Mangrove habitat suitability modeling: implications for multi-species plantation in an arid estuarine environment.

In southern Iran, Sirik Estuary hosts the only two-species (Rhizophora mucronata and Avicennia marina) mangrove forest in the northwesternmost edge of the Indian Ocean mangrove distribution. Aiming to protect its forest reserve and compensate for inevitable losses, this study utilized habitat suitability modeling (the Maxent model) to identify suitable afforestation zones for each species, independently. The model was calibrated using the location of successfully established mangrove saplings as presence points and an array of physical and sediment physio-chemical layers as predictive variables. The model yielded an acceptable training AUC value of 0.963 for A.marina and 0.982 for R.mucronata. Moreover, physical variables had the highest contribution to predicting suitable habitats with different levels of importance for each species. The majority of A.marina suitable habitats were distributed along the in-estuary creek banks, creating mangrove-lined waterways while the R.mucronata suitable habitats were mostly distributed at the base of the main water creeks in the seaward reaches of the estuary. According to the Mann-Whitney U test results, there was a statistically significant spatial niche segregation (z = - 12.14, p = 0.000, sig ≤ .05, 2-tailed) between the species' suitable habitats. The results showed that white mangroves tend to create mangrove-line structures along the water creeks penetrating inside the estuary while red mangroves mostly prefer the seaward side of the existing mangrove patches which are in danger of sea level rise.

Copper and zinc differentially affect root glutathione accumulation and phytochelatin synthase gene expression of Rhizophora mucronata seedlings: Implications for mechanisms underlying trace metal tolerance.

Mangroves are susceptible to contamination due to their proximity to shores and human activities. Exposure to excessive trace metals can disturb their physiological functions and may eventually lead to death. Rhizophora mucronata is a common species growing in the mangrove forests of Thailand. Previous studies have shown that seedlings of R. mucronata are tolerant of trace metal and that they accumulate a large metal content in their root tissue. However, knowledge of their tolerance mechanisms is still lacking. To elicit the role of metal detoxification and sequestration by phytochelatins (PC) in the roots of R. mucronata seedlings, the impacts of Cu and Zn exposure were assessed on 1) physiological characteristics 2) the concentration of glutathione (GSH), a precursor of PC and 3) the level of the transcripts encoding phytochelatin synthase (PCS), the key enzyme for PC biosynthesis. Seedlings of R. mucronata were exposed to Cu and Zn in a hydroponic experiment (200 mg Cu or Zn/L in 1/4× Hoagland solution containing 8‰ NaCl, single addition). We found that both trace metals were largely accumulated in the roots. Only Cu-treated seedlings showed a decrease in the photosynthetic efficiency, in line with observed toxicity symptoms (i.e. bent stems and slight wilting of leaves). Metal accumulation, however, did not induce oxidative stress in the roots as indicated by similar level of total reactive species and lipid peroxidation across treatments. The GSH content in the roots exposed to Cu was significantly reduced while no change was observed in Zn-exposed roots. Coordinated semi-quantitative PCR and RT-qPCR revealed pcs down-regulation in Cu-treated roots, whereas Zn-treated roots showed a down-regulation on day 1 and a subsequent recovery on day 5. Failure of detoxification and sequestration of excess Cu due to GSH limitation and down-regulation of pcs may lead to the phytotoxic effects observed in Cu-treated plants. Our results suggest that both GSH and PC play an important role in trace metal tolerance in R. mucronata seedlings.

Larvicidal Enzyme Inhibition and Repellent Activity of Red Mangrove Rhizophora mucronata (Lam.) Leaf Extracts and Their Biomolecules Against Three Medically Challenging Arthropod Vectors.

