Increase of beta-endorphin secretion by syringin, an active principle of Eleutherococcus senticosus, to produce antihyperglycemic action in type 1-like diabetic rats.

We employed streptozotocin-induced diabetic rats (STZ-diabetic rats) as type 1 diabetes-like animal models to investigate the mechanism(s) of antihyperglycemic action produced by syringin, an active principle purified from the rhizome and root part S of ELEUTHEROCOCCUS SENTICOSUS (Araliaceae). Bolus intravenous (i. v.) injection of syringin dose-dependently decreased the plasma glucose of STZ-diabetic rats in 30 minutes in a way parallel to the increase of plasma beta-endorphin-like immunoreactivity (BER). Syringin enhanced BER release from the isolated adrenal medulla of STZ-diabetic rats in a concentration-dependent manner from 0.001 to 10 micromol/l. Bilateral adrenalectomy in STZ-diabetic rats eliminated the activities of syringin (1 mg/kg, i. v.) including the plasma glucose-lowering effect and the plasma BER-elevating effect. Also, syringin failed to lower plasma glucose in the presence of micro-opioid receptor antagonists and/or in the micro-opioid receptor knockout diabetic mice. In conclusion, the obtained results suggest that syringin can enhance the secretion of beta-endorphin from adrenal medulla to stimulate peripheral micro-opioid receptors resulting in a decrease of plasma glucose in diabetic rats lacking insulin.

Stimulatory effect of paeoniflorin on the release of noradrenaline from ileal synaptosomes of guinea-pig in-vitro.

The effect of paeoniflorin (an active principle of Paeoniae Radix, commonly used in traditional Chinese medicine) on the release of noradrenaline (norepineprhine) from nerve terminals was investigated using guinea-pig isolated ileal synaptosomes. Release was determined as the amount of noradrenaline, quantified by high-performance liquid chromatography-electrochemical detection, from samples incubated with paeoniflorin or vehicle. Paeoniflorin stimulated the release of noradrenaline in a concentration-dependent manner without an effect on the level of lactate dehydrogenase in the bathing medium. Tetrodotoxin abolished the action of paeoniflorin at concentrations sufficient to block sodium channels. The depolarizing effect of paeoniflorin on the membrane potential was also illustrated by a concentration-dependent increase in the fluorescence of bisoxonol. Moreover, the effect of paeoniflorin on bisoxonol fluorescence in ileal synaptosomes seems more potent than that of 4-aminopyridine. That paeoniflorin causes influx of calcium ions via the depolarization of nerve terminals could be considered. The noradrenaline-releasing action of paeoniflorin was abolished by removal of calcium chloride from the bathing medium. This action of paeoniflorin was also attenuated by Rp-cAMP atconcentrations sufficientto inhibitthe action of cyclicAMP. Therefore, paeoniflorin could induce a calcium-dependent and cyclic-AMP-related release of noradrenaline from sympathetic nerve terminals of guinea-pig ileum. Guanethidine inhibited the noradrenaline-releasing action of paeoniflorin in a concentration-dependent manner. The effect of paeoniflorin on the increase of bisoxonol fluorescence was not modified by atropine. Release of noradrenaline by paeoniflorin from noradrenergic nerve terminals was characterized. These findings suggest that paeoniflorin can stimulate tetrodotoxin-sensitive depolarization of membranes to result in a calcium-dependent and cyclic-AMP-related release of noradrenaline from noradrenergic nerve terminals.

Caffeic acid as active principle from the fruit of Xanthium strumarium to lower plasma glucose in diabetic rats.

The antihyperglycemic effect of caffeic acid, one of the phenolic compounds contained in the fruit of Xanthium strumarium, was investigated. After an intravenous injection of caffeic acid into diabetic rats of both streptozotocin-induced and insulin-resistant models, a dose-dependent decrease of plasma glucose was observed. However, a similar effect was not produced in normal rats. An insulin-independent action of caffeic acid can thus be considered. Otherwise, this compound reduced the elevation of plasma glucose level in insulin-resistant rats receiving a glucose challenge test. Also, glucose uptake into the isolated adipocytes was raised by caffeic acid in a concentration-dependent manner. Increase of glucose utilization by caffeic acid seems to be responsible for the lowering of plasma glucose.

