Undescribed Anti-inflammatory Thalysiaketides from Marine Sponge Clathria (Thalysias) vulpina (Lamarck, 1814)

Two undescribed polyketide type compounds, thalysiaketide A and thalysiaketide B were isolated from a sponge of marine origin Clathria (Thalysias) vulpina (Lamarck, 1814). Thalysiaketide A exhibited significantly greater inhibitory potential against inflammatory 5-lipoxygenase (IC50 0.87 mM) and cyclooxygense-2 (IC50 0.93 mM) compared to those revealed by its thalysiaketide B analogue (IC50 ≥ 1.05 mM). The 5-lipoxygenase inhibitory activity of thalysiaketide A was considerably superior to ibuprofen (standard, IC50 > 4 mM). Higher degree of polar belongings (topological polar surface area 93.06) in conjunction with relatively lower docking parameters of thalysiaketide A with the aminoacyl residues of cyclooxygense-2 and 5-lipoxygenase (docking score -12.99 and -12.27 kcal/mol, respectively) recognized its prospective anti-inflammatory potential.

Polyketide-derived macrobrevins from marine macroalga-associated Bacillus amyloliquefaciens as promising antibacterial agents against pathogens causing nosocomial infections

Marine heterotrophs are treasured bio-resources of antimicrobial metabolites, and herein we report the biosynthetic potential of Bacillus amyloliquefaciens (ex. Fukumoto) Priest et al. (Bacillaceae) strain MTCC 12713 isolated from an intertidal macroalga Kappaphycus alvarezii (Doty) L.M.Liao (Rhodophyta: Solieriaceae). The bacterium showed promising biological activities against methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus faecalis. Genome mining of B. amyloliquefaciens MTCC 12713 predicted the gene clusters coding for biosynthesis of antibacterial metabolites. Bioactivity-guided purification was directed to isolate four homologous members of trans-acyltransferase polyketide synthase-derived antibiotics, which were classified as macrobrevin analogues. The compounds exhibited antibacterial activities against nosocomial pathogens, for example, methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Klebsiella pneumoniae and Pseudomonas aeruginosa with a range of MIC values from 1.56 to 6.25 μg/mL, although standard antibiotic chloramphenicol was active at 6.25-12.5 μg/mL. Conspicuously, the macrobrevin compound encompassing hexahydro-41-hydroxy-macrobrevin-31-acetate functionality, displayed considerably greater antagonistic activities against methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Vibrio parahaemolyticus, P. aeruginosa, K. pneumoniae, and Streptococcus pyogenes (MIC 1.56 μg/mL) compared to the positive controls and other macrobrevin analogues. Trans-AT polyketide synthase-stimulated biosynthetic pathway of macrobrevin compounds, through repetitive decarboxylative Claisen condensation between acetyl-S-KS domain and malonate-S-ACP units could corroborate the structural elucidation. In the genome mining study, among the 34 biosynthetic gene clusters, a hybrid trans-acyltransferase (trans-AT) pks/nrps gene cluster, which extends up to ∼81 Kb, was recognized in the genome of B. amyloliquefaciens MTCC 12713. The pks/nrps cluster revealed 46% similarity to trans-AT PKS-derived macrobrevin isolated from a mesophilic bacterium Brevibacillus sp. Leaf182 associated with the phyllosphere of the wild-type genotype of Arabidopsis thaliana. The binding positions for macrobrevins with S. aureus peptide deformylase showed docking score of larger than 14 kcal/mol, which was considerably greater than macrolactin N and actinonin (<10 kcal/mol). These present findings documented that the marine heterotrophic B. amyloliquefaciens MTCC 12713 could be used to develop prospective antibacterial agents belonging to macrobrevin analogues for biotechnological and pharmaceutical applications.

Marginolides A-B, polyether macrolide analogues from veined octopus Amphioctopus marginatus: anti-hypertensive leads attenuate angiotensin-converting enzyme

Angiotensin-I-converting enzyme (ACE) is considered as a major drug target for the treatment of hypertension as it catalyses the production of vasoconstrictor angiotensin II from angiotensin I. ACE inhibitor agents are an effective therapeutic strategy to control high blood pressure. Unprecedented polyether macrolides, marginolide A and B were isolated from the crude extract of marine octopus, Amphioctopus marginatus via bioassay-directed sequential chromatographic fractionation. Marginolide A displayed considerably greater ACE attenuation potential (IC₅₀ 0.58 mM) than that exhibited by marginolide B (IC₅₀ 0.72 mM). Higher antioxidant properties of marginolide A against the oxidant species (IC₅₀ ∼ 1 mM) also supported its potential ACE inhibitory activity. Higher polar characteristics along with acceptable hydrophobic-hydrophilic equilibrium (partition coefficient of octanol-water, log P_ow 2-4) revealed the potential anti-hypertensive activities of marginolides. This study recognized the anti-hypertensive properties of marginolides as promising pharmaceutical leads.

