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Abstract: The indole nucleus is one of the most important ring systems for pharmaceutical development. Various natural products of new molecular structures with diverse biological activities have been reported from marine flora and fauna, thus ensuring motivation in the search for newer natural products. The unique structural features of triindole containing three indole rings and impressive biological activities make these alkaloids an attractive target for drug discovery. This mini-review highlights the significance of various strategic innovations towards these structurally unique and simplest alkaloids of marine origin (i.e., pseudellone C, metagenetriindole A, araiosamine and bengacarboline) and highlights the isolation, structure, synthesis, biosynthesis and biological activities covering literature till 2023.

Because Goa is a favorite destination for international and national tourism, there is a great demand for seafood there. Formalin (30–40% of formaldehyde, FA) can be added as a preservative to many...

γ-Hydroxybutenolides (γ-HB) is an important structural core found in many bioactive marine natural products (MNPS). The γ-HB core containing NPS served as an inspiration to medicinal chemists to undertake designing of the new synthetic strategies to construct γ-HB core. Subsequently, it further results in the development of novel physiological and therapeutic agents. The most notable example includes manoalides, cacospongionolides, petrosaspongioide M and dysidiolide from marine sponges possessing anti-inflammatory properties. γ-HB containing MNPS were known to possess various pharmacological properties such as antimicrobial (acantholide B), cytotoxic (acantholide A-E, spongianolide A), inhibitors of secretory phospholipase A2 (cladocorans A and B), BACE inhibitors (ianthellidone G), etc. Moreover, the γ-HB moiety was explored as antifouling agents as well. Owing to their numerous biological activities and attractive molecular structures, there are lots of advances in the synthetic methodology of these compounds. This review gives the account on isolation and biological studies of MNPS with γ-HB skeleton as a core unit. Furthermore, the synthesis of selective γ-HB containing bioactive MNPS like manoalide, secomanoalide, cacospongionolides, luffarielloide and dysidiolide were highlighted in the article.

Bacterial resistance is a growing threat which represents major scourge throughout the world. The suitable way to control the present critical situation of antimicrobial resistance would be to develop entirely novel strategies to fight antibiotic resistant pathogens such as quorum sensing (QS) inhibitors or its combination with antibiotics. Anti QS agents can eliminate the QS signals and put the barrier in bio-film formation, consequently, bacterial virulence will be reduced without causing drug-resistance to the pathogens. Among the various anti QS agents identified, especially those of natural origin, furanones or acylatedhomoserine lactones (AHLs) are most popular. Semi-synthetic and synthetic inhibitors have shown greatest potential and have inspired chemists to design synthetically modified QS inhibitors with lactone moiety. This review focuses on anti QS agents (bio-film inhibitors) of both natural and synthetic origins. Further, the synthesis, structure activity relationship and anti QS activity covering literature from 2015 till March 2020 has been discussed.

The reaction between readily accessible N-aryl-3-phenylallylamines and maleic anhydride led to unexpected products – polysubstituted hydrogenated benzo[f]isoindole-4-carboxylic acids. This transformation proceeds through a previously unknown sequence of steps: N-acylation of the allylamine with maleic anhydride, intramolecular Diels-Alder reaction of the vinylarene in the intermediate N-maleamide, and Alder-ene reaction of the products of the previous two steps. Selected benzo[f]isoindoles displayed antiviral activity.

Secondary metabolites isolated from bioactive extracts of natural sources iteratively pioneer the research in drug discovery. Modern medicine is often inspired by bioactive natural products or the bio-functional motifs embedded in them. One of such consequential bio-functional motifs is the thiolane unit. Thiolane-based bioactive organic compounds have manifested a plethora of astonishing biological activities such as anti-viral, anti-cancer, anti-platelet, α-glucosidase inhibition, anti-HIV, immunosuppressive and anti-microbial activities which renders them excellent candidates in drug discovery. Hence, to scale up the accessibility of thiolane-based therapeutics its chemical syntheses is essential and in addition; a sneak peek in its biosynthesis would give a perspective for developing biomimetic syntheses. This review highlights the development of important thiolane-based therapeutics such as (i) Nuphar sesquiterpene thioalkaloids (ii) Thiosugar sulphonium salts from Salacia sp. (iii) Albomycins (iv) Thiolane-based therapeutics from Allium sp. (v) 4'-thionucleosides summarizing various synthetic strategies, biosynthesis and biological activity studies, covering literature till 2021. We anticipate that this review will inspire chemists and biochemists to take up the challenges encountered in the synthesis and development of thiolane-based therapeutics.

