Structural diversity, biosynthesis, and health-promoting properties of brown algal meroditerpenoids

Marine algae that constitute hundreds of millions of tons of biomass are the oldest representatives of the plant kingdom. Recently, there has been growing interest in the utilization of algae as sustainable feedstocks for natural products with an economic value. Among these natural products are the meroditerpenoids, which are renowned for their protective effects against oxidative stress, inflammation, cancer, obesity, diabetes, and neurodegenerative disorders. Meroditerpenoids have a mixed biosynthetic origin and display a wide range of structural diversity. Their basic structure consists of a ring system bearing a diterpenoid side chain. Structural variations are observed in terms of the functional groups and saturation/cyclization of the diterpenoid side chain. This review classifies algal meroditerpenoids as plastoquinones, chromanols, chromenes, chromones, cyclic meroditerpenoids, nahocols, and isonahocols and examines their potential applications in functional foods and biopharmacology. Their lipid solubility, low molecular weight, and propensity to cross the blood-brain barrier places meroditerpenoids as potential drug candidates. There is growing interest in the study of algal meroterpenoids, and recent research has reported the structure of several new meroterpenoids and their biological activities. Further research is needed to extend the use of algal meroditerpenoids in preclinical trials. Understanding the mechanism of their biosynthesis will allow the development of de novo biosynthesis and biomimetic synthesis strategies for the industrial-scale production of meroditerpenoids and their synthetic derivatives to aid pharmaceutical research. This review is the first to summarize up-to-date information on all brown algae-derived meroditerpenoids.

Diversity of Chromanol and Chromenol Structures and Functions: An Emerging Class of Anti-Inflammatory and Anti-Carcinogenic Agents

Natural chromanols and chromenols comprise a family of molecules with enormous structural diversity and biological activities of pharmacological interest. A recently published systematic review described more than 230 structures that are derived from a chromanol ortpd chromenol core. For many of these compounds structure-activity relationships have been described with mostly anti-inflammatory as well as anti-carcinogenic activities. To extend the knowledge on the biological activity and the therapeutic potential of these promising class of natural compounds, we here present a report on selected chromanols and chromenols based on the availability of data on signaling pathways involved in inflammation, apoptosis, cell proliferation, and carcinogenesis. The chromanol and chromenol derivatives seem to bind or to interfere with several molecular targets and pathways, including 5-lipoxygenase, nuclear receptors, and the nuclear-factor "kappa-light-chain-enhancer" of activated B-cells (NFκB) pathway. Interestingly, available data suggest that the chromanols and chromenols are promiscuitively acting molecules that inhibit enzyme activities, bind to cellular receptors, and modulate mitochondrial function as well as gene expression. It is also noteworthy that the molecular modes of actions by which the chromanols and chromenols exert their effects strongly depend on the concentrations of the compounds. Thereby, low- and high-affinity molecular targets can be classified. This review summarizes the available knowledge on the biological activity of selected chromanols and chromenols which may represent interesting lead structures for the development of therapeutic anti-inflammatory and chemopreventive approaches.