Plastoquinones from Sargassum yezoense; chemical structures and effects on the activation of peroxisome proliferator-activated receptor gamma

Antitumor Activity and Mechanism of Terpenoids in Seaweeds Based on Literature Review and Network Pharmacology

Seaweeds are a treasure trove of natural secondary metabolites. Terpenoids extracted from seaweeds are shown to possess a variety of antitumor cellular activities. However, due to the complex and diverse structures of terpenoids, their therapeutic targets and complex mechanisms of action have not been clarified. The present study summarises the research on terpenoids from seaweeds in oncological diseases over the last 20 years. Terpenoids show different degrees of inhibitory effects on different types of tumor cells, suggesting that terpenoids in seaweeds may have potential antitumor disease potential. Terpenoids with potential antitumor activity and their mechanism of action are investigated using network pharmacology. A total of 125 terpenoids and 286 targets are obtained. Proto-oncogene tyrosine-protein kinase Src(SRC), Signal transducer and activator of transcription 3 (STAT3), Mitogen-activated protein kinase (MAPK3, MAPK1), Heat shock protein HSP 90-alpha (HSP90AA1), Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and RAC-alpha serine/threonine-protein kinase (AKT1) are defined as core targets. According to GO function and Kyoto encyclopedia of genes and genomes(KEGG) enrichment analysis, terpenoids may affect the Phoshatidylinositol 3'-kinase (PI3K)-Akt signaling pathway, Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor resistance, Prostate cancer, MAPK signaling pathway, and Proteoglycans in cancer. In addition, the molecular docking results show that the selected terpenoids are all able to bind strongly to the active protein. Terpenoids may slow down the progression of cancer by controlling apoptosis, proliferation, and protein and enzyme binding.

Structural diversity, biosynthesis, and health-promoting properties of brown algal meroditerpenoids

Marine algae that constitute hundreds of millions of tons of biomass are the oldest representatives of the plant kingdom. Recently, there has been growing interest in the utilization of algae as sustainable feedstocks for natural products with an economic value. Among these natural products are the meroditerpenoids, which are renowned for their protective effects against oxidative stress, inflammation, cancer, obesity, diabetes, and neurodegenerative disorders. Meroditerpenoids have a mixed biosynthetic origin and display a wide range of structural diversity. Their basic structure consists of a ring system bearing a diterpenoid side chain. Structural variations are observed in terms of the functional groups and saturation/cyclization of the diterpenoid side chain. This review classifies algal meroditerpenoids as plastoquinones, chromanols, chromenes, chromones, cyclic meroditerpenoids, nahocols, and isonahocols and examines their potential applications in functional foods and biopharmacology. Their lipid solubility, low molecular weight, and propensity to cross the blood-brain barrier places meroditerpenoids as potential drug candidates. There is growing interest in the study of algal meroterpenoids, and recent research has reported the structure of several new meroterpenoids and their biological activities. Further research is needed to extend the use of algal meroditerpenoids in preclinical trials. Understanding the mechanism of their biosynthesis will allow the development of de novo biosynthesis and biomimetic synthesis strategies for the industrial-scale production of meroditerpenoids and their synthetic derivatives to aid pharmaceutical research. This review is the first to summarize up-to-date information on all brown algae-derived meroditerpenoids.

Macrocarquinoids A-C, new meroterpenoids from Sargassum macrocarpum

The production and accumulation of advanced glycation end products (AGEs) have been implicated in diabetes and diabetic complication. This study was conducted as a search for an AGE inhibitor from brown alga, Sargassum macrocarpum. Separation and purification were performed using AGEs inhibitory activity as an index, yielding isolation of 11 meroterpenoids, of which 3 were new compounds: macrocarquinoids A (1), B (6), and C (9). Their structures were elucidated using NMR spectral analysis with 2D techniques. All tested compounds showed AGEs inhibitory activity. Particularly, macrocarquinoid C (9) possessed the strongest activity (IC50: 1.0 mM) of isolated compounds. This activity was stronger than that of aminoguanidine (positive control).

Pharmacological and natural products diversity of the brown algae genus Sargassum

Sargassum (F. Sargassaceae) is an important seaweed excessively distributed in tropical and subtropical regions.

Seaweed Secondary Metabolites In Vitro and In Vivo Anticancer Activity

Isolation, finding or discovery of novel anticancer agents is very important for cancer treatment, and seaweeds are one of the largest producers of chemically active metabolites with valuable cytotoxic properties, and therefore can be used as new chemotherapeutic agents or source of inspiration to develop new ones. Identification of the more potent and selective anticancer components isolated from brown, green and red seaweeds, as well as studies of their mode of action is very attractive and constitute a small but relevant progress for pharmacological applications. Several researchers have carried out in vitro and in vivo studies in various cell lines and have disclosed the active metabolites among the terpenoids, including carotenoids, polyphenols and alkaloids that can be found in seaweeds. In this review the type of metabolites and their cytotoxic or antiproliferative effects will be discussed additionally their mode of action, structure-activity relationship and selectivity will also be revealed. The diterpene dictyolactone, the sterol cholest-5-en-3β,7α-diol and the halogenated monoterpene halomon are among the reported compounds, the ones that present sub-micromolar cytotoxicity. Additionally, one dimeric sesquiterpene of the cyclolaurane-type, three bromophenols and one halogenated monoterpene should be emphasized because they exhibit half maximal inhibitory concentration (IC₅₀) values between 1–5 µM against several cell lines.

