Pharmacological Applications of Phlorotannins: A Comprehensive Review

A Pharmacokinetic and Bioavailability Study of Ecklonia cava Phlorotannins Following Intravenous and Oral Administration in Sprague-Dawley Rats

This study examines the pharmacokinetics and bioavailability of phlorotannins from Ecklonia cava in rats following intravenous and oral administration. Known for their potent antioxidant, anti-inflammatory and many other bioactivities, these phlorotannins, particularly dieckol, 8,8'-bieckol, and phlorofucofuroeckol-A (PFF-A), were analyzed using high-performance liquid chromatography coupled with tandem mass spectrometry. Intravenous administration at 10 mg/kg allowed detectability in plasma for up to 36 h for dieckol and 8,8'-bieckol, but only 2 h for PFF-A. Oral administration at doses of 100 mg/kg and 1000 mg/kg showed limited detectability, indicating low bioavailability and rapid clearance, particularly for PFF-A. The pharmacokinetic data suggest non-linear increases in the maximum plasma concentration (Cmax) and area under the curve (AUC) with increasing doses, pointing to significant challenges in achieving systemic availability of these eckols through oral administration. This study underscores the necessity for advanced formulation strategies and alternative routes of administration to enhance systemic bioavailability. At the same time, this result also suggests their effects may be through non-systemic pathways such as gut microbiome modulation or lipid-rich tissue targeting. The findings lay a crucial foundation for the further development of Ecklonia cava phlorotannins as therapeutic agents, offering insights into their pharmacokinetic behavior and informing enhancements in future clinical utility.

RSM- and ANN-Based Multifrequency Ultrasonic Extraction of Polyphenol-Rich Sargassum horneri Extracts Exerting Antioxidative Activity via the Regulation of MAPK/Nrf2/HO-1 Machinery

Sargassum horneri (SH) is widely consumed as a healthy seaweed food in the Asia-Pacific region. However, the bioactive components contributing to its biological activity remain unknown. Herein, we optimized multifrequency ultrasonic-assisted extraction conditions to achieve higher antioxidant activity using a response surface methodology and an artificial neural network. High-resolution mass spectrometry (HRMS; negative mode) was used to tentatively identify the secondary metabolites in the optimized SH extract, which were further tested against oxidative stress in RAW264.7 cells. Additionally, the identified compounds were analyzed in silico to determine their binding energies with the Keap1 protein (4L7B). We identified 89 compounds using HRMS, among which 19 metabolites (8 polyphenolics, 2 flavonoids, 2 lignans, 2 terpenes, 2 tannins, 2 sulfolipids, and 1 phospholipid) were putatively reported for the first time in SH. The in vitro results revealed that optimized SH extract inhibited oxidative stress via the Nrf2/MAPKs/HO-1 pathway in a dose-dependent manner. This result was validated by performing in silico simulation, indicating that sargaquinoic acid and glycitein-7-O-glucuronide had the highest binding energies (-9.20 and -9.52 Kcal/mol, respectively) toward Keap1 (4L7B). This study offers a unique approach for the scientific community to identify potential bioactive compounds by optimizing the multivariant extraction processing conditions, which could be used to develop functional and nutraceutical foods.

Metabolite Profiling of Microwave-Assisted Sargassum fusiforme Extracts with Improved Antioxidant Activity Using Hybrid Response Surface Methodology and Artificial Neural Networking-Genetic Algorithm

Sargassum fusiforme (SF) is a popular edible brown macroalga found in Korea, Japan, and China and is known for its health-promoting properties. In this study, we used two sophisticated models to obtain optimized conditions for high antioxidant activity and metabolite profiling using high-resolution mass spectrometry. A four-factor central composite design was used to optimize the microwave-assisted extraction and achieve the maximum antioxidant activities of DPPH (Y1: 28.01 % inhibition), ABTS (Y2: 36.07 % inhibition), TPC (Y3: 43.65 mg GAE/g), and TFC (Y4: 17.67 mg CAE/g), which were achieved under the optimized extraction conditions of X1: 47.67 %, X2: 2.96 min, X3: 139.54 °C, and X4: 600.00 W. Moreover, over 79 secondary metabolites were tentatively identified, of which 12 compounds were reported for the first time in SF, including five phenolic (isopropyl 3-(3,4-dihydroxyphenyl)-2-hydroxypropanoate, 3,4-dihydroxyphenylglycol, scopoletin, caffeic acid 4-sulfate, and cinnamoyl glucose), two flavonoids (4',7-dihydroxyisoflavone and naringenin), three phlorotannins (diphlorethohydroxycarmalol, dibenzodioxin-1,3,6,8-tetraol, and fucophlorethol), and two other compounds (dihydroxyphenylalanine and 5-hydroxybenzofuran-2(3H)-one) being identified for the first time in optimized SF extract. These compounds may also be involved in improving the antioxidant potential of the extract. Therefore, optimized models can provide better estimates and predictive capabilities that would assist in finding new bioactive compounds with improved biological activities that can be further applied at a commercial level.

