Regioselective C-H Alkenylation and Unsymmetrical Bis-olefination of Heteroarene Carboxylic Acids with Ruthenium Catalysis in Water.

An efficient weak carboxylate-assisted oxidative cross-dehydrogenative C-H/C-H coupling (CDC) of heteroarenes with readily available olefins has been devised employing water as green solvent under ruthenium(II) catalysis. The reaction is operationally simple, accommodates a large variety of heteroaromatic carboxylic acids as well as olefins, and facilitates a diverse array of high-value olefin-tethered heteroarenes in high yields (up to 87%). The potential of this ortho-C-H bond activation strategy has also been exploited toward tunable synthesis of densely functionalized heteroarenes through challenging unsymmetrical bis-olefination process in a one-pot sequential fashion. Mechanistic investigation demonstrates a reversible ruthenation process and C-H metalation step might not be involved in the rate-determining step.

Surveillance of disease incidence in shrimp farms located in the east coastal region of India and in vitro antibacterial efficacy of probiotics against Vibrio parahaemolyticus.

We surveyed 130 shrimp farms located on the eastern coast of India to determine the prevalence of emerging diseases in Litopenaeus vannamei and Penaeus monodon. Live shrimps were collected from the farms based on external symptoms. The biochemical, molecular, and histopathology results confirmed infection with Enterocytozoon hepatopenaei (32.4%), Vibrio parahaemolyticus (27.7%), White Spot Syndrome Virus (25.4%), Vibrio alginolyticus (16.1%), Vibrio harveyi (13.1%), Monodon-type baculovirus (4.61%), and infectious Hematopoietic Necrosis Virus (2.3%) in the collected shrimps. Enterocytozoon hepatopenaei (EHP) occurred more frequently in L. vannamei than P. monodon, with the microsporidian spores in the hepatopancreas. In P. monodon, Monodon-type Baculovirus infection (33.3%) was dominant and small percentages of WSSV, IHHNV, V. alginolyticus, and V. harveyi were observed. A few ponds were observed with co-infection of EHP and WSSV (7.6%), V. parahaemolyticus and WSSV (4.6%) and also V. parahaemolyticus and EHP (6.1%). Among the Vibrio spp, V. parahaemolyticus showed the highest percentage of infection in L. vannamei. Overall, we found that shrimp were chiefly infected with EHP and V. parahaemolyticus. The impact of water quality parameters on shrimp diseases was not addressed in this study. In an antibiotic susceptibility study, V. parahaemolyticus isolated from L. vannamei ponds was susceptible to nitrofurantoin, chloramphenicol, oxytetracycline and tetracycline, but resistant to erythromycin and nalidixic acid. In a preliminary in vitro antibacterial activity assay, probiotics against V. parahaemolyticus showed high inhibitory activity and the results encourage further in-depth studies on the efficacy of probiotics for disease control and prevention in shrimp farms.

Genetic Identification of all Four Mangrove Mud Crab Species (genus Scylla) Using Multiple Molecular Markers.

Misleading identification and subsequent publications on biological, molecular, and aquaculture data of mangrove mud crab (genus Scylla de Hann 1833) is a major concern in many countries. In this study, multiple molecular markers were used for genetic identification of all four known mud crab species under genus Scylla collected from India, Philippines, Myanmar, Malaysia and Indonesia. Internal Transcribed Spacer (ITS-1), Polymerase chain reaction (PCR)-Restriction Fragment Length Polymorphism (PCR-RFLP) and PCR-based species-specific markers were used to resolve taxonomic ambiguity. PCR-RFLP techniques using NlaIV and BsaJI restriction endonucleases were efficient to differentiate four different mud crab species under genus Scylla with specific fragment profile. The results also justified the use of ITS-1 and PCR-based species-specific markers to identify mud crab species available in many countries quite rapidly and effectively. Several new molecular markers generated during the study are reported here to resolve the taxonomic ambiguity of Scylla species and the results reconfirmed that India is only having two commonly available mud crab species which was reported by the authors earlier.

A Cross-Dehydrogenative Annulation Strategy towards Synthesis of Polyfluorinated Phenanthridinones with Copper.