Bioactive Prenyl- and Terpenyl-Quinones/Hydroquinones of Marine Origin †

The sea is a rich source of biological active compounds, among which terpenyl-quinones/hydroquinones constitute a family of secondary metabolites with diverse pharmacological properties. The chemical diversity and bioactivity of those isolated from marine organisms in the last 10 years are summarized in this review. Aspects related to synthetic approaches towards the preparation of improved bioactive analogues from inactive terpenoids are also outlined.

Secondary Metabolites and Biological Activity of Invasive Macroalgae of Southern Europe

In this review a brief description of the invasive phenomena associated with algae and its consequences on the ecosystem are presented. Three examples of invasive algae of Southern Europe, belonging to Rodophyta, Chlorophyta, and Phaeophyta, were selected, and a brief description of each genus is presented. A full description of their secondary metabolites and biological activity is given and a summary of the biological activity of extracts is also included. In Asparagopsis we encounter mainly halogenated compounds. From Caulerpa, several terpenoids and alkaloids were isolated, while in Sargassum, meroterpenoids prevail.

Bioactive quinone derivatives from the marine brown alga Sargassum thunbergii induce anti-adipogenic and pro-osteoblastogenic activities

BACKGROUND

Health problems related to the lack of bone formation are a major problem for ageing populations in the modern world. As a part of the ongoing trend to develop natural substances that attenuate bone loss in osteoporosis, the effects of the edible brown alga Sargassum thunbergii and its active contents on adipogenic differentiation in 3T3-L1 fibroblasts and osteoblast differentiation in MC3T3-E1 pre-osteoblasts were evaluated.

RESULTS

Treatment with S. thunbergii significantly reduced lipid accumulation and expression of adipogenic differentiation markers such as peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein α and sterol regulatory element binding protein 1c. In addition, S. thunbergii successfully enhanced osteoblast differentiation as indicated by increased alkaline phosphatase activity along raised levels of osteoblastogenesis indicators, namely bone morphogenetic protein-2, osteocalcin and collagen type I. Two compounds, sargaquinoic and sargahydroquinoic acid, were isolated from active extract and shown to be active by means of osteogenesis inducement.

CONCLUSION

S. thunbergii could be a source for functional food ingredients for improved treatment of osteoporosis and obesity.

Alpha-amylase inhibitory activity and sterol composition of the marine algae, Sargassum glaucescens

BACKGROUND

Sargassum species (phaeophyceae) are economically important brown algae in southern parts of Iran. Sargassum is mainly harvested as a row material in alginate production industries and is a source of plant foods or plant bio-stimulants even a component of animal foods.

OBJECTIVE

In this study, Sargassum glaucescens, collected from the seashore of Chabahar, was employed for phytochemical and biological evaluations.

MATERIALS AND METHODS

For that purpose, the dried algae was extracted by methanol and subjected to different chromatographic separation methods.

RESULTS

Six sterols, fucosterol (1), 24(S)-hydroxy-24-vinylcholesterol (2), 24(R)-hydroxy-24-vinylcholesterol (3), stigmasterol (4), β-sitosterol (5) and cholesterol (6) were identified by spectroscopic methods including (1)H-NMR, (13)C-NMR and mass spectroscopy. In vitro alpha-amylase inhibitory test was performed on the methanolic extract and the results revealed a potent inhibition (IC50 = 8.9 ± 2.4 mg/mL) of the enzyme compared to acarbose as a positive control.

CONCLUSION

Various biological activities and distribution of sterols in Sargassum genus have been critically reviewed here. The results concluded that these algae are a good candidate for further anti-diabetic investigations in animals and human.

Chemical profiling (HPLC-NMR & HPLC-MS), isolation, and identification of bioactive meroditerpenoids from the southern Australian marine brown alga Sargassum paradoxum

A phytochemical investigation of a southern Australian marine brown alga, Sargassum paradoxum, resulted in the isolation and identification of four new (5, 9, 10, and 15) and nine previously reported (1, 2, 6-8, and 11-14) bioactive meroditerpenoids. HPLC-NMR and HPLC-MS were central to the identification of a new unstable compound, sargahydroquinal (9), and pivotal in the deconvolution of eight (1, 2, 5-7, and 10-12) other meroditerpenoids. In particular, the complete characterization and identification of the two main constituents (1 and 2) in the crude dichloromethane extract was achieved using stop-flow HPLC-NMR and HPLC-MS. This study resulted in the first acquisition of gHMBCAD NMR spectra in the stop-flow HPLC-NMR mode for a system solely equipped with a 60 μL HPLC-NMR flow cell without the use of a cold probe, microcoil, or any pre-concentration.

