The Analgesic Potential of Litsea Species: A Systematic Review.

Various plant species from the genus have been claimed to be beneficial for pain relief. The PRISMA approach was adopted to identify studies that reported analgesic properties of plants from the genus. Out of 450 records returned, 19 primary studies revealed the analgesic potential of nine species including (1) , (2) , (3) , (4) , (5) , (6) , (7) , (8) and (9) . Six of the species, 1, 3, 4, 7, 8 and 9, demonstrated peripheral antinociceptive properties as they inhibited acetic-acid-induced writhing in animal models. Species 1, 3, 4, 8 and 9 further showed effects via the central analgesic route at the spinal level by increasing the latencies of heat stimulated-nocifensive responses in the tail flick assay. The hot plate assay also revealed the efficacies of 4 and 9 at the supraspinal level. Species 6 was reported to ameliorate hyperalgesia induced via partial sciatic nerve ligation (PSNL). The antinociceptive effects of 1 and 3 were attributed to the regulatory effects of their bioactive compounds on inflammatory mediators. As for 2 and 5, their analgesic effect may be a result of their activity with the 5-hydroxytryptamine 1A receptor (5-HTR) which disrupted the pain-stimulating actions of 5-HT. Antinociceptive activities were documented for various major compounds of the plants. Overall, the findings suggested species as good sources of antinociceptive compounds that can be further developed to complement or substitute prescription drugs for pain management.