The first cross-dehydrogenative annulation of (hetero)aromatic amides with polyfluoro(hetero)arenes is presented. This operationally simple oxidative annulation process is mediated by inexpensive copper salt, accommodates a wide range of substrates with exquisite chemo- and regioselectivity profile, and produces demanding polyfluorinated phenanthridinones in high yields (up to 92 %). Using alkenyl amides under identical conditions, the synthesis of polyfluorinated 2-quinolones has also been accomplished. Given the importance of fluorinated heterocycles in the pharmaceutical industry and drug discovery, this work is highly significant.

Molecular markers reveal only two mud crab species of genus Scylla (Brachyura: Portunidae) in Indian coastal waters.

The taxonomic ambiguity of the Indian mud crab (genus Scylla de Hann 1833) is still a cause of concern as several papers have been published with misleading identification. This is the first attempt to resolve the taxonomic uncertainty of the mud crab commonly available in Indian coastal waters using molecular genetic markers (ITS-1 and sequencing of COI gene) combined with traditional morphometry. Additionally, we developed a PCR method by which Indian mud crab species can be identified rapidly and effectively. The results clearly indicate that the green morph of the Indian mud crab is Scylla serrata and the brown morph is S. olivacea. The S. serrata commonly mentioned in the literature from India is S. olivacea; the S. tranquebarica noted by many Indian researchers should belong to S. serrata. Caution should be taken when interpreting or implementing the biological, molecular, and aquaculture data in the literature.

Post-harvest losses in marine fisheries of Bangladesh.

Existing literature highlights significant income loss due to Post-Harvest Loss (PHL) across the fisheries value chain in developing countries like Bangladesh. This is attributed to inappropriate fishing tools, poor infrastructure, inadequate storage facilities, and inefficient transportation. This study estimated PHL and its determinants in Bangladesh's marine fisheries using the Questionnaire Loss Assessment Method (QLAM) based on data collected from 1132 respondents, including fishermen and traders, from October 2019 to March 2021. The results reveal that physical, market, and monetary PHL in marine fisheries are 0.82 %, 6.41 %, and $228.52 per ton, respectively. Annually, the country loses approximately $151 million due to PHL in marine fisheries, with the highest market losses in Snapper, Pomfret, and Hilsa fish. The main reasons for PHL include the duration of fish remain in the net after being caught, insufficient ice, lack of insulated containers and storage facilities, delayed marketing, and oversupply. The study suggests adopting modern harvesting technology, enforcing regulations for scientific gear, and increasing storage capacity at landing and selling points to reduce PHL in marine fisheries.

Estuarine mangrove niches select cultivable heterotrophic diazotrophs with diverse metabolic potentials-a prospective cross-dialog for functional diazotrophy.

Introduction: Biological nitrogen fixation (BNF), an unparalleled metabolic novelty among living microorganisms on earth, globally contributes ~88-101 Tg N year-1 to natural ecosystems, ~56% sourced from symbiotic BNF while ~22-45% derived from free-living nitrogen fixers (FLNF). The success of symbiotic BNF is largely dependent on its interaction with host-plant, however ubiquitous environmental heterotrophic FLNFs face many limitations in their immediate ecological niches to sustain unhindered BNF. The autotrophic FLNFs like cyanobacteria and oceanic heterotrophic diazotrophs have been well studied about their contrivances acclimated/adapted by these organisms to outwit the environmental constraints for functional diazotrophy. However, FLNF heterotrophs face more adversity in executing BNF under stressful estuarine/marine/aquatic habitats. Methods: In this study a large-scale cultivation-dependent investigation was accomplished with 190 NCBI accessioned and 45 non-accessioned heterotrophic FLNF cultivable bacterial isolates (total 235) from halophilic estuarine intertidal mangrove niches of Indian Sundarbans, a Ramsar site and UNESCO proclaimed World Heritage Site. Assuming ~1% culturability of the microbial community, the respective niches were also studied for representing actual bacterial diversity via cultivation-independent next-generation sequencing of V3-V4 rRNA regions. Results: Both the studies revealed a higher abundance of culturable Gammaproteobacteria followed by Firmicutes, the majority of 235 FLNFs studied belonging to these two classes. The FLNFs displayed comparable selection potential in media for free nitrogen fixers and iron-oxidizing bacteria, linking diazotrophy with iron oxidation, siderophore production, phosphorus solubilization, phosphorus uptake and accumulation as well as denitrification. Discussion: This observation validated the hypothesis that under extreme estuarine mangrove niches, diazotrophs are naturally selected as a specialized multidimensional entity, to expedite BNF and survive. Earlier metagenome data from mangrove niches demonstrated a microbial metabolic coupling among C, N, P, S, and Fe cycling in mangrove sediments, as an adaptive trait, evident with the co-abundant respective functional genes, which corroborates our findings in cultivation mode for multiple interrelated metabolic potential facilitating BNF in a challenging intertidal mangrove environment.

