Antioxidant properties (AOP) of leaves and teas of Morus alba L., Lagerstroemia
speciosa (L.) Pers. and Thunbergia laurifolia Lindl. as affected by
microwave, oven and freeze drying were assessed. Total phenolic content
(TPC), radical scavenging ability expressed as ascorbic acid equivalent capacity
(AEAC) and ferric reducing power (FRP) were screened using the Folin-
-Ciocalteu, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and potassium ferricyanide
assays, respectively. The effects of particle size were also investigated. Microwave
drying resulted in enhanced AOP in M. alba and T. laurifolia. Oven drying
resulted in declined AOP in T. laurifolia, with M. alba and L. speciosa relatively
unchanged. Significant increase in AOP was observed in freeze-dried leaves
of M. alba with L. speciosa and T. laurifolia showing no change or slight increase.
TPC, AEAC and FRP of ground microwave-, oven- and freeze-dried
leaves of M. alba extracted with 50% methanol were significantly higher than
shredded leaves. For tea infusions extracted with hot water, three categories
were recognised, i.e., species with shredded leaves yielding stronger AOP (M.
alba), species with ground leaves yielding stronger AOP (L. speciosa), and
species with ground and shredded leaves yielding comparable AOP (T. laurifolia).