Caulerpa okamurae

Identity and Taxonomy

Scientific Classification and Nomenclature

Caulerpa okamurae Weber Bosse (1898) is a marine green macroalga formally recognized as a distinct, currently accepted taxonomic entity. It belongs to the phylum Chlorophyta, class Ulvophyceae, order Bryopsidales, and family Caulerpaceae, and is distributed worldwide in tropical and subtropical oceans. The species epithet honors Kintaro Okamura (1867–1935), a pioneering Japanese phycologist, and was formally described in published form by Okamura in his 1916 work Icones of Japanese algae.

Within general seaweed taxonomy, C. okamurae is classified as a green alga. The genus Caulerpa belongs to the family Caulerpaceae among the green algae; its members are unusual in consisting of only one cell with many nuclei — also known as coenocytic or siphonous algae — making them among the largest single cells in the world. The thallus organization is multinucleate; unlike other algae, the thallus and its nuclei are not separated by cell walls but instead form one long mass of protoplasm surrounded by a single cell wall. The genus also possesses trabeculae, which are inward-growing cell-wall extensions passing through the central lumen of siphons; these are hypothesized to provide structural support, facilitate diffusion to the inner cytoplasm, and contribute to the diversity of growth forms found in the genus.

Natural Source and Geographic Distribution

As a marine green macroalga, C. okamurae is distributed worldwide in tropical and subtropical oceans. The genus is mostly found in tropical regions, though its distribution extends to temperate locations; diversity is highest in the Caribbean and the Indo-Malay region, as well as in southern Australia, where a majority of Caulerpa species are endemic. Within the genus, several species of the green seaweed genus Caulerpa are very popular as human food in the Indo-Pacific region, and the consumption of these seaweeds is well established in local traditions; currently, most Caulerpa species are collected from the wild and sold on markets.

Common Forms and Preparations

C. okamurae is one of the edible seaweed species with high nutritional content and economic value. As an edible green alga and a candidate for "green caviar," it is considered a new food material; its polysaccharides, as its main bioactive component, have been studied to possess hypoglycemic activity, immunoenhancing activity, and other biological properties. In research settings, the alga is most frequently processed into an ethanolic extract (commonly abbreviated COE — Caulerpa okamurae extract), a water-extracted and column-purified sulfated polysaccharide fraction, or a crude aqueous extract. In the Indo-Pacific, edible Caulerpa species contain proteins, fiber, minerals, vitamins, polyunsaturated fatty acids, and bioactive antioxidants. Cultivation is convenient because the plants can propagate through fragmentation; farming techniques include tying fragments to different types of infrastructure, and many Pacific countries use off-bottom methods where seaweeds are grown on cages or trays.

Traditional and Historical Use

Caulerpa is well known as nutritious food in Japan, Korea, and Southeast Asia countries. Because Caulerpa seaweed has been consumed for food in Japan, China, South Korea, and Australia, it has been a subject of investigation for potential functional health properties. Within East Asia, the seaweed has a documented history as a dietary item consumed either fresh or dried; the specific food traditions surrounding C. okamurae overlap with a broader regional practice of seaweed eating deeply embedded in Japanese and Korean culinary culture.

The consumption of these seaweeds is well established in local traditions, and for this reason several seaweed farms have been established, or are under assessment, with a view to providing additional sources of income for local communities. Peer-reviewed ethnobotanical and ethnopharmacological records specifically documenting the medicinal use of C. okamurae in named traditional systems (such as Kampo medicine or Korean traditional medicine) are limited in the available scientific literature; what exists are broader accounts of edible Caulerpa use in coastal communities. The genus as a whole occupies a culturally significant role in the food systems of coastal East and Southeast Asia, where freshly harvested thalli are consumed in salads and other preparations, valued for their crunchy texture and flavor.

Key Constituents and Active Compounds

Sulfated Polysaccharides

The most extensively characterized bioactive components of C. okamurae are its sulfated polysaccharides (SPs). Marine green algae have been considered valuable resources for the development of novel bioactive compounds; among the various constituents, water-soluble sulfated polysaccharides have been shown to have innovative and unique structures and numerous beneficial biological activities, such as anticoagulation, anticancer, antioxidation, and antiviral activities. A systematic study revealed that C. okamurae contains abundant characteristic sulfated xylogalactomannan; the molecule has a branched structure with (1→4)-β-D-Manp and (1→2)-β-D-Manp as the backbone. The primary isolated fraction CO-0-1 was mainly composed of mannose (Man), galactose (Gal), and xylose (Xyl) at the ratio of 4.4:4.0:1.4, with a molecular weight of 470 kDa and sulfate content of 12.78%.

