Chlorophyllphytolphytanic acid

Chlorophyll is the green pigment that enables plants to capture light for photosynthesis. Chlorophyll consists of a porphyrin ring with magnesium and the phytol side chain. Phytanic acid is a phvtol metabolite.

Abbreviations

CoA coenzyme A

MFP2 peroxisomal multifunctional protein 2 SCPx peroxisomal protein sterol carrier protein X

Phytanic acid

Figure 6.J8 Phytanic acid

Nutritional summary

Function: it lias been suggested that phytanic acid and other phytol metabolites specifically bind to RXR-likc receptors and participate in the regulation of the cell cycle.

Food sources: (ireen foods contain varying amounts of chlorophyll; the intensity of llic green coloration is a \ isual guide for the concentration. Plants also may contain significant amounts of phytol or phytanic acid. Dairy fat and meat fat from ruminants contain phytanic acid. Requirements: Not known.

Deficiency: No specific symptoms or chronic disease risk has been linked to low intake. Excessive intake There is no indication that high intake of chlorophyll or phytol with green foods or of phytanic acid w ith dairy or beef is harmful except in the rare indi-\iduals with genetically defective metabolism of phytanic acid (Refsum, Zellweger, and Sjogren-Larson syndromes).

Dietary sources

Foods contain various forms of chlorophyll and degradation products from which phytol can be released by bacterial action; the percentage of phytol generated during intestinal digestion of these compounds is presumed to be low (Avigan, 1966). Fresh spinach, one of the riches dietary sources of chlorophyll, contains about 7mg chlorophyll per gram dry weight (Anonymous, 1993).

Phytol is present in nuts, spinach, and coffee. Significant amounts (typically about 50-100 mg day) of the phytol metabolite phytanic acid (3,7.11,15-tetramethyl-hexa-decanoic acid both 3D- and 3L-isomers occur naturally) are consumed with a wide variety of foods (Steinberg, 1995). Sources with particularly high concentration include tuna in oil (0.57 mg/g dry matter), lamb (0.49 mg g dry matter) and other ruminant meat, and soya oil (0 14mg/g) (Masters-Thomas et a!., 1980).

A metabolite of phytanic acid, pristanic acid (2,6,10,14-letramethylpentadecanoie acid, both 2D- and 2L-isomers occur naturally), is present in some foods.

Another related compound is pristane (isoprcnoid alkane 2,6.l()J4-tetramelhyl-penladecane) which is a significant component (14%) of the unsaponifiablc fraction in shark liver oil.

Digestion and absorption

Food processing and digestion can convert chlorophyll into the derivatives pheophytin. pvropheophytin. and pheophorbide.

Phytanic and pristanic acid are nearly completely absorbed from the small intestine. Pancreatic lipase(FX"3.1.1.3land phospholipasesA2 (EC3.1J.4) and B (HC3.1.1.5) in the digestive tract release phytanic and pristanic acids from dietary triglycerides or other lipids, which arc then incorporated into mixed micelles. These micelles transfer their content into enterocytes through poorly understood mechanisms. Phytanic and pristanic acids can then be incorporated into triglycerides and other lipids and exported with chylomicrons, just like other long-chain fatty acids,

Transport and cellular uptake

Blood emulation: Phytanic acid is transported in all major lipoprotein classes and enters cells through receptor-mediated uptake; reverse transport from tissue deposits is thought to occur via HDL (Wierzbicki i 'tat.. IW).

Metabolism

Phytanic acid is metabolized mainly in liver and kidney, but not to a significant extent in hram, nerves, or muscles. Complete oxidation requires adequate supplies of ascorbate,

Phytanic acid

Phylanoyl-CoA ligase

(magnesium)

Phylanoyl-CoA ligase

(magnesium)

S-CoA

Phytanoyl-CoA

u-ketogl uta rate

Phytanoyl-CoA

Phytanoyl-CoA hydroxylase (ascorbate. iron)

u-ketogl uta rate succinate

2 - Hydroxypfiytanoy t-Co A

2 - H ycJrox yp h y t a noy I- C o A lyase (TPP. magnesium)

formyl-CoA

S-CoA

Prtstanal

ALDH3A2

NADH

Prístante acia

Phytanoyl-CoA hydroxylase (ascorbate. iron)

succinate

S-COA

2 - Hydroxypfiytanoy t-Co A

2 - H ycJrox yp h y t a noy I- C o A lyase (TPP. magnesium)

S-COA

J (ormyl Formate tetra hydrotolate tetrahydrotolaie "COH ligase (magnesium)

COOH

Figur* 6.3<f Omdarion of phytanic acid

(2Si-p™u™c acw imiCoA figüse i (magnesium) Ns.amp + PP

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