Valeria Sogos

Melanoma is a skin cancer caused by the malignant transformation of melanocytes and cutaneous melanoma represents the most aggressive and deadliest type of skin cancer with an increasing incidence worldwide. The main purpose of the present research was to evaluate the anticancer effects of the natural bioactive compounds xanthomicrol (XAN) and eupatilin (EUP) in human A375 malignant skin melanoma cells, a cell line widely used as an in vitro model of cutaneous melanoma. XAN and EUP are lipophilic methoxylated flavones with antioxidant, anti-inflammatory, and antitumor properties. The effects of XAN and EUP on cell viability, morphology, lipid profile, oxidative status, apoptosis, and mitochondrial membrane polarization were determined and compared in A375 cells. At 24 h-incubation (MTT assay), XAN significantly reduced viability at the dose range of 2.5–200 μM, while EUP showed a significant cytotoxicity from 25 μM. Moreover, both methoxylated flavones induced (at 10 and 25 μM, 24 h-incubation) marked cell morphological alterations (presence of rounded and multi-nucleated cells), signs of apoptosis (NucView 488 assay), and a noteworthy mitochondrial membrane depolarization (MitoView 633 assay), coupled to a marked lipid profile modulation, including variations in the ratio of phospholipid/cholesterol and a decrease in the oleic, palmitic, and palmitoleic acid amounts. Moreover, a remarkable time-dependent ROS generation (2′,7′-dichlorodihydrofluorescein diacetate assay) was observed during 3 h-incubation of A375 cancer cells in the presence of XAN and EUP (10 and 25 μM). Our results confirm the potential antitumor effect of natural EUP and XAN in cutaneous melanoma by the activation of multiple anticancer mechanisms.

Skin oxidative stress results in structural damage, leading to premature senescence, and pathological conditions such as inflammation and cancer. The plant‐derived prenylated pyrone–phloroglucinol heterodimer arzanol, isolated from Helichrysum italicum ssp. microphyllum (Willd.) Nyman aerial parts, exhibits anti‐inflammatory, anticancer, antimicrobial, and antioxidant activities. This study explored the arzanol protection against hydrogen peroxide (H 2 O 2 ) induced oxidative damage in HaCaT human keratinocytes in terms of its ability to counteract cytotoxicity, reactive oxygen species (ROS) generation, apoptosis, and mitochondrial membrane depolarization. Arzanol safety on HaCaT cells was preliminarily examined by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay and microscopic observation. The arzanol pre‐incubation (5–100 μM, for 24 h) did not induce cytotoxicity and morphological alterations. The phloroglucinol, at 50 μM, significantly protected keratinocytes against cytotoxicity induced by 2 h‐incubation with 2.5 and 5 mM H 2 O 2 , decreased cell ROS production induced by 1 h‐exposure to all tested H 2 O 2 concentrations (0.5–5 mM), as determined by the 2′,7′‐dichlorodihydrofluorescein diacetate (H 2 DCFDA) assay, and lipid peroxidation (thiobarbituric acid reactive substances [TBARS] method). The 2‐h incubation of keratinocytes with H 2 O 2 determined a significant increase of apoptotic cells versus control cells, evaluated by NucView® 488 assay, from the dose of 2.5 mM. Moreover, an evident mitochondrial membrane potential depolarization, monitored by fluorescent mitochondrial dye MitoView™ 633, was assessed at 5 mM H 2 O 2 . Arzanol pre‐treatment (50 μM) exerted a strong significant protective effect against apoptosis, preserving the mitochondrial membrane potential of HaCaT cells at the highest H 2 O 2 concentrations. Our results validate arzanol as an antioxidant agent for the prevention/treatment of skin oxidative‐related disorders, qualifying its potential use for cosmeceutical and pharmaceutical applications.