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Dive into the research topics where Paul V. Tan is active.

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Featured researches published by Paul V. Tan.


Journal of Ethnopharmacology | 2002

Leaf methanol extract of Bidens pilosa prevents and attenuates the hypertension induced by high-fructose diet in Wistar rats

Théophile Dimo; Silvere Vincent Rakotonirina; Paul V. Tan; Jacqueline Azay; Etienne Dongo; Gérard Cros

Chronic fructose treatment in rats has repeatedly been shown to elevate blood pressure in association with insulin resistance and hyperinsulinemia. The purpose of the current study was to investigate the effect of the leaf methanol extract of Bidens pilosa on systolic blood pressure (SBP) and plasma glucose, insulin, cholesterol, triglycerides and creatinine levels in rats with fructose-induced hypertension. Wistar rats that drank a 10% fructose solution for 3-6 weeks showed significant increase not only in plasma insulin and cholesterol levels but also in SBP. B. pilosa extract was able to prevent the establishment of hypertension and lower elevated blood pressure levels. The extract also reduced the highly elevated plasma insulin levels provoked by the high fructose diet. These results suggest that the leaf methanol extract of B. pilosa exerts its antihypertensive effect in part by improving insulin sensitivity.


Journal of Ethnopharmacology | 2000

Effects of methanol, cyclohexane and methylene chloride extracts of Bidens pilosa on various gastric ulcer models in rats

Paul V. Tan; Théophile Dimo; Etienne Dongo

Ethnobotanical studies have revealed that Bidens pilosa is used in the traditional management of wounds and chronic gastro-duodenal ulcers. This led us to screen the methanol, cyclohexane and methylene chloride extracts of the plant for anti-ulcerogenic activity using the HCl/ethanol gastric necrotizing solution. The methylene chloride extract, which showed the highest activity (100% inhibition) at a dose of 750 mg/kg compared with the methanol and cyclohexane extracts (41 and 46% inhibition, respectively), was further tested using the indomethacin-HCl/ethanol-, absolute ethanol- and pylorus ligation-induced ulcer methods. Pre-treatment with indomethacin significantly reduced the protective effect of the extract against HCl/ethanol solution to 31%. The extract had very little gastric mucosal protection against absolute ethanol (9.8% inhibition at 750 mg/kg) compared with the controls and neither reduced gastric acid secretion in vivo nor the acidity of gastric juice following in vitro incubation.


Journal of Ethnopharmacology | 1996

Eremomastax speciosa: effects of leaf aqueous extract on ulcer formation and gastric secretion in rats.

Paul V. Tan; Ngeh G. Nditafon; Maurice P. Yewah; Théophile Dimo; Foyere J. Ayafor

The anti-ulcerogenic potential of the aqueous extract of Eremomastax speciosa leaves was investigated using two methods of ulcer induction: HCl/EtOH-induced ulceration and pylorus ligation. With both methods, the extract inhibited gastric ulceration in a dose-related manner. The highest oral dose tested (190 mg/kg) completely inhibited gastric ulceration and significantly reduced gastric acidity compared with the controls. Incubation of gastric juice with the plant extract (190 mg/kg) significantly reduced the acidity of the incubated gastric juice compared with the controls.


Journal of Ethnopharmacology | 2001

Effects of the aqueous and methylene chloride extracts of Bidens pilosa leaf on fructose-hypertensive rats.

Théophile Dimo; Jacqueline Azay; Paul V. Tan; Jacques Pellecuer; Gérard Cros; Marc Bopelet; Jean Jacques Serrano

We investigated the effects of the aqueous (150-350 mg/kg) and methylene chloride (150-300 mg/kg) extracts of Bidens pilosa on fructose-induced hypertension in rats. Food and liquid intake were measured as well as systolic blood pressure and plasma levels of glucose, insulin, cholesterol, triglycerides and creatinine. Fructose feeding for 6 weeks induced hypertension, hyperinsulinemia and increased plasma triglyceride levels in male Wistar rats. The aqueous and methylene chloride extracts of B. pilosa reversed the high blood pressure and hypertriglyceridemia developed due to fructose feeding but did not have any effects on plasma levels of insulin and glucose. High doses of the extracts reduced plasma creatinine levels and tended to increase plasma cholesterol. These results suggest that the extracts of B. pilosa possess hypotensive effects whose mechanism of action is not related to insulin sensitivity.


