Antioxidant activity of Terminalia nigrovenulosa and Premna integrifolia extracts in soybean oil.
This study was to investigate the inhibition of linoleic acid peroxidation and the protective effects in stabilizing soybean oil of methanol extracts of Terminalia nigrovenulosa leaf (TnL), bark (TnB) and Premna integrifolia leaf (Pi). The parameters investigated were the inhibition percentage of a linoleic acid emulsion, peroxide values (PV), acid values (AV), TBA (thiobarbituric acid) values, p-anisidine values (AnV), and hexanal formation in soybean oil during storage. The results showed that TnL most effectively inhibited linoleic acid peroxidation with a inhibition percentage that varied from 13.45–82.59%, followed by TnB and BHA (butylated hydroxyanisole). Moreover, these plant extracts also showed an antioxidative effect for reducing the oxidation rate of soybean oil. The TnL extract was the most effective antioxidant and had higher activity than that of BHA for lowering the formation of primary (PV and AV) and secondary (AnV, TBA value, and hexanal concentration) products. The TnB and Pi extracts also possessed a highly effective antioxidant effect similar to BHA. These results indicate that the extracts of these plants have significant potential to be used as natural antioxidants to retard oil oxidation.