Abstract:
Pain is a symptom that results from particular physiological processes as injurious stimuli
characteristic of cell injury or disease. Several herbs including Phyllanthus lawii,
Diallium guineense, Jathropha gossypiofolia linn, Pangamia pinnata linn and Papaver
somniferrum have been reported for use to relieve various aches, such as headaches,
toothache, lower back pain and neuralgia. The objectives of this study were to extract,
isolate, characterize and determine the analgesic efficacy of compounds from Euphorbia
prostrata. The plant was collected from its natural habitat in Uasin-Gishu County and
samples processed as whole plant by air drying before grinding. Serial extraction was
carried out by soaking ground powder in three organic solvents (hexane, ethyl acetate and
acetone) of increasing polarity each for 48 hours before filtering and rotary evaporation
to dryness. Testing for analgesic activity was then carried out by Tail Immersion Model
using albino rats. The active extracts were packed on silica gel column for
chromatographic separation. Thin Layer Chromatography (TLC) was used to monitor the
fractions with the help of visualization reagents. Further bioassay was carried out for the
isolated fractions before purification by crystallization. Pure isolated fraction with the
highest analgesic activity was then characterized by UV-Vis, Fourier Transform-Infra Red
spectroscopy (FT-IR) and Gas Chromatography-Mass Spectroscopy (GC-MS). Results
showed that ethyl acetate crude extracts afforded best yield of 5.80%. The highest
analgesic activity was from ethyl acetate crude extract which significantly (p> 0.05)
increased the pain reaction time (PRT) to10.40 seconds compared to positive control
(Declofenac) that was 8.04seconds. Isolation by column chromatography afforded four
fractions: H 1 , H 2 , H 3 and H 4 from hexane crude extract and five fractions: E1, E 2 , E 3 , E 4
and E 5 from ethyl acetate crude extracts. Further bioassay and purification of the fractions
was done to yield fraction A which had optimum PRT of 6.21 seconds and UV λ max of 259
nm. By using spectroscopic methods, fraction A showed steroidal characteristics. This
was confirmed from FT-IR strong peaks of the fraction A at 3480 cm -1 (OH group,
alcohols), 3150-3400 cm -1 (C-H stretching, aliphatic), 1650 cm -1 (C=C, alkene),
1400
cm -1 (CH 2 ), 1050 cm -1 (cycloalkane) and 870 cm -1 (C-H vibration for unsaturated part) as
characteristic functional groups for steroids. GC-MS results showed pronounced
molecular peaks at m/z 412, 414 and 426 for retention time of 12.26, 13.04 and 13.21
minutes respectively. With the help of data obtained, fraction A is most probably having a
mixture of stigmasterol, β-sitosterol and cholest-5-en-3-ol, 24 propylidene. Analgesic
activity of Euphorbia prostrata is attributed to the presence of steroids. E. prostrata is
worth consideration for exploration in the quest for lead compounds in drug discovery
particularly analgesics.