Abstract
Calotropis procera is a perennial flowering plant of the Apocynaceae family, traditionally used in medicine to treat various ailments. Recent investigations have revealed its potential therapeutic activities such as anti-inflammatory, gastroprotective, analgesic, anti-obesity, and anti-diabetic properties. RP-HPLC qualitatively and quantitatively evaluated the phenolic acids and flavonoids in the ethanolic extract at two different wavelengths, 280 and 330 nm. In addition, total phenolic and flavonoid contents were measured via spectrophotometric determination in addition to the antioxidant activity. The antiproliferative effects of C. procera were investigated on two cancer cell lines: human colon (HCT-116) and breast (MCF-7) cancer. Several methods were utilised to analyse the effectiveness of the plant extract on the cytotoxicity, apoptosis, cell cycle progression, genes involved in the cell cycle, and protein expression profiles of HCT-116 and MCF-7 cells. These included the MTT assay, Annexin V-FITC/PI, analysis of the cell cycle, and Western blot. Results indicated that ferulic and caffeic acids were the major compounds at λmax 280 nm (1.374% and 0.561%, respectively), while the major compounds at λmax 325 nm were kaempferol and luteolin (1.036% and 0.512%, respectively). The ethanolic extract had significantly higher antioxidant activity (80 ± 2.3%) compared to ascorbic acid (90 ± 3.1%). C. procera extract exhibited dose-dependent cell growth inhibition, with an estimated IC50 of 50 μg/mL for MCF-7 and 55 μg/mL for HCT-116 cells at 24 h. Annexin V-FITC/PI confirmed the induction of apoptosis. Remarkably, cell cycle arrest occurred at the sub-G1 phase in MCF-7 cells, while in HCT-116 cells, it was observed at the G2-M phase. The sub-G1 arrest was associated with dysregulation of Akt, p-AKT, mTOR, and p-mTOR proteins, as confirmed by the Western blot analysis, while downregulation of CDK1, cyclin B1, and survivin caused G2-M arrest.