PARTICLE SIZE AND TEMPERATURE EFFECTS ON ANTIOXIDANT BY-PRODUCT ISOLATED FROM LEAF GUM EXTRACT OF MESONA PROCUMBENS HEMSL

A water extraction procedure for isolating antioxidants from dried aerial tissue of Mesona procumbens Hemsl. prior to leaf gum/starch composite gel preparation was developed, along with investigation of its antioxidative activities. The results showed that the highest contents of total phenolics and flavonoids were isolated from the dried aerial tissues when they were extracted under 100C for 2 h using the dried materials ground to 75-µm particle size. This water extract also had the highest antioxidative responses, as determined by 2,2-diphenyl-1-picrylhydrazy scavenging, ferric reducing antioxidant power, 2,2-azino-bis[3-ethyl-benzthiazoline-6-sulfonic acid] radical-scavenging, superoxide-scavenging and lipid peroxidation inhibition activities. The water extract produced under 100C condition also showed the greatest gel hardness and gel strength (prepared by using 2% cassava starch). Thus, the extracted antioxidants from aerial tissues of M. procumbens Hemsl. could be considered for some commercial applications. PRACTICAL APPLICATIONS Dried aerial tissues of Mesona procumbens Hemsl. contain polysaccharide gum, which are traditionally used to make jelly-type dessert or hot herb drink. These dried tissues also have many antioxidants that are helpful to human health. In the present study, we compared the levels of antioxidants isolated from the water extracts of M. procumbens Hemsl. samples, which were ground into fine powders with different particle sizes, before those water extracts were used to make starch composite gel. The antioxidant contents and the antioxidative activities varied with the different particle sizes and extraction temperatures. These results indicate that decreasing particle size and increasing extraction temperature enhance extraction efficiency and improve the quality of isolated antioxidants. The isolated antioxidants can be used as a potential additive for food and dietary items.