Background and Objective: Oxidative stress is a primary contributor to carcinogenesis, making antioxidant-rich medicinal plants highly relevant to cancer chemoprevention. The present study was designed to evaluate and compare the phytochemical composition and in-vitro antioxidant potential of hydroethanolic root extracts of Calotropis gigantea (CG) and Bauhinia variegata (BV).

Materials and Methods: Both plants were authenticated at the Botanical Survey of India, Jodhpur. Hydroethanolic extracts (70:30 ethanol:water) were prepared by cold maceration. Quantitative phytochemical analysis was performed for total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC), saponin index, and terpenoid content. Antioxidant activity was evaluated by five complementary assays: DPPH radical scavenging, ABTS radical cation decolorization, ferric reducing antioxidant power (FRAP), hydrogen peroxide (H₂O₂) scavenging, and reducing power assay. Ascorbic acid and Trolox served as reference standards. IC₅₀ values were calculated by linear regression.

Results: BV extract yielded a higher extractive value (14.92% w/w) and contained significantly greater TPC (89.36 ± 2.14 mg GAE/g) and TFC (68.93 ± 1.62 mg RE/g) compared to CG (TPC: 72.48 ± 1.92; TFC: 54.21 ± 1.47 mg RE/g). CG showed higher terpenoid content (63.84 ± 1.88 mg LE/g) and saponin index (280). BV demonstrated superior antioxidant activity across all assays with DPPH IC₅₀ = 48.2 μg/mL and ABTS IC₅₀ = 43.9 μg/mL, compared to CG (DPPH IC₅₀ = 64.8; ABTS IC₅₀ = 58.6 μg/mL). A significant positive correlation was established between TPC/TFC and radical scavenging activity (p < 0.01).

Conclusion: BV exhibits superior antioxidant activity attributable to its flavonoid-dominant phytochemical profile, whereas CG possesses a terpenoid- and cardenolide-rich composition. Both species offer promising chemopreventive potential through complementary redox-modulatory mechanisms.

KEYWORDS: Calotropis gigantea, Bauhinia variegata, antioxidant activity, DPPH, ABTS, FRAP, total phenolic content, total flavonoid content, oxidative stress, cancer chemoprevention.