The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO2 under sunlight. Mesoporous anatase TiO2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N2 adsorption-desorption isotherm studies and BJH analysis. The influence of catalyst properties such as the mesoporous network, pore volume and surface area on the kinetics of degradation of Amaranth as a function of irradiation time under natural sunlight has been monitored using UV-Vis spectroscopy. The highest rate constant value of 0.069 min-1 was obtained for the photocatalytic degradation of Amaranth using TiO2 synthesized via a urea assisted sol-gel synthesis method. The effect of the reaction conditions such as pH, TiO2 concentration and Amaranth concentration on the photodegradation rate has been investigated. The enhanced photocatalytic activity of synthesized TiO2 in comparison with P25 is attributed to the mesoporous nature of the catalyst leading to increased pore diameter, pore volume, surface area and enhanced charge carrier separation efficiency. New intermediates of photocatalytic degradation of Amaranth, namely, sodium-3-hydroxynaphthalene-2,7-disulphonate, 3-hydroxynaphthalene, sodium-4-aminonaphthalenesulphonate and sodium-4-aminobenzenesulphonate have been identified using LC-ESI-MS for the very first time, providing direct evidence for simultaneous bond cleavage pathways (-C-N-) and (-N[double bond, length as m-dash]N-). A new plausible mechanism of TiO2 catalysed photodegradation of Amaranth along with the comparison of its toxicity to that of its degradation intermediates and products is proposed.

(−)-Elemoxide, a fragrant compound was synthesised using commercially available elemol in four steps with overall yield of 32%. The cyclic ether skeleton was constructed via intramolecular hydroalkoxylation using I2 and PhSiH3 catalytic system. Also, intramolecular oxymercuration-demercuration was employed as an alternate approach for cyclization. The various regioselective strategies involving epoxidation of alkene, reduction of epoxide and intramolecular cyclization were the highlights of the work. The key intermediate diol serves as a versatile intermediate for the synthesis of elemoxide and elemene.

Macroalgae or seaweeds are the most abundant marine species occurring all over the world in all kinds of habitats. For several decades, the significance of organic metabolites isolated from marine algae has been demonstrated by their role in drug discovery and applications in clinical trials. The marine environment is a rich source of naturally occurring halogenated compounds. Many marine algae show exceptional biochemistry in the synthesis of brominated organic compounds such as bromophenols, bromoindoles, bromopyrroles, bromoterpenes, and polybrominated diphenyl ethers (PDBEs). Some of these compounds have been reported to have intriguing biochemical properties such as antibacterial, antifungal, and antihistamine activities. The brominated aromatic core containing compounds discussed in this chapter includes substituted diphenyl ethers, bromophenols, benzaldehyde, bromonaphthalene, and indoles. These molecules were reported to have a range of biological activities such as anticancer, antimicrobial, antioxidant, aldose reductase inhibition, etc. PDBE derivatives have also been reported to inhibit enzymes implicated in tumor development and antisclerotic plaque which indicate their potential as promising therapeutic agents. Moreover, 84 brominated terpenes isolated from various marine algae have been summarized along with their biological properties. Most of the terpenes were evaluated for anticancer activities against different human cancer cell lines. Overall this chapter presents a broad survey of bioactive brominated organic molecules isolated from marine algae around the world, as well as literature from 2005 to present day.

