Antifouling metabolites from the mangrove plant Ceriops tagal

Antifouling activity and biodegradable potential of the bioactive metabolites isolated from mangrove Avicennia officinalis L

The present study explores the antifouling potentials of ethanol extract of mangrove Avicennia officinalis. Results of antibacterial activity inferred that extract had strongly inhibited the growth of fouling bacterial strains with significant differences in halos (9-16 mm) and showed minimal bacteriostatic (12.5-100 µg ml-1) and bactericidal (25-200µg ml-1) values. It had also strenuously suppressed fouling microalgae with appreciable MIC (12.5 and 50 µg ml-1). The extract had also effectively deterred settlement of larvae of Balanus amphitrite and byssal thread of mussel Perna indica with lower EC50 (11.67 and 37.43 µg ml-1) and higher LC50 (257.33 and 817 µg ml-1) values. Further 100% recuperation of mussels from toxicity assay and therapeutic ratio of >20 substantiated its non-toxicity. GC-MS profile of bioassay guided fraction showed four (M1-M4) major bioactive metabolites. In silico biodegradability study revealed that metabolites M1 (Pentanoic acid, 5-methoxy-, phenyl ester) and M3 (Benzaldehyde, methyl-) have rapid biodegradation rates and eco-friendly in nature.

Antifouling coating based on biopolymers (PCL/ PLA) and bioactive extract from the sea cucumber Stichopus herrmanni

An important challenge to decrease the toxic effects of the common biocides in marine environments and to achieve suitable ecofriendly natural antifouling coatings is to find effective natural antifoulants and efficient biodegradable coatings. In this study, antifouling activities of nine bioactive extracts (non-polar to polar) from different organs of the sea cucumber Stichopus herrmanni were tested against five bacterial strains, barnacle and brine shrimp larvae. The ethyl acetate extract of the body wall showed the highest in-vitro antifouling activity including high antibacterial and anti-barnacle activities and low toxicity against the brine shrimp as non-target organism. Based on these results, 10 phr of the ethyl acetate extract from S.herrmanni was added to different coatings consisting of polycaprolactone (PCL)/polylactic acid (PLA) blends containing various compositions of PLA (0, 10, and 20 wt.%). Polyvinyl chloride panels were coated with the prepared antifouling coatings and immersed in seawater for three months. Panel coated with PCL 80% /PLA 20% containing 10 phr of the antifoulant (panel-5), showed the highest resistance against fouling settlement with fouling coverage of 41.66% (P < 0.05). In addition, the lowest fouling weight was measured in panel-5 as well (81.00 ± 9.85 g) (P < 0.05). These findings indicate the antibacterial and antifouling potential of semi-polar bioactive extracts from the S. herrmanni body wall as natural antifoulants, as well as the enhanced antifouling performance of PCL/the natural antifoulant coatings by adding PLA.

Bioassay Directed Fractionation of Petroleum Ether Extract of Aerial Parts of Ceriops tagal: Isolation of Lupeol as the Nematicidal Agent against Cyst Nematode Heterodera zeae

