Abstract:
Tabernaemontana divaricata is a medicinal plant belonging to the Apocynaceae
family. Native to South and Southeast Asia, it is widely cultivated as an ornamental
shrub due to its attractive white, pinwheel-like flowers. In Sinhalese, it is called
“Wathusudda”. The leaves of this plant have traditionally been used for medicinal
purposes, particularly in the treatment of inflammation and pain. Recently, a few
studies have investigated the antioxidant, anti-inflammatory, and anticancer
properties of related species within the same family. Therefore, this study aimed
to evaluate the bioactivity of T. divaricata, with a particular focus on its potential
cytotoxic effects. The leaves of T. divaricata were subjected to ethanol extraction
before analysis. Total phenolic content (TPC) was determined using the Folin
Ciocalteu method, while antioxidant activity was evaluated via DPPH (1,1
diphenyl-1-picrylhydrazyl) and ABTS (2,2′-azinobis-3-ethylbenzothiazoline-6
sulfonic acid) free radical scavenging assays in vitro. Anti-inflammatory activity
was assessed through the human red blood cell (HRBC) membrane stabilization
assay and the protein denaturation assay. Cytotoxicity was analyzed using the
MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assay
against the HeLa (cervical cancer) cell line. The extract exhibited a TPC of 114.32
± 5.76 mg GAE/g, while the flavonoid content was 21.66 ± 1.68 mg QE/g. The
leaf extract demonstrated high antioxidant activity, with an IC₅₀ = 0.01 mg/mL in
the DPPH assay (standard ascorbic acid IC₅₀ < 0.06 mg/mL). However, in the
ABTS assay, the extract showed a higher IC₅₀ value of 0.7 mg/mL (standard
ascorbic acid IC₅₀ = 0.06 mg/mL). In anti-inflammatory assays, the leaf extract
exhibited better activity in the HRBC assay (IC₅₀ = 0.1 mg/mL) (standard
ibuprofen IC₅₀ < 0.06 mg/mL) compared to the protein denaturation assay (IC₅₀ >
1 mg/mL) (standard ibuprofen IC₅₀ < 0.06 mg/mL). Cytotoxicity evaluation
revealed that the leaf extract inhibited 98.82% of HeLa cell viability at a
concentration of 1 mg/mL, with an IC₅₀ value of 0.1 mg/mL. T. divaricata
possesses considerable therapeutic potential, particularly as a natural source of
antioxidant and anticancer agents, warranting further mechanistic and in vivo
investigations.