Biochemicals produced by nature are always special in terms of their structures, properties, medicinal uses, and many more reasons. Nature has always challenged chemists by producing the complex structural skeletons. As a consequence, an impressive number of modern drugs have been derived from natural sources. These new chemicals may be obtained by the qualitative/quantitative extractions from different plants/crops/animals/microorganisms extract. Over the years, due to the outstanding developments in the field of analytical separation methods coupled with advances in structural characterization techniques, natural products research is leading in fronts as an ocean of novel and interesting chemical scaffolds. This chapter gives an in-depth review of the state-of-the-art techniques for the extraction, isolation, purification, and characterization of metabolites from natural sources. Special attention is focused on discussion of case studies involving isolation of marine, microbial, and terrestrial natural products with the help of suitable examples.

In recent years many sterols with potent biological activity have been identified from marine sources. Here we report the isolation of stigmast-5,24-dien-3-ol (fucosterol) as a major metabolite from the bioactive hexane-fraction of Sargassum tenerrimum using different chromatographic techniques. Moreover, the chemical defense of brown algae Sargassum tenerrimum was investigated using feeding assay performed in an aquarium and in the field.

A novel AIE-based fluorescent probe for the detection of trace amounts of nitrite and nitrate ions in water has been developed. The probe, a monoamine of tetraphenylethylene, spontaneously detects nitrites (or nitrates) by a fluorescence “turn-off” method via diazotization followed by formation of a non fluorescent TPE-azodye. The salient features of this method are high sensitivity and selectivity, cost effective synthesis, fast detection process and low detection limit.

(−)-6′-β-Fluoro-aristeromycin (2), a potent inhibitor of S-adenosylhomocysteine (AdoHcy) hydrolase, has been synthesized via stereoselective electrophilic fluorination followed by a purine base build-up approach. Interestingly, purine base condensation using a cyclic sulfate resulted in a synthesis of (+)-5′-β-fluoro-isoaristeromycin (2a). Computational analysis indicates that the fluorine atom controlled the regioselectivity of the purine base substitution.

Grewia nervosa is a herbal plant used in traditional medicine for different purposes. Bioassay-guided chemical fractionation of G. nervosa roots resulted in an identification of two known and one new compound, namely microgrewiapine A, homomicrogrewiapine, and N-methylmicrocosamine, respectively. Their structures were determined using combination of LC/HR-MS, 1 H-NMR, and IR spectral analyses and followed by comparison with those reported in the literature. The problematic separation of these alkaloids on traditional column chromatography (Silica gel, Octadecyl silane, Sephadex) was resolved by using HPLC. Structurally similar compounds from the piperidine family have been characterized by using HR-MS analysis in combination with NMR data of crude samples. The major constituent i.e. N-methylmicrocosamine isolated from the butanol fraction of methanol root extract (MRE) was found to possess the dose dependent α-glucosidase inhibition activity with an IC50 value of 53.40 μm. Furthermore, N-methylmicrocosamine showed maximum α-glucosidase inhibition of 97.48 ± 0.7% at 107.5 μm, which is approximately 1.3 × 103 fold higher than the activity shown by acarbose (97.72% inhibition at 61.95 mm), a standard anti-diabetic drug available commercially. This work also reports the in vitro α-glucosidase inhibitory activity of the major alkaloids isolated from G. nervosa for the first time.

Butanol fraction of sacoglossan Elysia grandifolia was investigated for identifying peptides using electrospray ionisation-tandem mass spectrometry (ESI-MS/MS). Without prior isolation, the structural determination is achieved on the basis of mass fragmentation pattern and comparison with the previously established data. The ESI-MS of the fraction in the positive ion mode gave clusters of singly and doubly charged molecular ion peaks. The ESI-MS spectrum showed peaks for the presence of the peptides kahalalides F, G, R and S reported earlier. In addition, it also showed molecular ion peaks at m/z 1557.8 [M+H]+ and doubly charged ions at m/z 779.4 [M+2H]2+, 790.4 [M+Na]2+ and 796.4 [M+K]2+. The MS/MS at m/z 779.4 [M+2H]+2 at collision energy 40 V obtained series of b and y fragment ions. The MS/MS spectrum showed identical fragment ion y6 at m/z 643 which revealed that cyclic part is identical with kahalalide F, R and S. Careful examination of the fragment ions b1 to b7 with their corresponding y fragment ions y12 to y6, respectively and by comparison of MS/MS pattern of kahalalide S, established that proline can be replaced by tyrosine amino acid residue. The mass difference between b4 ( m/z 511) and b5 ( m/z 674) is equal to 163 which is equivalent to mass residue of tyrosine. Their y fragment ions also quickly helped in fixing the puzzle. This resulted in the identification of the peptide sequence cyclo-[Val-(5-MeHex-Val-Thr-Val-Val-Tyr-Lys-Ile)Thr-Ile-Val-Phe-Dhb)] for the new cyclodepsipeptide, kahalalide Z3. Thus, ESI-MS/MS has set a trend in quick identification of new marine molecules.