Plant parasitic cyst nematode  Heterodera zeae  is a pest, causing substantial economic losses in agriculture. Organic pesticides, based on plant products have emerged as eco-benign nematicidal agents.  Ceriops tagal  is a well-known marine medicinal plant which has not been evaluated against any nematode. Petroleum ether extract of the aerial parts of the plant (CTP), exhibited promising activity against infective stage larvae of  H. zeae . On subjecting to classical solvent-solvent separation, it afforded petroleum ether soluble (CTP-S), methanol soluble ( CTPMS-1 , CTPMS-2) and insoluble (CTPM-IN-2) fractions, which exhibited activity against the cyst nematode within 24 h exposure. GC, GCMS and ESI-HRMS analyses of CTPMS-1 and CTPMS-2 fractions resulted in the identification of a number of compounds, including pentacyclic triterpenoids, lupeol ( 1 ), betunal ( 2 ), betulin ( 3 ), lupenone ( 4 ), betulonaldehyde ( 5 ), betulonic acid ( 7 ), methyl-3-acetoxy-27- O -(3,4-dihydroxy- E -cinnamoyl)-20(29)-lupen-28-oate ( 8 ) and  β -amyrin, along with phenylpropanoid esters, fatty acids and their derivatives, benzamide, and indole derivatives. CTPM-IN-2 which mainly contained lupeol ( 1 ) exhibited maximum nematicidal activity, with 91% and 93% mortality of the larvae of  H. zeae , after exposure for 72 h at the concentration of 0.5% and 1%, respectively. Its fractionation and purification through column chromatography resulted in the isolation and identification of four lupane-type triterpenoids  1 ,  3 ,  4  and betulinic acid ( 6 ). One of its most abundant column fractions CC-9-18 (145 mg) which exhibited substantial activity, with 81% mortality at the lowest concentration of 0.125% after 48 h of incubation mainly contained lupeol. It seems lupeol, a wide spread bio-privileged triterpenoid is the nematicidal principle of the plant as its authentic sample showed LC 50 value of 0.061 after 72 h exposure. It is for the first time that nematicidal activity is reported for any part of  C. tagal  and that of lupeol against  H. zeae.  Pentacyclic triterpenoids  1 - 8  are biosynthetically related. Of the twenty-four compounds isolated or identified in the present investigation only five constituents  1 ,  3 ,  6 ,  7  and palmitic acid have been isolated previously from  C. tagal .

Induction of cytotoxicity by Bruguiera gymnorrhiza in human breast carcinoma (MCF-7) cell line via activation of the intrinsic pathway

Breast cancer is among the frequently occurring cancer worldwide. The foremost underline aim of this study was to determine the growth inhibitory effect along with mechanistic study of a Bruguiera gymnorrhiza extract on MCF-7. The cytotoxicity activity was determined by using the MTS assay. Butanol extract exhibited the maximum cytotoxicity activity against the MCF-7 cells with IC₅₀ of 3.39 μg/mL, followed by diethyl ether and methanol extract (IC₅₀ at 16.22 μg/mL and 37.15 μg/mL, respectively) at 72 h. The DeadEnd^TM Colorimetric Apoptosis Detection System confirmed the induction of apoptosis (via DNA fragmentation) in MCF-7 cells. Both butanol and diethyl ether extracts of B. gymnorrhiza significantly increase the caspase-3 level. However, the diethyl ether extract induced higher caspase-9 levels compared to caspase-8, suggesting that the intrinsic pathway was the major route in the process of apoptosis. Thin-layer chromatography profiling demonstrated the presence of phenolic, terpene, and alkaloid compounds in crude methanol, diethyl ether, and butanol extracts. The phytochemicals present in the extracts of B. gymnorrhiza might have the potential to be a future therapeutic agent against breast cancer.

Biological evaluation of gallic acid and quercetin derived from Ceriops tagal: insights from extensive in vitro and in silico studies

Gallic acid (PubChem CID: 370) and quercetin (PubChem CID: 5280343) are major phenolic compounds in many mangrove plants that have been related to health cure. In the present study, the active fractions namely gallic acid (1) and quercetin (2) were isolated from the methanolic extract of leaves of Ceriops tagal in a Tropical mangrove ecosystem of Andaman and Nicobar Island (ANI), India. The chemical structures were determined by spectroscopic analysis: Fourier-Transform Infrared spectroscopy (FT-IR), ¹H, ¹³C Nuclear Magnetic Resonance (NMR) spectroscopy, and High-resolution mass spectrometry (HRMS). The anticancer activity of isolated compounds (1) and (2) were evaluated by in vitro assays against two human cancer cell lines namely, HeLa (Cervical) and MDA-MB231 (Breast) cancer cells revealed that IC₅₀ values of gallic acid (HeLa: 4.179197 ± 0.45 µg/ml; MDA-MB231: 80.0427 ± 0.19 µg/ml at 24 h) and quercetin (HeLa: 99.914 ± 0.18 µg/ml; MDA-MB231: 18.288382 ± 0.12 µg/ml at 24 h), respectively. Antioxidant properties of gallic acid (1) and quercetin (2) are found to be IC₅₀ value of 0.77 ± 0.41 µg/ml and 1.897 ± 0.81 µg/ml, respectively. Molecular docking results explained that gallic acid (1) and quercetin (2) showed estimated binding free energy (ΔG) of -5.4 and -6.9 kcal/mol towards drug target Bcl-B protein, respectively. The estimated inhibition constant (Ki) for these two molecules are 110 and 8.75 μM, respectively. The MD simulation additionally supported that quercetin molecule is significantly improved the structural stability of Bcl-B protein. The present study provides key insights about the importance of polyphenols, and thus leads to open the therapeutic route for anti-cancer drug discovery process.Communicated by Ramaswamy H. Sarma.

