Abstract:(+)-Cyanobacterin, a photosynthesis inhibitor of freshwater cyanobacterium Schytonema hofmanni, was synthesized in 6 steps from a readily accessible chiral synthon 5R-5-(l-menthyloxy)-2(5H)furanone.
“…A similar example was presented more recently by Ishibashi et al (see Scheme ): their synthesis of cyanobacterin, a photosynthesis inhibitor of freshwater cyanobacteria, commenced with the stereoselective addition of an isopropyl anion to menthyloxy furanone 4a . 7 Starting Sequence of the Cyanobacterin Synthesis by Ishibashi et al …”
Scheme 4. Synthesis of a Kuehneromycin A and Mniopetal Precursor According to Jauch 11 Scheme 5. Diels-Alder Reaction of o-Quinonoid Pyrone 12 Scheme 6. Synthesis of C-Ring Fragment of Cobyric Acid Scheme 7. Starting Sequence of the Cyanobacterin Synthesis by Ishibashi et al. 15
“…A similar example was presented more recently by Ishibashi et al (see Scheme ): their synthesis of cyanobacterin, a photosynthesis inhibitor of freshwater cyanobacteria, commenced with the stereoselective addition of an isopropyl anion to menthyloxy furanone 4a . 7 Starting Sequence of the Cyanobacterin Synthesis by Ishibashi et al …”
Scheme 4. Synthesis of a Kuehneromycin A and Mniopetal Precursor According to Jauch 11 Scheme 5. Diels-Alder Reaction of o-Quinonoid Pyrone 12 Scheme 6. Synthesis of C-Ring Fragment of Cobyric Acid Scheme 7. Starting Sequence of the Cyanobacterin Synthesis by Ishibashi et al. 15
“…Cyanobacterin (a chlorinated γ-lactone) (Figure 5) is another allelopathic substance that was isolated from the freshwater cyanobacterium Scytonema hofmanni that is highly toxic to other cyanobacteria and eukaryotic algae by interrupting photosynthetic electron transport [29]. There are two other structurally different cyanobacterins that were identified in Nostoc linckia that specifically inhibit electron transport in photosystem II [127,128]. A series of metabolites, such as nostocyclamide, nostocine A and nostocarboline (Figure 5) that were isolated from a Nostoc sp., exhibited toxic action against algae [129][130][131].…”
An increasing human population necessitates more food production, yet current techniques in agriculture, such as chemical pesticide use, have negative impacts on the ecosystems and strong public opposition. Alternatives to synthetic pesticides should be safe for humans, the environment, and be sustainable. Extremely diverse ecological niches and millions of years of competition have shaped the genomes of algae to produce a myriad of substances that may serve humans in various biotechnological areas. Among the thousands of described algal species, only a small number have been investigated for valuable metabolites, yet these revealed the potential of algal metabolites as bio-pesticides. This review focuses on macroalgae and microalgae (including cyanobacteria) and their extracts or purified compounds, that have proven to be effective antibacterial, antiviral, antifungal, nematocides, insecticides, herbicides, and plant growth stimulants. Moreover, the mechanisms of action of the majority of these metabolites against plant pests are thoroughly discussed. The available information demonstrated herbicidal activities via inhibition of photosynthesis, antimicrobial activities via induction of plant defense responses, inhibition of quorum sensing and blocking virus entry, and insecticidal activities via neurotoxicity. The discovery of antimetabolites also seems to hold great potential as one recent example showed antimicrobial and herbicidal properties. Algae, especially microalgae, represent a vast untapped resource for discovering novel and safe biopesticide compounds.
“…These biocides show growth inhibitory response on microorganisms including bacteria, viruses, fungi, and some invertebrates such as crustaceans, bivalves, and also some vertebrates like fish, birds, and mammals (Misra and Kaushik, 1989; Schwartz et al, 1990; Burja et al, 2001). These cyanotoxins have a great potential for developing an active biological compound that could be applied in crop fields as insecticides, herbicides, algicides, and fungicides due to their allelopathic effects (Biondi et al, 2004; Ishibashi et al, 2005; Berry et al, 2008; Rastogi and Sinha, 2009; Table 1). Numerous problems have been reported to arise from application of synthetic pesticides and thus production of biocides with low environmental risk is needed (Isman, 2006).…”
Section: A Growing Worldwide Market For Cyanobacterial and Algal Metamentioning
Cyanobacteria and algae having complex photosynthetic systems can channelize absorbed solar energy into other forms of energy for production of food and metabolites. In addition, they are promising biocatalysts and can be used in the field of “white biotechnology” for enhancing the sustainable production of food, metabolites, and green energy sources such as biodiesel. In this review, an endeavor has been made to uncover the significance of various metabolites like phenolics, phytoene/terpenoids, phytols, sterols, free fatty acids, photoprotective compounds (MAAs, scytonemin, carotenoids, polysaccharides, halogenated compounds, etc.), phytohormones, cyanotoxins, biocides (algaecides, herbicides, and insecticides) etc. Apart from this, the importance of these metabolites as antibiotics, immunosuppressant, anticancer, antiviral, anti-inflammatory agent has also been discussed. Metabolites obtained from cyanobacteria and algae have several biotechnological, industrial, pharmaceutical, and cosmetic uses which have also been discussed in this review along with the emerging technology of their harvesting for enhancing the production of compounds like bioethanol, biofuel etc. at commercial level. In later sections, we have discussed genetically modified organisms and metabolite production from them. We have also briefly discussed the concept of bioprocessing highlighting the functioning of companies engaged in metabolites production as well as their cost effectiveness and challenges that are being addressed by these companies.
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