Oxygenated cembranoids from the cultured and wild-type soft corals Sinularia flexibilis

Towards Sustainable Medicinal Resources through Marine Soft Coral Aquaculture: Insights into the Chemical Diversity and the Biological Potential

In recent decades, aquaculture techniques for soft corals have made remarkable progress in terms of conditions and productivity. Researchers have been able to obtain larger quantities of soft corals, thus larger quantities of biologically active metabolites, allowing them to study their biological activity in many pharmacological assays and even produce sufficient quantities for clinical trials. In this review, we summarize 201 secondary metabolites that have been identified from cultured soft corals in the era from 2002 to September 2022. Various types of diterpenes (eunicellins, cembranes, spatanes, norcembranes, briaranes, and aquarianes), as well as biscembranes, sterols, and quinones were discovered and subjected to bioactivity investigations in 53 different studies. We also introduce a more in-depth discussion of the potential biological effects (anti-cancer, anti-inflammatory, and anti-microbial) and the mechanisms of action of the identified secondary metabolites. We hope this review will shed light on the untapped potential applications of aquaculture to produce valuable secondary metabolites to tackle current and emerging health conditions.

Recent updates on Sinularia soft coral

Marine organisms are recognized as a rich source of bioactive secondary metabolites. The remarkable abundance and diversity of bioactive small molecules isolated from soft corals displayed their essential role in drug discovery for human diseases. Sterols and terpenes, particularly cembranolides, 14-membered cyclic diterpene, demonstrated numerous biological activities, such as antitumor, antimicrobial, antiviral, antidiabetic, anti-osteoporosis and anti-inflammatory. Accordingly, continuous investigation of marine soft corals will be the way for the discovery of a plentiful number of chemical diverse natural products with various biological potentials for prospective pharmaceutical industrial applications. Such review affords plenary inspection of the total secondary metabolites isolated from the Sinularia, from 2008 until 2020, besides their natural sources as well as bioactivities whenever possible.

New Antiproliferative Cembrane Diterpenes from the Red Sea Sarcophyton Species

The combination of liquid chromatography coupled to high resolution mass spectrometry (LC-HRESMS)-based dereplication and antiproliferative activity-guided fractionation was applied on the Red Sea-derived soft coral Sarcophyton sp. This approach facilitated the isolation of five new cembrane-type diterpenoids (1–5), along with two known analogs (6 and 7), as well as the identification of 19 further, known compounds. The chemical structures of the new compounds were elucidated while using comprehensive spectroscopic analyses, including one-dimensional (1D) and two-dimensional (2D) NMR and HRMS. All of the isolated cembranoids (1–7) showed moderate in vitro antiproliferative activity against a human breast cancer cell line (MCF-7), with IC₅₀ ranging from 22.39–27.12 µg/mL. This class of compounds could thus serve as scaffold for the future design of anticancer leads.

Marine Natural Products from Indonesian Waters

Natural products are primal and have been a driver in the evolution of organic chemistry and ultimately in science. The chemical structures obtained from marine organisms are diverse, reflecting biodiversity of genes, species and ecosystems. Biodiversity is an extraordinary feature of life and provides benefits to humanity while promoting the importance of environment conservation. This review covers the literature on marine natural products (MNPs) discovered in Indonesian waters published from January 1970 to December 2017, and includes 732 original MNPs, 4 structures isolated for the first time but known to be synthetic entities, 34 structural revisions, 9 artifacts, and 4 proposed MNPs. Indonesian MNPs were found in 270 papers from 94 species, 106 genera, 64 families, 32 orders, 14 classes, 10 phyla, and 5 kingdoms. The emphasis is placed on the structures of organic molecules (original and revised), relevant biological activities, structure elucidation, chemical ecology aspects, biosynthesis, and bioorganic studies. Through the synthesis of past and future data, huge and partly undescribed biodiversity of marine tropical invertebrates and their importance for crucial societal benefits should greatly be appreciated.