Phyco-linked vs chemogenic magnetite nanoparticles: Route selectivity in nano-synthesis, antibacterial and acute zooplanktonic responses

Despite the fact that magnetic iron oxide nanoparticles (Fe₃O₄-MNPs) considered as the most promising nanoparticles (NPs) in biomedicine and environmental biotechnology, their safety and ecotoxicological impacts of biogenic and chemogenic routes of Fe₃O₄-MNPs in the marine aquatic system is scarcely studied. In this work, we report the optimized and suitable phyco-synthesis route for nano-Fe₃O₄ based on the six selected species of the Persian Gulf seaweeds: Ulva prolifera, U. flexuosa, U. linza, U. intestinalis, U. clathrata, and Sargassum boveanum. Moreover, antibacterial activities and acute zooplanktonic responses in Artemia salina and acorn barnacle Amphibalanus amphitrite to chemogenic and biogenic Fe₃O₄-MNPs, were evaluated. Although all the seaweeds extract showed reducing potential for Fe₃O₄-MNPs green synthesis - mainly on the basis of characterization results- the algal route selectivity has been demonstrated to be important for the biosynthesis of magnetite NPs. Herein, the cubo-spherical and polydisperse U. prolifera-derived Fe₃O₄-MNPs with particles sizes of 9.59 nm were the best ones. The comparative zooplanktonic cytotoxicity of chemo- and bio-route of Fe₃O₄-MNPs exhibited no acute toxicity in nauplii and adults of A. salina (96-h EC₅₀ ≥ 1000 mg/L) and the potential of toxicity in A. amphitrite nauplii (48-h EC₅₀ = 466.5 and 842.3 mg/L for chemo- and bio-route of Fe₃O₄-MNPs, respectively). The in vitro antimicrobial activity of both chemo- and bio-route of magnetite NPs to selective human pathogenic bacteria and fungi (i.e. n = 11) showed strong antagonistic activity against Staphylococcus epidermidis, Bacillus subtilis, B. pumulis, and Saccharomyces cerevisiae. In conclusion, these findings demonstrate the optimized phyco-fabrication of Fe₃O₄-MNPs as promising nontoxic approach in ecobiotechnology, the new insight about the potential adverse effects of chemosynthesized Fe₃O₄-MNPs to crustacean zoo-organisms after their possible entrance into the marine environments, and bio/chemo-route Fe₃O₄-MNPs as pivotal agent for nanoantimicrobials.

Environmentally benign antifouling activity and toxic properties of bioactive metabolites from mangrove Excoecaria agallocha L

This study was aimed to investigate the antifouling (AF) potentials and toxic properties of methanol extract from leaves of mangrove Excoecaria agallocha. Antimicrofouling activity results inferred that this extract strongly inhibited fouling bacterial and microalgal growth. This extract had also inhibited the settlement of brown mussel Perna indica and larvae of barnacle Balanus amphitrite. Further, EC₅₀ < LC₅₀ and therapeutic ratio > 1 together propagated non-toxic nature of the extract. Mollusk foot adherence assay result showed complete inhibition of foot spreading and loss of attachment of common rocky fouler Patella vulgata to the substrata. Field assay results affirmed that this extract effectively deterred settlement of biofoulers. Purification and GC-MS analysis of bioassay-guided active spot evidenced presence of three major compounds (> 85%) responsible for the promising AF activity. The identified lead compounds subjected to an estimation (BIOWIN™) program developed by United States Environmental Protection Agency (USEPA) predicts that they are biodegradable in nature. Graphical abstract.

