The Underrepresented Quinolinone Alkaloids in Genera Penicillium and Aspergillus: Structure, Biology, and Biosynthetic Machinery.

Quinolone alkaloids are N-heterocycles with extensive structural diversity, mainly derived from in fungi from anthranilic acid and amino acids as precursors with a wide range of biological activities as antifungal, antimicrobial, anti-inflammatory, and insecticidal activities. The quinolone basic skeleton comprised of either 2-quinolones or 4-quinolones generated more than one hundred compounds. Several reviews discussed quinolones; particularly, the fluoroquinolones, yet few studies tackled natural quinolones. Many of these quinolones were not assayed for their antimicrobial potential despite their unique stereospecificity, which can supersede synthetic quinolones if their discovery is coupled with OMICS techniques, biochemical and molecular strategies as heterologous expression to maximize their yield. Herein, we conducted a comprehensive review of the quinolone's family in Aspergillus and Penicillium species, the exclusive producers of quinolones whether they are soil, endophytic or marine derived highlighting their isolation, chemical structures, pharmacological effects, structure activity relationships if any, and biosynthetic machinery. We believe that our initiative will pave the way for further development of natural quinolones as future antimicrobial agents.