Limonene and Fatty Acid Content of the Volatile Oil of Raphia australis Fruit Pulp and Their Synergistic In vivo Anti-inflammatory Activity

Aim: To evaluate the in vivo anti-inflammatory activity of the essential oil and fatty acid compositions of the volatile oil of Raphia australis fruit pulp.

Method: The oils of pulp and seed of Raphia australis were isolated using Clevenger apparatus and were further subjected to GC-MS analyses. Anti-inflammatory test was carried out on the pulp of Raphia australis oils using four groups of rats comprising six rats per group (n=5). Group one were administered normal saline (0.09 % v/v NaCl) while group 1, 2 and 3 were administered 40 mg kg-1(volatile oil), 80 mg kg-1 (volatile oil) and 100mg kg-1 aspirin, respectively. Inflammation was induced in all the groups using lipopolysaccharide.

Results: From the GCMS analysis, 20 compounds were detected in the oil of R. australis pulp while 19 compounds were shown to be present in the seed oil. The total fatty acid content of R. australis seed oil was 38.1 %. The rest were essential oil compounds (21.6 %). There are 6.6% unknown compounds present in the oil obtained from the seed of R. australis. The essential oil content of the pulp of R. australis was 68.6 %. The pulp contained 16 % of fatty acids with 9.1 % unknown compounds. The limonene content (38.4 %) of Raphia australis pulp was found to be about 6 times higher than that of the seed (6.3 %). However, the quantity of hexadecenoic acid obtained from the seed (34.4 %) was more than 3 times higher than the amount found in the pulp (10.8%). Other volatile compounds present in the pulp include 2-pentylfuran (3.2 %), germacrene D (7.1 %), nonanal (3.3 %) alpha cadinene (5.2 %), tertradecanoic acid (2.2 %) while nonanal (8.5 %), eicosane (3.9 %) b-pinene (2.2%), 2 pentyl furan (1.9%) and tetradecanoic acid (1.7 %) constitute the major component of the rest of the volatile oil of the seed of Raphia australis. The result of inflammatory activity of the volatile oil of Raphia australis pulp using adult male mice showed that 80 mg kg-1 dose of the oil elicited a significant anti-inflammatory effect (P<0.01) when compared to 100mg kg-1 of aspirin (P<0.01). The analgesic activities of aspirin (P<0.05) and the 80 mg kg-1 dose (P<0.05) of the oil were only significant in the inflammatory phase of the analgesic test.

Conclusion: These results show that the volatile oil of Raphia australis has therapeutic potential for use in the management of inflammation-related disorders.