Antifouling and toxic properties of the bioactive metabolites from the seagrasses Syringodium isoetifolium and Cymodocea serrulata

The present study documents the antifouling and toxic properties of seagrasses Syringodium isoetifolium and Cymodocea serrulata. For that, the seagrasses S. isoetifolium and C. serrulata were extracted individually using organic solvents viz. dichloromethane, acetone and methanol. Amongst the extracts, the maximum antimicrofouling and antimacrofouling activities were exhibited by methanol extracts of both the seagrasses. The Minimal Inhibitory Concentration (MIC) of methanolic extracts of seagrasses was ranged from 1.0 to 10µg/ml against test biofilm bacteria and microalgal strains. Similarly, 100% fouling inhibition of limpet Patella vulgata was found at 6.0mg/ml of methanolic extracts of seagrasses. The mussel Perna indica showed 50% of byssal production and attachment inhibition at 21.51±2.03, 17.82±1.07µg/ml and the anticrustaecean activity for 50% mortality of Artemia salina was recorded at 732.14±9.21 and 394.16±5.16µg/ml respectively for methanolic extracts of S. isoetifolium and C. serrulata. The minimal inhibitory and higher lethal concentrations of active methanol extracts shows it׳s less toxic nature. Based on the prolific results, methanol extracts of S. isoetifolium and C. serrulata were subjected to purification using silica gel column and thin layer chromatography. Then the active compounds of the bioassay guided fractions were partially characterized using gas chromatography coupled with mass spectroscopy (GC-MS) and keyed out that fatty acids (C16 to C24) were the major components which responsible for the antifouling properties of the candidate seagrasses.

Metabolites and bioactivities of Rhizophoraceae mangroves

This review examines the chemical compositions and bioactivities of mangrove plants belonging to the Rhizophoraceae family. The Rhizophoraceae family of true mangrove plants is the most common and is also widely distributed species. It consists of 24 species across four genera. Of the 24 species, 12 species remain unexamined for their phytochemical constituents. There have been 268 metabolites reported from 16 species. The key phytochemical constituents identified across the family are the diterpenoids and triterpenoids. The major diterpenoids include pimaranes, beyeranes, kaurenes, dolabranes and labdanes whereas the significant triterpenoids are lupanes, dammaranes and oleananes. Disulphides, dolabranes and labdanes are considered to be the chemotaxonomic markers of the genera Bruguiera, Ceriops and Rhizophora respectively.

Anti-quorum sensing potential of the mangrove Rhizophora annamalayana

The present study was carried out to assess the anti-quorum sensing (anti-QS) activity of bark extract obtained from the mangrove plant Rhizophora annamalayana Kathir. against Gram-negative bacteria. In microtitre plate assay, the bark extract at a concentration of 1 mg/ml inhibited the QS-dependent violacein production in Chromobacterium violaceum ATCC 12472. Further, the QS-dependent bioluminescence production in the aquatic bacterial pathogen Vibrio harveyi MTCC 3438 was also reduced to the level of 99 % when treated with the same concentration of the extract. Gas chromatography-mass spectrum analysis identified the presence of seven different chemical constituents, 1H-purin-6-amine, cycloheptasiloxane, cyclooctasiloxane, cyclononasiloxane, cyclononasiloxane octadecamethyl, cyclodecasiloxane eicosamethyl and 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane. The molecular docking analysis of the identified compounds revealed that the compounds cyclononasiloxane octadecamethyl and cyclodecasiloxane eicosamethyl exhibited the best docking energy with the QS receptors of C. violaceum and V. harveyi with that of the natural ligand N -hexanoyl- L -homoserine lactone (C6-HSL) and furanosyl borate diester (AI-2). Similarly, another compound 1,1,1,5,7,7,7-heptamethyl-3,3-bis(trimethylsiloxy)tetrasiloxane showed best docking energy only against C6-HSL. Thus, the results of the present study divulge the activity of R. annamalayana bark extract to interfere with bacterial QS.

