Allelopathic inhibition of teak leaf extract: a potential pre-emergent herbicide.
The effect of teak leaf extracts was tested on germination of rice and two weeds: junglerice and sedge. The methanol extract of deciduous leaves exhibited sustained inhibitory action (GI=56-61%) on junglerice whereas water extract inhibited sedge germination by 25-45%. No extract exhibited significant inhibition on rice. The activity of methanol extract on junglerice was enhanced by 1.7-2.1 times by column chromatography. The chloroform fraction was the most effective one exhibiting 100% inhibition on junglerice. Out of 5-11 compounds present in methanol extract and its column fractions, four phenolic acids (viz. salicylic acid, p-hydroxy benzoic acid, chlorogenic acid and tannic acid) were identified and quantified by HPTLC. Multiple Regression followed by Principal Component Analysis indicated the dependency of observed activity on salicylic acid content in various combinations with benzoic acid, tannic acid and chlorogenic acid in the plant. Further exploration of the methanol extract of the deciduous leaves was suggested for development of a potential pre-emergent herbicide.