Effects of precooling treatments of cosmos caudatus (ulam raja) methanolic extract on total flavonoid content and free radical scavenging activity / Noor Shahimah Mohd Shah

Cosmos caudatus (ulam raja) is one of the herbs that are consumed by several communities in Malaysia especially the Malay community that acts as a natural antioxidant. Many studies had been conducted in order to determine antioxidant activities of this plant. However, there still lacking of information regarding the effect of pre-cooling treatment in the total flavonoid content and antioxidant activities of C caudatus. The objective of this study is to determine the effect of precooling treatment on the total flavonoid content and antioxidant activity of C. caudatus. A methanolic extract of C. caudatus was analysed using aluminium chloride colorimetric assay for determination of total flavonoid content (TFC) and 1, l-diphenyl-2-picylhydrazyl free radical scavenging assay (DPPH) was used to determine the antioxidant activity. The result showed the total flavonoid content at temperature -20°C, 4°C and 25°C were 326.07±0.40, 299.47±1.15 and 208.03±0.40 mg QE/100 g dry weight respectively. There were significant differences (P < 0.05) between the temperatures at -20°C, 4°C and 25°C for the total flavonoid contents. While the antioxidant activity at temperature -20°C, 4°C and 25°C were 77.17±0.03%, 84.21 ±0.12% and 90.58±0.00% respectively. There were significant differences (P < 0.05) between the temperatures at -20°C, 4°C and 25°C for the antioxidant activities. As the conclusion freezing and refrigeration temperature does not significantly affect antioxidant activity. Total flavonoid content is not the main contributor of the antioxidant activity in C caudatus as reflected by the negative correlation result (R* = -0.994) between the two suggestive of other components in C caudatus contributing to the high antioxidant activity.