Paeoniflorin reverses guanethidine-induced hypotension via activation of central adenosine A1 receptors in Wistar rats.

1. Intravenous injection of paeoniflorin, a glycoside purified from the root of Paeonia lactiflora, reversed guanethidine-induced hypotension in Wistar rats. 2. Pretreatment with the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine inhibited this effect of paeoniflorin in a dose-dependent manner. 3. The action of paeoniflorin was not modified by 8-(p-sulfophenyl)theophylline, the polar antagonist of the adenosine A1 receptor, which is not able to enter the central nervous system. 4. We conclude that paeoniflorin can reverse guanethidine-induced hypotension via activation of adenosine A1 receptors in the brain of Wistar rats.

Isoferulic acid as active principle from the rhizoma of Cimicifuga dahurica to lower plasma glucose in diabetic rats.

Isoferulic acid extracted from the rhizome of Cimicifuga dahurica Maxim. (Ranunculaceae) has been determined to have in vivo antihyperglycemic activity. An antihyperglycemic action of isoferulic acid in spontaneously diabetic rats, similar to type I diabetes, is presented.

Antioxidant and hepatoprotective activity of punicalagin and punicalin on carbon tetrachloride-induced liver damage in rats.

Punicalagin and punicalin, isolated from the leaves of Terminalia catappa L., are used to treat dermatitis and hepatitis. Both compounds have strong antioxidative activity. The antihepatotoxic activity of punicalagin and punicalin on carbon tetrachloride (CCl4)-induced toxicity in the rat liver was evaluated. Levels of serum glutamate-oxalate-transaminase and glutamate-pyruvate-trans-aminase were increased by administration of CCl4 and reduced by drug treatment. Histological changes around the liver central vein and oxidation damage induced by CCl4 also benefited from drug treatment. The results show that both punicalagin and punicalin have anti-hepatotoxic activity but that the larger dose of punicalin induced liver damage. Thus even if tannins have strong antioxidant activity at very small doses, treatment with a larger dose will induce cell damage.

Identification of Anoectochilus formosanus and Anoectochilus koshunensis species with RAPD markers.

RAPD (random amplified polymorphic DNA) markers were developed to distinguish Anoectochilus formosanus from Anoectochilus koshunensis and their putative hybrids. Morphological differentiation of these two species beyond the flowering period is difficult. RAPD markers provide a rapid and easy tool for identification of the two Anoectochilus species. In the study, forty arbitrary decamer primers were screened, and nineteen species-specific RAPD markers generated from polymerase chain reactions (PCR) with eight random primers were obtained. Nine were specific to A. formosanus and ten to A. koshunensis. Two primers, OPC-08 and OPL-07, produced two markers, one specific to A. formosanus and the other specific to A. koshunensis, which simultaneously appeared in the hybrids pattern. The RAPD markers can be applied both to identification of A. formosanus and A. koshunensis species and to assessment of the extent fo hybridization in hybrids between them. This information facilitates the breeding program process.

Antihyperglycemic effects of paeoniflorin and 8-debenzoylpaeoniflorin, glucosides from the root of Paeonia lactiflora.

Paeoniflorin and 8-debenzoylpaeoniflorin were isolated from the dried root of Paeonia lactiflora Pall. (Ranunculaceae). They produced a significant blood sugar lowering effect in streptozotocin-treated rats and had a maximum effect at 25 min after treatment. This hypoglycemic action was also observed in normoglycemic rats only at 1 mg/kg. The antihyperglycemic activity of 8-debenzoylpaeoniflorin seems lower than that of paeoniflorin. Plasma insulin was not changed in paeoniflorin-treated normoglycemic rats indicating an insulin-independent action. Also, this glucoside reduced the elevation of blood sugar in glucose challenged rats. Increase of glucose utilization by paeoniflorin can thus be considered. There are no previous data showing the hypoglycemic activity of paeoniflorin and/or 8-debenzoylpaeoniflorin in rats.