Journal of Ethnopharmacology | 2002

Gastric cytoprotective anti-ulcer effects of the leaf methanol extract of Ocimum suave (Lamiaceae) in rats.

Paul V. Tan; Barthelemy Nyasse; Théophile Dimo; Christophe Mezui

The anti-ulcerogenic potential of the leaf methanol extract of Ocimum suave (Lamiaceae) was investigated using four methods of gastric lesion induction in experimental Wistar rats (150-200 g): (1) HCl/ethanol-induced gastric lesions, (2) Absolute ethanol-induced gastric lesions, (3) Indomethacin-HCl/ethanol-induced gastric lesions, (4) Pylorus ligation-induced gastric lesions. Administration of the extract of O. suave to the rats by oral route (75-500 mg/kg) dose-dependently prevented the formation of acute gastric lesions induced using the four experimental techniques. The dose-dependent reduction of lesion formation was in all cases accompanied by significant increases in gastric mucus production. At the dose of 250 mg/kg there was complete inhibition of gastric lesions induced using the HCl/ethanol solution. Pre-treatment, by intraperitoneal route, with indomethacin significantly reduced the ability of the extract to inhibit the formation of HCl/ethanol-induced lesions. When the rats were subjected to pylorus ligation, the dose of 500 mg/kg completely inhibited lesion formation but did not have any effect on gastric acid secretion compared with the controls. The mucus secretion promoting effect of the extract was most significant when the gastric environment was highly acidic. These results suggest that a new anti-ulcer therapy regimen may be formulated which does not require the use of antacids and anti-secretory agents.


Phytomedicine | 2000

Prophylactic and healing properties of a new anti-ulcer compound from Enantia chlorantha in rats.

Paul V. Tan; Barthelemy Nyasse; G.E. Enow-Orock; P. Wafo; E.A. Forcha

Decoctions prepared from Enantia chlorantha are used in the traditional treatment of some forms of ulcers. We have tested the anti-ulcer actions of a novel protoberberine-type alkaloid (7,8,-dihydro-8-hydroxypalmatine (1)) obtained from the bark of E. chlorantha using the HCl/ethanol, absolute ethanol and pylorus ligation techniques. The healing effect on chronic acetic acid-induced gastric ulcer was also tested. 1 (50 and 100 mg/kg) dose-dependently inhibited the formation of gastric ulcers induced by HCl/ethanol (35-52% inhibition), absolute ethanol (46-53% inhibition) and pylorus ligation (38-62% inhibition). The prophylactic actions were associated with significant increases in gastric mucus production compared with the controls. The significant inhibition of pylorus-ligated ulcers occurred at gastric acid concentrations (83 mEq/l) previously known to induce severe gastric ulceration in rats. The ulcer-healing test showed significant macromorphological and histological acceleration of healing following 10-day treatment with 1 (40 - 80 mg/kg). The results show that 1 has no anti-secretory effects. The prophylactic anti-ulcer effects are associated with enhanced mucus production, which is an important factor in the mechanism of the local healing process of chronic gastric ulcers.


Phytomedicine | 2001

Antihypertensive effects of Dorstenia psilurus extract in fructose-fed hyperinsulinemic, hypertensive rats

Théophile Dimo; A. Rakotonirina; Paul V. Tan; Etienne Dongo; A.B. Dongmo; Pierre Kamtchouing; Jacqueline Azay; B.M. Abegaz; Gérard Cros; T.B. Ngadjui

We examined the effect of methanol/methylene chloride extract of Dorstenia psilurus given by gastric intubation on systolic blood pressure, plasma glucose, insulin, cholesterol, triglycerides and creatinine in rats with fructose-induced hypertension. Male Wistar rats in groups of 6 animals each were fed fructose-rich diets or standard chow for 3 weeks and treated with 100 mg/kg/day or 200 mg/kg/day of plant extract or vehicle for 3 subsequent weeks. Systolic blood pressure was measured every three days using the indirect tail cuff method. Systolic blood pressure was higher in fructose-fed rats (142+/-2 mm Hg, p < 0.01) compared with the controls (112+/-2 mm Hg), and was lower in Dorstenia psilurus-treated groups (127+/-2 and 119+/-1 mm Hg for the dose of 100 and 200 mg/kg, respectively) compared with the fructose-fed rats. Plasma insulin, cholesterol and triglycerides were higher on the fructose-rich diet compared with the controls. Plasma insulin and cholesterol were lower in the Dorstenia psilurus-treated groups. These results suggest that, Dorstenia psilurus treatment could prevent and reverse high blood pressure induced by a diet rich in fructose probably by improvement of plasma insulin levels. The plant extract might prove useful in the treatment and/or prevention of hypertension.