Bacillibactin class of siderophore antibiotics from a marine symbiotic Bacillus as promising antibacterial agents

Preliminary antibacterial metabolite production screening unveiled that B. amyloliquefaciens MTCC 12,713 associated with the intertidal red alga Kappaphycus alverezii exhibited potential inhibitory effects against drug-resistant pathogens methicillin-resistant Staphylococcus aureus, vancomycin-resistant Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Four homologous siderophore types of bacillibactins were isolated from a heterotrophic marine bacterium through bioactivity-guided purification. All detectable natural product gene clusters in B. amyloliquefaciens MTCC 12,713 were analyzed by sequencing the complete genome of the bacterium. The studied compounds displayed broad spectrum bactericidal activity against multidrug-resistant strains with a range of minimum inhibitory concentration values from 1.56 to 6.25 µg/mL, whereas standard antibiotic chloramphenicol was active at 6.25 to 12.5 µg/mL. Structure-bioactivity relationship assessment showed that higher electronic values were responsible for antibacterial properties against the nosocomial pathogens. The 2, 3-dihydroxybenzoate (dhb)-assisted biosynthetic pathway of catecholate-enclosed bacillibactins was proposed through the bacillibactin synthase multienzyme complex catalysis followed by dimerization of dhbACEBF operons with 16 genes (~ 12 kb bacterial genome). The present findings recognized an undescribed 4-methoxy-11'-pentanoyloxy-bacillibactin C as a source of potential antibacterial agent for use against drug-resistant pathogens for pharmaceutical applications. KEY POINTS: • Bacillus amyloliquefaciens in association with Kappaphycus alverezii was isolated • Four antibacterial bacillibactin analogs were identified from symbiotic bacterium • 4-Methoxy-11'-pentanoyloxy-bacillibactin C showed potential antibacterial activity.

Erectcyanthins A-C from marine sponge Hyrtios erectus: anti-dyslipidemic agents attenuate hydroxymethylglutaryl coenzyme A reductase

Bioactivity-steered chromatographic purification of the solvent extract of marine sponge Hyrtios erectus (Thorectidae) led to the isolation of three undescribed cyanthiwigin-type diterpenoids, erectcyanthins A-C. Erectcyanthin B exhibited comparable attenuation activity against 3-hydroxy-3-methylglutaryl-coenzyme A reductase (IC₅₀ 0.07 mM) with that displayed by anti-dyslipidemic agent atorvastatin (IC₅₀ 0.08 mM). Comparatively greater antioxidant properties of erectcyanthin B (IC₅₀ ∼ 0.4 mM) than that displayed by erectcyanthin A (IC₅₀ ∼ 0.5 mM), erectcyanthin C and the standard α-tocopherol (IC₅₀ 1.5-1.7 mM) against oxidants also corroborated its promising bioactivity. Erectcyanthin B exhibited considerably greater anti-inflammatory activities (IC₅₀ 0.88-1.09 mM) than other erectcyanthin analogues in the series. The potential anti-dyslipidemic activity of erectcyanthins was linearly correlated with electronic parameter (topological polar surface area ∼ 74.6) along with balanced hydrophilic-lipophilic properties (logarithmic octanol-water partition coefficient 1.76). This study recognized the anti-dyslipidemic property of erectcyanthin B as a promising pharmaceutical lead.

Anti-inflammatory xenicane-type diterpenoid from the intertidal brown seaweed Sargassum ilicifolium

Chemical analysis of the organic extract from intertidal brown seaweed Sargassum ilicifolium (family Sargassaceae) characterised an undescribed xenicane-type diterpenoid sargilicixenicane, elucidated as 3-(17-hydroxy-14-methylhept-13-en-10-yl)-6-methylhexahydro-1H-cyclonona[c]furan-4,19-diyl diacetate (compound 1). The studied compound exhibited prospective free radical quenching potential (IC50 1.2-1.4 mM) in comparison with commercial antioxidant (α-tocopherol, IC50 > 1.40 mM). Attenuation property of sargilicixenicane against pro-inflammatory enzyme, 5-lipoxygenase (IC50 4.70 mM) was comparable with that displayed by the non-steroidal anti-inflammatory agent ibuprofen (IC50 4.51 mM). Greater selectivity index displayed by the studied xenicane-type diterpenoid (1.42) than that exhibited by ibuprofen (0.44) recognised the selective attenuation potential of the former against the inducible cyclooxygenase-2 and 5-lipoxygenase enzymes. Higher electronic parameters (topological polar surface area, 82.06) and balanced hydrophobic-hydrophilic property (octanol-water partition coefficient 2.94) coupled with docking score (-11.17 kcal mol-1) and lower binding energy (-9.61 kcal mol-1) with the active site of 5-lipoxygenase supported the significant anti-inflammatory properties of the studied xenicane-type diterpenoid.

