Nat Prod Res. 2015;29(6):535-42.
Probing occurrence of phenylpropanoids in Morinda citrifolia in relation to foliar diseases.
Mandal S, Rath C, Gupta CK, Nath V, Singh HS.

A major phenolic compound identified in noni leaf samples was 4-coumaric acid. Also present were 4-hydroxybenzoic acid, vanillic acid, 4-hydroxybenzaldehyde, vanillin and ferulic acid. Higher amounts of 4-coumaric acid, in combination with other phenolic compounds, may be why leaf disease rates were lower in certain samples. (original abstract available online at