ANTIOXIDANT PROPERTIES OF HIBISCUS: SPECIES VARIATION, ALTITUDINAL CHANGE, COASTAL INFLUENCE AND FLORAL COLOUR CHANGE

Antioxidant properties (AOP) of leaves and flowers of six Hibiscus species were screened. For leaves of Hibiscus rosa-sinensis and Hibiscus tiliaceus, the effects of altitudinal change and coastal influence respectively were assessed. Flowers of Hibiscus mutabilis, during colour change, were analysed. AOP evaluated were total phenolic content (TPC), total anthocyanin content (TAC), radical-scavenging activity expressed as ascorbic acid equivalent antioxidant capacity (AEAC), ferric-reducing power (FRP) and ferrous ion-chelating (FIC) ability. TPC, AEAC and FRP of leaves and flowers of H. tiliaceus were the greatest. The red flowers of H. rosa-sinensis and Hibiscus schizopetalus yielded the highest TAC and FIC ability. The AOP of leaves of highland populations of H. rosa-sinensis were greater than those of lowland. There was no distinct variation in AOP of leaves of inland and coastal populations of H. tiliaceus. The AOP of red flowers of H. mutabilis were greater than those of pink and/or white flowers. Overall ranking of flowers during colour change was red pink white.