Relationship between antioxidant properties and chemical composition of some Thai plants

Plants, which are rich in phenolic components, are of interest as sources of natural antioxidants. However, the biosynthesis of secondary metabolites is not well understood, and many plant components can act as antioxidants, so whole extracts from a wide range of plants need to be examined. To gain further knowledge in this area, the antioxidant activity and composition of organic solvent extracts from 28 Thai plants were investigated. A wide range of analytical parameters were studied including yield, phenolic compounds, flavonoids, moisture, ash, protein, fat, carbohydrate, dietary fiber, calcium, iron and vitamin C, and the data were analyzed by partial least square (PLS) regression analysis and principal component analysis (PCA) to allow correlation of the parameters and classification of the plants. The carbohydrate content was strongly associated with yield of extract. Antioxidant activity correlated well with phenolic and flavonoid contents, whereas the total phenolic compounds correlated weakly with other components except flavonoid content. In addition, fat and energy were useful parameters to distinguish seeds from other plant parts. These results provide useful data about the studied relationships and chemical patterns in plant tissues.