Covering: 2015 and 2016The chemistry and biology of natural guanidines isolated from microbial culture media, from marine invertebrates, as well as from terrestrial plants and animals, are reviewed. Emphasis is directed to the biosynthesis, total synthesis, ecological roles as well as on the evolution of guanidines isolated from natural sources.

A new method of screening was developed to generate 770 organic and water-soluble fractions from extracts of nine species of marine sponges, from the growth media of 18 species of marine-derived fungi, and from the growth media of 13 species of endophytic fungi. The screening results indicated that water-soluble fractions displayed significant bioactivity in cytotoxic, antibiotic, anti-Leishmania, anti-Trypanosoma cruzi, and inhibition of proteasome assays. Purification of water-soluble fractions from the growth medium of Penicillium solitum IS1-A provided the new glutamic acid derivatives solitumine A (1), solitumine B (2), and solitumidines A−D (3−6). The structures of compounds 1−6 have been established by analysis of spectroscopic data, chemical derivatizations, and vibrational circular dichroism calculations. Although no biological activity could be observed for compounds 1−6, the new structures reported for 1−6 indicate that the investigation of water-soluble natural products represents a relevant strategy in finding new secondary metabolites.

Degradation of the dye Remazol Brilliant Blue R (RBBR) by the marine-derived fungus Tinctoporellus sp. CBMAI 1061 led to the formation of four unprecedented anthraquinones, of which two were halogenated. Investigation of the RBBR degradation medium also led to the isolation of three new tremulene terpenes, of which two bear novel 2-hydroxy-or 2-methoxy-3,4-dihydro-2H-pyrrole N-oxide moieties. The products of RBBR degradation and of the fungus metabolism have been identified by analysis of spectroscopic data.