Antioxidant, anti-melanogenic, anti-inflammatory, and cytotoxic constituents of Butea monosperma (Lam.) Kuntze flowers

Phytochemical investigation of Butea monosperma (Lam.) Kuntze flowers resulted in the isolation of seven compounds: medicarpin (1), sulfuretin (2), liquiritigenin (3), kaempferol (4), butein (5), iso-butrin (6), and butrin (7). Structures were identified by 1D and 2D NMR and confirmed with literature data. Antioxidant assays (DPPH^•, ABTS^•+, FRAP) revealed butein (5) as the most active, followed by sulfuretin (2) and iso-butrin (6). Liquiritigenin (3) exhibited the strongest tyrosinase inhibition (IC₅₀ = 13.07 ± 2.58 µM) via competitive inhibition and effectively suppressed melanin production in MNT-1 cells, reducing pigmentation by 22-41%, outperforming α-arbutin without cytotoxicity. Compounds 4 and 5 showed potent anti-inflammatory activity, with NO inhibitory IC₅₀ values of 51.60 and 66.93 µM, respectively, while 2, 3, 5, and 6 exhibited moderate cytotoxicity against HeLa (IC₅₀ = 34-38 µM) and HCT116 cells (IC₅₀ = 21-28 µM). Overall, B. monosperma flowers provide multifunctional natural products with promising cosmetic and pharmaceutical potential.