Antarctic Macroalgae Palmaria decipiens (Rhodophyta, Palmariales) Extracts Present Antioxidant and Antitumor Activity against Colorectal Cancer

Abstract

Despite therapeutic advances in recent decades, colorectal cancer is still the third most frequent neoplasm worldwide, with significant morbidity and mortality in young and middle-aged adults. Therefore, advance in treatment options for patients who are afflicted with tumor subtypes without effective therapies is needed. Antarctica macroalgae are substances-producing organisms with important biological activities, in which antitumor properties are investigated, showing promising cytotoxic results. There are no reports so far showing antitumor activity of macroalgae Palmaria decipiens extracts against colorectal tumors. This study aims to evaluate the effect of macroalgae P. decipiens extract from Antarctic on tumor cell HCT-116 and non-tumor cell HaCaT lines. The phenolic compounds present were identified by high performance liquid chromatography. The antioxidant activity of the extracts was determined by the DPPH radical inhibition method and cytotoxicity was evaluated through MTT assay. Cell death events were identified using dual staining with acridine orange/ethidium bromide and flow cytometry. The quantification of phenolic compounds present in the extracts identified the presence of three main compounds among them is kaempferol. The metanolic extract showed inhibition within 72 h of treatment in HCT-116 and potential antioxidant activity. The results presented in this study point out an imbalance in the redox metabolism and also a loss of mitochondrial membrane potential integrity, most likely inducing cell death mechanisms after 72 h exposure to treatment with metanolic extract. These events could be observed by penetration of propidium iodide through membrane damage. The results indicate that the extract of the Antarctic macroalgae P. decipiens interferes in the mechanisms of action of colorectal cancer tumor cells, acting as a potential antitumor and antioxidant agent.