Recent advances in nutritional composition, phytochemistry, bioactive, and potential applications of Syzygium aromaticum L. (Myrtaceae)

Syzygium aromaticum is an aromatic plant native to Indonesia, and introduced to tropical regions worldwide. As an ingredient in perfumes, lotions, and food preservation, it is widely used in the food and cosmetic industries. Also, it is used to treat toothache, ulcers, type 2 diabetes, etc. A variety of nutrients such as amino acids, proteins, fatty acids, and vitamins are found in S. aromaticum. In addition to eugenol, isoeugenol, eugenol acetate, β-caryophyllene and α-humulene are the main chemical constituents. The chemical constituents of S. aromaticum exhibit a wide range of bioactivities, such as antioxidant, antitumor, hypoglycemic, immunomodulatory, analgesic, neuroprotective, anti-obesity, antiulcer, etc. This review aims to comprehend the information on its taxonomy and botany, nutritional composition, chemical composition, bioactivities and their mechanisms, toxicity, and potential applications. This review will be a comprehensive scientific resource for those interested in pursuing further research to explore its value in food.

Phloroglucinol Derivative Carbomer Hydrogel Accelerates MRSA-Infected Wounds’ Healing

Globally, wound infection is considered to be one of the major healthcare problems, with bacterial infections being the most critical threat, leading to poor and delayed wound healing, and even death. As a superbug, methicillin-resistant Staphylococcus aureus (MRSA) causes a profound hazard to public health safety, prompting us to search for alternative treatment approaches. Herein, the MTT test and Hoechst/propidium iodide (PI) staining demonstrated that PD was slightly less toxic to human fibroblasts including Human keratinocytes (HaCaT) cell line than Silver sulfadiazine (SSD), and Vancomycin (Van). In the MRSA-infected wound model, PD hydrogel (1%, 2.5%) was applied with for 14 days. The wound healing of PD hydrogel groups was superior to the SSD, Van, and control groups. Remarkably, the experimental results showed that PD reduced the number of skin bacteria, reduced inflammation, and upregulated the expression of PCNA (keratinocyte proliferation marker) and CD31 (angiogenesis manufacturer) at the wound site by histology (including hematoxylin–eosin (HE) staining, Masson staining) and immunohistochemistry. Additionally, no toxicity, hemocompatibility or histopathological changes to organs were observed. Altogether, these results suggested the potential of PD hydrogel as a safe, effective, and low toxicity hydrogel for the future clinical treatment of MRSA-infected wounds.

Bioactive Potential of Brown Algae

Marine-derived natural products are rich source of secondary metabolites with huge potentials including novel therapeutic agents. Marine algae are considered to be a good source of secondary metabolites with versatile bioactivities. During the last few decades, researches related to natural products obtained from brown algae have remarkably escalated as they contain active compounds with varied biologically activities like antimicrobial, anticancer, antioxidant, anti-inflammatory, antidiabetic, and antiparasitic properties. The main bioactive components such as phlorotannin, fucoxanthin, alginic acid, fucoidan, and laminarin have been briefly discussed here, together with their composition and biological activities. In this review, the biological function of extracts and the metabolites of brown algae as well as their pharmacological impacts with the description of the possible mechanism of their action are described and discussed. Also, this study is expected to examine the multifunctional properties of brown algae that facilitate natural algal products, including the ability to integrate these functional properties in a variety of applications.

Dieckol: a brown algal phlorotannin with biological potential

Dieckol [C36H22O18], is a naturally occurring phlorotannin found in some brown algal species. Dieckol is gaining more attention in the scientific community for its potential biological activities. It has been exhibited a broad spectrum of therapeutic functions including anti-bacterial, anti-cancer, anti-oxidant, anti-aging, anti-diabetic, neuroprotective, and other medicinal applications. Distinct emphasis has been given to extraction, purification, and biomedical applications of dieckol. This critical review comprises of in vitro, in vivo, and in silico biological properties of dieckol. An attempt has been made to evaluate the effectiveness, therapeutical application, and mechanism of dieckol against various diseases. The pharmacological significance, current status and the dosage of multifunctional dieckol and its mechanisms have been discussed in this review. Dieckol plays an important role in apoptosis induction via inhibiting the PI3K, AKT, mTOR and FAK signaling molecules. Dieckol remarkably inhibited the lipid accumulation in high fat diet induced animal models. Dieckol, a multifaceted compound will be beneficial in attenuating the action of various diseases and it could be a potential pharmaceutical and nutraceutical compound. Therefore, the combined effects of dieckol with existing drugs and natural compounds will be studied in future to optimize its benefits. Besides limited information on the toxicological action and dosage administration of dieckol on the human was reported to date. Overall, dieckol is a prospective health-promoting compound for the development of a novel drug against numerous diseases.