The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO

The biochemical mechanisms that marine sponges have developed as a chemical defense to protect themselves against micro and subsequent macrobiofouling process might comprise a potential alternative for the preventing attack of biofilm forming bacteria. The present study investigated the antimicrobial activity of a series of major secondary metabolites isolated from the sponges Fasciospongia cavernosa and Axinella donnani against fouling bacteria. Secomanoalide (1), dehydromanoalide (2) and cavernosine (3) have been isolated from F. cavernosa. Their structures were determined by MS, (1)H NMR spectra analyses and by comparison with those reported in the literature. The most promising activity was exhibited by the metabolites from A. donnani, that is, cerebroside (5) against three strains Aeromonas hydrophila subsp. salmonicida A449 and Erythrobacter litoralis. Our investigation revealed that combined metabolites 1, 2 and 3 retained strong activity but individual metabolite had moderate activity indicating that activity probably results from synergistic interactions between multiple compounds. The antibacterial screening of compounds 3, 5 and synergistic effect of 1-3 against fouling bacteria has been studied for the first time. Further, isolation of manoalide related compounds and their synergistic screening can be accelerated for the development of new biofilm inhibitors.

Marine organisms such as seaweeds, sponges and corals protect their own surfaces from fouling by their high anesthetic, repellant, and settlement inhibition properties. Within the marine ecosystem, evolution has allowed for the development of certain antifouling properties. Isatin is a biologically active chemical produced by an Alteromonas sp. strain inhibiting the surface of embryos of the cardiean shrimp Palaemon macrodectylus, which protect them from the pathogenic fungus Lagenidium callinectes. In present study, an antibacterial activity of isatin and its synthetic analogues were evaluated against different fouling bacteria in order to explore the structure activity relationships for the first time. The synthesized compounds along with parent isatin were tested against different ecologically relevant marine microorganisms by using the Kirby-Bauer disc diffusion method. Few synthetically modified isatin exhibited potent inhibitory activity at concentration of 2 μg/disc against Planococcus donghaensis, Erythrobacter litoralis, Alivibrio salmonicida, Vibrio furnisii. Overall, the modified analogues showed stronger activity than the parent marine natural product (isatin) and hence 1H-indole-2,3-dione scaffold has immense potential as future antibacterial/antifouling candidate.

An aggregation-induced emission (AIE) based “turn-on” fluorescent chemodosimeter for selective detection of Pb2+ions has been developed by making use of the strong affinity of lead ions for phosphate residues. The probe is a phosphate functionalized tetraphenylethylene derivative and the resulting lead–TPE complex has very low solubility in working solvent and triggers aggregation induced emission. The probe is highly efficient, cost-effective and shows a low detection limit of 10 ppb.

An efficient and versatile mechanochemical route to 2-aryl benzothiazoles and both 2-substituted and 1,2-disubstituted benzimidazole derivatives has been developed via a simple mortar–pestle grinding method. The mechanochemical agitation was found to be sufficient for smooth condensation between a variety of aromatic aldehydes and o-aminothiophenol/o-phenylenediamine followed by cyclization leading to the formation of the corresponding 1,3-benzazoles. The salient features of this new protocol are catalyst-free reaction, cleaner reaction profiles, absence of a work-up step, high yields, and short reaction times.