Novel Furanyl-Substituted Isochromanyl Class of Anti-Inflammatory Turbinochromanone from Brown Seaweed Turbinaria conoides

Organic extract of the brown seaweed Turbinaria conoides (Sargassaceae) was chromatographically fractionated to yield an undescribed furanyl-substituted isochromanyl metabolite, named as turbinochromanone, which was characterized as methyl 4-[(3S)-8-{[(3R)-4-ethyl-2,3-dihydrofuran-3-yl]methyl}-1-oxo-3,4-dihydro-1H-2-benzopyran-3-yl]butanoate. The isochromanyl derivative possessed comparable attenuation potential against 5-lipoxygenase (IC₅₀ 3.70 μM) with standard 5-lipoxygenase inhibitor drug zileuton (IC₅₀ 2.41 μM). Noticeably, the index of anti-inflammatory selectivity of turbinochromanone (∼1.7) was considerably greater than that exhibited by the standard agent diclofenac (1.06). Antioxidant properties of turbinochromanone against oxidants (IC₅₀ ∼24 μM) further supported its potential anti-inflammatory property. Greater electronic properties (topological polar surface area of 61.8) along with comparatively lesser docking parameters of the studied compound with aminoacyl residues of targeted enzymes (cyclooxygenase-2 and 5-lipoxygenase) (binding energy of -11.05 and -9.40 kcal mol^-1 , respectively) recognized its prospective anti-inflammatory potential. In an aim to develop seaweed-based natural anti-inflammatory leads, the present study isolated turbinochromanone as promising 5-lipoxygenase and cyclooxygenase-2 inhibitor, which could be used for pharmaceutical and biotechnological applications.

Conoidecyclics A-C from marine macroalga Turbinaria conoides: Newly described natural macrolides with prospective bioactive properties

Intertidal marine brown alga Turbinaria conoides (J.Agardh) Kützing (family Sargassaceae) is considered as one of the largely abundant species, available in the coastal zones of the Indian subcontinent. Bioactivity-guided chromatographic fractionation of the organic extract of T. conoides resulted in three previously undescribed macrocyclic lactone homologues, named as conoidecyclics A-C. Conoidecyclic A displayed greater attenuation potential against cyclooxygenase-2 (IC50 1.75 mM) and 5-lipoxygenase (IC50 4.24 mM) in comparison with other analogues. Conoidecyclic A exhibited higher attenuation potential against 5-lipoxygenase than that displayed by an anti-inflammatory agent, ibuprofen (IC50 4.51 mM). The higher selectivity index of conoidecyclic A (1.79) recognized its selective attenuation potential against the inducible cyclooxygenase-2 enzyme. Inhibition potential of conoidecyclic A against angiotensin converting enzyme-I (IC50 1.23 mM) and protein tyrosine phosphatase-1B (IC50 1.39 mM) were non-competitive, as deduced by kinetic studies. In-silico molecular modeling study of conoidecyclic A with the allosteric sites of the targeted enzymes exhibited least binding energy of -14.51 to -11.27 kcal mol-1 compared to those exhibited by other studied macrolide homologues. Reaction kinetic studies of conoidecyclic A coupled with lesser apparent Vmax inferred that it could efficiently bind with the allosteric site of targeted enzymes in a non-competitive manner to diminish the reaction velocity resulting in enzyme inhibition. Drug-likeness and predictive pharmacokinetic parameters of conoidecyclic A exhibited an acceptable oral bioavailability. These reports inferred that conoidecyclic A encompassing pentacosa macrocyclic moiety could be a promising therapeutic lead to inhibit the enzymes related to the development and progression of pathological conditions leading to inflammation, hypertension and type-2 diabetes.

Polygalacto-fucopyranose biopolymer structured nanoparticle conjugate attenuates glucocorticoid-induced osteoporosis: An in vivo study

Naturally occurring polysaccharide-structured nanoparticles have developed as promising materials for treatment of bone health disorders. Silver nanoparticle (ST-AgNP) structured from sulfated polygalacto-fucopyranose comprising of recurring structural entities of 2-SO3-α-(1 → 3)-fucopyranose and 6-O-acetyl-β-(1 → 4)-galactopyranose isolated from marine macroalga Sargassum tenerrimum demonstrated potential activities associated with osteogenesis. Subsequent treatment with ST-AgNP, activity of alkaline phosphatase (63 mU/mg) was raised in osteoblast stem cells (human mesenchymal, hMSC) than that in control (30 mU/mg). Intense growth of mineralized nodule on the surface of hMSC was apparent following treatment with ST-AgNP. Increased population of bone morphogenic protein-2 (23%) and osteocalcin+ cells (50%) on M2 macrophages were apparent following treatment with ST-AgNP (0.25 mg/mL). Glucocorticoid-induced in vivo animal model studies of ST-AgNP exhibited significant recovery of serum biochemical parameters along with serum estradiol and parathyroid hormone compared to disease control. Disease-induced groups treated with ST-AgNP showed the disappearance of osteoporotic cavities in the trabecular bone. Following treatment with ST-AgNP, serum calcium and phosphorus contents were significantly recovered.

