Pharmacological Activities of Extracts and Compounds Isolated from Mediterranean Sponge Sources

Integration of HPTLC with ATR-FTIR, HRMS and bioquantification for evaluation of antibacterial and antioxidant compounds in marine sponges

Marine sponges are an abundant source of unique bioactive compounds, offering immense potential for the development of innovative medicines. This study presents an analytical approach for the identification of bioactive compounds in marine sponge extracts. The approach capitalizes high-performance thin-layer chromatography (HPTLC) - Effect-Directed Analysis (EDA) with high-resolution mass spectrometry (MS) and Fourier-transform infrared (FTIR) spectroscopy, enabling identification of bioactive compounds. HPTLC-EDA was done to evaluate radical scavenging and antimicrobial activities against five pathogenic bacterial strains: Escherichia coli, Klebsiella pneumoniae, Bacillus spizizenii, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus (MRSA). The bioquantification of streptomycin and gallic acid was conducted using image analysis of HPTLC chromatograms, with subsequent analysis via antimicrobial assays against the aforementioned bacterial strains and DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assays. The developed HPTLC chromatograms, utilizing toluene:ethyl acetate:acetic acid (60:37.5:2.5, V/V/V) as a mobile phase for the first time, enabled the optimal separation of bioactive compounds from complex marine sponge extracts. Avarol from Dysidea avara was identified as the compound with the highest potential using FTIR and HRMS techniques. The study highlights a high-throughput, cost-effective approach for screening bioactive metabolites from marine sponges using HPTLC-bioassay. This approach accelerates therapeutic discovery and offers a sustainable, eco-friendly alternative to traditional methods.

Microbiome profiling and Actinomycetes isolation from tropical marine sponges

Marine sponges are well-known for their production of bioactive compounds, many of which are synthesized by their associated symbiotic microorganisms. Among these, Actinomycetes are of particular interest due to their ability to produce secondary metabolites with antimicrobial and antitumor activities. We aimed to investigate the bacterial microbiome of tropical marine sponges, with an emphasis on the diversity and distribution of Actinomycetes, employing both culture-dependent and culture-independent approaches. Five sponge samples (PF01-PF05) were collected from Sichang Island, Chonburi Province, Thailand. The bacterial communities were analyzed using 16S rRNA gene sequencing and bioinformatics tools, revealing a significant microbial diversity dominated by Cyanobacteria, Actinomycetota, and Chloroflexi. Notably, PF01 (Penares nux) exhibited the highest microbial diversity, while PF05 (Cacospongia sp.) had the lowest. Actinomycetes, particularly the genus Micromonospora, were successfully isolated from all samples, with PF03 (Ircinia mutans) yielding the highest number of strains. Culture-independent analysis identified a greater proportion of unculturable Actinomycetes compared to those isolated through traditional methods, underscoring the limitations of culture-dependent techniques. This study enhances our understanding of sponge-associated microbial diversity and highlights the potential for isolating Actinomycetes from these sponges for novel drug discovery and other bioprospective applications.

Evaluation of In Vitro Cytotoxic Potential of Avarol towards Human Cancer Cell Lines and In Vivo Antitumor Activity in Solid Tumor Models

The goal of this study was to determine the activity in vitro and in vivo of avarol, a sesquiterpene hydroquinone originating from the Dysidea avara sponge from the south Adriatic Sea, against different cancer cell lines and two types of mouse carcinoma. To investigate the in vitro cytotoxicity, a human cervix adenocarcinoma cell line (HeLa), human colon adenocarcinoma (LS174), human non-small-cell lung carcinoma (A549), and a normal human fetal lung fibroblast cell line (MRC-5) were used. The in vivo antitumor activity was investigated against two transplantable mouse tumors, the Ehrlich carcinoma (EC) and cervical cancer (CC-5). The effect of avarol on cancer cell survival, which was determined by the microculture tetrazolium test, confirmed a significant in vitro potency of avarol against the investigated cell lines, without selectivity towards MRC-5. The highest cytotoxicity was exhibited against HeLa cancer cells (10.22 ± 0.28 μg/mL). Moreover, potent antitumor activity against two tumor models was determined, as the intraperitoneal administration of avarol at a dose of 50 mg/kg resulted in a significant inhibition of tumor growth in mice. After three administrations of avarol, a 29% inhibition of the EC growth was achieved, while in the case of CC-5, a 36% inhibition of the tumor growth was achieved after the second administration of avarol. Therefore, the results indicate that this marine sesquiterpenoid hydroquinone could be a promising bioactive compound in the development of new anticancer medicine.