Sandensolide Induces Oxidative Stress-Mediated Apoptosis in Oral Cancer Cells and in Zebrafish Xenograft Model

Presently, natural sources and herbs are being sought for the treatment of human oral squamous cell carcinoma (OSCC) in order to alleviate the side effects of chemotherapy. This study investigates the effect of sandensolide, a cembrane isolated from Sinularia flexibilis, to inhibit human OSCC cell growth with the aim of developing a new drug for the treatment of oral cancer. In vitro cultured human OSCC models (Ca9.22, SCC9 and HSC-3 cell lines) and oral normal cells (HGF-1), as well as a zebrafish xenograft model, were used to test the cytotoxicity of sandensolide (MTT assay), as well as to perform cell cycle analysis and Western blotting. Both the in vitro bioassay and the zebrafish xenograft model demonstrated the anti-oral cancer effect of sandensolide. Moreover, sandensolide was able to significantly suppress colony formation and induce apoptosis, as well as cell cycle arrest, in OSCC by regulating multiple key proteins. Induction of reactive oxygen species (ROS) was observed in sandensolide-treated oral cancer cells. However, these apoptotic changes were rescued by NAC pretreatment. These findings contribute to the knowledge of the model of action of sandensolide, which may induce oxidative stress-mediated cell death pathways as a potential agent in oral cancer therapeutics.

Structural Elucidation and Structure-Anti-inflammatory Activity Relationships of Cembranoids from Cultured Soft Corals Sinularia sandensis and Sinularia flexibilis

New cembranoids 4-carbomethoxyl-10-epigyrosanoldie E (1), 7-acetylsinumaximol B (2), diepoxycembrene B (6), dihydromanaarenolide I (8), and isosinulaflexiolide K (9), along with 11 known related metabolites, were isolated from cultured soft corals Sinularia sandensis and Sinularia flexibilis. The structures were elucidated by means of infrared, mass spectrometry, and nuclear magnetic resonance techniques, and the absolute configurations of 1, 4, 9, and 15 were further confirmed by single-crystal X-ray diffraction analysis. The absolute configurations of these coral metabolites and comparison with known analogues showed that one hypothesis (that cembrane diterpenes possessing an absolute configuration of an isopropyl group at C1 obtained from Alcyonacean soft corals belong to the α series, whereas analogues isolated from Gorgonacean corals belong to the β series) is not applicable for a small number of cembranoids. An in vitro anti-inflammatory study using LPS-stimulated macrophage-like cell line RAW 264.7 revealed that compounds 9-14 significantly suppressed the accumulation of pro-inflammatory proteins, iNOS and COX-2. Structure-activity relationship analysis indicated that cembrane-type compounds with one seven-membered lactone moiety at C-1 are potential anti-inflammatory agents. This is the first culture system in the world that has successfully been used to farm S. sandensis.

Sinulariolide Suppresses Human Hepatocellular Carcinoma Cell Migration and Invasion by Inhibiting Matrix Metalloproteinase-2/-9 through MAPKs and PI3K/Akt Signaling Pathways

Sinulariolide is an active compound isolated from the cultured soft coral Sinularia flexibilis. In this study, we investigate the migration and invasion effects of sinulariolide in hepatocellular carcinoma cell HA22T. Sinulariolide inhibited the migration and invasion effects of hepatocellular carcinoma cells in a concentration-dependent manner. The results of zymography assay showed that sinulariolide suppressed the activities of matrix metalloproteinase (MMP)-2 and MMP-9. Moreover, protein levels of MMP-2, MMP-9, and urokinase-type plasminogen activator (uPA) were reduced by sinulariolide in a concentration-dependent manner. Sinulariolide also exerted an inhibitory effect on phosphorylation of c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinases (ERK), phosphatidylinositol 3-kinase (PI3K), Akt, Focal adhesion kinase (FAK), growth factor receptor-bound protein 2 (GRB2). Taken together, these results demonstrated that sinulariolide could inhibit hepatocellular carcinoma cell migration and invasion and alter HA22T cell metastasis by reduction of MMP-2, MMP-9, and uPA expression through the suppression of MAPKs, PI3K/Akt, and the FAK/GRB2 signaling pathway. These findings suggest that sinulariolide merits further evaluation as a chemotherapeutic agent for human hepatocellular carcinoma.