Novel amylomacins from seaweed-associated Bacillus amyloliquefaciens as prospective antimicrobial leads attenuating resistant bacteria

The rise in antibiotic-resistant bacterial strains prompting nosocomial infections drives the search for new bioactive substances of promising antibacterial properties. The surfaces of seaweeds are rich in heterotrophic bacteria with prospective antimicrobial substances. This study aimed to isolate antibacterial leads from a seaweed-associated bacterium. Heterotrophic Bacillus amyloliquefaciens MTCC 12716 associated with the seaweed Hypnea valentiae, was isolated and screened for antimicrobial properties against drug-resistant pathogens. The bacterial crude extract was purified and three novel amicoumacin-class of isocoumarin analogues, 11'-butyl acetate amicoumacin C (amylomacin A), 4'-hydroxy-11'-methoxyethyl carboxylate amicoumacin C (amylomacin B) and 11'-butyl amicoumacin C (amylomacin C) were isolated to homogeneity. The studied amylomacins possessed potential activities against Pseudomonas aeruginosa, vancomycin-resistant Enterococcus faecalis, Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus, and Shigella flexneri with a range of minimum inhibitory concentration values from 0.78 to 3.12 µg/mL, although standard antibiotics ampicillin and chloramphenicol were active at 6.25-25 µg/mL. Noticeably, the amylomacin compound encompassing 4'-hydroxy-11'-methoxyethyl carboxylate amicoumacin C functionality (amylomacin B), displayed considerably greater antagonistic activities against methicillin-resistant S. aureus, vancomycin-resistant E. faecalis, Vibrio parahaemolyticus, Escherichia coli, and K. pneumoniae (minimum inhibitory concentration 0.78 μg/mL) compared to the positive controls and other amylomacin analogues. Antimicrobial properties of the amylomacins, coupled with the presence of polyketide synthase-I/non-ribosomal peptide synthetase hybrid gene attributed the bacterium as a promising source of antimicrobial compounds with pharmaceutical and biotechnological applications.

A Leap Forward Towards Unraveling Newer Anti-infective Agents from an Unconventional Source: a Draft Genome Sequence Illuminating the Future Promise of Marine Heterotrophic Bacillus sp. Against Drug-Resistant Pathogens

During the previous decade, genome-built researches on marine heterotrophic microorganisms displayed the chemical heterogeneity of natural product resources coupled with the efficacies of harnessing the genetic divergence in various strains. Herein, we describe the whole genome data of heterotrophic Bacillus amyloliquefaciens MB6 (MTCC 12,716), isolated from a marine macroalga Hypnea valentiae, a 4,107,511-bp circular chromosome comprising 186 contigs, with 4154 protein-coding DNA sequences and a coding ratio of 86%. Simultaneously, bioactivity-guided purification of the bacterial extract resulted in six polyketide classes of compounds with promising antibacterial activity. Draft genome sequence of B. amyloliquefaciens MB6 unveiled biosynthetic gene clusters (BGCs) engaged in the biosynthesis of polyketide-originated macrolactones with prospective antagonistic activity (MIC ≤ 5 µg/mL) against nosocomial pathogens. Genome analysis manifested 34 putative BGCs necessitated to synthesize biologically active polyketide-originated frameworks or their derivatives. These results provide insights into the genetic basis of heterotrophic B. amyloliquefaciens MTCC 12,716 as a prospective lead for biotechnological and pharmaceutical applications.

Ulvapyrone, a pyrone-linked benzochromene from sea lettuce Ulva lactuca Linnaeus (family Ulvaceae): newly described anti-inflammatory agent attenuates arachidonate 5-lipoxygenase

Green marine macroalgae, particularly Ulva lactuca, is an essential constituent of the cuisines in many Asian countries. The present work aims to separate a bioactive pyrone attached benzochromene analogue, named as ulvapyrone from the organic extract of U. lactuca, followed by its structural characterisation as 2-{(6a'-hydroxyethyl-4'-methyltetrahydro-2H-pyran-2'-one)-6'-yl}-4-methyl-7-ethylacetate-8-hydroxy-7, 8-dihydrobenzo [de]chromene. Ulvapyrone exhibited prospective inhibition property against arachidonate 5-lipoxygenase (IC₅₀ ∼1 mg mL^-1) comparable to that demonstrated by ibuprofen (IC₅₀ 0.9 mg mL^-1), which connoted its anti-inflammatory activity. The studied benzochromene exhibited promising antioxidant potential (IC₅₀ 0.5-0.6 mg mL^-1), which further reinforced its attenuation property against 5-lipoxygenase. Bioactivities of ulvapyrone were linearly correlated with electronic parameter (topological polar surface area ∼102) along with less binding energy (-8.22 kcal mol^-1) with the allosteric site of 5-lipoxygenase. In silico predictions of physicochemical parameters along with absorption, distribution, metabolism and excretion could recognise the acceptable oral bioavailability of ulvapyrone.