Ecological restoration at pilot-scale employing site-specific rationales for small-patch degraded mangroves in Indian Sundarbans.

To date, degraded mangrove ecosystem restoration accomplished worldwide primarily aligns towards rehabilitation with monotypic plantations, while ecological restoration principles are rarely followed in these interventions. However, researchers admit that most of these initiatives' success rate is not appreciable often. An integrative framework of ecological restoration for degraded mangroves where site-specific observations could be scientifically rationalized, with co-located reference pristine mangroves as the target ecosystem to achieve is currently distinctively lacking. Through this experimental scale study, we studied the suitability of site-specific strategies to ecologically restore degraded mangrove patches vis-à-vis the conventional mono-species plantations in a highly vulnerable mangrove ecosystem in Indian Sundarbans. This comprehensive restoration framework was trialed in small discrete degraded mangrove patches spanning ~ 65 ha. Site-specific key restoration components applied are statistically validated through RDA analyses and Bayesian t-tests. 25 quantifiable metrics evaluate the restoration success of a ~ 3 ha degraded mangrove patch with Ridgeline distribution, Kolmogorov-Smirnov (K-S) tests, and Mahalanobis Distance (D2) measure to prove the site's near-equivalence to pristine reference in multiple ecosystem attributes. This restoration intervention irrevocably establishes the greater potential of this framework in the recovery of ecosystem functions and self-sustenance compared to that of predominant monoculture practices for vulnerable mangroves.

Palladium-Catalyzed Electrooxidative Hydrofluorination of Aryl-Substituted Alkenes with a Nucleophilic Fluorine Source.

Herein, we report an electrocatalytic hydrofluorination of aryl-substituted alkenes with a nucleophilic fluorine source. The merger of palladium catalysis with electrooxidation enables the transformation of various substrates ranging from styrenes to more challenging α,ß-unsaturated carbonyl derivatives to the corresponding benzylic fluorides. This method can also be applied to the late-stage modification of pharmaceutical derivatives. Mechanistic studies suggest that the generation of a high-valent palladium intermediate via anodic oxidation is the crucial step in this electrocatalytic hydrofluorination.

Detection of a bibenzyl core scaffold in 28 common mangrove and associate species of the Indian Sundarbans: potential signature molecule for mangrove salinity stress acclimation.

Bibenzyl derivatives comprising two benzene rings are secondary plant metabolites with significant therapeutic value. To date, bibenzyl derivatives in the Plant kingdom have been primarily identified in bryophytes, orchids, and Cannabis sativa. The metabolic cost investment by plant species for the synthesis of these bioactive secondary metabolites is rationalized as a mechanism of plant defense in response to oxidative stress induced by biotic/abiotic factors. Bibenzyl derivatives are synthesized from core phenylpropanoid biosynthetic pathway offshoots in plant species. Mangrove and mangrove associate species thrive under extreme ecological niches such as a hypersaline intertidal environment through unique adaptive and acclimative characteristics, primarily involving osmotic adjustments followed by oxidative stress abatement. Several primary/secondary bioactive metabolites in mangrove species have been identified as components of salinity stress adaptation/acclimation/mitigation; however, the existence of a bibenzyl scaffold in mangrove species functioning in this context remains unknown. We here report the confirmed detection of a core bibenzyl scaffold from extensive gas chromatography-mass spectrometry and gas chromatography-flame ionization detection analyses of 28 mangrove and mangrove associate species from the Indian Sundarbans. We speculate that the common presence of this bibenzyl core molecule in 28 mangrove and associate species may be related to its synthesis via branches of the phenylpropanoid biosynthetic pathway induced under high salinity, which functions to detoxify reactive oxygen species as a protection for the maintenance of plant metabolic processes. This finding reveals a new eco-physiological functional role of bibenzyls in unique mangrove ecosystem.

Mitochondrial DNA variation in natural populations of endangered Indian feather-back fish, Chitala chitala.