Sesquiterpenes, Alkaloids, and Other Secondary Metabolites

Therapeutic potency of pure compounds isolated from Caulerpa is promising as antiviral, antimicrobial, cytotoxic, immunostimulatory, anti-obesity, cardioprotective, hepatoprotective, and hypolipidemic agents; metabolites such as caulerpin, caulersin, and caulerpenyne have attracted great attention in structure elucidation and total synthesis owing to their uncommon structural complexity and interesting pharmacological properties. The genus produces a number of secondary metabolites thought to be related to its toxicity and peppery taste, including the red pigment alkaloid caulerpin and its derivative caulerchlorin, and the amine mixture caulerpicin.

Caulerpenyne, a sesquiterpene originally isolated from the genus, has been found in multiple species. Caulerpenyne is a major metabolite of the Caulerpa genus in the form of sesquiterpenoids and has been shown to inhibit lipase activity in vivo competitively. The bisindole alkaloid caulerpin has received its own pharmacological characterization: in vitro assays demonstrated that caulerpin significantly reduced nitric oxide, TNF-α, IL-6, and IL-12 levels in macrophages stimulated with LPS + IFN-γ without affecting cell viability; in silico toxicity predictions using Protox 3.0 reinforce a favorable safety profile, and molecular docking and molecular dynamics simulations revealed high-affinity binding to the glucocorticoid receptor ligand-binding domain (GR-LBD), suggesting a mechanism of action similar to dexamethasone.

Macronutrients and Micronutrients

Wang et al. (2018) analyzed the nutritional components of C. okamurae, indicating that the contents of iron (Fe) and selenium (Se) are 381 mg/kg and 14.66 mg/kg, respectively. More broadly across the genus, the genus Caulerpa contains a high amount of iron (up to 81.3 mg per 100 g of dry matter in C. racemosa), magnesium, and calcium. PUFA content is approximately 60.8% of total fatty acids, dominated by α-linolenic acid; amino acids dominating the protein fraction are aspartic and glutamic acid. Carbohydrate content across the genus can range from 3.6% to 83.2% of dry matter, depending on the species.

Pigments

The main pigments of Caulerpa are chlorophyll a and b. Additional carotenoid pigments present in the genus include β-carotene and other photoprotective compounds relevant to its antioxidant profile.

Mechanisms of Action

Anti-Adipogenic and Anti-Obesity Mechanisms

The ethanolic extract of C. okamurae (COE) significantly inhibited lipid accumulation and reduced the expression of the master regulator of adipogenesis — peroxisome proliferator-activated receptor-γ (PPARγ), sterol regulatory element binding protein-1c (SREBP-1c), and CCAAT/enhancer-binding protein-α (C/EBPα) — in 3T3-L1 adipocytes. In the adipose tissue of COE-treated high-fat-diet (HFD)-fed mice, significant reductions were found in PPARγ, C/EBPα, fatty acid synthase (FAS), SREBP-1c, cluster of differentiation 36 (CD36), and acetyl-CoA synthetase.

Anti-Inflammatory Mechanisms

COE (250 µg/mL) significantly inhibited the lipopolysaccharide-induced inflammatory response in RAW 264.7 macrophages by downregulating NO production, nitric oxide synthase 2 expression, and nuclear translocation of nuclear factor-κB (NF-κB). In a 2025 cell study focused on periodontal inflammation, extracts dose-dependently reduced NO production, downregulated mRNA levels of proinflammatory cytokines, inhibited iNOS expression, and suppressed the phosphorylation of IKKα/β in P. gingivalis-stimulated RAW 264.7 macrophages.

Pulmonary Anti-Fibrotic Mechanisms

Caulerpa okamurae extract mitigates pulmonary fibrosis in vivo and in vitro; COE inhibited fibrosis markers by modulating TGFβ/SMAD/MAPK pathways and lowered NLRP3 inflammasome activation.

Anticoagulant Mechanisms

Polysaccharides of C. okamurae have been studied to possess hypoglycemic activity and immunoenhancing activity; its characteristic sulfated xylogalactomannan is the principal compound investigated for anticoagulant properties. In comparative assessments of the genus, C. peltata showed the highest anticoagulant activity among Caulerpa species at approximately 151 IU/mg heparin equivalents, whereas C. okamurae had comparatively weak anticoagulant activity in early assay data (Maeda et al., 1991), although more structurally detailed recent work on its xylogalactomannan has renewed interest in this property.