In recent years many sterols with unusual structures and promising biological profiles have been identified from marine sources. Here we report the isolation of a series of 24-alkylated-hydroxysteroids from the soft coral Sinularia kavarattiensis, acting as pregnane X receptor (PXR) modulators. Starting from this scaffold a number of derivatives were prepared and evaluated for their ability to activate the PXR by assessing transactivation and quantifying gene expression. Our study reveals that ergost-5-en-3β-ol (4) induces PXR transactivation in HepG2 cells and stimulates the expression of the PXR target gene CYP3A4. To shed light on the molecular basis of the interaction between these ligands and PXR, we investigated, through docking simulations, the binding mechanism of the most potent compound of the series, 4, to the PXR. Our findings provide useful functional and structural information to guide further investigations and drug design.

Biofouling is the undesirable growth of organisms on artificial and natural structures immersed in either seawater or freshwater. It causes huge economic loss and also the global prohibition on known antifouling agents has led to an increased search for safe and effective antifouling agents. In the past, marine natural products have shown tremendous potential by providing new skeletons that could be used as eco-friendly antifouling agents. The library of the 2-aryl benzimidazole core inspired from marine natural products (oroidin and bromoageliferin) was identified and synthesized to explore the antifouling/antifungal properties for the first time. Twelve 2-aryl benzimidazole derivatives were synthesized and evaluated for their antifouling performance against 10 strains of marine biofilm forming bacteria developed on copper panels exposed for 14 days at Dona Paula, Arabian Sea, India. These compounds were also evaluated for their antibacterial and antifungal activities. Two compounds, i.e. 4j and 4l, showed a broad spectrum of antifouling activities against nine marine fouling species, whereas 2-(furan-2-yl)-1H-benzo[d]imidazole 4g showed strong antifungal activity against the clinical pathogen Aspergillus niger. Our results reveal that the 2-aryl substituent on the benzimidazole core had strong impact on their biological profile. Moreover, here we report the first study of the benzimidazole library as a target in 10 representative fouling strains.

Marine natural product is recognized as a fruitful source of drug development due to their rare structural entities and diverse biological activities, and consequently, publicized number of metabolites as new medicines. Although extensive progress has been made in identifying novel bioactive molecules from marine source, great endeavor are still needed to explore these molecules for medicinal applications. Marine fungi are one of the important source of natural products, exhibiting a wide range of biological activities. (+)-Varitriol, isolated from the marine fungus Emericella variecolor, has shown 100-fold increased potency over the mean toxicity towards variety of cancer cell lines. Hence (+)-varitriol, an antitumour marine natural product has been a fascinating target for total synthesis over the last decade. The intense search for developing new approaches coupled with its biological activity has resulted in a wealth of methods towards the synthesis of this molecule. But, unfortunately only limited analogues have been synthesized and evaluated for their biological activities. Thus, there are still demands to modify aromatic part as well as sugar moiety of varitriol, which could provide the opportunity for further SAR studies to discover potential lead anticancer agents. This review describes the different strategies developed for the synthesis of varitriol and its analogues in various laboratories around the world covering literature from 2002 till date. The construction of challenging fashionable furanoside ring as well as substituted styrene derivatives are crucial steps in most of the reported synthetic endeavors.

A new polymeric organocatalyst is prepared by free radical copolymerization of allyl diglycol carbonate (ADC) and Boc-protected allyl prolinate and evaluated as a chiral catalyst for aldol and Michael reaction.

K-7174, a GATA-specific inhibitor, is a putative anti-inflammatory agent that attenuates effects of inflammatory cytokines in certain cell types. An expeditious four-step synthesis of K-7174 is described in this paper. The route employs Wittig olefination and bis-alkylation of homopiperazine as the key reactions. The iodinecatalyzed isomerization of the Z-isomer results in complete conversion to the E-isomer is the highlight of our synthetic endeavors.

