Mandelamide Isolated from Prunus persica Flowers Attenuates TNF-α–Driven Oxidative and Inflammatory Responses in Human Skin Cells

Skin aging is driven by both intrinsic and extrinsic factors, including ultraviolet (UV) radiation and environmental stressors. Tumor necrosis factor-alpha (TNF-α) is a key pro-aging cytokine that promotes reactive oxygen species (ROS) production, leading to collagen degradation and inflammatory responses in skin cells. In this study, we investigated the protective effects of Prunus persica flower extract and its major constituents (1–4) against TNF-α–induced oxidative and inflammatory responses in human dermal fibroblasts (HDFs) and human epidermal keratinocytes (HEKs). In HDFs, the extract and isolated compounds significantly suppressed TNF-α–induced ROS generation and matrix metalloproteinase-1 (MMP-1) secretion while enhancing collagen synthesis. Notably, mandelamide (4) markedly reduced MMP-1 secretion (from 7.53 ± 0.28 to 2.97 ± 0.12, p < 0.001) and restored collagen levels (from 3.3 ± 0.03 to 19.1 ± 0.58, p < 0.001). In HEKs, mandelamide attenuated the production of inflammatory mediators under TNF-α stimulation and further suppressed MMP expression while restoring the mRNA expression of hyaluronan synthase genes under TNF-α/ interferon-γ (IFN-γ) co-stimulation. Importantly, mandelamide exhibited selective activity under inflammatory conditions without affecting basal cellular states. Collectively, these findings demonstrate that mandelamide is a key bioactive constituent of Prunus persica (P. persica) flowers and exerts protective effects against inflammation-associated skin aging through the modulation of oxidative stress and extracellular matrix homeostasis.