), Piper betle. (L.), Spilanthes acmella. (L.) Murray, and Zingiber zerumbet. (L.) Roscoe ex Sm. and the methanol extract of Boesenbergia rotunda.. Chloroform extract of Alpinia galanga. demonstrated the greatest inhibition zones of 29.1 and 23.7 mm against Staphylococcus aureus. and MRSA, respectively. The MIC values of this extract against Staphylococcus aureus. and MRSA were 128 and 256 µg/ml and the MBC values were 256 and 256 µg/ml, respectively. An active compound, 1′-acetoxy-chavicol acetate, was identified with MIC values against MRSA and Staphylococcus aureus. of 64 and 128 µg/ml, respectively.

Inhibitory effects of corymine, an alkaloidal component from the leaves of Hunteria zeylanica, on glycine receptors expressed in Xenopus oocytes.

We previously reported that corymine, an alkaloidal compound extracted from the leaves of Hunteria zeylanica native to Thailand, potentiated convulsions induced by either picrotoxin or strychnine. Therefore, to clarify the mechanism of action of corymine, the effects of corymine on gamma-aminobutyric acid (GABA) and glycine receptors were examined. We used Xenopus oocytes expressing these receptors and the two-electrode voltage-clamp method. The receptors expressed in oocytes injected with rat brain and spinal cord RNA showed the pharmacological properties of GABAA and glycine receptors, respectively. Corymine (1-100 microM) partially (20-30%) reduced the GABA responses in oocytes injected with rat brain RNA, while marked (up to 80%) dose-dependent reductions were observed in the glycine responses in oocytes injected with rat spinal cord RNA. These observations suggest that corymine was more effective against the glycine receptors than the GABA receptors. The ED50 of corymine on the glycine response was 10.8 microM. Corymine, at 30 microM, caused a shift to the right, with a lower maximal response, of the glycine concentration-response curve. This indicated that the action of corymine on glycine receptors is neither competitive nor purely non-competitive. These observations suggest that a binding site other than the glycine recognition site of the glycine receptors is the site of action of corymine.

Antiinflammatory constituents from Eclipta prostrata using RAW264.7 macrophage cells.

The whole plant extract of Eclipta prostrata and its isolated compounds were tested for their antiinflammatory effects against lipopolysaccharide (LPS)‐induced nitric oxide (NO), prostaglandin E2 (PGE2) and tumor necrosis factor‐alpha (TNF‐α) release in RAW264.7 cells, as well as for the antiinflammatory mechanism of the active compound on mRNA expression. Among the isolated compounds, orobol (5) exhibited the highest activity against NO release with an IC50 value of 4.6 μm, followed by compounds 1, 2 and 4 with IC50 values of 12.7, 14.9 and 19.1 μm, respectively. The IC50 value of compound 5 against PGE2 release was found to be 49.6 μm, whereas it was inactive towards TNF‐α (IC50 > 100 μm). The mechanism of orobol (5) was found to down‐regulate iNOS and COX‐2 mRNA expression in a concentration‐dependent manner. The present study may support the traditional use of Eclipta prostrata for the treatment of inflammatory‐related diseases. Copyright

Medicinal plants with significant activity against important pathogenic bacteria

Interest in the study of medicinal plants as a source of pharmacologically active compounds has increased worldwide. This study is a broad screening of 31 plant species against a wide range of pathogenic bacteria, including Acinetobacter baumannii, Bacillus cereus, Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Listeria monocytogenes, Pseudomonas aeruginosa, Salmonella spp., Shigella flexneri, Staphylococcus aureus, Streptococcus mutans, and Streptococcus pyogenes. The agar disk diffusion method showed that most plants were more active against gram-positive than gram-negative bacteria. Streptococcus pyogenes was the most sensitive organism inhibited by nearly all of the extracts (97.6%), followed by Bacillus cereus (63.4%) and Staphylococcus aureus (61.0%). The ethanol extracts of Rhodomyrtus tomentosa (Aiton) Hassk. (Myrtaceae) (leaf) and Eleuterine americana Merr. (bulb) exhibited good antibacterial activity against gram-positive bacteria. The minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of Rhodomyrtus tomentosa ranged from 3.9 to 7.8 and 7.8 to 125 μg/mL, respectively, while those of Eleuterine americana were 120–125 and 250–1000 μg/mL, respectively. Quercus infectoria G. Olivier (Fagaceae) and Piper betle L. (Piperaceae) showed a broad spectrum of activity. The ethanol extract from the nut galls of Quercus infectoria demonstrated significant activity against all important pathogens. It inhibited the growth of all pathogens, with MIC values of 62.5–1000 μg/mL. The MBC ranged from 125 to 1000 μg/mL in most species, except Enterococcus faecalis. The ethanol extract from Piper betle (leaves) demonstrated antibacterial activity against almost all species with the same MIC and MBC values, ranging from 125 to 500 μg/mL.