Flexibilide obtained from cultured soft coral has anti-neuroinflammatory and analgesic effects through the upregulation of spinal transforming growth factor-β1 in neuropathic rats

Chronic neuroinflammation plays an important role in the development and maintenance of neuropathic pain. The compound flexibilide, which can be obtained from cultured soft coral, possesses anti-inflammatory and analgesic effects in the rat carrageenan peripheral inflammation model. In the present study, we investigated the antinociceptive properties of flexibilide in the rat chronic constriction injury (CCI) model of neuropathic pain. First, we found that a single intrathecal (i.t.) administration of flexibilide significantly attenuated CCI-induced thermal hyperalgesia at 14 days after surgery. Second, i.t. administration of 10-μg flexibilide twice daily was able to prevent the development of thermal hyperalgesia and weight-bearing deficits in CCI rats. Third, i.t. flexibilide significantly inhibited CCI-induced activation of microglia and astrocytes, as well as the upregulated proinflammatory enzyme, inducible nitric oxide synthase, in the ipsilateral spinal dorsal horn. Furthermore, flexibilide attenuated the CCI-induced downregulation of spinal transforming growth factor-β1 (TGF-β1) at 14 days after surgery. Finally, i.t. SB431542, a selective inhibitor of TGF-β type I receptor, blocked the analgesic effects of flexibilide in CCI rats. Our results suggest that flexibilide may serve as a therapeutic agent for neuropathic pain. In addition, spinal TGF-β1 may be involved in the anti-neuroinflammatory and analgesic effects of flexibilide.

Bioactive cembranoids, sarcocrassocolides P-R, from the Dongsha Atoll soft coral Sarcophyton crassocaule

New cembranoids, sarcocrassocolides P–R (1–3) and four known compounds (4–7) were isolated from the soft coral Sarcophyton crassocaule. The structures of the metabolites were determined by extensive spectroscopic analysis. Compounds 3–5 and 7 were shown to exhibit cytotoxicity toward a limited panel of cancer cell lines and all compounds 1–7 displayed potent in vitro anti-inflammatory activity in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells by inhibiting the expression of inducible nitric oxide synthase (iNOS) protein. Compound 7 also showed significant activity in reducing the accumulation of cyclooxygenase-2 (COX-2) protein in the same macrophage cells.

Withanolide-based steroids from the cultured soft coral Sinularia brassica

Seven novel withanolides, sinubrasolides A-G (1-7), have been isolated from the cultured soft coral Sinularia brassica. The structures of the new metabolites were determined by extensive spectroscopic analyses, and the absolute configuration of 1 was established by X-ray crystallographic analysis. The cytotoxicities of compounds 1-7 against a limited panel of cancer cell lines also were determined.

Sinulariolide induced hepatocellular carcinoma apoptosis through activation of mitochondrial-related apoptotic and PERK/eIF2α/ATF4/CHOP pathway

Sinulariolide, an active compound isolated from the cultured soft coral Sinularia flexibilis, has potent anti-microbial and anti-tumorigenesis effects towards melanoma and bladder cancer cells. In this study, we investigated the effects of sinulariolide on hepatocellular carcinoma (HCC) cell growth and protein expression. Sinulariolide suppressed the proliferation and colony formation of HCC HA22T cells in a dose-dependent manner and induced both early and late apoptosis according to flow cytometry, Annexin V/PI stain and TUNEL/DAPI stain analyses. A mechanistic analysis demonstrated that sinulariolide-induced apoptosis was activated through a mitochondria-related pathway, showing up-regulation of Bax, Bad and AIF, and down- regulation of Bcl-2, Bcl-xL, MCl-1 and p-Bad. Sinulariolide treatment led to loss of the mitochondrial membrane potential, release of mitochondrial cytochrome c to the cytosol, and activation of both caspase-9 and caspase-3. Sinulariolide-induced apoptosis was significantly blocked by the caspase inhibitors Z-VAD-FMK and Z-DEVD-FMK. The increased expression of cleaved PARP also suggested that caspase-independent apoptotic pathway was involved. In the western blotting; the elevation of ER chaperones GRP78; GRP94; and CALR; as well as up-regulations of PERK/eIF2α/ATF4/CHOP; and diminished cell death with pre-treatment of eIF2α phosphatase inhibitor; salubrinal; implicated the involvement of ER stress-mediated PERK/eIF2α/ATF4/CHOP apoptotic pathway following sinulariolide treatment in hepatoma cells. The current study suggested sinulariolide-induced hepatoma cell cytotoxicity involved multiple apoptotic signal pathways. This may implicate that sinulariolide is a potential compound for the treatment of hepatocellular carcinoma.

