The anti-amoebic activity of some medicinal plants used by AIDS patients in southern Thailand.

The anti-amoebic activities of chloroform, methanol and water extracts from 12 Thai medicinal plants (39 extracts) commonly used by AIDS patients in southern Thailand were screened, at a concentration of 1,000 microg/ml, against Entamoeba histolytica strain HTH-56:MUTM and strain HM1:IMSS growing in vitro. The extracts were incubated with 2x10(5) E. histolytica trophozoites/ml of medium at 37 degrees C under anaerobic conditions for 24 h. The cultures were examined with an inverted microscope and scored (1-4) according to the appearance and numbers of the trophozoites. The extracts that caused inhibition were selected and retested using the same conditions but with concentrations that ranged from 31.25 to 1,000 microg/ml using E. histolytica strain HM1:IMSS, and the IC(50) values for each extract were calculated. The chloroform extracts from Alpinia galanga (IC(50) 55.2 microg/ml), Barleria lupulina (IC(50) 78.5 microg/ml), Boesenbergia pandurata (IC(50) 45.8 microg/ml), Piper betle (IC(50) 91.1 microg/ml) and Piper chaba (IC(50) 71.4 microg/ml) and the methanol extract from B. pandurata (IC(50) 57.6 microg/ml) were all classified as "active", i.e. with an IC(50) of less than 100 microg/ml, whereas those from Murraya paniculata (IC(50) 116.5 microg/ml) and Zingiber zerumbet (IC(50) 196.9 microg/ml) were classified as being "moderately active". The IC(50) of a standard drug, metronidazole, was 1.1 microg/ml.

The in vitro anti-giardial activity of extracts from plants that are used for self-medication by AIDS patients in southern Thailand.

This study evaluated the anti-giardial activity of chloroform, methanol and water extracts of 12 medicinal plants (39 extracts), commonly used as self medication by AIDS patients in southern Thailand. The plant extracts and a standard drug, metronidazole, were incubated with 2x10(5) trophozoites of Giardia intestinalis per millilitre of growth medium in 96-well tissue culture plates under anaerobic conditions for 24 h. The cultures were examined with an inverted microscope and the minimum inhibitory concentration and the IC50 value for each extract was determined. The chloroform extracts from Alpinia galanga, Boesenbergia pandurata, Eclipta prostrata, Piper betle, Piper chaba, Zingiber zerumbet, and the methanol extracts from B. pandurata and E. prostrata were classified as "active", i.e. with an IC50 of <100 microg/ml, whereas the chloroform extract from Murraya paniculata was classified as being "moderately active". This study shows that extracts from some medicinal plants have potential for use as therapeutic agents against G. intestinalis infections.

Study on tablet binding and disintegrating properties of alternative starches prepared from taro and sweet potato tubers.

To demonstrate the potential alternative sources of starch used in tablet formulations, starches from taro (TS) and sweet potato (SPS) tubers were prepared with obtained yields of 11.0 and 9.6%, respectively. Both TS and SPS met USP22-NF17 identification and specifications. Their equilibrium moisture contents and gelatinization temperatures were comparable with those of commercial starch, whereas amylose contents of TS and SPS were 21.38% w/w and 41.76% w/w, respectively. Both were found to possess similar flow characteristics. To evaluate TS and SPS as granulating agents and disintegrants, tablets with controlled compression loads were prepared by incorporating a starch candidate with dibasic calcium phosphate in paste and powders forms, respectively. Tablets were then evaluated based on compressibility, friability, and disintegration. It was found that the binding and disintegrating performance of both TS and SPS was similar to that of commercial cornstarch.

Analgesic and Antipyretic Activities of n-Butanol Alkaloids Extracted from the Stem Bark Hunteria Zeylanica and its Major Constituent, Strictosidinic Acid, in Mice.