ADP-mimicking platelet aggregation caused by rugosin E, an ellagitannin isolated from Rosa rugosa Thunb.

Among the nine ellagitannins, rugosin E was the most potent platelet aggregating agent with an EC50 of 1.5 +/- 0.1 microM in rabbit platelets and 3.2 +/- 0.1 microM in human platelets. The aggregations caused by rugosin E and ADP were inhibited by EGTA, PGE1, mepacrine, sodium nitroprusside and neomycin, but not by indomethacin, verapamil, TMB-8, BN52021 and GR32191B. Rugosin E-induced thromboxane formation was suppressed by indomethacin, EGTA, PGE1, verapamil, mepacrine, TMB-8 and neomycin. ADP-scavenging agents, such as CP/CPK and apyrase inhibited concentration-dependently ADP (20 microM)-, but not rugosin E (5 microM)-induced platelet aggregation. In thrombin (0.1 U/ml)-treated and degranulated platelets, rugosin E and ADP still caused 63.5 +/- 3.0% and 61.2 +/- 3.5% of platelet aggregation, respectively. Selective ADP receptor antagonists, ATP and FSBA inhibited rugosin E- and ADP-induced platelet aggregations in a concentration-dependent manner. Both rugosin E and ADP did not induce platelet aggregation in ADP (1 mM)-desensitized platelets. In contrast to ADP, rugosin E did not decrease cAMP formation in washed rabbit platelets. Both rugosin E and ADP did not cause phosphoinositide breakdown in [3H]myo-inositol-labeled rabbit platelets. In fura-2/AM-load platelets, both rugosin E and ADP induced increase in intracellular calcium concentration and these responses were inhibited by ATP and PGE1. All these data suggest that rugosin E may be an ADP receptor agonist in rabbit platelets.

Superoxide anion scavenge effect of Quercus glauca Thunb. in whole blood of patients with ankylosing spondylitis.

Nine phenolic compounds, catechin (1), epicatechin (2), gallocatechin (3), epigallocatechin (4), procyanidin B-4 (5), catechin-3-O-rhamnoside (6), rutin (7), querglanin (8) and isoquerglanin (9) were isolated from oak leaves (Quercus glauca Thunb. Fagaceae), and the latter two (8, 9) were identified as new compounds. Several Quercus species have been used in folk medicine as an astringent for hemorrhoids and for treatment of inflammation, jaundice, and tumor. In this study, these compounds were tested for scavenging effects of the superoxide anion in the whole blood of patients with ankylosing spondylitis by means of an ultra-sensitive chemoluminescence (CL) analyzer and lucigenin amplification. The results showed that at a concentration of 2.3 x 10(-5) M, isoquerglanin (9) displayed the strongest inhibition activity (73.55%), followed by querglanin (8) (68.81%) and then gallocatechin (3) and epigallocatechin (4) (66.97 and 60.17% inhibition, respectively). In addition, the blood chemoluminescence (CL) level of patients with ankylosing spondylitis was inhibited by superoxide dismutase (SOD) but not by catalase, suggesting that superoxide anion is the major component of reactive oxygen species (ROS) involved in this assay system.

In vitro inhibitory effects of chebulinic acid on the contractile responses of cardiovascular muscles.

1. The effects of chebulinic acid, which has been shown to elicit blood pressure lowering effect in rats, on aortic vascular contraction as well as cardiac contraction were studied in rats. 2. Chebulinic acid had no effect on KCl-induced aortic contraction, but irreversibly inhibited the contractile responses to phenylephrine in an apparently non-competitive manner. Chebulinic acid also inhibited contractile responses of rat aorta to 5-hydroxytryptamine and angiotensin II. 3. Chebulinic acid inhibited the binding of [3H]-prazosin to dog aortic microsomal membranes in a concentration-dependent manner with an IC50 value of 0.34 mmol/L. Results of saturation binding experiments suggest a mixed mode of inhibition by chebulinic acid (i.e. a decrease in both the maximal number of binding sites and the affinity for prazosin). 4. Chebulinic acid concentration-dependently and reversibly inhibited the maximal left ventricular pressure of rat heart in a Langendorff preparation with 50% inhibition occurring at a concentration of 0.3 nmol/L. 5. We conclude that chebulinic acid exerts non-specific inhibitory actions in vascular preparations. Its inhibitory effect on cardiac contraction was reversible and three orders of magnitude more potent than that on vascular contraction. We suggest that the hypotensive effect of chebulinic acid is probably mediated via the decrease in cardiac output resulting from reduced left ventricular contraction.

