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This review explores the natural products of seagrass that are to be exploited for their bioactive potential. Beside from portraying the presence of a wide array of secondary compounds such as phenols, flavonoids, sterols and lipids from different seagrass species, the focus is on novel natural products projecting towards their biological applications. Though there are a significant number of reports on the abundance of secondary metabolites from seagrass and their bioactive derivatives, only a small number of reports explore their functional and defensive characteristics. Efforts have been made to collate the available information on seagrass natural products and clarify their function and metabolic pathway's. It is emphasized that metabolic profiling of seagrass should be extensively progressed to obtain a deeper knowledge about the specific roles of each natural product. The investigation of seagrass natural products for their bioactive potential would most likely result in the detection of surprising and unexpected novel chemical structures and clinical leads that may be useful to mankind.Keywords: natural products, phenolic compounds, phenylpropanoid derivatives, seagrasses, secondary metabolites Seagrasses-the Marine AngiospermsSeagrasses, a functional group of flowering plants rooted in the world's coastal oceans, are well known for their secondary metabolites. The current comprehensive review on "Bioactive natural products from marine angiosperms'' was performed in such a way that recent discoveries in the field of seagrass secondary metabolism need to be reviewed. In this review is not possible to detail in a just few pages the full gamut of studies, since our understanding of natural products from seagrasses has increased markedly in the last few decades. Several studies have documented the abundance of these natural metabolites in seagrasses and some have focused on their bioactive potential. Though there are probably 72 species of seagrasses worldwide, only a few have been explored for their natural products and their determinant role. Recently, the secondary metabolites of P. oceanica were compiled 1 , appraised and were summarized into 51 natural products including phenols, phenylmethane, phenylethane, phenylpropane derivatives and their esters, chalkones and flavonoids. These chemical compounds synthesized by secondary metabolic pathways are not involved in the normal growth, development or reproduction but usually have roles in adaptation processes under stress conditions.A severe or long lasting stress factor could induce an excessive shift between primary and secondary metabolism and consequently, a diversion of essential available resources from growth to defense 2 , since the products of primary metabolism are the precursors for secondary metabolic pathways. The topics provided in this paper are limited to seagrass secondary metabolism although it has become clear that a clear line between primary and secondary metabolism cannot be drawn. Hence, the present review aims to collate th...

Insect pests of agricultural crops have establish immunological tolerance against fungal infection caused by pathogens via different humoral and cellular processes. Fungal infection can be prevented by insect antioxidant and detoxifying enzymes, but there is no clear understanding of how they physiologically and biochemically interact. Our study aims to examine the antioxidant and detoxifying enzyme defense systems of the pest insect Spodoptera litura in response to infection by Metarhizium flavoviride. At 48 h following exposure to M. flavoviride, antioxidant enzyme levels were modified, and phenoloxidase and total hemocyte count were decreased significantly. The amount of detoxifying enzymes increased significantly. M. flavoviride appears to directly affect the S. litura immune system and results in decreased immunity. In a bioassay, M. flavoviride was found to be harmful to S. litura larvae in their third and fourth instar stage. M. flavoviride may be an effective tool in the control of S. litura larvae. Such entomopathogenic fungi represent cheaper, pollution free, target specific, promising alternatives to synthetic chemical tools in the for control insect pests.

Insect pests represent a major threat to human health and agricultural production. With a current over‐dependence on chemical insecticides in the control of insect pests, leading to increased chemical resistance in target organisms, as well as side effects on nontarget organisms, the wider environment, and human health, finding alternative solutions is paramount. The employment of entomopathogenic fungi is one such potential avenue in the pursuit of greener, more target‐specific methods of insect pest control. To this end, the present study tested the chemical constituents of Metarhizium anisopliae fungi against the unicellular protozoan malaria parasite Plasmodium falciparum, the insect pests Anopheles stephensi Listen, Spodoptera litura Fabricius, and Tenebrio molitor Linnaeus, as well as the nontarget bioindicator species, Eudrilus eugeniae Kinberg. Fungal crude chemical molecules caused a noticeable anti‐plasmodial effect against P. falciparum, with IC50 and IC90 values of 11.53 and 7.65 µg/mL, respectively. The crude chemical molecules caused significant larvicidal activity against insect pests, with LC50 and LC90 values of 49.228−71.846 µg/mL in A. stephensi, 32.542−76.510 µg/mL in S. litura, and 38.503−88.826 µg/mL in T. molitor at 24 h posttreatment. Based on the results of the nontarget bioassay, it was revealed that the fungal‐derived crude extract exhibited no histopathological sublethal effects on the earthworm E. eugeniae. LC‐MS analysis of M. anisopliae‐derived crude metabolites revealed the presence of 10 chemical constituents. Of these chemicals, three major chemical constituents, namely, camphor (15.91%), caprolactam (13.27%), and monobutyl phthalate (19.65%), were highlighted for potential insecticidal and anti‐malarial activity. The entomopathogenic fungal‐derived crude extracts thus represent promising tools in the control of insect pests and malarial parasites.