The larvicidal potential of crude leaf extracts of Rhizophora mucronata, the red mangrove, using diverse solvent extracts of the plant against the early fourth instar larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti mosquito vectors was analyzed. The acetone extract of R. mucronata showed the greatest efficacy: for Cx. quinquefasciatus (LC50 = 0.13 mg/mL; LC90 = 2.84 mg/mL), An. stephensi (LC50 = 0.34 mg/mL; LC90 = 6.03 mg/mL), and Ae. aegypti (LC50 = 0.11 mg/mL; LC90 = 1.35 mg/mL). The acetone extract was further fractionated into four fractions and tested for its larvicidal activity. Fraction 3 showed stronger larvicidal activity against all the three mosquito larvae. Chemical characterization of the acetone extract displayed the existence of several identifiable compounds like phytol, 3,7,11,15-tetramethyl-2-hexadecen-1-ol, 1-hexyl-2-nitrocyclohexane, eicosanoic acid etc. Enzyme assay displayed that R. mucronata active F3-fractions exert divergent effects on all three mosquitos' biochemical defensive mechanisms. The plant fractions displayed significant repellent activity against all the three mosquito vectors up to the maximum repellent time of 210 min. Thus, the bioactive molecules in the acetone extract of R. murconata leaves showed significant larvicidal and enzyme inhibitory activity and displayed novel eco-friendly tool for mosquito control.

Ethnopharmacology, Phytochemistry, and Global Distribution of Mangroves-A Comprehensive Review.

Mangroves are ecologically important plants in marine habitats that occupy the coastlines of many countries. In addition to their key ecological importance, various parts of mangroves are widely used in folklore medicine and claimed to effectively manage a panoply of human pathologies. To date, no comprehensive attempt has been made to compile and critically analyze the published literature in light of its ethnopharmacological uses. This review aims to provide a comprehensive account of the morphological characteristics, ethnobotany, global distribution, taxonomy, ethnopharmacology, phytochemical profiles, and pharmacological activities of traditionally used mangroves. Out of 84 mangrove species, only 27 species were found to be traditionally used, however not all of them are pharmacologically validated. The most common pharmacological activities reported were antioxidant, antimicrobial, and antidiabetic properties. Mangroves traditionally reported against ulcers have not been extensively validated for possible pharmacological properties. Terpenoids, tannins, steroids, alkaloids, flavonoids, and saponins were the main classes of phytochemicals isolated from mangroves. Given that mangroves have huge potential for a wide array of medicinal products and drug discovery to prevent and treat many diseases, there is a dire need for careful investigations substantiated with accurate scientific and clinical evidence to ensure safety and efficient use of these plants and validate their pharmacological properties and toxicity.

Tolerance Mechanisms to Copper and Zinc Excess in Rhizophora mucronata Lam. Seedlings Involve Cell Wall Sequestration and Limited Translocation.

Rhizophora mucronata is a common mangrove growing in habitats subjected to heavy metal (HM) contamination. Understanding their physiological responses to copper (Cu) and zinc (Zn) excess and underlying tolerance mechanisms is crucial to assess impacts of metal pollution on mangrove community. Seedlings were treated with Cu or Zn (0, 50 or 100 mg per plant) by means of a single addition. At day 3 and 7, Cu and Zn accumulation, photosynthetic efficiency, superoxide dismutase and peroxidase activity, non-protein thiols, reactive oxygen species and lipid peroxidation in roots and leaves were measured. R. mucronata restricted Cu and Zn translocation, thus accumulated HM mainly in roots while kept the leaves unaffected. However, high root HM did not induce oxidative stress nor anti-oxidative defense as HM were largely deposited in cell wall. We concluded that HM tolerance strategies of R. mucronata seedlings are exclusion and restriction of translocation to the vital photosynthetic tissue.

Two new coumarins and a new xanthone from the leaves of Rhizophora mucronata.

Two new coumarins (1, 2) and a new xanthone (3), together with 14 known compounds-eight coumarins (4, 5, 9, 10, 12-15), three xanthones (11, 16, 17), a benzoic acid (6) and two flavonones (7, 8)-were isolated from the leaves of Rhizophora mucronata. The structures of the compounds were elucidated by spectroscopic (IR, MS, and NMR) analyses. The isolated compounds were tested for cytotoxicity against human cancer cell lines HL-60 and HeLa. Among these compounds, only compound 16 inhibited the growth of both HeLa (IC50 = 4.8 µM) and HL-60 (IC50 = 1.0 µM) cells. Compounds 4, 7, 10, and 12 exhibited moderate activity against HeLa cells (IC50 = 3.8-8.3 µM). Compounds 5, 9, 11, and 17 showed moderate activity against HL-60 cells (IC50 = 2.2-6.3 µM). Higher selectivity against HL-60 cell lines was observed for compounds 5, 9, 11, and 16 with SI values (NIH 3T3/HL-60) of 8.6, 19.2, 9.4, and 10.2, respectively.