Antihypertensive effect of corilagin in the rat.

The antihypertensive effect of corilagin, one of the ellagitannins purified from the seeds of Euphoria longana Lam. (Sapindaceae), was investigated in the spontaneously hypertensive rat (SHR). Administration of corilagin into conscious SHR at 5 mg/kg produced an antihypertensive effect equivalent to that induced by 1 mg/kg of guanethidine. This dose-dependent hypotensive effect was comparable with that observed in anesthetized SHR animals. Corilagin did not modify the baroreflex sensitivity in phenylephrine-challenged SHR. Corilagin reduced plasma noradrenaline in a dose-dependent fashion, an effect that was maintained in adrenalectomized rats. Failure of the antagonists for alpha2-adrenoceptors, idazoxan and yohimbine, as well as for dopamine receptors, haloperidol and domperidone, to reverse the antihypertensive actions of corilagin ruled out the participation of these receptors. Moreover, corilagin attenuated the pressor effects of methoxamine and Bay K8644 to a similar degree, indicating the direct effect of corilagin on vascular activity in rats. These results suggest that corilagin possesses the ability to lower blood pressure through the reduction of noradrenaline release and (or) direct vasorelaxation.

Differential inhibition of reverse transcriptase and cellular DNA polymerase-alpha activities by lignans isolated from Chinese herbs, Phyllanthus myrtifolius Moon, and tannins from Lonicera japonica Thunb and Castanopsis hystrix.

Two lignans, phyllamycin B and retrojusticidin B isolated from Phyllanthus myrtifolius Moon have been demonstrated to have a strong inhibitory effect on human immunodeficiency virus-1 reverse transcriptase activity (HIV-1 RT), but much less inhibitory effect on human DNA polymerase-alpha (HDNAP-alpha) activity. Fifty percent inhibitory concentrations of phyllamycin B and retrojusticidin B were determined to be 3.5 and 5.5 microM for HIV-1 RT, and 289 and 989 microM for HDNAP-alpha, respectively. The mode of inhibition was found to be non-competitive inhibition with respect to template-primer and triphosphate substrate. Several tannins such as caffeoylquinates (CQs) isolated from Lonicera japonica Thunb, galloylquinates (GQs) and galloylshikimates (GSs) purified from Castanopsis hystrix were shown to have a much less selective inhibitory effect on HIV-1 RT.

Influence of acetonylgeraniin, a hydrolyzable tannin from Euphoria longana, on orthostatic hypotension in a rat model.

Acetonylgeraniin, an active principle isolated from the seeds of Euphoria longana Lam. (Sapindaceae), reversed the fall in arterial blood pressure in conscious hypertensive rats (SHRs) with orthostatic hypotension induced by injection of hexamethonium into animals subjected to 90 degrees head-up tilts for 60 seconds. However, acetonylgeraniin failed to affect prazosin-induced orthostatic hypotension. Plasma noradrenaline (NA) and mean blood pressure were elevated dose-dependently by an intravenous injection of acetonyl-geraniin into the rats; this increase in blood pressure was totally abolished by prazosin. Failure of hexamethonium or pentolinium, the blockers of ganglionic nicotinic receptors, to influence the NA releasing action of acetonylgeraniin ruled out the participation of ganglionic stimulation. This NA-releasing action of acetonylgeraniin was, however, totally abolished by the inhibitors of noradrenergic nerve terminals, guanethidine or bretylium. Also, the activity of this tannin was not modified by adrenalectomy. Thus, a direct release of NA from the noradrenergic nerve terminals by acetonylgeraniin seems responsible for the reversing of orthostatic hypotension.