Antioxidant spiropharanone, an undescribed variant of trans-decalin spiro-γ-lactone, from pharaoh cuttlefish Sepia pharaonis: Twin inhibitors of inflammatory 5-lipoxygenase and serine protease dipeptidyl peptidase-4

Marine pharaoh cuttlefish Sepia pharaonis (family Sepiidae) is regarded as an economically important class of cephalopod in the coastal Mediterranean and Asian regions. Bioassay-guided chromatographic purification of solvent extract of S. pharaonis led to the identification of a trans-decalin based spirolactone, spiropharanone, which was characterized as 1-hydroxy-7-(4'-methoxy-3-methylbut-2-enyl)-3,9,15-trimethyl-8-oxo-octahydro-5H-spiro[furan-8,9-naphtho]-8-yl-acetate by spectroscopic techniques. Spiropharanone exhibited significantly greater anti-inflammatory activity by attenuating pro-inflammatory 5-lipoxygenase (IC₅₀ 1.02 mM) than the non-steroidal drug ibuprofen (IC₅₀ 4.61 mM, p ≤ .05). Superior antioxidant properties of spiropharanone against free radicals (EC₅₀ ~1.20 mM) and other oxidants (hydroxyl [EC₅₀ 0.97 mM] and superoxide [EC₅₀ 1.47 mM] scavenging) also reinforced its promising anti-inflammatory activity. The studied spiropharanone also exhibited significant attenuation toward insulin secretion regulating enzyme dipeptidyl peptidase-4 (IC₅₀ 0.92 mM) recognizing its anti-hyperglycemic potential. Significantly higher electronic properties (topological polar surface area ~100) combined with balanced hydrophilic-lipophilic properties (partition coefficient of logarithmic octanol-water ~3) and lesser docking parameters of spiropharanone demonstrated that the compound could be utilized as an important bioactive lead against oxidative stress, inflammation, and hyperglycemic-related ailments. PRACTICAL APPLICATIONS: Nutritionally rich edible marine pharaoh cuttlefish Sepia pharaonis occupies a prominent place among seafood fisheries owing to the presence of bioactive nutrients and functional food ingredients. These marine cuttlefish are widely distributed along the Asian and Mediterranean coasts, and consumed as culinary delicacy for decades. An undescribed trans-decalin spirolactone, spiropharanone was isolated from the organic extract of S. pharaonis based on bioactivity-assisted sequential chromatographic fractionation. Spiropharanone displayed promising antioxidant potential along with attenuation properties against inducible pro-inflammatory 5-lipoxygenase and insulin secretion regulating enzyme dipeptidyl peptidase-4. This study established the ameliorating potential of a naturally derived marine food constituent against inflammatory and diabetic ailments, and thus anticipated as functional food lead in pharmaceutical formulations towards inflammation and maintaining glucose homeostasis.

Difficidin class of polyketide antibiotics from marine macroalga-associated Bacillus as promising antibacterial agents

A heterotrophoic Bacillus amyloliquefaciens MTCC12713 isolated from an intertidal macroalga Kappaphycus alverezii displayed promising antibacterial activities against multidrug-resistant bacteria. Genome mining of the bacterium predicted biosynthetic gene clusters coding for antibacterial secondary metabolites. Twenty-one membered macrocyclic lactones, identified as difficidin analogues bearing 6-hydroxy-8-propyl carboxylate, 9-methyl-19-propyl dicarboxylate, 6-methyl-9-propyl dicarboxylate-19-propanone, and (20-acetyl)-6-methyl-9-isopentyl dicarboxylate (compounds 1 through 4) functionalities were purified through bioassay-guided fractionation. The difficidin analogues exhibited bactericidal activities against vancomycin-resistant Enterococcus faecalis, methicillin-resistant Staphylococcus aureus, and other drug-resistant strains, such of Klebsiella pneumonia and Pseudomonas aeruginosa with the minimum inhibitory concentration of about 2-9 × 10^-3 μM. A plausible enzyme-catalyzed biosynthetic pathway that is generated through addition of acrylyl initiator unit by repetitive decarboxylative Claisen condensation modules with malonate units was recognized, and their structures were corroborated with gene organization of the dif operon, which could comprehend dif A-O (~ 70 kb). Drug-likeness score for 5-ethoxy-28-methyl-(9-methyl-19-propyl dicarboxylate) difficidin (compound 2, 0.35) was greater than those of other difficidin analogues, which corroborated the potential in vitro antibacterial properties of the former. The present study demonstrated the potential of difficidin analogues for pharmaceutical and biotechnological uses against the bottleneck of emergent drug-resistant pathogens. KEY POINTS: • Difficidins were isolated from marine alga associated Bacillus amyloliquefaciens. • Whole-genome mining of bacterial genome predicted biosynthetic gene clusters. • Greater drug-likeness for difficidin 2 confirmed its potent antibacterial activity.