Previous imaging and postmortem studies have reported a lower brain volume and a smaller size and density of neurons in the dorsolateral prefrontal cortex (dlPFC) of subjects with major depressive disorder (MDD). These findings suggest that synapse number and function are decreased in the dlPFC of patients with MDD. However, there has been no direct evidence reported for synapse loss in MDD, and the gene expression alterations underlying these effects have not been identified. Here we use microarray gene profiling and electron microscopic stereology to reveal lower expression of synaptic-function–related genes (CALM2, SYN1, RAB3A, RAB4B and TUBB4) in the dlPFC of subjects with MDD and a corresponding lower number of synapses. We also identify a transcriptional repressor, GATA1, expression of which is higher in MDD and that, when expressed in PFC neurons, is sufficient to decrease the expression of synapse-related genes, cause loss of dendritic spines and dendrites, and produce depressive behavior in rat models of depression.

Pyrrolam A is a microbial metabolite, structurally related to plant alkaloids of the necine-type, and was isolated from the bacterial strain of Streptomyces olivaceus along with the related alkaloids pyrrolams B–D. The synthesis of ( S )- and ( R )-pyrrolam A has attracted the attention of chemists in recent years, with 10 syntheses reported to date. The reported routes utilize the advantages of chiral proline as a starting material, with pyrrolidine nucleus as source of one of the two rings on which the second ring has been constructed. This review discusses the isolation of the deceptively simple pyrrolizidine alkaloid pyrrolam A, its biological studies, synthesis, and computational studies on the stability of the double bond in its strained bicyclic skeleton. In addition, the synthesis of pyrrolams B–C and their relationship to pyrrolam A is also discussed.

On the basis of the potent biological activity of cyclopentenyl-pyrimidines, fluorocyclopentenyl-pyrimidines were designed and synthesized from D-ribose. Among these, the cytosine derivative 5a showed highly potent antigrowth effects in a broad range of tumor cell lines and very potent antitumor activity in a nude mouse tumor xenograft model implanted with A549 human lung cancer cells. However, its 2'-deoxycytidine derivative 5b did not show any antigrowth effects, indicating that 2'-hydroxyl group is essential for the biological activity.

A straightforward synthesis of (S)-pyrrolam A is described. The synthesis involves in situ generation of the phosphorane 3, followed by an intramolecular Wittig reaction to furnish (S)-pyrrolam A.

Nature continues to be most important in the delivery of new drugs or lead structures and the oceans are important resources of structurally unique natural products. The major occupation of marine natural product chemists in recent years has been the search for potential pharmaceuticals. As a result, various new classes of potential pharmacophores against various diseases have been identified. Over the past five decades the search for new drugs has expanded, to those produced by marine macroorganisms and their associated microbes obtained from marine sources. Indeed, many of the pharmaceutical, agrochemical, and crop protection industry are based on the exploitation of microbial natural products. Fungi isolated from substrates such as marine plants (algae, sea grasses), invertebrates (ascidians, sponges, tunicates, etc.), vertebrates (fish), sands, sediments, and seawater itself have been found to yield novel bioactive natural products, many of which have highly complex structures, making them difficult to be supplied economically via chemical synthesis. This review chapter covers the literature on novel bioactive metabolites of marine-derived fungi published in years 2010–14. Metabolites from Aspergillus sp., Penicillium sp., Trichoderma sp., Chaetomium globosum, Phomopsis sp., Phoma sp., and Fusarium sp. will be highlighted in this chapter. It also gives a brief overview of progress of the marine fungal chemistry over past 5 years.

Marine sponges are considered to be a rich source of biologically active secondary metabolites with unique and diverse chemical structures. They constitute nearly one third of the secondary metabolites isolated from marine organisms. Chemicals obtained from marine sponges find a wide range of pharmaceutical values, and as a result of these properties, isolation and identification of lead molecules from marine sponges continued to play a leading role in drug discovery research. Some of the molecules obtained from marine sponges have entered in market, while many are under clinical and preclinical trials. There is convincing report about the role of ecology on the production of these valuable secondary metabolites by marine organisms including sponges. The unique body structure of marine sponges which can filter and absorb nutrients from surrounding environment and unique adaptation to variable conditions lead sponges as a major source of bioactive metabolites among the marine organisms. Alkaloids constitute one of the main classes of secondary metabolites isolated from marine sponges. They have wide range of chemical structures and exist in derivatives of several heterocyclic rings. Alkaloids were found almost in all marine sponges and exhibited a wide range of biological activities. This chapter reviews on the various alkaloids, viz., pyridoacridine, indole, isoquinoline, pyridine, piperidine, quinolizidine, steroidal, and bromotyrosine alkaloid isolated from various marine sponges. A brief review on these alkaloids with their diverse structures available in each class along with their biological significance has been presented. The class of alkaloid along with the name of sponge from which the alkaloids were isolated and chemical structures of these alkaloids are presented.