Immunostimulatory Mechanisms

Sulfated polysaccharides are able to interact with surface receptors of animal cells and participate in several processes including cell recognition, cell adhesion, and the regulation of cellular processes; molecules with immunostimulatory effects may become interesting therapeutic agents because they are capable of potentiating natural defenses against immunosuppressive conditions, including in individuals undergoing cancer treatment. Within the genus, promising immunostimulatory effects were observed using polysaccharides from Caulerpa species; particularly, the fraction CLGP4 showed the highest sulfate content (21.26% dry weight) and in-vitro stimulation of macrophages by increasing proliferation, phagocytosis, and production of nitric oxide (NO) and phosphatase activity.

Scientific Evidence by Area of Use

1. Obesity and Metabolic Syndrome

Animal study (2017): Because Caulerpa seaweed has been consumed for food in Japan, China, South Korea, and Australia, Sharma et al. hypothesized that C. okamurae may have anti-obesity effects and tested this hypothesis using an animal model of high-fat diet (HFD)-induced obesity in C57BL/6 mice. COE significantly decreased body weight, fat weight, and liver weight in HFD-fed mice. Markers of weight gain — including free fatty acids, triglyceride, total cholesterol, glucose, and insulin in plasma, and free fatty acid, triglyceride, total cholesterol, and total lipid in the liver — were significantly reduced in COE-treated HFD-fed mice. This effect was described as comparable to that of positive control Garcinia cambogia extract, which has been approved by the Korean Food and Drug Administration as a weight-loss food supplement in South Korea. The study concluded that COE is effective in preventing body weight gain and fat accumulation and reduces plasma and hepatic lipid profiles.

In vitro study (2020): A subsequent study examined whether COE could inhibit obesity-mediated inflammation, improve glucose metabolism, and increase insulin sensitivity, using in vitro cell models of RAW 264.7 macrophages and 3T3-L1 adipocytes; the findings suggested that COE has potential to treat or prevent obesity-induced metabolic disorders. The study co-cultured 3T3-L1 adipocytes in direct contact with lipopolysaccharide-stimulated RAW 264.7 macrophages and induced insulin resistance in 3T3-L1 adipocytes with TNF-α in the presence or absence of 250 µg/mL of COE.

Evidence strength: Preliminary. All anti-obesity evidence for C. okamurae itself is from animal and cell-culture models only. No human clinical trials have been published. While preclinical findings are promising, clinical studies in humans remain limited; current evidence primarily stems from laboratory and animal research, and more comprehensive clinical trials are necessary to conclusively validate its efficacy and safety.

2. Inflammation and Periodontal Health

In vitro study (2025): A 2025 study from Wonkwang University investigated the anti-inflammatory effects of C. okamurae extracts on periodontal health. The results demonstrated that C. okamurae extracts exhibited no cytotoxicity in RAW 264.7 macrophages at tested concentrations of 0.2, 2, 20, and 200 µg/mL. The extracts dose-dependently reduced NO production, downregulated mRNA levels of proinflammatory cytokines, and inhibited iNOS expression in P. gingivalis-stimulated RAW 264.7 macrophages, a model commonly used to study periodontal inflammation. mRNA expression levels of TNF-α, IL-6, and IL-1β were quantified, and the protein expression of iNOS, p-IKKα/β, p-IκBα, and NF-κB p65 was examined by Western blot and immunofluorescence.

Evidence strength: Preclinical (in vitro only). No clinical or animal data exist for this specific application.

3. Pulmonary Fibrosis

Combined in vitro / in vivo study (2025): COE is derived from a green seaweed widely consumed in East Asia and is known for its anti-obesity properties; the study investigated its potential in pulmonary fibrosis (PF) using TGFβ-stimulated MRC-5 lung fibroblasts and bleomycin (BLM)-induced PF in C57BL/6 mice. In vitro, COE significantly reduced fibrotic markers (α-SMA, MMP1, Col1a1, and vimentin) and suppressed inflammatory mediators (IL-1β, IL-6, and COX2) by downregulating TGFβ/SMAD2/3 and MAPK signaling. In vivo, COE attenuated fibrotic features in BLM-treated mice by modulating the TGFβ/SMAD/MAPK pathway; interestingly, COE decreased plasma levels of IL-1β, an indicator of suppressed NLRP3 inflammasome activation; this effect was further validated in LPS- and nigericin-treated bone marrow-derived macrophages; these findings highlight COE's action in mitigating fibrosis and inflammation, underscoring its potential as a novel therapeutic for PF.