Anti-inflammatory β-sitosterols from the Asiatic loop-root mangrove Rhizophora mucronata attenuate 5-lipoxygenase and cyclooxygenase-2 enzymes

Four biogenic β-sitosterol analogues were identified from methanolic extract of the leaves of loop-root mangrove Rhizophora mucronata. These were characterized as 4, 14, 23-trimethyl-3β-sitosterol (1), 7-ethyl-3β-sitosterol (2), sitosteryl-3β-(3³E)-pent-3³-enoate (3) and 12α-hydroxy-3β-sitosterol (4) based on comprehensive spectroscopic techniques. Anti-inflammatory activities of β-sitosterol 4 against pro-inflammatory enzymes 5-lipoxygenase and cyclooxygenase-2 were found to be significantly higher (IC₅₀ 1.85 and 1.92 mM, respectively) compared to those demonstrated by compounds of 1-3 (p < 0.05). These β-sitosterol analogues disclosed superior selectivity indices (1.43-2.07) with regard to inducible cyclooxygenase-2 than its constitutive isoform cyclooxygenase-1, when compared to the standard, ibuprofen (0.44). Antioxidant properties of 12α-hydroxy-β-sitosterol (4) were found to be significantly greater (IC₅₀ 1.43-1.67 mM) than those of other sitosterol analogues. Structure-activity correlation analyses put forward that the bioactive potencies of the titled β-sitosterols were positively correlated to their electronic parameters. Molecular docking simulations were carried out in the active sites of 5-lipoxygenase/cyclooxygenase-2, and the docking scores and binding energies of the studied β-sitosterol analogues were positively correlated with their attenuation properties against 5-lipoxygenase and cyclooxygenase-2.

Anti-inflammatory pregnane-type steroid derivatives clathroids A-B from the marine Microcionidae sponge Clathria (Thalysias) vulpina: Prospective duel inhibitors of pro-inflammatory cyclooxygenase-2 and 5-lipoxygenase

Two pregnane-type of steroid derivatives characterized as 5α-pregna-3β-methyl pent-3-enoate-12β, 16β diol-20-one (clathroid A) and 12β,15β- dihydroxypregna-4,6-diene-3,20-dione (clathroid B) were purified from the crude extract of the marine sponge, Clathria (Thalysias) vulpina (family Microcionidae) by extensive chromatographic fractionation. Spectroscopic methods including nuclear magnetic resonance spectroscopy were employed to characterize the purified clathroids A-B. The studied compounds exhibited duel inhibitory potentials against pro-inflammatory cyclooxygenase-2 and 5-lipoxygenase (median inhibitory concentration, IC₅₀ < 1 mM), whereas the attenuation property of clathroid A against 5-lipoxygenase (IC₅₀ 0.85 mM) was greater than the standard anti-inflammatory ibuprofen (IC₅₀ 4.51 mM, p < 0.05). Greater selectivity index (anti cyclooxygense-2/anti cyclooxygense-1) of the studied clathroids (>1) than ibuprofen (0.43) attributed the greater selective attenuation properties towards pro-inflammatory inducible cyclooxygenase-2 than its constitutive isoenzyme cyclooxygenase-1. The antioxidant potentials of clathroid A against 2, 2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (IC₅₀ 0.80 mM) and diphenyl-1-picrylhydrazyl (IC₅₀ 0.83 mM) free radicals were greater than those of clathroid B (IC₅₀ 0.86-0.96 mM). Structure-activity analyses showed that the bioactivities of the clathroids were directly related to their electronic parameters coupled with permissible hydrophobic properties. Clathroid A exhibited grater electronic parameter (topological polar surface area tPSA, 83.83) than clathroid B (74.60) and ibuprofen (37.30), which were found to be in agreement with the prospective anti-inflammatory profile of clathroid A. Clathroid A exhibited higher number of hydrogen bonding interactions with 5-lipoxygenase active site and lesser docking values, such as docking score (DS -12.90 kcal mol^-1) and inhibition constant (Ki 1.11 nM) than those recorded by clathroid B (DS -10.49 kcal mol^-1; Ki 13.88 nM). The molecular binding properties of clathroid A with 5-lipoxidase inferred that its docking score/ binding energy were positively correlated with their in vitro bioactivie potentilas. A putative biosynthetic pathway of the studied clathroids was proposed from a pregnenolone precursor. The present study recognized the potential of clathroid A isolated from C. (Thalysias) vulpina as prospective anti-inflammatory lead that could find its use in medicinal applications.

Polygalacto-fucopyranose from marine alga as a prospective antihypertensive lead

Consumption of marine alga-based polysaccharides as additional functional foods can endow with health benefits by diminishing the risk of chronic diseases. A polygalacto-fucopyranose characterized as [→1)-2, 4-SO3-α-Fucp-(3 → 1)-{2-SO3-α-Fucp-(3→}] with [(4 → 1)-6-OAc-β-Galp-(4→] side chain isolated from marine alga Sargassum wightii exhibited potential antihypertensive activity. Upon treatment with studied polygalactofucan (50 mg/kg BW), serum hypertension biomarkers troponin-T (1.3 pg/mL), troponin-I (1.2 μg/dL) and angiotensin-II converting enzyme (0.18 pg/mL) were significantly recovered in hypertensive rats compared to disease control. Serum cardiovascular risk indices of diseased rats were significantly decreased (< 10%, p < 0.05) after administration of the studied galactofucan (50 mg/kg BW) related to hypertension group (> 17%), and were comparable with standard antihypertensive agent telmisartan (8.3-10.2% at 2 mg/kg BW). The studied compound was safe for consumption as obvious from the high LD50 value (>5 g/kg), and could be developed as a prospective functional food ingredient attenuating the pathophysiological attributes causing hypertension-related conditions.

