Evaluation of the Anti-inflammatory and Antioxidant Activities of Selected Resin Exudates

Abstract

Plant resins are reported to have high medicinal values due to their content of bioactive metabolites. Few reports were found in the last two decades concerning the chemistry and anti-inflammatory activity of the resins belonging to Eucalyptus and Araucaria genera. Therefore, the exudate resins of Eucalyptus maculata, Araucaria excelsa and Araucaria bidwillii were evaluated for their phenolic and flavonoid content, together with their possible anti-inflammatory potential via carrageenan-induced paw edema in rats at the doses of 100, 200, and 400 mg/kg. The methanol extract of E. maculata (MEME) kino resin was the richest in phenolics (572.82 ± 1.75 μg GAE/mg extract), and flavonoids (11.60 ± 0.01 μg QE/mg extract). The MEME (400 mg/kg) showed the most significant percentage inhibition of paw oedema (50.91%), compared to indomethacin (66.11%). The extract also decreased serum malondialdehyde (MDA) (42%), nuclear factor kappa B (NF-κB) (42.7%), tumor necrosis factor-alpha (TNF-α) (40.5%), cyclooxygenase-2 (COX-2) (42%) and nitric oxide (NO) (23%). In addition, it increased antioxidant enzymes; reduced glutathione (GSH) (2.6-fold) and superoxide dismutase (SOD) (1.3-fold), compared to control group. Moreover, it displayed a profound antioxidant property with IC50 of 6.83 ± 0.77μg/mL compared to trolox (IC50 21.18 ± 0.59 μg/mL) using DPPH assay. The methanol extract of E. maculata resin was standardized by HPLC to contain 68.21 mg of 7-O-methyl aromadendrin (MA)/g extract. These findings suggest that E. maculata kino resin is a potent antioxidant with potential therapeutic efficacy for treating inflammation.