In vitro immunomodulatory activity and in vivo anti-inflammatory and analgesic potential with gastroprotective effect of the Mediterranean red alga Laurencia obtusa

Context: Red algae have been recognized as a rich natural source of compounds possessing interesting biological and pharmacological activities.

Objective: This work investigates anti-inflammatory, analgesic and gastroprotective activities of MeOH/CH₂Cl₂ crude extract and its fractions F1 (50% MeOH) and F2 (80% MeOH) from the whole alga plant Laurencia obtusa Hudson (Rhodomelaceae).

Materials and methods: Anti-inflammatory activity was evaluated in vitro using cytometric bead array (CBA) technology to follow up the secretion of tumour necrosis factor alpha (TNF-α) in lipopolysaccharide activated THP-1 monocytic cells at doses of 10–250?μg/mL and in vivo using carrageenan-induced paw oedema in Wistar rats at doses of 25, 50, 100 and 200?mg/kg. Crude extract and fractions were tested at the doses of 25, 50, 100 and 200?mg/kg for peripheral and central analgesic activity by acetic acid-induced writhing test and hot-plate method, respectively, in Swiss albino mice. Gastroprotective activity was evaluated using HCl/ethanol-induced gastric ulcer test in rats at doses of 25, 50, 100 and 200?mg/kg.

Results: Crude extract, F1 and F2 showed an interesting inhibition of TNF-α secretion with IC₅₀ values of 25, 52 and 24?μg/mL, respectively, and a significant anti-inflammatory activity in vivo (p?< 0.01), 3?h after carrageenan injection, the oedema inhibition was 55.37%, 52.18% and 62.86%, respectively, at the dose of 100?mg/kg. Furthermore, they showed a significant peripheral analgesic activity with 53.79%, 55.92% and 57.37% (p?< 0.01) of writhing inhibition, respectively. However, no significant activity was found in the hot-plate test. An interesting gastroprotective effect was observed with crude extract and its fractions F1 and F2 with a gastric ulcer inhibition of 65.48%, 77.42% and 81.29%, respectively, at the dose of 50?mg/kg.

Discussion and conclusion: These results suggest that L. obtusa might be used as a potential source of natural anti-inflammatory and analgesic agents with gastroprotective effect.