Phytol

Phytol (florasol, phytosol) is an acyclic hydrogenated diterpene alcohol that is used as a precursor for the manufacture of synthetic forms of vitamin E and vitamin K1, as well as in the fragrance industry. Its other commercial uses include cosmetics, shampoos, toilet soaps, and detergents, as well as in some cannabis distillates as a diluent or for flavoring. Its worldwide use has been estimated to be approximately 0.1–1.0 metric tons per year.

Humans
Refsum disease (also known as adult Refsum disease) is an autosomal recessive disorder that results in the accumulation of toxic stores of phytanic acid in tissues and frequently manifests as a variable combination of peripheral polyneuropathy, cerebellar ataxia, retinitis pigmentosa, anosmia, and hearing loss. Although humans cannot derive phytanic acid from chlorophyll, they can convert free phytol into phytanic acid. Thus, patients with Refsum disease should limit their intake of phytanic acid and free phytol. The amount of free phytol in numerous food products has been reported.

Rats
It was found to cause pulmonary hemorrhage and necrosis of nose, throat and lung tissue when exposed in aerosol to Sprague Dawley rats, with no safe dose range being established. A majority of the phytol rats turned out dead or moribund, leading to 2nd-day termination of the 14-day study.

Other vertebrates
In ruminants, the gut fermentation of ingested plant materials liberates phytol, a constituent of chlorophyll, which is then converted to phytanic acid and stored in fats. In shark liver it yields pristane.

Controversy
In 2020, Tokyo Smoke, a Canadian cannabis company owned by Canopy Growth at the time; pulled every phytol-containing product from their shelves and issued a 48 hour deadline to suppliers, demanding 'written confirmation' if it was included. A year later, David Heldreth, a former CSO of True Terpenes, a company that still listed it as a product; along with Andrew Freedman, investigated the matter, filing a request under the Access to Information Act to unredact the study causing the product removals. In the same year, the Canadian government published an amendment to Canadian cannabis regulations regarding "flavours in cannabis extracts".

Roles in nature
Insects, such as the sumac flea beetle, are reported to use phytol and its metabolites (e.g. phytanic acid) as chemical deterrents against predation. These compounds originate from host plants.

Indirect evidence has been provided that, in contrast to humans, diverse non-human primates can derive significant amounts of phytol from the hindgut fermentation of plant materials.

Modulator of transcription
Phytol and/or its metabolites have been reported to bind to and/or activate the transcription factors PPAR-alpha and retinoid X receptor (RXR). The metabolites phytanic acid and pristanic acid are naturally occurring ligands. In mice, oral phytol induces massive proliferation of peroxisomes in several organs.

Possible biomedical applications
Phytol has been investigated for its potential anxiolytic, metabolism-modulating, cytotoxic, antioxidant, autophagy- and apoptosis-inducing, antinociceptive, anti-inflammatory, immune-modulating, and antimicrobial effects.

Geochemical biomarker
Phytol is likely the most abundant acyclic isoprenoid compound present in the biosphere and its degradation products have been used as biogeochemical tracers in aquatic environments.