Tender Leaf Extract of Terminalia catappa Antinociceptive Activity in Rats

Abstract

In Sri Lankan folklore, the juice of tender leaves of Terminalia catappa L. (Combretaceae) is recommended for pains, including headaches. However, the validity of this claim is not fully scientifically proven. The aim of this study was to investigate analgesic, antihyperalgesic and anti-inflammatory activities of this juice/extract in rats. Tender leaves were macerated in a mortar to obtain juice/extract (40% v/w; 2.5 g of leaves produced 1 mL extract). Different doses of the extract (5, 10, or 15 mL kg -1) or water were orally administered to male rats and the 10 mL kg -1 dose to female rats of different stages of estrous cycle. 1, 3 and 5 h later, analgesic potential was determined. Different sets of rats, were orally treated with 10 mL kg -1 of extract and these rats were subjected to carrageenan induced paw edema, inflammatory and formalin induced pain tests. All the 3 doses were well tolerated. The 10 and 15 mL kg -1 doses significantly (P < 0.05) increased the reaction time and changed the % maximum possible effect at 3 h post treatment in the hot plate test. In contrast, none of the doses exhibited analgesic activity in the tail flick test. Further, in the females, the 10 mL kg -1 dose induced a significant analgesia as in males, and this effect was not affected by the stage of the estrous cycle. The antinociceptive action of the extract was not blocked by naloxone nor by metachlopramide. Further, the extract was devoid of sedative activity. In the carrageenan study, the extract showed neither anti-inflammatory nor antihyperalgesic activities. In the formalin pain test, the extract significantly reduced the pain in the early phase but not in the late phase. It was concluded that T. catappa leaf extract is useful as an analgesic but not as an antihyperalgesic in mild to moderate pain, supporting its folklore use in Sri Lanka.