The pharmacological activities of the n -butanol alkaloids extracted from the stem bark of Hunteria zeylanica (Retz) Gardn. ex Thw. ( H. zeylanica ) and its major constituent, strictosidinic acid, on nociceptive response using writhing and hot plate tests, the antipyretic activity in yeast-induced fever, pentobarbital-induced sleep, and locomotor activity were examined in mice. Oral administration of H. zeylanica extract at 200 mg/kg significantly decreased the number of contortions and stretchings induced by acetic acid but not heat-induced pain. Strictosidinic acid (5-20 mg/kg, p.o.) also produced a similar effect but less pronounced than the extract. The antipyretic effect of strictosidinic acid (5-20 mg/kg, p.o.) was stronger than that of the extract (100-200 mg/kg, p.o.). The H. zeylanica extract dose-dependently (50-200 mg/kg, p.o.) prolonged the duration of pen-tobarbital-induced sleep but had no sign ificant effect on locomotor activity. No effect of strictosidinic acid was noted on both pentobarbital-induced sleep and locomotor activity. These results suggest that the H. zeylanica extract possesses peripheral analgesic and mild antipyretic effects and its major constituent, strictosidinic acid, exerts a similar analgesic effect with marked antipyretic activity.

Inhibitory effects of corymine-related compounds on glycine receptors expressed in Xenopus oocytes.

We examined the effects of 4 corymine-related compounds on glycine-induced chloride current in Xenopus oocytes. Dihydrocorymine, N-demethyl-3-epi-dihydrocorymine and deformylcorymine dose-dependently decreased the glycine current with IC50 values of 34, 37 and 55 microM, respectively. The effect of these compounds on the glycine current was more potent than that of pleiocarpamine (IC50 > 1 mM). N-demethyl-3-epi-dihydrocorymine and dihydrocorymine, at 100 microM, also decreased the gamma-aminobutyric acid-induced current by 65% and 22%, respectively, whereas deformylcorymine and pleiocarpamine failed. The inhibitory action of deformylcorymine on the glycine current was noncompetitive. These results suggest that deformylcorymine is a novel specific noncompetitive glycine receptor antagonist. The structure-activity relationship of these compounds was discussed.

A possible mechanism underlying corymine inhibition of glycine-induced Cl- current in Xenopus oocytes.

We previously reported that corymine, an alkaloid extracted from the leaves of Hunteria zeylanica native to Thailand, inhibited glycine-induced chloride current using a receptor expression model of Xenopus oocytes. In this study, we investigated the mechanism underlying the inhibitory action of this alkaloid on glycine current using the same model. Corymine inhibited glycine current in a noncompetitive fashion. Co-application with strychnine, a competitive glycine receptor antagonist, or 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), a Cl- channel blocker, corymine decreased the ED50 value of strychnine, but did not change that of DIDS. Moreover, the inhibitory effects of corymine and either strychnine or DIDS were additive. The desensitization phase of glycine current showed two exponentials and corymine preferentially inhibited the fast component, whereas strychnine affected both of them to the same extent and DIDS preferentially inhibited the slow component. When these drugs were applied repeatedly, the inhibitory effects of corymine and strychnine were not use-dependent and reversible, while the effect of DIDS was use-dependent and irreversible. The inhibitory effect of corymine on gamma-aminobutyric acid (GABA) current was less potent than the effect on glycine current, while this alkaloid failed to affect acetylcholine and serotonin currents. These results demonstrate that corymine inhibits glycine-gated CI- channels by interacting with the site different from that of DIDS.

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.

Behavioral studies on alkaloids extracted from the leaves of Hunteria zeylanica.

The effects of a crude methanol extract, butanol- and chloroform-fractions, and a pure compound, corymine, extracted from the leaves of H. zeylanica on locomotor activity and rearing, pentobarbital-induced sleep, and drug-induced convulsions were studied in mice. The methanol extract dose-dependently decreased rearing without a significant effect on locomotor activity at doses of 15, 60 and 120 mg/kg. It did not significantly prolong the sleeping time but potentiated the convulsions induced by strychnine, but not that by either picrotoxin or pentylenetetrazole, at a dose of 120 mg/kg. The butanol-fraction significantly prolonged sleeping time at a dose of 125 mg/kg but did not affect either of the convulsive drugs. The chloroform fraction prolonged sleeping time at doses of 62.5 and 125 mg/kg and potentiated the convulsions induced by either strychnine or picrotoxin, but not that by pentylenetetrazole, at doses of 15, 30, 60 and 120 mg/kg. Corymine did not significantly prolong sleeping time, but potentiated the convulsions induced by either strychnine or picrotoxin, not by pentylenetetrazole, at doses of 2, 8 and 15 mg/kg. These results suggest that crude alkaloidal extracts of H. zeylanica leaves produce biphasic effects on the central nervous system (CNS), depression and stimulation, while the pure compound, corymine, has a unique central stimulatory effect in mice.