Characterization of terpenoids from the root of Ceriops tagal with antifouling activity

One new dimeric diterpenoid, 8(14)-enyl-pimar-2'(3')-en-4'(18')-en-15'(16')-endolabr- 16,15,2',3'-oxoan-16-one (1) and five known terpenoids: Tagalsin C (2), Tagalsin I (3), lup-20(29)-ene-3β,28-diol (4), 3-oxolup-20(29)-en-28-oic acid (5) and 28-hydroxylup- 20(29)-en-3-one (6) were isolated from the roots of the mangrove plant Ceriops tagal. Their structures and relative stereochemistry were elucidated by means of extensive NMR, IR and MS analysis. The antifouling activity against larval settlement of the barnacle Balanus albicostatus were evaluated using capsaicin as a positive control. All these terpenoids exhibited antifouling activity against cyprid larvae of the barnacle without significant toxicity. The structure-activity relationship results demonstrated that the order of antifouling activity was diterpenoid (Compound 2) > triterpenoid (Compounds 4, 5 and 6) > dimeric diterpenoid (Compounds 1 and 3). The functional groups on the C-28 position of lupane triterpenoid significantly affect the antifouling activity. The diterpenoid dimmer with two identical diterpenoid subunits might display more potent antifouling activity than one with two different diterpenoid subunits. The stability test showed that Compounds 2, 4, 5 and 6 remained stable over 2-month exposure under filtered seawater.

Antifeedant diterpenoids against Tribolium castaneum from the stems and twigs of Ceriops tagal (Rhizophoraceae)

The screening of several Chinese mangrove plants for insecticidal principles showed that ethanol extract of Ceriops tagal stems and twigs possessed significant feeding deterrent activity against the red flour beetle, Tribolium castaneum (Family: Rhizophoraceae). From the ethanol extract, three feeding deterrent diterpenoids were isolated by bioassay-guided fractionation. The compounds were identified as tagalsin A, B, and H on the basis of their phytochemical and spectral data. Tagalsin A, B, and H exhibited strong feeding deterrent activity against T. castaneum adults with EC₅₀ values of 375.3 ppm, 277.3 ppm, and 285.45 ppm, respectively.

Antifouling activity of simple synthetic diterpenoids against larvae of the barnacle Balanus albicostatus Pilsbry

Five new pimarane diterpenoids 1-5 were synthesized using ent-8(14)-pimarene-15R,16-diol as starting material. The structures were elucidated by means of extensive NMR and MS analysis. The antifouling activity against larval settlement of the barnacle Balanus albicostatus were evaluated using capsaicin as a positive control. Compounds 1-3 and 5 showed more potent antifouling activity than capsaicin. Compound 5, which exhibited almost the same antifouling activity as starting material, showed better stability than starting material. These compounds all showed antifouling activity in a non-toxic way against larval settlement of the barnacle B. albicostatus. Analysis of structure-activity relationships (SAR) demonstrated that the substituents on the C-15 and C-16 position of pimarane diterpenoid were responsible for the antifouling activity.

Dolabranes from the Chinese Mangrove, Ceriops tagal

Six new dolabranes, named tagalsins P-U (1-6), were isolated from stems and twigs of a Chinese mangrove, Ceriops tagal, along with seven known dolabranes, an abietane, and a pimarane. The structures of these compounds were established on the basis of spectroscopic data or comparison with data in the literature. The relative configurations of tagalsins P and Q (1, 2), two new 15,16-dinor-dolabranes, were confirmed by means of single-crystal X-ray diffraction analysis. This is the first report of 16-nordolabranes and 15,16-dinordolabranes from plants of the Ceriops genus. Tagalsins Q (2), R (3), and U (6) showed moderate antifeedant activity against the third-instar larvae of Brontispa longissima at a concentration of 1 mg/mL. However, none of the new dolabranes exhibited significant activity against human cancer cell lines.