Seasonal Evaluation of Phlorotannin-Enriched Extracts from Brown Macroalgae Fucus spiralis

Fucus spiralis that was collected in the four seasons was submitted to an extraction with ethanol:water (crude extracts Et80), followed by a liquid-liquid fractionation with organic solvents (fraction He from n-hexane; aqueous fractions AQ1, AQ2, AQ3 and AQ4; ethyl acetate fraction EA), with the aim of obtaining phlorotannin-enriched extracts. All the extracts (Et80, He, AQ1, AQ2, AQ3, AQ4 and EA) that were obtained for the F. spiralis of the four seasons were evaluated for their antioxidant capacity and total phenolic compounds. The summer extracts presented the highest contents in polyphenols (TPC), as well as the highest ferric reducing antioxidant power (FRAP), when compared to the samples from the other seasons. The reductive percentage of the DPPH (2,2-diphenyl-1-picryl-hydrazyl-hydrate) compound was similar between the seasons. For all the seasons, the EA extract showed the highest polyphenol content (TPC), and the highest antioxidant capacity (highest ferric reducing power (FRAP) and lowest concentration needed to reduce 50% of the DPPH compound), which is in agreement with a phlorotannin-enriched fraction. This study revealed that the polyphenol content and antioxidant power of the F. spiralis extracts are influenced by the time of harvest, as well as by the solvents used for their extraction.

Antimicrobial and Anti-Quorum Sensing Activities of Phlorotannins From Seaweed (Hizikia fusiforme)

Multidrug-resistant bacteria (MDR) are becoming a global health problem, and scientists are continuously investigating new strategies to fight against MDR. Seaweeds are an important source of biological compounds and can serve as natural sources for bacterial infection control. This study evaluated the antimicrobial and anti-quorum sensing (QS) activities of phlorotannins from Hizikia fusiforme. The phlorotannins exhibited antimicrobial activity against selected bacterial pathogens and inhibited QS activity of the reporter strain Chromobacterium violaceum 12472 by inhibiting purple pigment production. Phlorotannins can decrease the bacterial motility, reduce the production of extracellular protease, hemolysin, and pyocyanin and inhibit biofilm formation of Pseudomonas aeruginosa. In vivo studies showed that phlorotannins can reduce P. aeruginosa inflicted mortality in Caenorhabditis elegans. This study shows that phlorotannins from H. fusiforme have certain antimicrobial and anti-quorum sensing activities and have the potential to control bacterial infection for pharmaceutical usage.

Topical Application of Phlorotannins from Brown Seaweed Mitigates Radiation Dermatitis in a Mouse Model

Radiation dermatitis (RD) is one of the most common side effects of radiotherapy; its symptoms progress from erythema to dry and moist desquamation, leading to the deterioration of the patients’ quality of life. Active metabolites in brown seaweed, including phlorotannins (PTNs), show anti-inflammatory activities; however, their medical use is limited. Here, we investigated the effects of PTNs in a mouse model of RD in vivo. X-rays (36 Gy) were delivered in three fractions to the hind legs of BALB/c mice. Macroscopic RD scoring revealed that PTNs significantly mitigated RD compared with the vehicle control. Histopathological analyses of skin tissues revealed that PTNs decreased epidermal and dermal thickness compared with the vehicle control. Western blotting indicated that PTNs augmented nuclear factor erythroid 2-related factor 2 (NRF2)/heme oxygenase-1 (HO-1) pathway activation but attenuated radiation-induced NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) and inflammasome activation, suggesting the mitigation of acute inflammation in irradiated mouse skin. PTNs also facilitated fast recovery, as indicated by increased aquaporin 3 expression and decreased γH2AX (histone family member X) expression. Our results indicate that topical PTN application may alleviate RD symptoms by suppressing oxidative stress and inflammatory signaling and by promoting the healing process. Therefore, PTNs may show great potential as cosmeceuticals for patients with cancer suffering from radiation-induced inflammatory side effects such as RD.

In Vitro Anticancer and Radiosensitizing Activities of Phlorethols from the Brown Alga Costaria costata

The anticancer and radiosensitizing effects of high-molecular-weight phlorethols CcPh (Mw = 2520 Da) isolated from the brown algae of Costaria costata on human colorectal carcinoma HCT 116 and HT-29 cells were investigated. Phlorethols CcPh possessed cytotoxic activity against HT-29 (IC50 = 92 μg/mL) and HCT 116 (IC50 = 94 μg/mL) cells. CcPh at non-toxic concentrations inhibited the colony formation in colon cancer cells and significantly enhanced their sensitivity to low non-toxic X-ray irradiation. The combinatory effect of radiation and CcPh was synergistic (Combination index < 0.7). Algal phlorethols might be prospective candidates as radiosensitizers to improve the scheme of radiotherapy.