Spatial coverage of mangrove communities in the Arabian Gulf.

Mangroves are the natural protectors of the coast, carbon sinks, and a nursery to many terrestrial as well as aquatic organisms. Different effects caused by natural forces together with anthropogenic factors have reduced mangrove cover on a global scale, yet little is known about the overall surface covered by mangroves in the Arabian Gulf. Therefore, the aim of this study was to examine their spatial coverage and distribution along the Gulf coastlines, using 25 satellite imagery recently acquired from Landsat 8 data for the year 2017. This study found about 165 km2 of fragmented scattered mangroves, mostly intense in the United Arab Emirates, where plantation projects have likely played a significant role in increasing their cover over the years. Whereas mangrove in Kuwait is rare, areas like Bahrain, Qatar and Saudi Arabia remained stable with a slight increase. However, mangroves in Iran appear to suffer a decline throughout the years.

Rhizophora mucronata attenuates beta-amyloid induced cognitive dysfunction, oxidative stress and cholinergic deficit in Alzheimer's disease animal model.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, characterized by accumulation and deposition of Aß peptide in human brain. The present study aimed to determine the protective effect of catechin rich extract of MERM (methanolic extract of Rhizophora mucronata) on Aß (25-35) induced cognitive impairment and neuronal toxicity in mice. In the present study AD characteristics were induced by intracerberoventricular administration of aggregated Aß (25-35) in the Swiss albino mice. Learning and memory deficits were assessed using behavioral assays such as Morris water maze, Y-maze and step down avoidance tasks. Oxidative stress mediated impairment were assessed by measuring the activities of enzymatic and non-enzymatic antioxidants, level of apoptotic protein and oxidative markers in the hippocampus and frontal cortex region. Histolopathological analysis of brain was also carried out. Results illustrated that oral treatment of MERM (200 and 400 mg/kg bw) significantly attenuated Aß (25-35) induced memory impairment as evaluated by behavioral tests. In addition treatment with MERM attenuated the elevation of ß-secretase activity accompanying the reduced level of Aß (25-35) in the cortex and hippocampus of brain. MERM also enhanced the cognitive function by significantly inhibiting AChE, BuChE and MAO-B. Furthermore, MERM attenuated lipid peroxidation, protein oxidation, restored the antioxidant status and inhibited neuronal apoptosis by down-regulating the level of caspase 3 and Bax protein. These data suggest that MERM rich in catechin can act as promising drug for AD treatment because of its antioxidant, anti-apoptotic and reducing Aß oligomer activities.

Physiology and proteomics analyses reveal the response mechanisms of Rhizophora mucronata seedlings to prolonged complete submergence.

Mangrove seedlings are subject to natural tidal inundation, while occasional flooding may lead to complete submergence. Complete submergence reduces light availability and limits gas exchange, affecting several plant metabolic processes. The present study focuses on Rhizophora mucronata, a common mangrove species found along the coasts of Thailand and the Malay Peninsula. To reveal response mechanisms of R. mucronata seedlings to submergence, a physiological investigation coupled with proteomic analyses of leaf and root tissues was carried out in plants subjected to 20 days of control (drained) or submerged conditions. Submerged seedlings showed decreased photosynthetic activity, lower stomatal conductance, higher total antioxidant capacity in leaves and higher lipid peroxidation in roots than control plants. At the same time, tissue nutrient ion content displayed organ-specific responses. Proteome analysis revealed a significant change in 240 proteins in the leaves and 212 proteins in the roots. In leaves, most differentially accumulated proteins (DAPs) are associated with nucleic acids, stress response, protein transport, signal transduction, development and photosynthesis. In roots, most DAPs are associated with protein metabolic process, response to abiotic stimulus, nucleic acid metabolism and transport. Our study provides a comprehensive understanding of submergence responses in R. mucronata seedlings. The results suggest that submergence induced multifaceted stresses related to light limitation, oxidative stress and osmotic stress, but the responses are organ specific. The results revealed many candidate proteins which may be essential for survival of R. mucronata under prolonged submergence.