Inhibition of NF-κB transcriptional activation in HepG2 cells by diterpenoids from the soft coral Sinularia maxima

Anti-inflammatory transcriptional effects of nineteen compounds (1–19) from the soft coral Sinularia maxima were evaluated using NF-κB luciferase and reverse transcriptase polymerase chain reaction. Compounds 1, 2, 4, 8, 15, 17, and 18 significantly inhibited TNFα-induced NF-κB transcriptional activity in HepG2 cells in a dose-dependent manner, with IC₅₀ values ranging from 15.81 ± 2.29 to 29.10 ± 1.54 μM. Furthermore, the transcriptional inhibitory function of these compounds was confirmed by a decrease in intercellular adhesion molecule-1 and inducible nitric oxide synthase gene expression levels in HepG2 cells. These results provide a scientific rationale for the use of the soft coral S. maxima warrant further studies to develop new agents for the prevention and treatment of inflammatory.

Flexibilisquinone, a new anti-inflammatory quinone from the cultured soft coral Sinularia flexibilis

A new quinone derivative, flexibilisquinone (1), was isolated from the cultured soft coral Sinulariaflexibilis, originally distributed in the waters of Taiwan. The structure of quinone 1 was established by extensive spectroscopic methods, particularly 1D and 2D NMR experiments. In the in vitro anti-inflammatory effects test, quinone 1 was found to significantly inhibit the accumulation of the pro-inflammatory iNOS and COX-2 proteins of the LPS-stimulated RAW264.7 macrophage cells.

A soft coral natural product, 11-episinulariolide acetate, inhibits gene expression of cyclooxygenase-2 and interleukin-8 through attenuation of calcium signaling

Epidermal growth factor receptor (EGFR) is overexpressed in many types of cancer cells. EGFR-mediated signaling involves inflammatory gene expression including cyclooxygenase (COX)-2 and interleukin (IL)-8, and is associated with cancer pathogenesis. In a search of phytochemicals with anti-inflammatory activity, the COX-2 and IL-8 inhibitory activities of some marine compounds were examined. After screening these compounds 11-episinulariolide acetate (1) from soft coral exhibited the most potent activity. Reverse-transcription PCR; western blotting; ELISA and luciferase assays were used to test the effect of compound 1 on EGF-stimulated expressions of COX-2 and IL-8 in A431 human epidermoid carcinoma cells. After exposure to 10 μM of compound 1, expression levels of COX-2 and IL-8 were reduced. In addition; intracellular Ca²⁺ increase and Ca²⁺-dependent transcription factor activation were blocked by compound 1. Thus, compound 1 can potentially serve as a lead compound for targeting Ca²⁺ signaling-dependent inflammatory diseases.

Cembrane derivatives from the soft corals, Sinularia gaweli and Sinularia flexibilis

A new norcembranoidal diterpene, 1-epi-sinulanorcembranolide A (1), and a new cembranoidal diterpene, flexibilin D (2), were isolated from the soft corals, Sinularia gaweli and Sinularia flexibilis, respectively. The structures of new metabolites 1 and 2 were elucidated by spectroscopic methods, and compound 2 was found to significantly inhibit the accumulation of the pro-inflammatory iNOS and COX-2 proteins of the lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. In addition, S. flexibilis yielded a known cembrane, 5-dehydrosinulariolide (3); the structure, including its absolute stereochemistry, was further confirmed by single-crystal X-ray diffraction analysis.

Flexibilins A-C, new cembrane-type diterpenoids from the Formosan soft coral, Sinularia flexibilis

Three new cembrane-type diterpenoids, flexibilins A-C (1-3), along with a known cembrane, (-)-sandensolide (4), were isolated from the soft coral, Sinularia flexibilis. The structures of cembranes 1-4 were elucidated by spectroscopic methods. The structure of 4, including its absolute stereochemistry, was further confirmed by single-crystal X-ray diffraction analysis. Cembrane 2 displayed a moderate inhibitory effect on the release of elastase by human neutrophils.

