Abstract:
Antioxidants neutralize free radicals and reduce oxidative damage in biological
systems and food matrices. Growing concerns over synthetic antioxidant safety have driven
interest in plant-based alternatives. Osbeckia octandra (Heen Bovitiya) is an indigenous Sri
Lankan medicinal plant traditionally used in herbal treatments, known for its rich phytochemical
profile. This study evaluated the antioxidant properties of O. octandra leaf extract. Leaves were
dried, powdered, and extracted using 80% (V/V) methanol under varying shaking times (1, 6, 12,
24, and 48 hours) and dilution factors (1:10, 1:50, 1:100, 1:200, and 1:250; sample: solvent).
Statistical analysis was performed using R Studio, with mean values compared via Tukey post-
hoc test in triplicates. Total phenolic content (TPC) and total flavonoid content (TFC) were
determined using Folin–Ciocalteu and Aluminium Chloride colorimetric assays, respectively.
The highest TPC (888.37 ± 0.1 mg GAE/g (mg gallic acid equivalents per gram)) was recorded
at 24 hours with 1:250 dilution, while maximum TFC (2.27 ± 0.06 mg QU/g (mg quercetin
equivalents per gram)) was obtained at 24 hours with 1:100 dilution. Antioxidant activity was
assessed through DPPH (2,2-diphenyl-1- picrylhydrazyl) and ABTS (2,2’-azino-bis (3-ethyl
benzo thiazoline-6-sulphonic acid)) radical scavenging assays. The DPPH IC50 was 37.17
μg/mL at 24 hours and 1:250 dilution, comparable to standard ascorbic acid, while the ABTS
IC50 was 24.00 μg/mL under the same conditions, reflecting stronger activity. Overall, O.
octandra leaves demonstrated significant (p<0.05) antioxidant properties. The biphasic extraction
pattern observed indicates differential compound release and stability, with prolonged extraction
potentially causing degradation. These findings support the development of standardized
extraction protocols and establish Heen bovitiya as a promising natural antioxidant for food
preservation and functional product applications.
