A water extract of leaves and stems of Psychotria sarmentosa has analgesic and antihyperalgesic activity in rats

Abstract

An unboiled water extract (UBE) of stems and leaves of Psychotria sarmentosa Blume (Family: Rubiaceae) is drunk by some men in Sri Lanka after being physically assaulted, indicating that it may have potent analgesic and/or anti-inflammatory activity. However, these activities are not described in either the Sri Lankan Ayurveda Pharmacopoeia or the Deshiya Chikithsa system of medicine practised in Sri Lanka. The aim of this study was to investigate whether an UBE of these parts of P. sarmentosa has such activities. Different doses of the UBE (7.5, 15.0 and 22.5 ml/kg) or vehicle were administered orally to rats. 1 and 3 h later, the analgesic potential was determined using hot plate and tail flick tests. In another set of rats, the highest dose of UBE was orally administered, and paw oedema induced with 1% carrageenan. Anti-inflammatory activity (up to 4 h) and antihyperalgesic activity (at 1 h) were determined (by the hot plate technique). All the doses of UBE were well tolerated and the highest had potent analgesic activity (in both tests, in terms of reaction time and % maximum possible effect) and antihyperalgesic activity (measured 1 h post-treatment). The UBE had no anti-inflarmnatory activity. Its analgesic activity was comparable to that of indomethacin and was not blocked by naloxone, (opioid receptor blocker), metochlopramide (dopamine receptor blocker) or atropine (cholinergic receptor blocker). We conclude that the antinociceptive activity of the UBE was mediated both spinally and supraspinally, and the antihyperalgesic activity spinally. Both actions may have been mediated through a paracetamol type of action. Med Sci Res 27:715-718 © 1999 Lippincott Williams & Wilkins