Oxygenated Cembranoids from the Soft Coral Sinularia flexibilis

Chemical examination of the Taiwanese soft coral Sinularia flexibilis led to the isolation of five cembrane-based diterpenoids 1-5, including two new metabolites, 11-acetylsinuflexolide (1) and 11-acetyldihydrosinuflexolide (2). The structures of the new metabolites were determined based on extensive spectroscopic analysis, particularly mass spectrometry and 2D NMR (1H-1H COSY, HMQC, HMBC, and NOESY) spectroscopy. Metabolites 1, 3 and 4 exhibited moderate to weak cytotoxicity to human tumor cell lines, HeLa, HEp-2, MCF-7 and MDA-MB-231.

A new spatane diterpenoid from the cultured soft coral Sinularia leptoclados

A new spatane diterpenoid, leptoclalin A (1), along with two previously reported known norcembranoid diterpenes (2 and 3), were isolated from a cultured soft coral Sinularia leptoclados. The structures were determined by extensive spectroscopic analyses and by comparison with the spectral data of related known compounds. Metabolite 1 is rarely found in spatane skeletons reported from soft corals. In addition, compound 1 exhibited weak cytotoxicity towards human tumor cell lines T-47 D and K-562.

Norcembranoidal diterpenes from a Formosan soft coral Sinularia sp

Two norcembranoidal diterpenes, 5-episinuleptolide acetate (1) and scabrolide D (2), were isolated from a Formosan octocoral identified as Sinularia sp. The structures of norcembranoids 1 and 2 were established by spectroscopic methods and by comparison of the spectral data with those of known analogues and 1 was proven to be a new natural product. Norcembranoid 1 was found to exhibit cytotoxicity toward a panel of tumor cells.

New cembrane diterpenoids from a Hainan soft coral Sinularia sp

Five new cembrane diterpenoids, named sinuflexibilins A-E (1-5), along with nine other known diterpenoids (6-14), have been isolated from the organic extract of a Hainan soft coral Sinularia sp. Their structures were determined on the basis of extensive spectroscopic analyses and by comparison of their spectral data with those of related metabolites. Compound 13, flexibilide, exhibited significant inhibitory activity of NF-κB activation using the cell-based HEK293 NF-κB luciferase reporter gene assay.

Sinularin from indigenous soft coral attenuates nociceptive responses and spinal neuroinflammation in carrageenan-induced inflammatory rat model

Three decades ago, the marine-derived compound sinularin was shown to have anti-edematous effects on paw edema induced by carrageenan or adjuvant. To the best of our knowledge, no new studies were conducted to explore the bioactivity of sinularin until we reported the analgesic properties of sinularin based on in vivo experiments. In the present study, we found that sinularin significantly inhibits the upregulation of proinflammatory proteins, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) and upregulates the production of transforming growth factor-β (TGF-β) in lipopolysaccharide (LPS)-stimulated murine macrophage RAW 264.7 cells according to western blot analysis. We found that subcutaneous (s.c.) administration of sinularin (80 mg/kg) 1 h before carrageenan injection significantly inhibited carrageenan-induced nociceptive behaviors, including thermal hyperalgesia, mechanical allodynia, cold allodynia, and hindpaw weight-bearing deficits. Further, s.c. sinularin (80 mg/kg) significantly inhibited carrageenan-induced microglial and astrocyte activation as well as upregulation of iNOS in the dorsal horn of the lumbar spinal cord. Moreover, s.c. sinularin (80 mg/kg) inhibited carrageenan-induced tissue inflammatory responses, redness and edema of the paw, and leukocyte infiltration. The results of immunohistochemical studies indicate that s.c. sinularin (80 mg/kg) could upregulate production of TGF-β1 in carrageenan-induced inflamed paw tissue. The present results demonstrate that systemic sinularin exerts analgesic effects at the behavioral and spinal levels, which are associated with both inhibition of leukocyte infiltration and upregulation of TGF-β1.

Two new cembrane-based diterpenoids from the marine soft coral Sinularia crassa

Two new cembrane diterpenes, sicrassarines A and B (compounds 1 and 2), were isolated from the Taiwanese soft coral Sinularia crassa. The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis, particularly mass spectroscopy and 2D NMR (¹H–¹H COSY, HMQC, HMBC, and NOESY) spectroscopy.

Trends in the discovery of new marine natural products from invertebrates over the last two decades--where and what are we bioprospecting?

