Abstract:
Physiological and biochemical processes in the human body may result in overproduction
of free radicals leading to oxidative damage to biomolecules (e.g. lipids, proteins, DNA).
Usage of medicinal plant products has increased recently due to their beneficial properties
such as antioxidant, anticancer, hypoglycaemic and hypolipidaemic activities. The present
study was designed to assess the in vitro antioxidant activity and free radical scavenging
capacity of ten medicinal plants; Belimal (Aegle marmelos), Iramusu (Hamidesmus
indicus), Ranawara (Cassia auriculata), Walkottamalli (Scoparia dulcis), Nelli (Phyllanthus
emblica), Rasakinda (Tinospora cordifolia), Polpala (Aerva lanata), Babila (Sida
rhombifolia), Beligeta (Aegle marmelos) and Venivel (Coscinium fenestratum), which are
extensively used in the Ayurvedic system in Sri Lanka. Water extracts were used to
evaluate the antioxidant and free radical scavenging activity by different methods; DPPH,
ABTS and FRAP. The total Phenolic (TPC) and Total Flavonoid Content (TFC) were also
assessed. There was a significant difference (P<0.05) between the antioxidant activities of
the tested extracts. The TPC and TFC values of the extracts varied from 5.22 ± 0.08 -
295.94 ± 3.65 mg Gallic Acid Equivalent (GAE)/g dry weight and 0.97 ± 0.002 - 115.01 ±
1.69 mg Catechin Equivalent (CE)/g dry weight respectively. The DPPH and ABTS radical
scavenging activity was higher for the Nelli extract while the least activity was observed in
the Venivel extract. As per the DPPH· and ABTS radical scavenging activities, the Nelli
extract exhibited the highest FRAP activity while the polpala extract showed the least
activity. A positive, significant linear relationship between antioxidant activity and TPC and
TFC content showed that phenolic compounds and flavonoids were the dominant
antioxidant components in the tested medicinal plants.