Evidence strength: Early preclinical (in vitro and mouse model). No human data exist.

4. Glucose Metabolism and Diabetes

Polysaccharides of C. okamurae as its main bioactive component have been studied to possess hypoglycemic activity. The broader genus has been studied for antidiabetic effects: diverse bioactivities including antidiabetic properties have been reported across the genus. The anti-adipogenic studies with COE in cell culture also demonstrated improvements in glucose uptake and insulin signaling in adipocyte models, representing in vitro evidence for glucose-metabolism modulation, but no dedicated human or animal study specifically for glycemic control using C. okamurae extract had been published in the accessible peer-reviewed literature as of mid-2025.

Evidence strength: Preliminary; primarily in vitro and mechanistic; limited to cell models and inferences from the polysaccharide literature.

5. Anticoagulation

Research on the sulfated xylogalactomannan from C. okamurae was described as expanding the utilization and development of the alga; marine green algae have been considered valuable resources for novel bioactive compounds, and among various constituents, water-soluble sulfated polysaccharides have been shown to have anticoagulation activities. However, in comparative species profiling of the genus, the anticoagulant activity of C. okamurae polysaccharides was historically characterized as weak relative to other Caulerpa species. The 2024 structural study of sulfated xylogalactomannan from C. okamurae (Zhu et al., published in the International Journal of Biological Macromolecules) demonstrated anticoagulant activity in biochemical assays, representing the most detailed characterization of this property to date.

Evidence strength: Preclinical / biochemical assay only. No in vivo data for anticoagulation specifically from C. okamurae polysaccharides.

6. Immunostimulation

Promising immunostimulatory effects were observed using polysaccharides from Caulerpa species; in particular, one high-sulfate-content polysaccharide fraction showed in vitro stimulation of macrophages by increasing proliferation, phagocytosis, and production of nitric oxide and phosphatase activity. These findings derive from the related species C. lentillifera, not exclusively from C. okamurae, though the polysaccharide backbone structures (xylogalactomannans) are shared between the species.

Evidence strength: Preclinical (cell-based) for the genus; specific in vitro data for C. okamurae extracts corroborating this effect are limited but consistent with genus-level patterns.

7. Antioxidant Activity

Various sulfated polysaccharide fractions detected in Caulerpa have been assessed for antioxidant activity, with applications suggested in anticoagulant, immune-stimulatory, antioxidant, and anti-Herpes simplex activities. Across the genus, antioxidant capacity has been evaluated by multiple standard assays (DPPH free-radical scavenging, ferrous chelation, total antioxidant capacity), with mixed results depending on the species and fraction tested.

Evidence strength: Primarily in vitro across the genus; species-specific antioxidant data for C. okamurae itself are limited to biochemical assays; no clinical data exist.

Body Systems and Health Areas Associated with Caulerpa okamurae

• Metabolic system: Inhibition of adipogenesis; reduction of body weight, fat mass, and plasma lipid parameters (animal evidence).
• Immune system: Macrophage activation, NF-κB pathway modulation, cytokine regulation (in vitro).
• Cardiovascular / coagulation system: Anticoagulant potential via sulfated polysaccharides (biochemical assay evidence, historically weak for this species).
• Respiratory system: Attenuation of fibrotic and inflammatory pathways in pulmonary fibrosis models (preclinical, 2025).
• Oral / periodontal system: Inhibition of P. gingivalis-induced macrophage inflammation (in vitro, 2025).
• Endocrine / glycemic system: Hypoglycemic polysaccharide activity; insulin sensitivity improvement in cell models.
• General nutrition: Source of dietary minerals (notably iron, selenium), polyunsaturated fatty acids, and dietary fiber consistent with whole food intake.

Dosage Forms and Dosages Reported in Studies

No human clinical dosage recommendations exist in the peer-reviewed literature. Dosages reported in published experimental studies are as follows:

• In vitro anti-obesity / anti-inflammatory (2020 cell study): COE was tested at 250 µg/mL in co-cultures of RAW 264.7 macrophages and 3T3-L1 adipocytes.
• In vitro anti-inflammatory / periodontal (2025 cell study): Concentrations of 0.2, 2, 20, and 200 µg/mL were evaluated for cytotoxicity and anti-inflammatory activity in RAW 264.7 macrophages.
• Animal anti-obesity study (2017, Nutr Res): The ethanolic extract COE was administered to C57BL/6 mice fed a high-fat diet; specific dietary dosing concentrations are reported in the primary publication (Sharma et al., Nutrition Research, 2017, Vol. 47, pp. 44–52).
• Sulfated polysaccharide structural/anticoagulant study (2024): The isolated fraction CO-0-1 was characterized at a molecular weight of 470 kDa and 12.78% sulfate content for structural and biological assay purposes.

