Phytyl fatty acid esters in vegetables pose a risk for patients suffering from Refsum’s disease

Abstract

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.

Phytol and Phytyl Fatty Acid Esters: Occurrence, Concentrations, and Relevance

“…The fact that PFAE were detected in ripe red and yellow bell pepper but not in unripe green ones led to the assumption that the esterified phytol was also derived from chlorophyll breakdown due to the turnover of chloroplasts into chromoplasts during ripening . However, this was in contrast to the finding, that only unripe green olives but not ripe black ones contained PFAE and thus another yet unknown factor may be involved in the formation of PFAE …”

“…Due to the high fat content of olives (≈14%), the concentration of PFAE in olives was rather high (up to 7.5 mg/100 g olives). Yet, another study of Krauß et al found much lower PFAE levels in unripe green olives (≈0.09 mg/100 g) while PFAE were not detected in ripe black ones (of different origins).…”

“…Red and yellow bell pepper featured phy‐16:0, phy‐18:0, phy‐20:0, phy‐21:0, phy‐22:0, phy‐23:0, and phy‐24:0 at 1–11 mg/100 g fresh weight (FW) . Other vegetables which contained PFAE in their edible parts were cucumber (0.02–0.04 mg PFAE‐derived phytol per 100 g FW), carrots (0.02–0.06 mg PFAE‐derived phytol per 100 g FW), grapes (0.05–0.07 mg PFAE‐derived phytol per 100 g FW), rocket salad (2.2–4.2 mg PFAE‐derived phytol per 100 g FW), and chili pepper (0.7–2.4 mg PFAE‐derived phytol per 100 g FW) . For these matrices and for olives, the phytol moiety derived from PFAE was determined after saponification …”

“…Additionally, focused open‐vessel microwave assisted extraction in combination with a water trap was found particularly suitable for the lipid extraction of vegetable matrices for the water bound in the plant cells is driven out gently during the extraction. Thus, it allowed the lipids to be extracted without the necessity to dry the samples first …”

“…Only recently, however, it was discovered that PFAE might be a source for bioavailable phytol. In an in vitro‐digestion experiment the lipid extract of red bell pepper containing PFAE as well as a synthesized PFAE standard was treated with artificial digestion fluids . Hereby, the different steps of human digestion were simulated by adding artificial saliva, gastric juice, intestinal juice, and bile one after another.…”