Genetic variation at mitochondrial cytochrome b (cyt b) and D-loop region reveals the evidence of population sub-structuring in Indian populations of highly endangered primitive feather-back fish Chitala chitala. Samples collected through commercial catches from eight riverine populations from different geographical locations of India were analyzed for cyt b region (307 bp) and D-loop region (636-716 bp). The sequences of the both the mitochondrial regions revealed high haplotype diversity and low nucleotide diversity. The patterns of genetic diversity, haplotypes networks clearly indicated two distinct mitochondrial lineages and mismatch distribution strongly suggest a historical influence on the genetic structure of C. chitala populations. The baseline information on genetic variation and the evidence of population sub-structuring generated from this study would be useful for planning effective strategies for conservation and rehabilitation of this highly endangered species.

Wave induced coastal flooding along the southwest coast of India during tropical cyclone Tauktae.

The coastal flood during the tropical cyclone Tauktae, 2021, at Chellanam coast, Kerala, India, has invited wide attention as the wave overtopping severely affected coastal properties and livelihood. We used a combination of WAVEWATCHIII and XBeach to study the coastal inundation during high waves. The effect of low-frequency waves and the rise in the coastal water level due to wave setup caused the inundation at Chellanam, even during low tide with negligible surge height. Wave setup raised the water level at the coast with steep slopes to more than 0.6 m and peaked during low tide, facilitating wave breaking at the nearshore region. The coastal regions adjacent to these steep slopes were subjected to severe inundation. The combined effect of long and short waves over wave setup formed extreme wave runups that flooded inland areas. At gently sloping beaches, the longwave component dominated and overtopped the seawalls and damaged households along the shoreline. The study emphasizes the importance of longwave and wave setup and its interaction with nearshore bathymetry during the high wave. The present study shall lead to the development of a coastal inundation prediction system for the low-lying hot spots using the combination of WAVEWATCHIII and XBeach models.

Population genetic structure and phylogeography of cyprinid fish, Labeo dero (Hamilton, 1822) inferred from allozyme and microsatellite DNA marker analysis.

We examined population structure of Labeo dero (Hamilton, 1822) from different riverine locations in India using 10 polymorphic allozyme and eight microsatellite loci. For analysis, 591 different tissue samples were obtained from commercial catches covering a wide geographic range. Allozyme variability (An = 1.28-1.43, Ho = 0.029-0.071) was much lower than for microsatellites (An = 4.625-6.125, Ho = 0.538-0.633). Existence of rare alleles was found at three allozyme (MDH-2, GPI and PGDH) and at two microsatellite loci (R-3 and MFW-15). Deviation from Hardy-Weinberg equilibrium (P < 0.05, after the critical probability levels were adjusted for sequential Bonferroni adjustment) could be detected at three loci (EST-1, -2 and XDH) whereas, after correction for null alleles, two microsatellite loci (MFW-1,-15) deviated from HWE in the river Yamuna. Fst for all the samples combined over all allozyme loci was found to be 0.059 suggesting that 5.9% of the total variation was due to genetic differentiation while microsatellite analysis yielded 0.019 which was concordant to mean Rst (0.02). Hierarchical partition of genetic diversity (AMOVA) showed that greater variability (approx. 95%) was due to within population component than between geographical regions. Based on distribution of genetic differentiation detected by both markers, at least five different genetic stocks of L. dero across its natural distribution could be identified. These results are useful for the evaluation and conservation of L. dero in natural water bodies.

Prospects and challenges of yellow flesh pangasius in international markets: secondary and primary evidence from Bangladesh.

The projected increase in aquaculture production by 2030 will mostly occur in countries of Asia and Africa, including Bangladesh. The pangasius (Pangasianodon hypophthalmus) produced in Bangladesh, the second-largest producer globally, is mainly consumed by low-income domestic consumers and is poorly demanded in international markets. One reason for this is the yellow flesh of fish; consumers generally in mainstream international markets prefer to fish with white flesh. Reviewing secondary evidence and analyzing primary data, this article assesses the underlying reasons for the discolored pangasius flesh in Bangladesh and synthesizes strategies for avoiding discoloration to induce exports. The findings indicate that farming practices with high stocking density, infrequent water exchange, high organic matter in pond water, and the growth of carotenoid-containing cyanobacteria contribute to the discoloration of pangasius flesh. Artificial and natural pigments in feed and poor post-harvest handling of fish are also contributing factors. Furthermore, a positive correlation between water exchange, price, and yield at the farm is found, which indicates that farm-gate price and yield per hectare can increase with more frequent water exchange. The findings of this study provide strong evidence that improved aquaculture practices can solve the problem of discolored pangasius flesh and establish an export-oriented pangasius industry in Bangladesh.

