Background: Pimenta racemosa tree has many traditional uses where its leaves are used as herbal tea for treatment of flatulence, gastric disorder, osteoarthritis, colds and fever in addition to its analgesic and anti-inflammatory activities. So, this study aimed to isolate phenolic constituents of 80% aqueous methanol extract (AME) of leaves and evaluate its biological activities.
Methods: The defatted AME was chromatographed and structures of the isolated compounds were elucidated using UV, NMR spectroscopy and UPLC-ESI-MS analysis. Antioxidant activity was investigated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capacity. Anti-inflammatory activity was evaluated using carrageenan - induced paw oedema, while antinociceptive activity was determined by chemical and thermal stimuli. Anti-ulcerogenic effect of AME against gastric damage induced by ethanol in Wister male albino rats was evaluated. Also, hepatoprotective activity was investigated through determination of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) following oral administration of paracetamol. Both of Anti-ulcerogenic and hepatoprotective activities (125, 250 and 500 mg/kg b.wt.) were supported by histopathological examinations.
Results: Gallic acid (1), methyl gallate (2), avicularin (3), quercetin 3-O-β-D-arbinopyranoside (4), quercetin 3-O-β-D-glucopyranoside (5), quercetrin (6), cynaroside (7), strictinin (8), castalagin (9), grandinin (10) quercetin (11) and ellagic acid (12) were isolated. AME showed significant radical scavenging activity (SC50 = 4.6 μg/mL), promising anti-inflammatory effect through inhibition of oedema and antinociceptive activity by reduction in number of writhes after acetic acid injection and prolongation of reaction time towards the thermal stimulus. AME reduced the gastric mucosal lesions compared with ethanol control and ranitidine groups, ALT at the three doses and AST only at 125 and 250 mg/kg b.wt., when compared with paracetamol group. The results were confirmed by histopathological studies.
Conclusion: P. racemosa leaves are rich in phenolic compounds and showed significant biological activities.
Keywords: Anti-inflammatory; Anti-ulcerogenic; Antinociceptive; Hepatoprotective; Myrtaceae; Phenolic compounds; Pimenta racemosa.