The extract form used in most studies is an ethanolic extract or a hot-water-extracted and column-purified polysaccharide fraction. Polysaccharides as the main bioactive component have been studied across published research. No standardized dosage forms (capsules, tablets, standardized extracts) have been established or approved by any regulatory body.

Safety Considerations

General Toxicity Profile of the Genus

Although the genus Caulerpa is known to exhibit high toxicity in some contexts, it was found to be of low risk to humans under normal dietary conditions. Nevertheless, several species-level safety concerns have been documented for the genus and are relevant to C. okamurae as a member.

Inherent Secondary Metabolites

Toxicities and mortalities from intake of edible algae have been reported in species of the Gracilaria, Caulerpa, and Acanthophora genera, associated with their bioaccumulation of contaminants such as excess iodine, heavy metals, cyanotoxins, or toxic inherent compounds such as caulerpenyne, manauealides A and C, prostaglandin E2, polycavernosides, aplysiatoxins and their derivatives. Several species of Caulerpa have been investigated and bioactive principles such as caulerpin and caulerpicin have been isolated; caulerpin produces mild anesthetic action, difficulty in breathing, sedation, and loss of balance, and the toxic syndrome has been reported to be somewhat similar to that produced by ciguatera fish poisoning.

The concentration of caulerpenyne varies with water depth and temperature but is always higher in invasive strains. Toxicological evaluation of caulerpenyne in human hematopoietic progenitor cell cultures has been reported in the literature (Parent-Massin, 1996, Journal of Toxicology and Environmental Health 47(1):47–59).

Cytotoxicity Testing of C. okamurae Extracts

In the most recent dedicated cell-safety assessment, C. okamurae extracts exhibited no cytotoxicity in RAW 264.7 macrophages at concentrations of 0.2, 2, 20, and 200 µg/mL. The alkaloid caulerpin, found in the genus, showed a favorable acute in vivo safety profile in a 2025 study: in vivo, caulerpin exhibited no signs of acute toxicity at an oral dose of 100 mg/kg.

Heavy Metal Bioaccumulation

The genus is known to have a high bioaccumulation rate, which can make it less than ideal to consume on a regular basis. This is a documented concern for seaweeds grown in coastal or coastal-aquaculture environments exposed to industrial or agricultural runoff. The extent to which any individual sample of C. okamurae poses a heavy-metal risk depends entirely on the provenance and purity of the source material, and this has not been systematically characterized in the published literature for this specific species under dietary supplement conditions.

Anticoagulant Drug Interaction Potential

Water-soluble sulfated polysaccharides found in Caulerpa, including C. okamurae, have documented anticoagulant activities. Although anticoagulant potency for C. okamurae specifically was historically characterized as weak, the structural properties of the sulfated xylogalactomannan isolated in the 2024 study indicate that individuals on anticoagulant or antiplatelet therapy should be aware of this class of bioactive compound. No human pharmacokinetic or drug-interaction studies have been published for C. okamurae.

Absence of Regulatory Approval

The seaweed genus Caulerpa is still chemically and pharmacologically underexplored. More investigations are required in order to get the full picture of its nutritional, industrial, agricultural, and clinical applications. Neither the U.S. Food and Drug Administration (FDA), the European Medicines Agency (EMA), the European Food Safety Authority (EFSA), nor the World Health Organization has issued a specific monograph, safety opinion, or approval for Caulerpa okamurae as a dietary supplement ingredient.

Summary of Evidence

Caulerpa okamurae is an edible marine green macroalga with a documented history of dietary use in East and Southeast Asia. Its principal bioactive constituents — sulfated xylogalactomannans, sesquiterpenes (including caulerpenyne), and the bisindole alkaloid caulerpin — have been associated, in preclinical research, with anti-adipogenic, anti-inflammatory, anticoagulant, and immunostimulatory properties. The anti-obesity and anti-metabolic-disorder evidence from 2017 and 2020 (ethanolic extract in mice and cell culture) and the more recent 2025 work on periodontal inflammation and pulmonary fibrosis represent the most developed body of species-specific research. All currently available evidence is preclinical (in vitro and animal model); no human clinical trials have been published for any application of C. okamurae. Evidence strength across all areas of use should therefore be characterized as preliminary and insufficient to support efficacy claims in humans.

References

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