PHAEOPHYCEAE

All seaweeds are classified as belonging to the plant sub-kingdom Thallophyta and are usually identified primarily by colour. All have chlorophyll as their photosynthetic base so all are green, but the green is then covered by another pigment such as brown or red. Some colours seem to overlap, and shade can change with the season or age of the weed. Green light penetrates further into the water than red so brown seaweeds can live in deeper water. They also prefer cooler water temperatures. The Phaeophyceae are a family of large brown algae, (macro algae), the largest and longest of the seaweeds. They absorb medium wavelength green light and contain the pigment fucoxanthin.

Fucus vesiculosus

Bladderwrack, kelp

Description

A tough, leathery, brown and olive green seaweed with branching, flat, wavy-edged but not toothed offshoots, and a conspicuous midrib. Each branch has 2 or sometimes 3 gas bladders grouped together in the body of the frond, and in season, reproductive bodies at branch tips—yellowish in male plants and more green in female plants. The holdfast is a blob or lumpy disc with cells on the underside which secrete a kind of glue which sticks the plant to the rock.

Odour—fishy; taste—mucilaginous and salty.

Family Phaeophyceae

Habitat and distribution

A middle shore species growing in more sheltered sites where the waves have lost much of their power, in cooler waters of the Atlantic and Baltic seas.

Parts used

The whole thallus or plant, harvested at any time of the year.

Active constituents

1) Trace metals (up to 0.4%) especially rich in iodine (up to 0.2%),1 some of which is bound organically to proteins or amino acids and the rest occurs as iodides

2) Phenols predominantly phlorotannins (around 10%—these are water soluble phenolic compounds composed of polymers of phloroglycinol^2,3). Also fucols, fucophlorethols, catechin and gallic acid³

3) Polysaccharides of various types including alginic acid and fucoidans.^4,5 (Fucoidans contain sulphated units of the sugar L-fucose, they are found in other seaweeds and vary in their chemical structure.) Mucilage is composed of these polysaccharides

4) Sterols (around 0.3%) mainly as free fucosterol⁶

Also contains pigments and polar lipids.⁷ Polypeptides referred to as phytochelatins have been identified—the plant uses a process of chelation by these sulphur-rich polypeptides to protect itself from toxic metals and the level of polypeptides therefore changes in response to the concentration of metals present.⁸

Nutritional constituents

Vitamins: β-carotene

Minerals: Calcium, manganese, potassium, zinc, iron, copper and molybdenum.^3,9 Metal content depends on levels present in environment.

Actions

1) Anti-obesic

2) Thyroid modulator

3) Antirheumatic

Scientific information

Fucus has been an official medicine in some countries, used in the treatment of obesity. It has been fairly well characterised chemically in recent times, as it is a monitor of sea pollution because of its ability to accumulate metal ions.

There are not many studies on the medicinal properties of the whole herb but constituent polysaccharides and phlorotannins have shown a range of pharmacological activities.

Endocrine

In vitro—Fucus has anti-oestrogenic activity both by reducing oestrogen levels in cell cultures and by competing with oestrodiol binding at both α- and β-oestrogen receptor sites.¹⁰

In vivo—A pilot study has indicated that Fucus lengthened the cycle of pre-menopausal women experiencing abnormal menstrual cycles, reduced their oestrogen and increased their progesterone levels.¹¹ This has led to the suggestion that dietary intake of kelp by Japanese women may be a factor in their reduced risk of hormone-dependent cancers.¹¹

In diets deficient in iodine it seems that Fucus may aid weight reduction due to increased thyroid function and therefore an increased metabolic rate.¹² The use of the herb to help with weight loss is historical and was shown in studies conducted some time ago but there is no modern research into this effect.^13,14

Antimicrobial

In vitro—Various isolated fractions of bladderwrack are bactericidal,^15,16 have a limited antifungal activity¹⁷ and are antiviral to HIV,^18,19 herpes, vesicular stomatitis virus and cytomegalovirus.²⁰

Fucoidan reduces the adhesion of Helicobacter pylori to gastric cells²¹ and inactivates pepsin.²²

Other

In vitro—There is current interest in fucoidan from several sources and various properties have been found for the type found in Fucus. It complexes with toxins from snake venom, inactivating them;²³ may help wound healing;^24,25 may inhibit angiogenesis,²⁶ is anticoagulant^26,27 and fibrinolytic, can inhibit fertilisation and alters macrophage cytokine production.²⁹

Both fucoidan³⁰ and phlorotannins³¹ have antioxidant activity.

In vivo—The herb decreased skin thickness and increased its elasticity when applied topically as a 1% gel and may help reduce the effect of aging.³²

Medicinal uses

Gastro-intestinal tract

Fucus contains a high content of soluble fibre. In powdered form, it acts as a very beneficial and gentle bulk laxative:

• constipation

Endocrine system

• hypothyroidism
• myxoedema
• obesity
• lymphadenoid goitre

Musculoskeletal

The herb has been used for joint problems:

• rheumatism
• rheumatoid arthritis

Externally

• rheumatism

Pharmacy

Three times daily

Infusion of dried thallus	–   0.8–10 g
Tincture 1:5 (25%)	–   4–10 ml
Fluid Extract (25%)	–   1–2 ml
Powder	–   15 ml or three teaspoons daily as a laxative

CONTRAINDICATIONS—Cardiac problems, pregnancy, lactation and hyperthyroidism.

Precautions and/or safety

As Fucus is able to accumulate metals it can also accumulate toxic waste that may be in the surrounding seawater.33–35 In particular the existence of high levels of arsenic³⁶ are a potential source of concern and a case of nephrotoxicity linked to arsenic levels in Fucus tablets has been reported.³⁷ The herb should only be gathered from unpolluted waters and should be screened for toxic metals.

There is a report of an obese patient developing ventricular tachycardia/fibrillation after using a herbal preparation containing a mixture of dandelion, boldo and bladderwrack.³⁸

In excess it can, according to the BHC, cause hyperthyroidism, tremor, increased pulse rate and elevated blood pressure. The current safe level for iodine intake in the USA is 1000 micrograms a day.

Historical uses

Used externally for scrofula; scrofulous tumours; rickets; to strengthen limbs; enlarged or hardened glands.