Phytyl fatty acid esters (PFAE) are esters of fatty acids with the isoprenoid alcohol phytol (3,7R,11R,15-tetramethylhexadec-2E-enol). In this study, PFAE were identified and quantified in bell pepper using gas chromatography with mass spectrometry (GC-MS). All red (n = 14) and yellow (n = 6) samples contained six or seven PFAE at 0.9-11.2 mg/100 g fresh weight. By contrast, PFAE were not detected in green bell pepper samples (n = 3). PFAE might eventually be a source for bioavailable phytol, which can be transformed into phytanic acid by humans. Phytanic acid cannot be properly degraded by patients who suffer from Refsum's disease (tolerable daily intake (TDI) ≤ 10 mg of phytanic acid). The phytol moiety of the PFAE (0.4-5.4 mg/100 g fresh weight) would contribute up to ∼50% to the TDI with the consumption of only one portion of bell pepper fruit pulp.

Patients suffering from Refsum’s disease show mutations in the enzyme necessary for the degradation of phytanic acid. Accumulation of this tetramethyl-branched fatty acid in inner organs leads to severe neurological and cardiac dysfunctions which can even result in death. Thus, patients with Refsum’s disease have to follow a specific diet resigning foods with high levels of phytanic acid and trans-phytol like products from ruminant animals with a tolerable daily intake (TDI) of ≤ 10 mg/d. We recently reported the occurrence of phytyl fatty acid esters (PFAE, trans-phytol esterified with a fatty acid) in bell pepper with trans-phytol amounts of up to 5.4 mg/100 g fresh weight (FW). In this study we carried out in vitro-digestion experiments of PFAE with artificial digestion fluids. Our results demonstrate that PFAE actually are a source for bioavailable trans-phytol and thus add to the TDI. Eating only one portion of bell pepper (∼150 g) could therefore lead to exploitation of the TDI of up to 81%. Analysis of additional vegetable matrices showed that also rocket salad with up to 4.2 mg/100 g FW trans-phytol bound in PFAE represents a risk-relevant food for patients with Refsum’s disease and should therefore be taken into account.

Tocopheryl fatty acid esters (TFAE) consist of tocopherols esterified to fatty acids, but only little is known about this substance class. In this study, twelve vegetable groups were screened on TFAE and contents of (free) tocopherols and TFAE were determined in red bell pepper, red chili pepper, cucumber and walnut (n = 5, respectively). Intact TFAE were separated by solid phase extraction from free tocopherols and analyzed by GC/MS. Highest TFAE values were determined in chili pepper (4.0–16 mg/100 g fresh weight, FW) and walnut (4.1–12 mg/100 g FW), followed by bell pepper (1.3–1.5 mg/100 g FW) and cucumber (0.06–0.2 mg/100 g FW). Contribution of TFAE to the total tocopherol content ranged from 7–84%. Neither the treatment with artificial digestion juices nor exposure to sunlight showed degradation of TFAE. This substance class might represent a hitherto overlooked storage form for free tocopherols in plants as they occur to be more stable. But as the ester bond in medium chain TFAE seems not to be fissile in the human body, they might not contribute in the same way as free tocopherols to the vitamin E activity of vegetables and might have to be determined separately.

Bell pepper is one of the most cultivated crops in the world. By means of δ 13 C and δ 15 N values (‰), red bell peppers from Germany, The Netherlands, and Spain could be distinguished from each other. German fruits cultivated under greenhouse conditions were extremely depleted in 13 C with δ 13 C values for fatty acids of partly less than −50‰. The strong depletion in 13 C was in accordance with the use of biomethane-derived CO 2 as growth regulator in the greenhouses. Seasonal variations in the δ 13 C values (‰) of German samples were tentatively assigned to varying CO 2 enrichment during the annual production cycle. δ 13 C values (‰) of Dutch samples also correlated with greenhouse production, whereas Spanish samples most likely originated from open field cultivation. Additionally, the use of color measurement as a tool for presorting the samples was investigated in order to slim the scattering ranges of δ 13 C and δ 15 N values (‰) for clearer differentiation.

Phytyl fatty acid esters (PFAE) are long chain isoprenoid esters consisting of phytol esterified to fatty acids. Phytol, which is mainly known as side chain of the plant pigment chlorophyll, is released during chlorophyll breakdown. PFAE mainly function as storage forms for free phytol to protect plant cells as phytol shows membrane toxic properties. Surprisingly, only scattered data on PFAE can be found in the literature. For instance, PFAE are known to occur in mosses, selected leaves of higher plants, and also in some fruits and vegetables. As PFAE seem to be fissile in the human body, their phytol moiety is bioavailable and can be converted into phytanic acid. Patients with Refsum's disease cannot metabolize phytanic acid and accumulate it in blood and organs with severe consequences. For treatment, patients must keep a special diet avoiding foods with high amounts of phytanic acid or free phytol with the tolerable daily intake being ≤10 mg. In addition, PFAE in fruits and vegetables directly add to the intake of phytol or rather phytanic acid. Therefore, their contents must be taken into account regarding dietary recommendations. This review summarizes the literature data on occurrence, concentrations, and analytical methods for the determination of PFAE. Practical application: The data provided give an overview of matrices containing PFAE which also include edible plant parts. This information can help improving the life quality of patients suffering from Refsum's disease. Additionally, a summary of different analytical methods for the determination of PFAE is presented which will hopefully encourage further research on this class of esters. Phytyl fatty acid esters (PFAE) are long chain isoprenoid esters consisting of trans‐phytol esterified with fatty acids. They are reported to occur in several mosses and algae, in leaves of some higher plants as well as in selected fruits and vegetables. In contrast to chlorophyll, PFAE are found to be a potential source for bioavailable trans‐phytol. Free trans‐phytol is known as a precursor for phytanic acid which cannot be metabolized by patients with Refum's disease. Hence, edible plant parts with elevated PFAE levels add to the daily tolerable intake of phytanic acid for these patients. This review gives an overview of occurrence, variability, and contents of PFAE and summarizes various analytical methods for their determination.