Marine ecosystems (>70% of the planet’s surface) comprise a continuous resource of immeasurable biological activities and immense chemical entities. This diversity has provided a unique source of chemical compounds with potential bioactivities that could lead to potential new drug candidates. Many marine-living organisms are soft bodied and/or sessile. Consequently, they have developed toxic secondary metabolites or obtained them from microorganisms to defend themselves against predators [1]. For the last 30–40 years, marine invertebrates have been an attractive research topic for scientists all over the world. A relatively small number of marine plants, animals and microbes have yielded more than 15,000 natural products including numerous compounds with potential pharmaceutical potential. Some of these have already been launched on the pharmaceutical market such as Prialt® (ziconotide; potent analgesic) and Yondelis® (trabectedin or ET-743; antitumor) while others have entered clinical trials, e.g., alpidin and kahalalide F. Amongst the vast array of marine natural products, the terpenoids are one of the more commonly reported and discovered to date. Sesterterpenoids (C25) and triterpenoids (C30) are of frequent occurrence, particularly in marine sponges, and they show prominent bioactivities. In this review, we survey sesterterpenoids and triterpenoids obtained from marine sponges and highlight their bioactivities.

In the past few decades, marine natural products bioprospecting has yielded a considerable number of drug candidates. Two marine natural products have recently been admitted as new drugs: Prialt (also known as ziconotide) as a potent analgesic for severe chronic pain and Yondelis (known also as trabectedin or E-743) as antitumor agent for the treatment of advanced soft tissue sarcoma. In this protocol, methods for bioactivity-guided isolation, purification and identification of secondary metabolites from marine invertebrates such as sponges, tunicates, soft corals and crinoids are discussed. To achieve this goal, solvent extraction of usually freeze-dried sample of marine organisms is performed. Next, the extract obtained is fractionated by liquid-liquid partitioning followed by various chromatographic separation techniques including thin layer chromatography, vacuum liquid chromatography, column chromatography (CC) and preparative high-performance reversed-phase liquid chromatography. Isolation of bioactive secondary metabolites is usually monitored by bioactivity assays, e.g., antioxidant (2,2-diphenyl-1-picryl hydrazyl) and cytotoxicity (microculture tetrazolium) activities that ultimately yield the active principles. Special care should be taken when performing isolation procedures adapted to the physical and chemical characteristics of the compounds isolated, particularly their lipo- or hydrophilic characters. Examples of isolation of compounds of different polarities from extracts of various marine invertebrates will be presented in this protocol. Structure elucidation is achieved using recent spectroscopic techniques, especially 2D NMR and mass spectrometry analysis.

Fungal endophytes are receiving increasing attention by natural product chemists due to their diverse and structurally unprecedented compounds which make them interesting candidates for drug discovery. One fungal genus which is especially productive with regard to the accumulation of a diverse array of mostly bioactive compounds is Pestalotiopsis. This review demonstrates the unique chemical diversity of taxa from this genus and describes their reported bioactivities. To date, alkaloids, terpenoids, isocoumarin derivatives, coumarins, chromones, quinones, semiquinones, peptides, xanthones, xanthone derivatives, phenols, phenolic acids, and lactones, have been reported from Pestalotiopsis species, making this genus a particularly rich source for bioprospecting when compared with other fungal genera. More than 130 different compounds that have been isolated from various species of Pestalotiopsis are covered in this review and their structures are reported within a biogenetic context. Bioassays disclosed that antifungal, antimicrobial, and antitumor activities are the most notable bioactivities of secondary metabolites isolated from this genus. Possible biogenetic pathways for monoterpenes, sesquiterpenes, quinones, and lactones that are covered in this review article are also illustrated.

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