Pharmacological Evaluation And Characterization Of The Antiulcer Constituents Of Stem Bark Extract Of Bridelia Ferruginea Benth (Euphorbiaceae)

ABSTRACT

Peptic ulcer disease (PUD) is a sore in the lining of the stomach or duodenal mucosa. The search

for an ideal antiulcer drug continues and has also been extended to medicinal plants. Bridelia

ferruginea Benth (Euphorbiaceae) is a plant used in traditional medical practice in South West

Nigeria. This study was aimed at evaluating the antiulcer activity and mechanisms of the extract

of the stem bark and to isolate the bioactive constituents responsible for the antiulcer activity.

Methanol extract (ME) was obtained by cold maceration and concentration in vacuo. ME was

partitioned in chloroform-methanol-water (2:2:1) mixture to obtain the chloroform (CF) and

aqueous methanol (AMF) fractions. The extract and fractions were subjected to biological

activity-guided screening using indomethacin-induced ulcer as activity-guide. Based on higher

ulcer protection given by CF, it was fractionated in a silica gel and eluted with gradient mixtures

of n-hexane-ethyl acetate to obtain six broad fractions (I – VI). Fractions III and VI offered the

highest protection on screening for biological activity. Purification of fractions III and VI in a

sephadex LH-20 column with methanol as eluent gave compounds I (BF1) and II (BF2)

respectively. The antiulcer activity of BF1 and BF2 was done using the activity-guide and the

structural identities established using nuclear magnetic resonance (1H-NMR, 13C-NMR) and

electron impact mass (EIM) spectroscopies. The extract was subjected to phytochemical analysis

using conventional methods. The oral acute toxicity of ME was determined in mice. The

antiulcer activity of ME, bioactive column fractions and isolated compounds was investigated

using indomethacin, ethanol, cold-restraint stress and pyloric ligation-induced ulcers in rats. The

mechanisms of antiulcer activity were studied using gastric acid secretion induced by pyloric

ligation in rats, proton pump inhibition using inhibition of H+ K+ ATPase activity in vitro,

determination of the roles of endogenous nitric oxide and sulfhydryl compounds using the effects

of L-NAME (L-nitroarginine methylester) and NEM (N-ethylmaleimide) respectively on ulcer

indices in ethanol-induced ulcer and antioxidant activity using DPPH radical scavenging activity.

The results showed that ME tested positive to saponins, reducing sugars, tannins, carbohydrates,

flavonoids, glycosides, alkaloids, steroids, proteins and terpenoids. No lethality was observed in

the mice on oral administration of doses up to 5000 mg/kg. There were no obvious signs of

abnormal behavioural changes in the mice. The extract, fractions and isolated compounds

produced significant (p < 0.05) dose-related inhibition of indomethacin, ethanol, cold restraint

stress and pyloric ligation-induced ulcers. The isolated compounds, BF1 and BF2, significantly

(p < 0.05) decreased the total acid and volume of gastric secretion and elevated the pH. The

fractions and isolated compounds significantly (p < 0.05) inhibited the activity of H+ K+ ATPase

in a dose-dependent manner. The isolated compounds, BF1 and BF2 did not increase gastric

lesion indices in L-NAME pre-treated rats but they significantly (p < 0.05) increased ulcer

indices in the NEM pre-treated rats. The extract, fractions and isolated compounds scavenged

DPPH radical in a dose-dependent manner. Comparison of the spectral data of BF1 and BF2 with

the published libraries of isolated compounds revealed their identities to be β-sitosterol and β-

sitosterol-3-O-βD-glucopyranoside respectively.