Herein, a sensitive fluorimetric assay for dissolved carbon dioxide (dCO2) was developed by using ion-induced self-assembly of a tetraphenylethylene derivative by taking advantage of its aggregation induced emission property. Chitosan, a commercially available polymer having amine functionality was utilized for the ion induced assay. In the presence of dCO2, the amine groups in the chitosan get protonated to convert neutral chitosan to a positively charged species, triggering negatively charged tetraphenylethene derivative (probe 1) to aggregate with it by electrostatic interaction. The aggregation causes intense blue fluorescence output from the system. The extent of the aggregation is reliant on the charge density of polymer, which is equivalent to dCO2 concentration. A linear relationship from 5 to 50 μM of dCO2, with a limit of detection of 5 × 10(-6) M (0.00127 hPa) was obtained. This is the first report for detecting dCO2 utilizing the AIE property.

Bis(indolyl)methane (BIM) alkaloids are an important group of bioactive natural products predominantly found in marine organisms. Thus, compounds like arsindoline A and B, vibrindole A, arundine, and trisindoline are found in marine bacteria, while the related compound, streptindole is obtained from Streptococcus faecium IB 37, found in human feces. In recent years, these molecules, which display a wide range of biological properties (antibacterial, antiviral, anti-oxidant, neurotoxic activity etc.), have attracted the attention of several synthetic and natural product chemists. This review lists selected bis(indolyl)methane analogues reported from different natural sources to date, together with their biological properties and synthesis. 1 Introduction 2 Occurrence, Isolation, Structure Elucidation, and Biological Activity 3 Synthetic Approaches towards Bis(indolyl)methanes 4 Conclusions

Ceramides are important intracellular second messengers that play a role in the regulation of cell growth, differentiation and programmed cell death. Analysis of these second messengers requires a sensitive and specific analytical method to detect individual ceramide species and to differentiate between them. Eight molecular species of ceramide were identified from the marine sponge Haliclona cribricutis using electrospray ionization tandem mass spectrometry (ESI-MS/MS). From this marine sponge, N-hencicosanoyl (N21:0) to N-hexasanoyl (N26:0) octadecasphing-4 (E)-enine have been reported for the first time. The ESI-MS spectra gave several strong protonated [M+H]+molecular ions with the corresponding bis (2-ethyl hexyl) phthalate adduct [M+H+DHEP]+. The collision-induced dissociation on ceramides at m/z 622.7337, 636.7645, 650.7789, 664.7925 and 678.8130 conducted at low-collision energy produced product ions with good characteristic at m/z 252.31, 264.32, 278.33, 282.33 and 296.35 for d18: 1 sphingosine, regardless of the length of the fatty chain. The MS/MS of the phthalate adduct [M+H+DHEP]+at m/z 1013.1820, 1027.1971, 1041.2176, 1055.2394 and 1069.2573 also yielded characterizing product ions for sphingosine and confirmed the molecular ion at m/z 391 for bis (2-ethyl hexyl) phthalate. The major ions in the [M+H]+and [M+H+DHEP]+were due to neutral loss of [M+H–H2O]+and [M+H–(H2O)2]+.

Aliphatic aldehydes such as butyr- or cyclohexylaldehyde afford no or trace amounts of products upon reaction with (I).