Antihypertensive activity of 6-O-galloyl-D-glucose, a phenolic glycoside from Sapium sebiferum.

The antihypertensive activity of a phenolic glycoside contained in the leaves of Sapium sebiferum was investigated. From intravenous screening using spontaneously hypertensive rats, 6-O-galloyl-D-glucose was identified as an active substance. The hypotensive action of this compound appears to be produced by an inhibition of noradrenaline release and/or a direct vasodilatation.

Effect of flavan-3-ol tannins purified from Camellia sinensis on lipid peroxidation of rat heart mitochondria.

We induced lipid peroxidation in rat heart mitochondria with FeSO4 and compared the inhibitory effect of various flavan-3-ol tannins on it. These tannins were purified from Chinese tea (Camellia sinensis). Oxygen consumption and malondialdehyde formation were used to quantitate the amount of lipid peroxidation. The free radical scavenger activity of tannins was then measured with a diphenyl-p-picrylhydrazyl method. These tannins significantly inhibited lipid peroxidation at micromolar concentration. Their potencies were higher than that of Trolox, a water soluble analogue of vitamin E. Since epicatechin-3-O-gallate, epigallocatechin-3-O-gallate and gallocatechin-3-O-gallate were more potent than other flavan-3-ol tannins in these assays, we considered that a galloyl group in 3-O-position increased the scavenger activity of flavan-3-ol tannins as well as their potency in inhibiting lipid peroxidation.

Antihypertensive principles from the leaves of Melastoma candidum.

Three active principles were isolated from the leaf of Melastoma candidum using the screening of hypotensive effects on spontaneously hypertensive rats (SHR). Intravenous injection of castalagin, procyanidin B-2, or helichrysoside into SHR lowered the mean blood pressure in a dose-dependent manner, with helichrysoside being the most potent compound. Plasma noradrenaline (NA) levels, both basal in SHR and elevated in normal rats through cold-stress stimulation, were attenuated by these compounds in a way which was not influenced by adrenalectomy. Decrease of NA release from sympathetic nerves was assumed to be responsible. Moreover, the hypertensive effect of various vasoconstrictors in anesthetized rats was reduced by helichrysoside. The same results were also observed in castalagin or procyanidin B-2 treated animals. The results indicate that the three principles possess the ability to lower blood pressure through a decrease of sympathetic tone as well as due to direct vasodilatation in SHRs.

Tannins and related compounds. CXXII. New dimeric, trimeric and tetrameric ellagitannins, lambertianins A-D, from Rubus lambertianus Seringe.

Chemical examination of the leaves of Rubus lambertianus Seringe (Rosaceae) has led to the isolation of four new ellagitannins, which were characterized on the basis of chemical and spectroscopic evidence to be dimers [lambertianins A (6) and B (7)], a trimer [lambertianin C (8)] and a tetramer [lambertianin D (10)], all having sanguisorbic acid ester group(s) as linking unit(s) between glucopyranose moieties. Furthermore, HPLC analyses of fifteen Rubus species collected in Japan and Taiwan revealed that the trimer (8) and the tetramer (10), together with sanguiin H-6 (1), occur widely in these species.

Antihepatotoxic activity of phenolic flavan-3-ols and their derivatives.

The protective activity against carbon tetrachloride induced hepatotoxicity of several phenolic flavan-3-ols and their derivatives has been assessed. Our research showed that monomers possessing a pyrogallol moiety as the B-ring had greater activity and this was not directly related to the stereo-chemistry of the hydroxyl group at C-3 in the flavan unit. However, when a galloyl group was linked to the hydroxyl group to form a gallate, this product exhibited markedly more activity than other analogs. These results suggest that the antihepatotoxic activity of phenolic flavan-3-ols and their derivatives seem to be related to the galloylation at the C-3 hydroxyl group in the flavan skeleton rather than the structure of another moiety or the degree of condensation.