It is acknowledged that marine invertebrates produce bioactive natural products that may be useful for developing new drugs. By exploring untapped geographical sources and/or novel groups of organisms one can maximize the search for new marine drugs to treat human diseases. The goal of this paper is to analyse the trends associated with the discovery of new marine natural products from invertebrates (NMNPI) over the last two decades. The analysis considers different taxonomical levels and geographical approaches of bioprospected species. Additionally, this research is also directed to provide new insights into less bioprospected taxa and world regions. In order to gather the information available on NMNPI, the yearly-published reviews of Marine Natural Products covering 1990-2009 were surveyed. Information on source organisms, specifically taxonomical information and collection sites, was assembled together with additional geographical information collected from the articles originally describing the new natural product. Almost 10000 NMNPI were discovered since 1990, with a pronounced increase between decades. Porifera and Cnidaria were the two dominant sources of NMNPI worldwide. The exception was polar regions where Echinodermata dominated. The majority of species that yielded the new natural products belong to only one class of each Porifera and Cnidaria phyla (Demospongiae and Anthozoa, respectively). Increased bioprospecting efforts were observed in the Pacific Ocean, particularly in Asian countries that are associated with the Japan Biodiversity Hotspot and the Kuroshio Current. Although results show comparably less NMNPI from polar regions, the number of new natural products per species is similar to that recorded for other regions. The present study provides information to future bioprospecting efforts addressing previously unexplored taxonomic groups and/or regions. We also highlight how marine invertebrates, which in some cases have no commercial value, may become highly valuable in the ongoing search for new drugs from the sea.

Tetrahydrofuran cembranoids from the cultured soft coral Lobophytum crassum

Three new cembranoids, culobophylins A-C (1-3), along with two known compounds (4 and 5) were isolated from the cultured soft coral Lobophytum crassum. The structures of these compounds were elucidated on the basis of their spectroscopic data and comparison of the NMR data with those of known analogues. Among these metabolites, 2 is rarely found in cembranoids possessing an isopropyl moiety with an epoxide group. Compound 1 exhibited significant cytotoxic activity against HL60 and DLD-1 cancer cell lines.

Bioactive cembranoids from the dongsha atoll soft coral Sarcophyton crassocaule

Seven new cembranoids, sarcocrassocolides F–L (1–7), have been isolated from a soft coral Sarcophyton crassocaule. Their structures were determined by extensive spectroscopic analysis. Most new compounds exhibited significant cytotoxic activity against a limited panel of cancer cell lines, and the structure–activity relationship was studied. Compounds 1–7 were found to display significant in vitro anti-inflammatory activity in LPS-stimulated RAW264.7 macrophage cells by inhibiting the expression of the iNOS protein. Compound 4 was also found to effectively reduce the level of COX-2 protein.

Bioactive cembrane-based diterpenoids from the soft coral Sinularia triangular

Chemical examination of the Taiwanese soft coral Sinularia triangular led to the isolation of five cembrane-based diterpenoids 1-5, including two new metabolites, triangulenes A (1) and B (2). The structures of the new metabolites were determined on the basis of extensive spectroscopic analysis, particularly mass spectroscopy and 2D NMR ((1)H-(1)H COSY, HMQC, HMBC, and NOESY) spectroscopy. Metabolites 3 and 5 exhibited moderate cytotoxicity to human tumor cell lines CCRF-CEM and DLD-1. Furthermore, 3-5 displayed significant in vitro anti-inflammatory activity in lipopolysaccharide-stimulated RAW264.7 macrophage cells by inhibiting the expression of the iNOS protein. Metabolites 4 and 5 also effectively reduced the expression of the COX-2 protein in the macrophages.

Cembranoids from the soft corals Sinularia granosa and Sinularia querciformis

Two new cembranoids, namely granosolides C (1) and D (2), along with one known cembranoid 4, were isolated from the soft coral Sinularia granosa. Chemical investigation of Sinularia querciformis also afforded one new cembranoid, querciformolide E (3), along with four known cembranoids 4-7. The structures of these compounds were elucidated on the basis of their spectroscopic data. Both 4 and 5 were shown to significantly inhibit the accumulation of the pro-inflammatory inducible nitric oxide synthase protein in lipopolysaccharide-stimulated RAW264.7 macrophage cells.