Anti-allergic activity of the Morinda citrifolia extract and its constituents

Morinda citrifolia (Rubiaceae), commonly known as noni is distributed throughout tropical and sub-tropical regions of the world. Anti-allergic effects of noni have not been reported despite the clinical usage as an anti-allergic agent.

To investigate the anti-allergic effects of the 50% ethanolic extract of M. citrifolia fruits and leaves (MCF-ext and MCL-ext), dinitrofluorobenzene (DNFB)-induced triphasic cutaneous reaction and picryl chloride-induced contact dermatitis (PC-CD) tests were performed.

In DNFB-induced triphasic cutaneous reaction, oral administration of MCF-ext and MCL-ext exhibited dose-dependent inhibition of cutaneous reaction at 1 h (immediate phase response) after the DNFB challenge. MCF-ext also inhibited ear swelling at 24 h (late phase response) and 8 days (very late phase response) after the DNFB challenge. The effect of MCL-ext on the immediate phase response was attributed to the anti-degranulation from RBL-2H3 cells, while MCF-ext had no significant effect on degranulation. The active components of anti-degranulation activity in MCL-ext were determined to be ursolic acid, rutin and kaempferol-3-O-α-L-rhamnopyranosyl-(1→6)-β-D-glucopyranoside. In the PC-CD test, both MCF-ext and MCL-ext showed an anti-swelling effect but the potency of MCF-ext was stronger than MCL-ext.

These data suggest that noni fruits and leaves can be a daily consumable material for the prevention of allergic symptoms.