FTIR- and LC-MS/MS-Identified Phytochemicals and In Vitro Cytotoxic, Antioxidant and Anti-Inflammatory Activities of Oroxylum indicum Extracts Obtained by Microwave-Assisted Extraction

Acne vulgaris is a chronic inflammatory disorder of the pilosebaceous units. Although the overcolonization of Cutibacterium acnes is a primary contributor to acne development, acne-related inflammation is typically driven by a combination of pro-inflammatory cytokines and oxidative stress mediated by reactive oxygen species (ROS). This study aimed to screen extracts of Oroxylum indicum to assess its potential as an anti-acne candidate for cosmetic formulations. Bark (OB), leaf (OL), pod (OP), and seed (OS) extracts of O. indicum were obtained by microwave-assisted extraction (MAE) with 50% (v/v) and 70% (v/v) aqueous ethanol. The extracts were subjected to UV–Vis and Fourier transform infrared (FTIR) spectroscopic analyses and skin-related cytotoxicity, antioxidant, and anti-inflammatory activity assays. UV–Vis and FTIR spectral analyses suggested the presence of phenolic compounds in O. indicum extracts. The antioxidant (free-radical-scavenging) activity of most extracts against DPPH radicals was evident from their IC₅₀ values ranging between 0.35 ± 0.06 mg/mL and 0.54 ± 0.04 mg/mL, while that of MAE-OB50 and MAE-OP50 was 1.04 ± 0.08 mg/mL and 1.06 ± 0.15 mg/mL, respectively. Most extracts, with the exception of the pod extracts, exhibited a low level of cytotoxicity at 200 μg/mL in HaCaT and MRC-5 cells. Anti-inflammatory activities affecting nitric oxide (NO) production were observed in the O. indicum extracts MAE-OL50 (IC₅₀: 128.00 ± 2.80 μg/mL), MAE-OB70 (IC₅₀: 178.72 ± 3.52 μg/mL), MAE-OL70 (IC₅₀: 126.26 ± 0.71 μg/mL), and MAE-OS70 (IC₅₀: 147.03 ± 0.59 μg/mL). The predominant phytochemicals in MAE-OL50, MAE-OB70, MAE-OL70, and MAE-OS70, tentatively identified by liquid chromatography–tandem mass spectrometry (LC-MS/MS), belong to flavonoids and their glycosides, methoxylated flavones, isoflavones, phenolic glycosides, and sugar-related metabolites. The results suggest that O. indicum extracts could be promising candidate ingredients for cosmetic formulations targeting inflammation-associated and oxidative stress-related skin concerns, such as acne-prone skin.