Abstract:
The anxiolytic and antinociceptive properties of the leaf extract and fraction of Phyllanthus muellerianus Kuntze (Phyllanthaceae) were investigated.The extract (MME; 500.18 g; 10%w/w), obtained by cold maceration in 1:1 mixture of methylene chloride: methanol for 48 h, was fractionationed in a silica gel column which yielded the ethyl acetate fraction (EF; 199.2 g; 39.83% w/w). The extract and fraction were subjected to phytochemical analysis. Acute toxicity of MME was determined in mice using the oral route. Anxiolytic-like activity of MME and EF was investigated in mice using behavioural paradigms of anxiety on the Elevated Plus Maze (EPM) and the Light and Dark box tests. Antinociceptive activity was evaluated using abdominal writhing induced by acetic acid in rats and paw-licking induced by formalin in mice. The results showed that MME and EF gave positive reactions for alkaloids, carbohydrates, flavonoids, glycosides, reducing sugar, saponins, steroids, tannins, terpenoids and resins. Acute toxicity test on MME established an oral LD50>5000 mg/kg in mice. MME and EF caused a significant (P<0.05) increase in the duration of stay, time spent on the open arm and central platform of the EPM, the number of entries into the open arm and rearing behaviour. They also caused a significant (P<0.05) decrease in the duration of stay and number of entries in the closed arm, grooming activity, number of head dips, stretch attend posture and number of urine streaks and fecal boli. In the Dark and Light box, MME and EF significantly (P<0.05) increased the time spent in the light areaand decreased the time spent in the dark area, They also significantly (P<0.05) increased the number of line crossings and transition between the light and dark areas, the rate of peeking out of the dark box, and number of entries into the light chamber. They also caused significant (P<0.05) reduction in the number of fecal boli produced in the light and dark box. MME and EFsignificantly (P<0.05) reduced the number of abdominal writhes induced by acetic acid and the duration of paw-licking in the two phases of formalin-induced paw-licking test. A comparison of the magnitude of activity in all the tests showed the order of potency EF>MME.
