Natural products from Pluchea sagittalis act as inhibitors of photosynthesis in vitro.

Four compounds were isolated from roots and aerial parts of Pluchea sagittalis (Asteraceae), 3, 5-dihydroxy-6, 7, 3', 4'-tetramethoxiflavunol (1), 5-hydroxymethylfurfural (2), 3, 4-dimethoxybenzaldehyde (3) and 2, 3, 4-trihydroxybenzaldeyde (4). Their herbicidal potential was detected by polarographic techniques. All of them inhibited the non-cyclic electron transport on basal, phosphorylating and uncoupled conditions from HO to methylviologen (MV); thus, they act as Hill reaction inhibitors.