Three new lupane-type triterpenes from Ceriops tagal

Three new lupane-type triterpenes, 3 alpha-O-trans-feruloylbetulinic acid (1), 3 alpha-O-trans-coumaroylbetulinic acid (2) and 3beta-O-cis-feruloylbetulin (3), together with 10 known triterpenes (4-13), were isolated from the aerial parts of the mangrove plant Ceriops tagal. The structures of the three new compounds were established by means of spectroscopic data analyses and chemical methods.

Natural products as antifouling compounds: recent progress and future perspectives

Since early 2008, an increasing number of countries have ratified an international treaty to ban the application of antifouling (AF) coatings based on organotin compounds (eg tributyltin (TBT) and triphenyltin). As a result, the demand for environmentally friendly, non-toxic or low-toxicity AF compounds and technologies (green AF agents) has become an urgent reality. Marine coatings based on Cu2O and various other biocides have a negative impact on the environment and they must eventually be replaced by new, effective, and environmentally friendly AF compounds. This mini-review describes important AF compounds discovered from a variety of organisms from 2004 until mid 2009, and discusses recent and general trends in the discovery of AF compounds. Finally, a perspective on the future of AF compound development is presented. The discussion is aimed at updating scientists and engineers on the current challenges facing AF research.

A new atisane-type diterpene from the bark of the mangrove plant Excoecaria agallocha

A new atisane-type diterpene, ent-16alpha-hydroxy-atisane-3,4-lactone (4) and three known diterpenes, ent-16alpha-hydroxy-atisane-3-one (1), ent-atisane-3beta,16alpha-diol (2), ent-3,4-seco-16alpha-hydroxyatis- 4(19)-en -3-oic acid (3) were isolated from the bark of the mangrove plant Excoecaria agallocha. Their structures and relative stereochemistry were elucidated by means of extensive NMR and MS analysis. Compound 3 exhibited significant anti-microfouling activity against the adherence of Pseudomonas pseudoalcaligenes, with an EC(50) value of 0.54+/-0.01 ppm.

Herbal plants as a promising source of natural antifoulants: evidence from barnacle settlement inhibition

A series comprising hexane, ethyl acetate, ethanol and aqueous extracts from six common Chinese herbs (Carpesium abrotanoides, Melia toosendan, Cnidium monnieri, Vitex negundo, Stemona sp. and Sophora flavescens) was investigated for antifouling (AF) activity against cypris (cyprids) larvae of the barnacle Balanus albicostatus. All extracts tested except the aqueous extract from Stemona sp. significantly inhibited the settlement of cyprids, the most potent being the ethyl acetate extract of S. flavescens (EC(50) value 2.08 microg ml(-1)), from which an AF compound, identified as 2'-methoxykurarinone, was isolated using bioassay-guided procedures. Furthermore, the AF activity of this compound was found to be highly reversible and greater than that of the three other natural products from S. flavescens, namely matrine, oxymatrine and oxysophocarpine. These compounds have been used commercially in China for their pharmaceutical activities, but their AF activities have not previously been evaluated. Analysis of structure-activity relationships suggested that the N-1 nitrogen atom in matrine plays a crucial role in AF activity. Overall, the present findings indicate that herbal plants are a valuable source of novel AF agents.

New A-nor steroids and their antifouling activity from the Chinese marine sponge Acanthella cavernosa

A chemical examination of the Chinese sponge Acanthella cavernosa resulted in the isolation of three new A-ring contracted steroids, the ethyl esters of 2beta-hydroxy-4,7-diketo-A-norcholest-5-en-2-oic acid (1), 24S-ethyl-2beta-hydroxy-4,7-diketo-A-norcholest-5-en-2-oic acid (2), and 2beta-hydroxy-4,7-diketo-24R-methyl-A-norcholest-5,22(E)-dien-2-oic acid (3), along with four other known steroids (4-7). The structures were determined on the basis of extensive spectroscopic analysis. Compounds 1-3 showed antifouling activity toward the settlement inhibition of Balanus albicostatus with the EC(50) values of 8.2, 23.5, 31.6 microg/mL, respectively.