Evaluation of analgesic and antistress potential of methanolic stem wood extract of Microdesmis puberula Hook.f. ex Planch (Pandaceae) in mice

Summary. Microdesmis puberula Hook.f. ex Planch (Pandaceae) is used in traditional African medicine in the management of painful disorder and erectile dysfunction. This study was carried out to investigate the analgesic and antistress properties of the methanolic stem wood extract of Microdesmis puberula in mice. The analgesic effect was investigated using acetic acid-induced mouse writhing and hot plate tests while the antistress activity was investigated using the forced swimming test and immobilization stress-induced gastric ulcer. The extract (600 - 2400 mg/kg: p.o.) produced significant (P < 0.05) dose-dependent inhibition of pain response elicited by acetic acid while also increasing the nociceptive reaction latency in the hot plate tests. The extract at 600 mg/kg produced significant reduction in the duration immobility, however, a non-significant decrease was observed at 1200 and 2400 mg/kg. Stress exposure (150 min rat restrained at 4°C) increased the ulcer index in vehicle control group. However, Microdesmis puberula pretreatment decreased the stress-induced increase in ulcer index. Furthermore, Microdesmis puberula showed a “U”-shaped dose–response curve in decreasing ulcer index. Phytochemical analysis of the extract showed the presence of flavonoids, saponins and cardiac glycosides. The acute toxicity study showed that the extract has a wide margin of safety when administered orally but when it was administered intraperitoneally, it has a median lethal dose of 1412.5mg/kg. The findings in this study suggest that the methanolic stem wood extract of Microdesmis puberula possesses analgesic activity possibly mediated through peripheral and central mechanisms and also possesses significant antistress activity probably due to modulation of hypothalamic–pituitary–adrenal (HPA) and monoaminergic mechanisms. Industrial relevance. The WHO has indicated that as many as 80% of all people living in the developing countries make use of herbal medicine as their main source of healthcare. In recent years, many people living in industrialized countries have begun taking a second look at herbal medicines due to the rising cost of medicine and healthcare in their own nations. The alternative health industry has become a billion dollar a year business, and this is driving the quest to find new plants or chemicals which are useful. The present study will help the industry to produce herbal drug with less adverse effect, affordable and effective in the treatment of painful and acute stress disorders. Keywords. Microdesmis puberula; immobilization; forced swimm