Microalgae: An Untapped Resource for Natural Antimicrobials

Abstract

Numerous biochemical compounds are synthesized by algae in a wide variety of ecosystems. To date, more than 18,000 new bioactive compounds have been isolated from marine algae; most are still uncharacterized. Therefore, the identification of novel prospective antimicrobials from microalgae presents a unique opportunity. A number of investigations have explored the therapeutic potential of algal extracts and extracellular compounds from a wide range of microalgae; they have confirmed antibacterial, antiprotozoal, antiviral, antifungal, and anti-plasmodial activity. Chemical groups such as phenols, fatty acids, indoles, ter-penes, acetogenins, and some volatile halogenated hydrocarbons derived from microalgae have shown antimicrobial activity. For example, supercritical extracts of the microalgal Chaetoceros muelleri have shown antimicrobial activity due to its lipid composition. Many algal species are also effective against a range of bacteria. For example, Pithophora oedogonium targets Salmonella and Staphylococcus spp. The algae Rivularia bullata, Nostoc spongiaeforme, Codium fragile, Colpomenia peregrina Sauvageau, Cystoseira barbata, and Zanardiniatypus are active against many Gram-negative and Gram-positive bacteria. Multidrug-resistant bacteria pose an increasing challenge to global health, with the future efficacy of antimicrobial drugs being uncertain. Most antimicro-bial agents that are successfully used in clinical practice have drawbacks such as toxicity, lack of efficacy, and high costs; furthermore, their frequent use can