Clathriketal, a new tricyclic spiroketal compound from marine sponge Clathria prolifera attenuates serine exopeptidase dipeptidyl peptidase-IV

An undescribed tricyclic spiroketal compound clathriketal was purified from the solvent extract of the Microcionidae sponge Clathria prolifera, and was characterised as 7-(hydroxymethyl)-13-methoxy-3,11-dimethyl-4-oxo-octahydrospiro[chromene-9,13-pyran]-11-yl propionate by spectroscopic experiments. Clathriketal exhibited significant anti-hyperglycemic property by attenuating serine protease dipeptidyl peptidase-IV (IC₅₀ 0.37 mM), and its activity was comparable with the standard diprotin A (IC₅₀ 0.31 mM). The spiroketal also exhibited significant inhibitory potentials against carbolytic enzymes α-glucosidase (IC₅₀ 0.43 mM) and α-amylase (IC₅₀ 0.41 mM). Superior antioxidant properties of clathriketal against the oxidants, 2, 2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid and 2, 2-diphenyl-1-picrylhydrazyl (IC₅₀ ∼1.2 mM) also reinforced its promising anti-hyperglycemic activity. Considerably greater topological surface area (91.29) coupled with lesser steric parameters of clathriketal, as elucidated from the structure-activity relationship analyses could further ascribe the improved ligand-receptor interactions resulting in its prospective anti-hyperglycemic activity. Molecular docking analysis of clathriketal with dipeptidyl peptidase-IV recorded lesser binding energy (-9.63 kcal/mol), which further corroborated its prospective antihyperglycemic activity.

Apoptotic effect of chromanone derivative, hyrtiosone A from marine demosponge Hyrtios erectus in hepatocellular carcinoma HepG2 cells

The tumor suppressor proteins p53 and p27 exhibited a significant role in the survival of cells and regulation of cellular division and growth. In majority of the human tumors, particularly in hepatocellular carcinoma, these proteins are inactivated by mutation or deletion, and are considered to predict the pathophysiology related to liver cancer. The present study evaluated the activation of the p53 and p27 pathways as a useful therapeutic tool to attenuate hepatocellular carcinoma. Three undescribed homologous chromanone derivatives, hyrtiosones A-C were isolated from the organic extract of marine demosponge Hyrtios erectus (family Thorectidae). Preliminary bioactivity assessments found that hyrtiosone A exhibited prospective anti-inflammatory (IC₅₀ 1.02-1.86 mM) and antioxidant (IC₅₀ 0.74-0.83 mM) properties. Molecular docking analysis of the hyrtiosones using p53-murine double minute complex revealed lesser docking parameters for hyrtiosone A (binding energy -11.12 kcal mol^-1, docking score -12.18 kcal mol^-1) thereby attributing its greater bioactivity. Hyrtiosone A was furthermore analyzed for in vitro anticancer activity in hepatocellular carcinoma HepG2 cells. Morphological assessment of hyrtiosone A treated HepG2 cell line by acridine orange/ethidium bromide fluorescence staining revealed greater number of apoptotic cells, and was found to be comparable with the cells treated with the standard doxorubicin. Further the Annexin V-fluorescein isothiocyanate assay of hyrtiosone A treated HepG2 cell line by flow cytometry displayed greater number of early apoptotic cells (51.24%) than that exhibited by the standard (21.45%). Cell cycle distribution analysis showed that hyrtiosone A arrested the S and G2/M phase of cell cycle and upregulate the gene expression of p53 and p27 in hepatocellular carcinoma HepG2 cells.

Cistobislactone, an undescribed variant of 14-membered bislactonic macrodiolide, from old-lady octopus Cistopus indicus (family Octopodidae) attenuates inflammatory lipoxygenase

Chemical evaluation of specialised metabolites from the old-lady marine octopus Cistopus indicus (family Octopodidae) led to the isolation of an undescribed 14-membered bislactonic macrodiolide cistobislactone, which was characterized as 12-(4'-ethyl-6'-methoxy-3'-methyl-hex-1-enyl)-5,11-dihydroxy-6-methyl-1,7-dioxacyclotetradeca-3,9-diene-2,8-dione. Cistobislactone exhibited noticeably greater inhibitory potential against 5-lipoxygenase (IC₅₀ 2.06 mM) compared to standard anti-inflammatory agent ibuprofen (IC₅₀ 4.61 mM, p < 0.05). Superior antioxidant properties of cistobislactone against the oxidants (IC₅₀ ∼1.8 mM) also reinforced its promising anti-inflammatory activity. Higher electronic properties (topological polar surface area of 102.3) and balanced hydrophobicity (logarithm of octanol-water coefficient ∼3) could recognize its higher interaction at the enzyme active site resulting in an effective attenuation of 5-lipoxygenase and efficient inter-membrane permeability. Comparatively lesser binding energy (-6.5 kcal mol^-1) and docking score (-7.5 kcal mol^-1) of cistobislactone with the aminoacyl residues of 5-lipoxygenase could further recognize its anti-inflammatory potential.