A modified method for efficient RNA isolation from mangrove root tissues rich in secondary metabolites.

Secondary metabolites in mangroves often interfere with RNA extraction yielding poor concentration and quality, which is unsuitable for downstream applications. As existing protocols yielded low-quality RNA from root tissues of Kandelia candel (L.) Druce and Rhizophora mucronata Lam., an optimized method was developed for improving the quality and yield of RNA. Compared with three other methods, this optimized protocol gave better RNA yield and purity for both species. The absorbance ratios were ≥1.9 for A260/280 and A260/230, while RNA integrity number values ranged from 7.5 to 9.6. Results show that our modified method is efficient in obtaining high-quality RNA from mangrove roots and is suitable for downstream experiments such as cDNA synthesis, real-time quantitative PCR and next-generation sequencing.

Assessment of the Genetic Diversity and Population Structure of Rhizophora mucronata along Coastal Areas in Thailand.

Unique and biodiverse, mangrove ecosystems provide humans with benefits and contribute to coastal protection. Rhizophora mucronata, a member of the Rhizophoraceae family, is prevalent in the mangrove forests of Thailand. R. mucronata's population structure and genetic diversity have received scant attention. Here, we sequenced the entire genome of R. mucronata using 10× Genomics technology and obtained an assembly size of 219 Mb with the N50 length of 542,540 bases. Using 2857 single nucleotide polymorphism (SNP) markers, this study investigated the genetic diversity and population structure of 80 R. mucronata accessions obtained from the mangrove forests in Thailand. The genetic diversity of R. mucronata was moderate (I = 0.573, Ho = 0.619, He = 0.391). Two subpopulations were observed and confirmed from both population structure and principal component analysis (PCA). Analysis of molecular variance (AMOVA) showed that there was more variation within populations than between them. Mean pairwise genetic differentiation (FST = 0.09) showed that there was not much genetic difference between populations. Intriguingly, the predominant clustering pattern in the R. mucronata population did not correspond to the Gulf of Thailand and the Andaman Sea, which are separated by the Malay Peninsula. Several factors could have influenced the R. mucronata genetic pattern, such as hybridization and anthropogenic factors. This research will provide important information for the future conservation and management of R. mucronata in Thailand.

Phytochemistry and Anticancer Effects of Mangrove (Rhizophora mucronata Lam.) Leaves and Stems Extract against Different Cancer Cell Lines.

The biologically active components of the methanol extracts of R. mucronata were identified using GC/MS. The anticancer effects of each methanol extract from the leaves and stem were evaluated against cancer and non-cancer cell lines. The MTT assay was used in order to evaluate cell viability, and the IC50 and the selectivity indices were calculated in relation to a positive control (doxorubicin). The results showed that 11 and 8 different chemical compounds were found in the methanol extracts from the leaves and stems of R. mucronata, respectively. The active constituents of R. mucronata leaves and stems had anticancer effects against colon cancer (CaCo-2), with IC50 levels of 127 ± 4 µg/mL and 107 ± 6 µg/mL, respectively, and on breast cancer (MCF-7), with IC50 levels of 158 ± 10 µg/mL and 138 ± 4 µg/mL, respectively. These were both greater than their effects on prostate cancer (PC-3), for which they showed IC50 levels of 480 ± 14 µg/mL and 294 ± 3 µg/mL, respectively. However, the anticancer effect of the stems on lung cancer (A549) (IC50 = 155 ± 10 µg/mL) was greater than that of the leaves (IC50 = 376 ± 9 µg/mL) in comparison with doxorubicin. Neither the stems nor the leaves of R. mucronata showed any cytotoxicity against normal cells (WI-38), with the IC50 being 932 ± 30 µg/mL for the leaves and 629 ± 3 µg/mL for the stems.

