In general terms, the bioactivity of algal and microalgal extracts can be tested using two big groups of techniques: chemical and biological methods. Since no universal method to test bioactivity exists, marine extracts are commonly evaluated by using several methods.

As will be seen in Sect. 4, most of the bioactive compounds that can be found in algae and microalgae have been described to possess antioxidant activity; thus, most of the chemical methods that will be explained in this section are directed to measure different parameters related to the antioxidant activity.

On the other hand, marine compounds have been associated with a high number of bioactivities (mainly pharmacological activities) that can be tested by biological or biochemical methods. In this sense, several reviews covering both general and specific subject areas of marine pharmacology have been published. This kind of review arti­cles has been grouped by Mayer et al. [105] as: (a) general marine pharmacology;

(b) antimicrobial marine pharmacology; (c) cardiovascular pharmacology; (d) antituberculosis, antimalarial, and antifungal marine pharmacology; (e) antiviral marine pharmacology; (f) anti-inflammatory marine pharmacology; (g) nervous system marine pharmacology; and (h) miscellaneous molecular targets.