In Vitro and in Vivo Efficacy of Different Ointment Formulations Containing Centaurium erythraea Rafn. Aerial Extract

<b>Background:</b><i>Centaurium erythraea Rafn</i>. (<i>C. erythraea</i>) is a medicinal plant traditionally used in European folk medicine for the treatment of wounds, skin inflammations, and other dermatological conditions, in addition to its well-documented systemic antioxidant and anti-inflammatory effects. However, its topical applications remain insufficiently investigated, particularly using plant material collected from Romania. The purpose of this study was to prepare different ointment formulations containing <i>C. erythraea</i> Rafn. extract obtained from the aerial parts of the plant, using various excipients, and to evaluate their in vitro and in vivo efficacy. <b>Methods:</b> The phytochemical profile of <i>C. erythraea</i> extract was characterized using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The lyophilized extract was pre-dissolved in different solubilizing agents-Transcutol^® P (diethylene glycol monoethyl ether), Capryol^® 90 (propylene glycol monocaprylate), or a combination of both-and then incorporated into five ointment formulations. Texture analysis and an in vitro membrane diffusion study were performed. The antioxidant capacity of the formulations was assessed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ferric reducing antioxidant power (FRAP), and total phenolic content (TPC) assays. Anti-inflammatory activity was evaluated in vitro using tumor necrosis factor-alpha (TNF-α)-induced interleukin-1 beta (IL-1β) production in human keratinocyte (HaCaT) cells, and in vivo using a carrageenan-induced rat paw edema model. <b>Results:</b> LC-MS/MS identified 18 polyphenolic compounds, with hyperoside (3.78 ± 0.05 µg/mL), protocatechuic acid (1.13 ± 0.06 µg/mL), chlorogenic acid (1.07 ± 0.06 µg/mL), and quercetin (0.53 ± 0.03 µg/mL) as the principal constituents. The formulation containing both Transcutol^® P and Capryol^® 90 exhibited the most pronounced antioxidant activity (65% DPPH inhibition; 69.71 ± 0.83 mg gallic acid equivalent/mL) and significantly reduced IL-1β levels by 45.7% compared to the inflamed control. In vivo, this formulation showed comparable anti-edematous effects to a methylprednisolone ointment. Furthermore, it demonstrated the highest skin permeation efficiency, with a quercetin diffusion coefficient of 35.12 × 10^-5 cm²/min. <b>Conclusions:</b> These findings highlight the therapeutic potential of <i>C. erythraea</i> extract from aerial parts in topical formulations and underscore the enhancing role of Transcutol^® P and Capryol^® 90 in improving both the pharmacodynamic and pharmacokinetic properties of bioactive compounds.