Rhizophora mucronata Lam. (Mangrove) Bark Extract Reduces Ethanol-Induced Liver Cell Death and Oxidative Stress in Swiss Albino Mice: In Vivo and In Silico Studies.

The bark extract of Rhizophora mucronata (BERM) was recently reported for its prominent in vitro protective effects against liver cell line toxicity caused by various toxicants, including ethanol. Here, we aimed to verify the in vivo hepatoprotective effects of BERM against ethanol intoxication with the prediction of potential targets employing in silico studies. An oral administration of different concentrations (100, 200 and 400 mg/kg body weight) of BERM before high-dose ethanol via intraperitoneal injection was performed in mice. On day 7, liver sections were dissected for histopathological examination. The ethanol intoxication caused liver injury and large areas of necrosis. The pre-BERM administration decreased the ethanol-induced liver damage marker tumor necrosis factor-alpha (TNF-α) expression, reduced hepatotoxicity revealed by nuclear deoxyribonucleic acid (DNA) fragmentation and decreased oxidative stress indicated by malondialdehyde and glutathione contents. Our in silico studies have identified BERM-derived metabolites exhibiting the highest predicted antioxidant and free radical scavenger activities. Molecular docking studies showed that most of the metabolites were predicted to be enzyme inhibitors such as carbonic anhydrase inhibitors, which were reported to stimulate the antioxidant defense system. The metabolites predominantly presented acceptable pharmacokinetics and safety profiles, suggesting them as promising new antioxidant agents. Altogether, the BERM extract exerts antioxidative activities and shows promising hepatoprotective effects against ethanol intoxication. Identification of related bioactive compounds will be of interest for future use at physiological concentrations in ethanol-intoxicated individuals.

Insights into the mechanically resilient, well-balanced polymeric membranes by incorporating Rhizophora mucronata derived activated carbon for sustainable wastewater decontamination.

In this study, hydrophilic activated carbon has been prepared and used to synthesize innovative activated carbon/polysulfone mixed matrix membranes (MMMs). These membranes were investigated in terms of membrane morphology, hydrophilicity, antifouling ability, and metal ions rejection. The activated carbon (AC) was prepared from a simple chemical activation method using Rhizophora mucronata propagules, which are rich in aerenchyma cells and possess a high surface area. The hydrophilicity of the MMMs is enhanced by the incorporation of activated carbon, which is confirmed by the measurement of equilibrium water contact angle, water uptake and pure water flux. The optimized concentration of 0.625 wt% activated carbon (A2) incorporated mixed matrix membrane exhibits better rejection efficiencies of 98 ± 0.5%, 99 ± 0.5%, 92 ± 2%, and 44 ± 1% for Pb+2, Cd+2, Hg+2, and F- with the permeate flux of 28.27, 31.88, 33.21, 43.82 L/m2/h, respectively. The fabricated mixed matrix membranes demonstrated an excellent flux recovery ratio and reversible fouling, when filtrating a mixed feed solution containing 200 ppm BSA, 10 ppm Pb+2 and 10 ppm Cd+2. The optimized A2 membrane showed excellent long-term stability up to 120 h without compromising in permeate flux and rejection efficiency. Finally, a numerical investigation using a usual transport model has shown that dielectric exclusion was the most probable mechanism that can physically explain experimental trends.

Estimation of carbon pools in the biomass and soil of mangrove forests in Sirik Azini creek, Hormozgan province (Iran).

Despite the increasing interest in mangroves as one of the most carbon-rich ecosystems, arid mangroves are still poorly investigated. We aimed to improve the knowledge of biomass and soil carbon sequestration for an arid mangrove forest located at the Azini creek, Sirik, Hormozgan Province (Iran). We investigated the biomass and organic carbon stored in the above and belowground biomass for three different regions selected based on the composition of the principal species: (1) Avicennia marina, (2) mixed forest of A. marina and Rhizophora mucronata, and (3) R. mucronata. Topsoil organic carbon storage to 30 cm depth was also estimated for each analyzed area. Biomass carbon storage, considering both aboveground (AGB) and belowground biomass (BGB), was significantly different between the cover areas. Overall, the mean forest biomass (MFB) was 283.1 ± 89 Mg C ha-1 with a mean C stored in the biomass of 128.9 ± 59 Mg C ha-1. Although pure Rhizophora stand showed the lowest value of above and below tree carbon (AGC + BGC); 17.6 ± 1.9 Mg C ha-1), soil organic carbon stock in sites under Rhizophora spp. was significantly higher than in the site with pure stand of Avicennia spp. Overall, forest soil stored the highest proportion of Sirik mangrove ecosystem organic carbon (59%), with a mean value of 188.3 ± 27 Mg C ha-1. These results will contribute to broaden the knowledge and the dataset available, reducing the uncertainties related to estimates and modeling of carbon pools in arid mangrove ecosystem, which also represent an important climatic threshold of mangrove worldwide distribution.