Inhibitory effect of alkaloids extracted from the stem bark of Hunteria zeylanica on 5-lipoxygenase activity in vitro.

The effects of alkaloid extract from the stem bark of Hunteria zeylanica Gard. (H. zeylanica) on the activities of cyclooxygenase and 5-lipoxygenase in A23187-stimulated rat mast cells were investigated. H. zeylanica alkaloid extract (0.3-300 micrograms/ml) inhibited leukotriene C4 (LTC4) production by 5-lipoxygenase in a concentration-dependent manner and it blocked the production by 50% at 300 micrograms/ml. On the other hand, the extract had no effect on prostaglandin D2 (PGD2) production by cyclooxygenase. Neither (-)-eburnamine nor pleiomutinine, major constituents of H. zeylanica alkaloid extract, inhibited the production of PGD2 and LTC4 in the A23187-stimulated mast cells. The inhibition of arachidonic acid metabolism via 5-lipoxygenase pathway may be due to minute amounts of other components as stated in the Discussion.

Effects of alkaloids extracted from the stem bark of Hunteria zeylanica on acute inflammation in experimental animals.

The effects of crude alkaloids extracted from the stem bark of Hunteria zeylanica GARD. (H. zeylanica) on acute inflammatory responses such as carrageenin-induced paw edema in rats and croton oil- and arachidonic acid-induced ear edema in mice were investigated. Oral administration of H. zeylanica alkaloid extract (200-400 mg/kg) significantly suppressed the paw swelling induced by carrageenin. In the croton oil-induced ear edema, topically applied H. zeylanica alkaloid extract, at doses of 200 and 400 mg/ml, also significantly reduced ear edema. Moreover, the extract (50-200 mg/kg, p.o.) reduced in a dose-dependent manner the ear swelling induced by topically applied arachidonic acid (2 mg/ear). These results suggest that the inhibitory effects of H. zeylanica alkaloid extract on acute edema formation are partly due to inhibition of 5-lipoxygenase and cyclooxygenase activity.

Antinociceptive and antipyretic effects of alkaloids extracted from the stem bark of Hunteria zeylanica.

Effects of crude alkaloids extracted from the stem bark of Hunteria zeylanica Gard. (H. zeylanica) on nociceptive responses, capillary permeability, yeast-induced hyperthermia, pentobarbital-induced sleep, and spontaneous motor activity were investigated. Oral administration of 50 mg/kg H. zeylanica alkaloid extract significantly decreased the number of writhings induced by intraperitoneal acetic acid. The extract at 100-200 mg/kg significantly increased nociceptive threshold of the inflamed but not the non-inflamed paw in the Randall-Selitto test. Moreover, in the formalin test, the extract (100 mg/kg) significantly decreased licking activity in the late phase without affecting the activity in the early phase. However, the extract did not produce antinociceptive effect in the hot plate test, while it inhibited increase of vascular permeability induced by acetic acid in the capillary permeability test. Moreover, the extract dose-dependently reduced yeast-induced hyperthermia in rats without affecting normothermia. It did not affect pentobarbital-induced sleep, but significantly increased locomotor activity at 100 mg/kg. These results suggest that H. zeylanica alkaloid extract possesses antinociceptive and antipyretic effects, and that the former effect may be mediated by its anti-inflammatory action.

Hunterioside, first biose bound monoterpenoid indole alkaloid from Hunteria zeylanica.

A novel glycosidic alkaloid, hunterioside, together with strictosidinic acid was isolated from Hunteria zeylanica, and the structure was found to be 6'-alpha-D-glucoside of strictosidinic acid. This isolation is the first finding of a bioside congener of monoterpenoid indole alkaloid glucosides.