Combined application of ascorbic acid and endophytic N-fixing Azotobacter chroococcum Avi2 modulates photosynthetic efficacy, antioxidants and growth-promotion in rice under moisture deficit stress

This group has previously reported the role of ascorbic acid (AA) as an antioxidant for survivability and ability to enhancing diazotrophic efficacy in Azotobacter chroococcum Avi2 under hydrogen peroxide (H₂O₂) stress. However, the present study showed the combined application of AA and Avi2 in drought-susceptible (IR64 and Naveen) and drought-tolerant (Ankit and Satyabhama) rice cultivars to determine their photosynthetic efficacy (chlorophyll fluorescence-imaging), antioxidants, and plant growth-promotion (PGP) under moisture deficit stress (MS, -60 kPa). The results indicated that combined application of AA and Avi2 significantly (p < 0.05) increased the total chlorophyll, relative water content, electrolytic leakage, super oxide dismutase, and catalase activities in all rice cultivars as compared to other MS treatments, whereas stress indicators like proline and H₂O₂ contents were proportionally increased under MS and their concentration were normalized under combined application of AA and Avi2. Photochemical quenching, non-photochemical quenching, photosynthetic electron transport rate, and the effective quantum efficiency were found to be increased significantly (p < 0.05) in Avi2 + AA as compared to other MS treatments. Moreover, rice roots harbored significantly (p < 0.05) higher copy number of nifH gene in Avi2 + AA treatment followed by Avi2 compared to flooded control and other MS treatments. Combined application of AA and Avi2 also increased the grain yield significantly (p < 0.05) by 7.09 % and 3.92 % in drought-tolerant (Ankit and Satyabhama, respectively) and 31.70 % and 34.19 % in drought-susceptible (IR64 and Naveen, respectively) rice cultivars compared to MS treatment. Overall, the present study indicated that AA along with Avi2 could be an effective formulation to alleviate MS vis à vis enhances PGP traits in rice.

Euryfuranyl compounds from edible species of cuttlefish as potential anti-inflammatory leads attenuating NF-κB signaling cascade in lipopolysaccharide-activated macrophages

Nuclear factor-kappa B is an inducible transcription element, which was considered as an important regulator of immune functions, and plays a critical role to induce inflammatory reactions. In this study, we have demonstrated the anti-inflammatory potentials of previously undescribed (4 → 13)-abeo-euryfuranyls (1-2) from the spineless cuttlefish Sepiella inermis in lipopolysaccharide-stimulated macrophages. The euryfuranyl bearing (4 → 13)-abeo-euryfuranyl-2-ene-6-hydroxymethyl-propanoate framework (compound 1) displayed prominent inhibitory effects against pro-inflammatory cyclooxygenase-2 (IC₅₀ 0.36 mM) and 5-lipoxygenase (IC₅₀ 0.70 mM). Additionally, it suppressed the generation of inducible nitric oxide synthase along with cyclooxygenase-2 and 5-lipoxygenase in lipopolysaccharide-stimulated macrophages. The euryfuranyl analogue (1) down-regulated the mRNA expression of cyclooxygenase-2 and nuclear factor-κB signaling pathway in lipopolysaccharide-activated macrophage cells by hindering the degradation of inhibitor-κB proteins, and transfer of the subunit NF-κB p⁶⁵ to the nucleus from the cytosol. These results demonstrated that the euryfuranyl analogue could be explored as a promising anti-inflammatory therapeutic lead attenuating nuclear factor-κB signaling cascade.

Marine Macroalgal Polygalactan-Built Nanoparticle Construct for Osteogenesis

Naturally derived polysaccharide biopolymer-based nanoparticles with their size and drug release potentials have appeared as promising biomaterials for osteogenic differentiation. A metallic nanoparticle (GS-AgNP) prepared from a sulfated polygalactan characterized as →3)-2-O-methyl-O-6-sulfonato-β-d-galactopyranosyl-(1 → 4)-2-O-methyl-3,6-anhydro-α-d-galactopyranose-(1→ isolated from the marine macroalga Gracilaria salicornia exhibited a prospective osteogenic effect. Upon treatment with the studied GS-AgNP, alkaline phosphatase activity (88.9 mU/mg) was significantly elevated in human mesenchymal osteoblast stem cells (hMSCs) compared to that in the normal control (33.7 mU/mg). A mineralization study of GS-AgNPs demonstrated an intense mineralized nodule formation on the hMSC surface. A fluorescence-activated cell sorting study of osteocalcin and bone morphogenic protein-2 (BMP-2) expression resulted in an increased population of osteocalcin (78.64%) and BMP-2-positive cells (46.10%) after treatment with GS-AgNPs (250 μg/mL) on M2 macrophages. A time-dependent cell viability study of GS-AgNPs exhibited its non-cytotoxic nature. The studied polygalactan-built nanoparticle could be developed as a promising bioactive pharmacophore against metabolic bone disorder and the treatment for osteogenesis therapy.