Marine natural product is recognized as a fruitful source of drug development due to their rare structural entities and diverse biological activities, and consequently, publicized number of metabolites as new medicines. Although extensive progress has been made in identifying novel bioactive molecules from marine source, great endeavor are still needed to explore these molecules for medicinal applications. Marine fungi are one of the important source of natural products, exhibiting a wide range of biological activities. (+)-Varitriol, isolated from the marine fungus Emericella variecolor, has shown 100-fold increased potency over the mean toxicity towards variety of cancer cell lines. Hence (+)-varitriol, an antitumour marine natural product has been a fascinating target for total synthesis over the last decade. The intense search for developing new approaches coupled with its biological activity has resulted in a wealth of methods towards the synthesis of this molecule. But, unfortunately only limited analogues have been synthesized and evaluated for their biological activities. Thus, there are still demands to modify aromatic part as well as sugar moiety of varitriol, which could provide the opportunity for further SAR studies to discover potential lead anticancer agents. This review describes the different strategies developed for the synthesis of varitriol and its analogues in various laboratories around the world covering literature from 2002 till date. The construction of challenging fashionable furanoside ring as well as substituted styrene derivatives are crucial steps in most of the reported synthetic endeavors.

The antifouling activity of the products is examined revealing that (IIIe) and (VIb) are active against marine fouling bacteria making them promising candidates for the development of new antifouling agents.

Synthesis of two linear indoloquinolines i.e. 6H-indolo[2,3-b]quinoline & 11-hydroxy-10H-indolo[3,2-b]quinoline, and spiro[2H-indole-2,3′-oxindole] from a common intermediate, (2-nitrophenyl)methylidene-dihydro-indolone derivative is described using microwave-mediated reductive cyclization as the key step.

Dibenzodioxins bearing multiple electron withdrawing groups were synthesized using a simple one-step methodology including examples of molecules possessing electron acceptor groups in both ends. As a consequence internal charge delocalization occurs and the optical spectra are found to be bathochromically shifted compared to similar examples known thus far. A theoretical analysis of the molecular orbitals reveals the origin of the peaks in the dibenzodioxin optical spectra. Select examples exhibit in vitro neuro-cytotoxicity against glioma cell line C6, a finding which enhances existing knowledge about the pharmacologically relevant structural motifs in dibenzodioxins.

Hygrine is an important biosynthetic intermediate for tropane alkaloids. A synthesis of (−)-hygrine starting from l -proline is described. The acetonyl side chain of hygrine was fashioned through the Wittig reaction followed by regioselective Wacker oxidation. In addition, this Letter provides the first synthesis of (−)-norhygrine.

Mass spectrometry (MS) has emerged as an invaluable technique with a wide array of applications ranging from forensic, proteomic, and metabolomic to clinical studies. With the development of different ionization techniques and mass analyzers, even challenging samples can be analyzed, thereby making mass spectrometry an important analytical tool in the field of characterization of bioactive molecules ranging from small metabolites to large macromolecular assemblies. MS is the only technique that offers the combination of high sensitivity with structural information. This chapter demonstrates the application of MS in the determination of different classes of bioactive compounds with a special emphasis on peptides, alkaloids, and lipids. A case study has been demonstrated for each class of compounds that might be helpful for early learners in the field of mass spectrometry. This also shall be of interest to the biochemical, biomedical, and pharmaceutical communities, and those working in other branches of analytical bioscience.

Vibrational spectroscopy is a widely used analytical technique that requires a short analysis time, less sample quantity, and provides nondestructive and situ analysis of biological samples. Infrared and Raman spectroscopies have been used for the characterization of organic and inorganic compounds as well as natural products including macromolecules such as polysaccharides, proteins, and highly insoluble melanin pigments. Although the techniques give less precise structural information, they are widely used for fast, nondestructive, and green analysis, which is not possible with the other complementary techniques such as NMR and mass spectroscopies. The technique coupled with NMR and mass can provide a strong platform for natural product analysis. This chapter presents the basic concepts of infrared and Raman spectroscopies and their application to the structure characterization of compounds such as polysaccharides, alkaloids, terpenes, flavonoids, sterols, sideorophores, and insoluble melanin pigments isolated from marine organisms.

A new polymeric organocatalyst is prepared by free radical copolymerization of allyl diglycol carbonate (ADC) and Boc-protected allyl prolinate and evaluated as a chiral catalyst for aldol and Michael reaction.