Pro-Apoptotic Activity of the Marine Sponge Dactylospongia elegans Metabolites Pelorol and 5-epi-Ilimaquinone on Human 501Mel Melanoma Cells

The natural environment represents an important source of drugs that originates from the terrestrial and, in minority, marine organisms. Indeed, the marine environment represents a largely untapped source in the process of drug discovery. Among all marine organisms, sponges with algae represent the richest source of compounds showing anticancer activity. In this study, the two secondary metabolites pelorol (PEL) and 5-epi-ilimaquinone (EPI), purified from Dactylospongia elegans were investigated for their anti-melanoma activity. PEL and EPI induced cell growth repression of 501Mel melanoma cells in a concentration- and time-dependent manner. A cell cycle block in the G1 phase by PEL and EPI was also observed. Furthermore, PEL and EPI induced significant accumulation of DNA histone fragments in the cytoplasmic fraction, indicating a pro-apoptotic effect of both compounds. At the molecular level, PEL and EPI induced apoptosis through the increase in pro-apoptotic BAX expression, confirmed by the decrease in its silencing miR-214-3p and the decrease in the anti-apoptotic BCL-2, MCL1, and BIRC-5 mRNA expression, attested by the increase in their silencing miRNAs, i.e., miR-193a-3p and miR-16-5p. In conclusion, our data indicate that PEL and EPI exert cytotoxicity activity against 501Mel melanoma cells promoting apoptotic signaling and inducing changes in miRNA expression and their downstream effectors. For these reasons could represent promising lead compounds in the anti-melanoma drug research.

A 4/8 Subtype α-Conotoxin Vt1.27 Inhibits N-Type Calcium Channels With Potent Anti-Allodynic Effect

A novel 4/8 subtype α-conotoxin, Vt1.27 (NCCMFHTCPIDYSRFNC-NH₂), was identified from Conus vitulinus in the South China Sea by RACE methods. The peptide was synthesized and structurally characterized. Similar to other α-conotoxins that target neuronal nicotinic acetylcholine receptor (nAChR) subtypes, Vt1.27 inhibited the rat α3β2 nAChR subtype (IC₅₀ = 1160 nM) and was inactive at voltage-gated sodium and potassium channels in rat sensory neurons. However, Vt1.27 inhibited high voltage-activated N-type (Ca_V2.2) calcium channels expressed in HEK293T cells with an IC₅₀ of 398 nM. An alanine scan of the peptide showed that residues Phe⁵, Pro⁹, Ile¹⁰, and Ser¹³ contribute significantly to the inhibitory activity of Vt1.27. The molecular dockings indicate that Vt1.27 inhibits the transmembrane region of Ca_V2.2, which is different from that of ω-conotoxins. Furthermore, Vt1.27 exhibited potent anti-allodynic effect in rat partial sciatic nerve injury (PNL) and chronic constriction injury (CCI) pain models at 10 nmol/kg level with the intramuscular injection. The pain threshold elevation of Vt1.27 groups was higher than that of α-conotoxin Vc1.1 in CCI rat models. These findings expand our knowledge of targets of α-conotoxins and potentially provide a potent, anti-allodynic peptide for the treatment of neuropathic pain.

Marine Demospongiae: A Challenging Treasure of Bioactive Compounds

In the last decades, it has been demonstrated that marine organisms are a substantial source of bioactive compounds with possible biotechnological applications. Marine sponges, in particular those belonging to the class of Demospongiae, have been considered among the most interesting invertebrates for their biotechnological potential. In this review, particular attention is devoted to natural compounds/extracts isolated from Demospongiae and their associated microorganisms with important biological activities for pharmacological applications such as antiviral, anticancer, antifouling, antimicrobial, antiplasmodial, antifungal and antioxidant. The data here presented show that this class of sponges is an exciting source of compounds, which are worth developing into new drugs, such as avarol, a hydroquinone isolated from the marine sponge Disidea avara, which is used as an antitumor, antimicrobial and antiviral drug.