Evaluation of the Antimycobacterial Activity of Extracts from Plants Used as Self-Medication by AIDS Patients in Thailand

ABSTRACT Chloroform, methanol, and water extracts from medicinal plants used as self-medication by AIDS patients in Thailand were evaluated for their antimycobacterial activity using the microplate Alamar blue assay. The crude extracts exhibited antimycobacterial activity with minimum inhibitory concentrations (MICs) of 0.12–1000 µg/ml. The chloroform extract of Alpinia galanga. rhizomes and Piper chaba. fruits had strong inhibitory effects with MIC values of 0.12 and 16 µg/ml, respectively. The active compounds, 1′-acetoxychavicol acetate from Alpinia galanga. and piperine from Piper chaba. had MIC values of 0.024 and 50 µg/ml, respectively.

Uterine relaxant effects of Curcuma aeruginosa Roxb. rhizome extracts.

The effects and plausible mechanism of action of Curcuma aeruginosa Roxb. (Zingiberaceae) rhizome chloroform and methanol extracts on the uterine contraction were investigated using isolated uterus strips from estrogen primed rats. The contractile responses were recorded isometrically with a Grass FT03 force transducer connected to a MacLab system. The experiments were carried out on both nonstimulated, agonist- and KCl-stimulated uteri. In the nonstimulated uterus, the two extracts (10-400 microg/ml) had no significant effect. In contrast, in the stimulated uterus, the chloroform and methanol extracts exerted concentration-dependent inhibition of the contractions induced by oxytocin (1 mU/ml), prostaglandin F2alpha (PGF2alpha, 0.5 microg/ml), ACh (3x10(-6) M) and KCl (40 mM) with the IC50 (inhibition of force) of 31.4, 58.59, 56.21 and 29.28 microg/ml; and 57.79, 69.3, 223.8 and 69.19 microg/ml, respectively. Verapamil, the reference L-type calcium channel blocker, exhibited a similar pattern of inhibition with the IC50 of 0.03, 0.25, 0.35 and 0.04 microg/ml. The IC50 of diclofenac against a PGF2alpha-induced contraction was 31.36 microg/ml. It is known that the contraction induced by agonists and KCl is mainly due to calcium influx through the voltage-gated L-type calcium channels opened indirectly or directly by agonist-receptor activation and KCl. Thus, it is speculated that the two plant extracts might inhibit uterine contraction by interrupting the influx of Ca2+ probably through voltage-gated L-type calcium channels. This possibility was further substantiated by the ability of the extracts to shift the CaCl2-contraction curves to the right. As the methanol extract also reduced the contraction of oxytocin in Ca2+-free EDTA solution; thus, it is suggested that part of its action may be involved with an intracellular mechanism. The effect of the two extracts did not involve the activation of beta2-adrenoceptors since their effects were unaffected by propranolol. Based on the inhibitory effect of the extracts on the oxytocin-induced contraction, it is concluded that the extracts might be useful as tocolytic agents for the prevention of preterm labor. Their effects on the inhibition of PGF2alpha-induced contractions also seem useful for the treatment of dysmenorrhea. There are reports by others that the plant rhizome contains beta-pinene and sesquiterpenes. In addition, there is evidence that these compounds possess spasmolytic effects in the rat intestine and uterus. Therefore, the uterine relaxant effect of the plant extracts could be due to beta-pinene and some sesquiterpene lactones contents. The methanol extract is less potent than the chloroform extract, and this might be due to the lower amount of terpene compounds or different compounds may involve in this action.

Anti-allergic and antioxidative activities of some compounds from Thai medicinal plants

Evaluation of the anti-allergic and antioxidative activities of compounds from Thai medicinal plants demonstrated that lawsone methyl ether significantly exhibited the inhibitory effect on degranulation in RBL-2H3 cells with an EC50 of 26.71 µM, while quercetin, a standard control, had an EC50 of 10.02 µM. Other compounds from Thai medicinal plants including lucidin-ω-methyl ether, bergenin, homorapanone, strictosidinic acid and barakol, had no effect on the degranulation assay. In a DPPH radical scavenging assay, strictosidinic acid and barakol were more potent than the positive control, BHT. The EC50 values of strictosidinic acid and barakol were 27.68 and 39.62 µM, respectively. Other tested compounds, including lawsone methyl ether, bergenin, homorapanone and lucidin-ω-methyl ether, had weak antioxidative activities or no activity. In a nitrite assay, only lawsone methyl ether reduced nitrite production with an EC50 of 10.27 µM in RAW 264.7 cells. In conclusion, lawsone methyl ether suppresses degranulation in RBL-2H3 cells and reduces nitrite production in RAW 264.7 cells whereas strictosidinic acid and barakol have an antiradical action against DPPH.