Alkaloids from endophytic fungus Aspergillus fumigatus HQD24 isolated from the Chinese mangrove plant Rhizophora mucronata.

Chemical investigation of endophytic fungus Aspergillus fumigatus HQD24, isolated from the flower of Rhizophora mucronata led to the isolation of eight alkaloids, including pyripyropene A (1), 1,11-dideacetyl-pyripyropene A (2), pyripyropene E (3), chaetominine (4), tryptoquivaline J (5), fumitremorgin C (6), 1-acetyl-ß-carboline (7), and nicotinic acid (8). Their structures were unambiguously elucidated on the basis of extensive spectroscopic data and comparison with the data of literature. Compound 2 was known as a synthetic product and isolated as a natural product for the first time. The immunosuppressive and cytotoxic activities of all isolated compounds were evaluated.

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

Four biogenic ß-sitosterol analogues were identified from methanolic extract of the leaves of loop-root mangrove Rhizophora mucronata. These were characterized as 4, 14, 23-trimethyl-3ß-sitosterol (1), 7-ethyl-3ß-sitosterol (2), sitosteryl-3ß-(33E)-pent-33-enoate (3) and 12α-hydroxy-3ß-sitosterol (4) based on comprehensive spectroscopic techniques. Anti-inflammatory activities of ß-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 ß-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-ß-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 ß-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 ß-sitosterol analogues were positively correlated with their attenuation properties against 5-lipoxygenase and cyclooxygenase-2.

Leaf tissue specific transcriptome sequence and de novo assembly datasets of Asiatic mangrove Rhizophora mucronata Lam.

Transcriptome data is beneficial to explore molecular mechanisms of extreme adaptations in non- model organisms like mangroves. In this data article, five major datasets and two data sub sets of a salt secreting mangrove, Rhizophora mucronata Lam. were described. A combination of Illumina HiSeq 2500, Trinity, BLAST X, Bowtie 2 and BLAST 2GO was used for RNA Seq, de novo assembly, transcript annotation, gene expression estimation and gene ontology annotation respectively. The RNA Sequence (Read 1 and Read 2) in Sequence Read Archive amounting to 46,366,348 paired end raw reads is the first data set made open for de novo or comparative transcript assembly. Assembled sequences of 93960 gene transcripts constitute the second data set in Transcriptome Shotgun Assembly. The gene/protein annotations to the assembled transcripts give two sub data sets containing 93960 each of GenBank and GenPept entries with comprehensive cDNA and translated protein sequences of genes. Of these, predicted proteins for 87768 coding sequences, mapped to UniProtKB serve as the third data set. The gene expression levels of the annotated transcripts comprise the fourth data set in Gene Expression Omnibus. The fifth data set in Figshare includes 44,028 gene ontology terms extracted for 21,073 confident transcripts. The data sets provide a valuable resource for further analyses including transcriptomic changes in response to environmental stresses.

HPLC characterization, acute and sub-acute toxicity evaluation of bark extract of Rhizophora mucronata in Swiss Albino mice.