Copper-Catalyzed 8-Aminoquinoline-Directed Oxidative C-H/N-H Coupling for N-Arylation of Sulfoximines.

A copper-catalyzed cross-dehydrogenative C-H/N-H coupling has been devised to access a series of N-arylated sulfoximines in high yield from 8-aminoquinoline-derived benzamides and sulfoximines. The reaction is scalable, and mechanistic studies favor the involvement of an organometallic pathway, where C-H bond cleavage is presumed to be the kinetically relevant step. The utility of sulfoximine-coupled benzamides was displayed through the nickel-catalyzed acceptorless dehydrogenative olefination of benzyl alcohols.

Cross-Dehydrogenative Coupling/Annulation of Arene Carboxylic Acids and Alkenes in Water with Ruthenium(II) Catalyst and Air.

A cross-dehydrogenative coupling of arene carboxylic acids with olefins is reported with ruthenium(II) catalyst employing air and water as green oxidant and solvent, respectively. It offers a robust synthesis of valuable phthalide molecules. A one-pot sequential strategy is also disclosed to access Heck-type products that are apparently difficult to make directly from arene carboxylic acids.

Evaluation of genetic variation in the clown Knifefish, Chitala chitala, using allozymes, RAPD, and microsatellites.

Twenty-seven enzyme systems, six random amplified polymorphic DNA (RAPD) primers, and two microsatellite loci were tested to determine intraspecific divergence in the natural population of the endangered Indian featherback fish, Chitala chitala, for the first time. The 262 samples of C. chitala were collected from six riverine locations in India: the Satluj, Ganga (Ghagra, Bhagirathi, and Brahmaputra), Mahanadi, and Narmada river systems. The analysis revealed population subdivisions, with an F(ST) value from 0.1235 (95% confidence 0.0868-0.1621) for RAPD and a combined F(ST) of 0.0344 (95% confidence 0.0340-0.0350) for microsatellite loci. An analysis of 38 allozyme loci did not reveal any polymorphism in the samples from any of the riverine localities; a possible explanation for this could be that the ancestors of Chitala could have faced a population reduction in prehistoric periods, as low allozyme variation is also reported for other species of Chitala from south Asia.

Streamlined Ruthenium(II) Catalysis for One-Pot 2-fold Unsymmetrical C-H Olefination of (Hetero)Arenes.

The potential of carboxylate-directed Ru(II)-catalyzed C-H bond activation has been exploited in the first example of challenging 2-fold unsymmetrical cross-dehydrogenative olefination of (hetero)aromatic carboxylic acids. This highly regioselective protocol operates in one pot under a single catalytic system and tolerates a wide spectrum of carboxylic acids as well as activated olefins. A rare example of an unsymmetrical meta-bis-olefination approach has also been successfully engineered via a tailored unsymmetrical double C-H functionalization and concomitant decarboxylation process.

Atom Transfer Oxidative Radical Cascade of Aryl Alkynoates towards 1,1-Dichalcogenide Olefins.

An oxidative trifunctionalization of aryl alkynoates has been devised via the chalcogenide radical triggered intramolecular 1,4-aryl migration/decarboxylation cascade to prepare 1,1-dichalcogenide tetrasubstituted alkenes in high yields (up to 98 %). This operationally simple reaction proceeds under metal-free conditions, can be executed on gram scale, and highlights formal 1,1-difunctionalization of alkynes. Synthetic potential of this protocol was demonstrated through a twofold cascade rearrangement to access highly conjugated tetra-selenylated alkenes along with a cross-dehydrogenative annulation to prepare fluorene derivative.

Recent Advancements in Transition-Metal-Catalyzed One-Pot Twofold Unsymmetrical Difunctionalization of Arenes.

Transition-metal-catalyzed direct C-H bond activation reactions have been embraced as a powerful synthetic tool to access diverse functionalized arenes. However, site-selective incorporation of multiple distinct functionalities in an arene has always been a formidable challenge. Recent efforts from the synthetic community have disclosed a few dynamic synthetic approaches to fabricate multifunctionalized arenes in one-pot using a single catalytic system. These reports manifested the immense potential of such approaches to expedite contemporary organic synthesis towards building molecular complexity. In this minireview, we have illustrated the recent progress in this area, highlighting the contribution from several synthetic chemists including our group.