## 1 Introduction
The understanding of physicochemical properties is crucial for the application of DHA and other PUFAs in food science, pharmaceuticals and nutritional supplements due to their behavior in formulations and their biological effects being directly influenced by these properties. Nowadays, the role of n-3 PUFAs has advanced significantly with the growing understanding of the unique specialized proresolving lipid mediators [14]. However, the extraction method also plays a role, as the quality of unconventional lipids largely depends on these extraction techniques [15]. The properties of DHA include physical properties in which the solubility is hydrophobic and insoluble in water. Density and viscosity, as typical for fatty acids, are influenced by their degree of unsaturation and temperature. More unsaturation usually correlates with lower viscosity. DHA has lower density and viscosity compared to saturated and monounsaturated fatty acids and has a melting point around \(-44\)\({}^{\circ}\)C. The multiple double bonds lower the melting point compared to saturated fatty acids of similar molecular weight. The chemical properties include oxidation in which the reactivity can lead to the formation of lipid peroxides and other degradation products, which can be catalyzed by heat, light and metal ions, affecting the stability and shelf life of DHA-containing products. Moreover, DHA can undergo hydrogenation, a chemical reaction that adds hydrogen atoms to the double bonds, converting them into single bonds and producing more saturated fatty acids and also can undergo esterification and isomerization, potentially affecting its biological activity [14,16]. Furthermore, in DHA and EPA there are potential spectroscopic techniques and chemometric analyses for rapid measurement in algal oil. The best predictions for both were achieved via nuclear magnetic resonance spectroscopy, in which the determination coefficients of crossvalidation values were 0.963 and 0.967 [17]. PUFAs are described to be essential for the synthesis of eicosanoids, such as prostaglandam (PGs), prostacyclin, thromboxane, leukotrienes (LTs) and others. However, the activity of  
Figure 1: Chemical structure of DHA. Figure 2: Chemical structure of AA. the eicosanoids depends on the kind of PUFA that it is derived from [18]. Those eicosanoids that come from n-3 PUFA are described to have an anti-inflammatory effect, which is why in recent years there has been a growing interest in possible therapeutic use on several diseases [19]. On the other hand, eicosanoids that come from n-6 PUFAs have a pro-inflammatory effect, which has been described as a predisposing factor for cancer and other diseases [20]. It is worth mentioning that in the last decades there has been an interesting change in the proportion of fatty acids present in the human diet. Historically, humans consumed 1:1 proportion of n-3 and n-6 fatty acids in the diet. However, in today's Western diet there is a 1:20 proportion of n-3/n-6 fatty acids, which is a substrate that leads to various inflammatory diseases [21]. There is a large amount of studies about the health benefits of n-3 PUFA supplementation, including its use for different diseases, such as the improvement of lipid profile and reduction of inflammation parameters such as tumor necrosis factor \(\alpha\) (TNF-\(\alpha\)) or high sensitivity C-Reactive Protein [22], the decrease in the severity of non-alcoholic fatty liver disease by reducing hepatic steatosis and liver injury [23], the enhancement of the neurocognitive function [24], the modulation of membrane-associated signal transduction involved in cancer pathogenesis and suppression of systemic inflammation [25] and many other diseases. Despite the promising properties attributed to n-3 PUFAs, their translation into a clinical context encounters several challenges. One notable issue pertains to the potential adverse effects that n-3 PUFAs may pose to patients and the scarcity of evidence derived from human trials.