AIM: Rhizophora mucronata, commonly called as 'red mangrove' grows in the tropical and sub-tropical regions and on the sheltered shores. The bioactive compounds from the plant have been used in the treatment of wide range of diseases. Though the beneficial effects have been reported, the safety and toxicological studies are not carried out. Hence, major bioactives have been identified by HPLC and then acute and sub-acute toxicity studies of (BERM) in Swiss Albino mice have been carried out. MAIN METHODS: HPLC fingerprinting was carried out of BERM for the characterization of bioactives. BERM as a single dose was given orally at 800, 1600 mg/kg and 3200 mg/kg by a stainless steel cannula to the mice. Then the mice were observed for 14 days for mortality and behavioural changes. Food, water intake and body weight changes were also observed throughout the study period. On the fifteenth day, the mice were anesthetized with isofluorane and blood was withdrawn for haematological and biochemical analysis. The animals were sacrificed by overdose of isofluorane and organs such as liver, kidney, lungs and spleen were dissected out for histopathological analysis. There was no mortality of the mice even in 3200 mg/kg dose, stating that the oral LD50 of BERM is more than 5000 mg/kg. In terms of Sub-acute toxicity, for a period of 28 days repeated dose of 400 mg/kg and 800 mg/kg as an optimum dose and a control group was kept with only distilled water at 5 ml/kg against the treated groups. On 29th day, the mice from all groups were sacrificed and blood was withdrawn and organs such as liver, kidney, lungs and spleen were dissected out for the assessment of internal tissues, wherein no abnormalities were observed in the treatment groups as compared to the control. The blood parameters, biochemical analysis of the treated groups were well within the range, histopathological confirmed the findings wherein the organs viz, liver, kidneys, lungs and spleen possessed normal architecture. KEY FINDINGS: Based on HPLC results, prominent 5 major compounds viz: Diadzein, Epicatechin, Hesperidin, Diosmin and Quercitrin respectively were identified. Isolated changes observed in the haematological, biochemical and histopathological studies were not dose related and showed the safety of the bark extract. Similarly, the sub-acute toxicity of BERM has been conducted for 28 days, wherein repeated dose of 400 mg/kg and 800 mg/kg and control group was given orally. There were no abnormalities found both in external and internal parameters. SIGNIFICANCE: Based on the study it is concluded that the bark extract of Rhizophora mucronata (BERM) is safe at 1000 mg/kg or less on repeated dosage can be considered as a safe dose for pharmacological efficacy studies.

De novo transcriptome analysis of Rhizophora mucronata Lam. furnishes evidence for the existence of glyoxalase system correlated to glutathione metabolic enzymes and glutathione regulated transporter in salt tolerant mangroves.

The accumulation of a metabolic by product - methylglyoxal above a minimal range can be highly toxic in all organisms. Stress induced elevation in methylglyoxal inactivates proteins and nucleic acids. Glutathione dependent glyoxalase enzymes like glyoxalase I and glyoxalase II together with glutathione independent glyoxalase III play inevitable role in methylglyoxal detoxification. Glyoxalase genes are generally conserved but with obvious exceptions. Mangroves being potent harsh land inhabitants, their internal organelles are constantly been exposed to elevated levels of methylglyoxal. First and foremost it is important to detect the presence of glyoxalases in mangroves. De novo transcriptome analysis of mangrove species Rhizophora mucronata Lam., identified eleven putative glyoxalase proteins (RmGLYI-1 to 5, RmGLYII-1 to 5 and RmGLYIII). Molecular characterization proposed PLN02300 or PLN02367 as the key domains of RmGLYI proteins. They possess molecular weight ranging from 26.45 to 32.53 kDa and may localize in cytosol or chloroplast. RmGLYII proteins of molecular weight 28.64-36 kDa, carrying PLN02398 or PLN02469 domains are expected to be localized in diverse cellular compartments. Cytosolic RmGLYIII with DJ-1/PfpI domain carries a molecular weight 26.4 kDa. Detailed structural analysis revealed monomeric nature of RmGLYI-1 and RmGLYII-1 whereas RmGLYIII is found to be homodimer. Molecular phylogenetic analysis and multiple sequence alignment specified conserved metal ion/substrate binding residues of RmGLY proteins. Estimation of relative expression of glyoxalases under salt stress indicated the prominence of RmGLYI and RmGLYII over RmGLYIII. The aforementioned prominence is supported by salt induced expression difference of glutathione metabolic enzymes and glutathione regulated transporter protein.