Dyeing of cotton yarn with the aqueous extract of the leaves of Eupatorium odoratum L. in Thailand and associated extract toxicity studies

Flavonoid constituents from the aqueous extract of the leaves of Eupatorium odoratum , an invasive weed in Thailand, have potential use as dyestuffs for cotton dyeing. It was found that cotton yarn, which was pretreated with a chitosan solution (with and without a crosslinking glyoxal solution), followed by dyeing with E. odoratum extract in the presence of the inorganic mordant, alum, provided better depth of shade ( K/S ) and also gave better fastness to light and washing than the untreated cotton yarn. Pretreated cotton yarn with the biomordant solution from Memecylon scutellatum leaves gave relatively poor light and wash fastness of the resultant dyed cotton in the presence of alum. From the toxicity studies, the aqueous extract of the leaves of E. odoratum before and after dyeing showed a high toxicity level to the earthworm ( Diplocardia communis ) and the guppy fish ( Poecilia reticulate ). Therefore, it is strongly suggested that E. odoratum aqueous extract after dyeing should be significantly diluted before discharged into the environment.