An assessment on heavy metal (Al, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) accumulation by seven seagrass species of Lakshadweep group of islands was carried out using multivariate statistical tools like principal component analysis (PCA) and cluster analysis (CA). Among all the metals, Mg and Al were determined in higher concentration in all the seagrasses, and their values varied with respect to different seagrass species. The concentration of the four toxic heavy metals (Cd, Pb, Zn and Cu) was found higher in all the seagrasses when compared with the background values of seagrasses from Flores Sea, Indonesia. The contamination factor of these four heavy metals ranged as Cd (1.97-12.5), Cu (0.73-4.40), Pb (2.3-8.89) and Zn (1.27-2.787). In general, the Pollution Load Index (PLI) calculated was found to be maximum for Halophila decipiens (58.2). Results revealed that Halophila decipiens is a strong accumulator of heavy metals, followed by Halodule uninervis and Halodule pinifolia, among all the tested seagrasses. Interestingly, the small-leaved seagrasses were found to be efficient in heavy metal accumulation than the large-leaved seagrass species. Thus, seagrasses can better be used for biomonitoring, and seagrasses can be used as the heavy metal sink as the biomass take usually long term to get remineralize in nature.

Entomopathogenic fungi from microbial sources are a powerful tool for combating insecticide resistance in insect pests. The purpose of the current study was to isolate, identify, and evaluate bag-formulated entomopathogenic fungal conidial virulence against insect pests. We further investigated the enzymatic responses induced by the entomopathogenic fungi as well as the effect on a non-target species. Entomopathogenic fungi were isolated from the Palamalai Hills, India, using the insect bait method, and the Metarhizium majus (MK418990.1) entomopathogen was identified using biotechnological techniques (genomic DNA isolation and 18S rDNA amplification). Bag-formulated fungal conidial efficacy (2.5 × 103, 2.5 × 104, 2.5 × 105, 2.5 × 106, and 2.5 × 107 conidia/ml) was evaluated against third instar larvae of Spodoptera frugiperda at 3, 6, 9, and 12 days of treatment, and acid and alkaline phosphatases, catalase, and superoxide dismutase enzymatic responses were evaluated at 3 days post-treatment. After 12 days of treatment, non-target assays on the earthworm Eudrilus eugeniae were performed using an artificial soil assay. Results of the bag formulated fungal conidial treatment showed that S. frugiperda had high susceptibility rates at higher concentrations (2.5 × 107 conidia/ml) of M. majus. Lower concentration of 2.5 × 103 conidia/ml caused 68.6% mortality, while 2.5 × 107 conidia/ml caused 100% mortality at 9 days post treatment. Investigation into enzymatic responses revealed that at 3 days post M. majus conidia exposure (2.5 × 103 conidia/ml), insect enzyme levels had significantly changed, with acid and alkaline phosphatases, and catalase enzymes significantly reduced and superoxide dismutase enzymes significantly raised relative to the control. After 12 days of treatment, no sublethal effects of M. majus conidia were observed on E. eugeniae, with no observed damage to gut tissues including lumen and epithelial cells, the nucleus, setae, coelom, mitochondria, and muscles. This study offers support for the use of fungal conidia in the target-specific control of insect pests.

Phosphate-solubilizing bacterial strains (6 Nos.) were isolated from the rhizosphere soils of two seagrasses (Halophila ovalis (R. Br.) Hook and Halodule pinifolia (Miki) Hartog) in the Vellar estuary. Experimental studies found that the strain PSSG6 was effective in phosphate solubilization with Phosphate Solubilization efficiency index E = 375 ± 8.54, followed by the strain PSSG5 with Phosphate Solubilization efficiency index E = 275 ± 27.3. Of the 6 strains isolated, the strains PSSG4 and PSSG5 belonged to the genus Bacillus, and PSSG1, PSSG2 and PSSG3 were identified as Citrobacter sp., Shigella sp., and Klebsiella sp., respectively, by conventional method, and PSSG6 was identified as Bacillus circulans using conventional and molecular methods.

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