Journal of Ethnopharmacology | 1998

Effects of leaf aqueous extract of Bidens pilosa (Asteraceae) on KCl- and norepinephrine-induced contractions of rat aorta

Théophile Dimo; Silver Rakotonirina; René Kamgang; Paul V. Tan; Albert Kamanyi; Marc Bopelet

The effect of leaf aqueous extract of Bidens pilosa Linn. on KCl- and norepinephrine-induced contractions of rat aortic strips was studied. In aortic strips with endothelium intact, contractions induced using 60 mM KCl and 10(-5) M norepinephrine were dose-dependently relaxed by the extract, a more significant effect being seen with norepinephrine-induced contractions. Following mechanical damage to the aortic endothelium, inhibition of contractions was more prominent (105%) with the norepinephrine-induced contractions compared with KCl-induced contractions (15%) when the maximal dose (8 mg/ml) of the extract was used. The results suggest that the relaxation effect of the extract may be due to the blockade of the influx of extracellular Ca2+ into the cell.


Journal of Ethnopharmacology | 2000

Anti-ulcer actions of the bark methanol extract of Voacanga africana in different experimental ulcer models in rats.

Paul V. Tan; Veronique B Penlap; Barthelemy Nyasse; Joseph D.B Nguemo

The antiulcerogenic effects of the bark methanol extract of Voacanga africana were studied using various experimental ulcer models in rats. The effects of the extract on the volume of gastric juice, gastric pH, acid output, mucus production and peptic activity were recorded, as well as the preventive action against lesions caused by HCl/ethanol and indomethacin. Oral administration of the extract (500-750 mg/kg) inhibited the formation of gastric lesions induced by HCl/ethanol (40-63% inhibition). The inhibitory effect against HCl/ethanol was significantly (P<0.01) suppressed by pre-treatment of the rats with indomethacin (30 mg/kg, i.p.). The extract significantly reduced gastric lesion formation in pylorus ligated rats, but this was not associated with an increase in gastric mucus production or with a reduction in acid content, volume of gastric secretion or pepsin activity of the gastric juice.


Phytomedicine | 2000

Anti-ulcer compound from Voacanga africana with possible histamine H2 receptor blocking activity

Paul V. Tan; Barthelemy Nyasse

Voacanga africana is used in Cameroonian ethnomedicine for the treatment of peptic ulcers. We have tested the cytoprotective, anti-secretory and ulcer healing actions of an alkaloid (TN) obtained from the fruit extract. Oral administration of TN (50-100 mg/kg) dose-dependently prevented ulcer formation by HCl/ethanol (36-75%), absolute ethanol (43-75%), HCl-ethanol/indomethacin (58-84%), Pylorus ligation (31-100%), cold restraint stress (68-100%) and histamine (49-100%). The inhibitory effect at 50 and 100 mg/kg against HCl/ethanol was not suppressed by pre-treatment with indomethacin (20 mg/kg, i.p.). TN reduced Shay-ligated gastric acid secretion from 77 mEq/l in the controls to 46 and 25 mEq/l for the 50 and 100 mg/kg doses. Augmented histamine-induced gastric acid secretion was reduced from 84 mEq/l in the controls to 45 and 21 mEq/l for the two doses of TN, with total inhibition of gastric and duodenal ulcers by the 50 mg/kg dose. Healing rate of chronic acetic acid-induced ulcers was 62 and 83%, respectively, for the dose of 50 and 100 mg/kg of TN compared with the controls. TN has gastric anti-secretory effects similar to histamine receptor blockers. Its cytoprotective and ulcer healing properties are related to its ability to strengthen gastric mucosal defenses through enhanced gastric mucus production.

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Etienne Dongo

University of Yaoundé I

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Maurice Boda

University of Yaoundé I

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Jacqueline Azay

University of Montpellier

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Gérard Cros

University of Montpellier

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