Synthetic cannabinoid quinones: preparation, in vitro antiproliferative effects and in vivo prostate antitumor activity

Chromenopyrazolediones have been designed and synthesized as anticancer agents using the multi-biological target concept that involves quinone cytotoxicity and cannabinoid antitumor properties. In cell cytotoxicity assays, these chromenopyrazolediones have antiproliferative activity against human prostate cancer and hepatocellular carcinoma. It has been shown that the most potent, derivative 4 (PM49), inhibits prostate LNCaP cell viability (IC₅₀ = 15 μM) through a mechanism involving oxidative stress, PPARγ receptor and partially CB₁ receptor. It acts on prostate cell growth by causing G₀/G₁ phase arrest and triggering apoptosis as assessed by flow cytometry measurements. In the in vivo treatment, compound 4 at 2 mg/kg, blocks the growth of LNCaP tumors and reduces the growth of PC-3 tumors generated in mice. These studies suggest that 4 is a good potential anticancer agent against hormone-sensitive prostate cancer.

Marine natural products

This review covers the literature published in 2011 for marine natural products, with 870 citations (558 for the period January to December 2011) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1152 for 2011), together with the relevant biological activities, source organisms and country of origin. Biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Sargaquinoic acid isolated from Sargassum siliquastrum inhibits lipopolysaccharide-induced nitric oxide production in macrophages via modulation of nuclear factor-κB and c-Jun N-terminal kinase pathways

Nitric oxide (NO) is a crucial molecule in inflammatory diseases and is synthesized from L-arginine by a specific enzyme, NO synthase (NOS). The expression of inducible NOS (iNOS) is activated in macrophages by various stimuli, such as lipopolysaccharide (LPS), a wall component of gram-negative bacteria. LPS binds to toll-like receptor 4 (TLR4) on the macrophage surface and activates several downstream signaling pathways, including mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB pathways. This study investigated whether sargaquinoic acid isolated from Sargassum siliquastrum might have anti-inflammatory activity and interfere with NO production in macrophages by disrupting LPS-induced signaling. This study was conducted in vitro using RAW264.7 murine macrophages. LPS-stimulated cells were treated with sargaquinoic acid, and the effects on NO production, iNOS expression, and involvement of the NF-κB signaling pathway were investigated by Griess assay, western blotting, and confocal microscopy. The results demonstrated that sargaquinoic acid inhibited the production of NO and the expression of the iNOS protein in LPS-stimulated RAW264.7 macrophages. Moreover, sargaquinoic acid inhibited the degradation of inhibitory-κB protein (IκB)-α and the nuclear translocation of NF-κB, a key transcription factor for the regulation of iNOS expression. Also, sargaquinoic acid influenced the phosphorylation of JNK1/2 MAPK, except ERK1/2 and p38 MAPKs, stimulated by LPS. These results suggest that sargaquinoic acid specifically prevents NO production in macrophages via the blockade of NF-κB activation and may thus have therapeutic applications in various inflammatory diseases.

Towards a better understanding of medicinal uses of the brown seaweed Sargassum in Traditional Chinese Medicine: a phytochemical and pharmacological review

ETHNOPHARMACOLOGICAL RELEVANCE

For nearly 2000 years Sargassum spp., a brown seaweed, has been used in Traditional Chinese Medicine (TCM) to treat a variety of diseases including thyroid disease (e.g. goitre).

AIMS OF THE REVIEW

To assess the scientific evidence for therapeutic claims made for Sargassum spp. in TCM and to identify future research needs.

BACKGROUND AND METHODS

A systematic search for the use of Sargassum in classical TCM books was conducted and linked to a search for modern phytochemical and pharmacological data on Sargassum spp. retrieved from PubMed, Web of Knowledge, SciFinder Scholar and CNKI (in Chinese).

RESULTS AND DISCUSSION

The therapeutic effects of Sargassum spp. are scientifically plausible and may be explained partially by key in vivo and in vitro pharmacological activities of Sargassum, such as anticancer, anti-inflammatory, antibacterial and antiviral activities. Although the mechanism of actions is still not clear, the pharmacological activities could be mainly attributed to the major biologically active metabolites, meroterpenoids, phlorotanins and fucoidans. The contribution of iodine in Sargassum for treating thyroid related diseases seem to have been over estimated.

CONCLUSIONS

The bioactive compounds in Sargassum spp. appear to play a role as immunomodulators and could be useful in the treatment of thyroid related diseases such as Hashimoto's thyroiditis. Further research is required to determine both the preventative and therapeutic role of Sargassum spp. in thyroid health.