Abstract

Chrome VI(Cr 6+) is a hazardous form of chrome that poses a grave danger to unsuspecting users of leather products. Phenolic acids in organic tanning materials have been known to reduce such free radicals into their stable less harmful states which in this case is chrome III (Cr3+). This study was carried out to investigate the potential of Plectranthus barbatus leaf extract in blocking the oxidation of trivalent chrome to the hexavalent species in leather through pretanning and retanning formulations. Preliminary tests were carried out to determine the Total Phenolic Content (TPC) of the leaf extract followed by analysis of the respective free radical scavenging activity. The level of Cr6+ in respective tanned samples was determined and compared with values of samples from chrome solo tannage. An average TPC (mgGAE/g) was 22.84 and 28.18 with ES50 values of 180μg/ml and 160μg/ml respectively for aqueous and methanolic leaf extracts. Artificially aged leathers posted average Cr6+ concentrations of 0.4mg/kg and 0.7mg/kg for pretanned and retanned samples respectively as compared to 18.5mg/kg in wet-blue leather. The results showed that Plectranthus barbatus leaf extract potentially minimised the formation of Cr6+ in leather products.