Intraspecific variation of meroditerpenoids in the brown alga Stypopodium zonale guiding the isolation of new compounds

Abstract Intraspecific variation on meroditerpenoids production by the brown marine alga Stypopodium zonale at four different populations along the Brazilian coast was analyzed using Principal Component Analysis over high-performance liquid chromatography profiles from algae extracts. The ordination of the samples by the similarities of their chromatographic traits showed the existence of three chemotypes: (i) the populations Búzios and Abrolhos which were characterized by the presence of atomaric acid (1), (ii) the population Atol das Rocas which contained the compound stypoldione (2), and (iii) the population Marataízes which was characterized by other peaks that guided the isolation of three new meroditerpenoids stypofuranlactone (3), 10,18-dihydroxy-5′a-desmethyl-5′-acetylatomaric acid (4), and the 10-keto-10-deisopropyliden-5′a-desmethyl-5′-acetylatomaric acid (5) together with the known compound the 10-keto-10-deisopropyliden-atomaric acid (6). The structures and relative stereochemistry of 3, 4 and 5 were elucidated by NMR and MS techniques. The observed chemical differences among populations of S. zonale can be related to its geographic distribution and can open an avenue to the discovery of new compounds in algae.

Diterpenes from marine brown alga Dictyota guineensis (Dictyotaceae, Phaeophyceae)

The crude extract of the marine brown alga Dictyota guineensis was analyzed by high-resolution gas chromatography-mass spectrometry (HRGC-MS). Five diterpenes were identified: dictyol E (the most abundant diterpene), dictyotadiol, dictyoxide, isopachydictyol A and pachydictyol A, all diterpenes from the chemical group I, i.e., mainly prenylated derivatives of known sesquiterpene skeletons that result from a first cyclization of geranyl-geraniol between positions 1 and 10. These diterpenes are known for their activity against bacteria, fungi and other activities. The results characterize D. guineensis as a species that yields exclusively diterpenes from group I, with low oxidation and low structural complexity. On Brazilian coasts, only D. mertensii provides exclusively prenylated guaiane diterpenes. Although D. guineensis presents alternate branches and fixing by rhizoidal branches, it is easily distinguishable from D. mertensii by the much narrower stem, short stature and flabelliform habit of the former species. On the other hand, both species have been characterized as producers of diterpenes of group I, in particular, prenylated guaiane. However, D. guineensis has a majority dictyol E in the lipophilic extract, while D. mertensii produces more complex prenylated guaianes, like dictyol H.