Human TRPA1 activation by terpenes derived from the essential oil of daidai, Citrus aurantium L. var. daidai Makino

Abstract

Daidai (bitter orange, Citrus aurantium) is characterized by its fresh citrus scent. In Japanese cuisine, its juice is an important ingredient. As tons of industrial waste is obtained while processing the daidai juice, additional utilization of this waste has great social value. In our study, we prepared the essential oil from the waste obtained during daidai juice processing and demonstrated that the oil activates human TRPA1 (hTRPA1). This oil contains 10 types of terpenes, all of which activated hTRPA1 with an EC50 value of 6–167 µM. To our knowledge, this study is the first to show a hTRPA1 activation by five terpenes: linalyl acetate, geranyl acetate, osthole, geranyl propionate, and neryl acetate. Because physiological benefits of TRPA1 agonists, such as enhancement of energy metabolism and promotion of skin barrier recovery, have been reported, the oil could be a promising ingredient for anti-obesity food products and cosmetics.

Selected essential oils and their mechanisms for therapeutic use against public health disorders. An overview

“…In previous studies its agonists showed improvement of energy metabolism. All these results suggest that BOEO could be an agent with good prospects for obesity therapy, although further studies are needed to verify this assumption [40]. Further TRP channel activities from EOs are known for cinnamon-oil (cinnamaldehyde: TRPA1 agonist), clove-oil (eugenol: TRPV1-, TRPA1-, and TRPM8-agonist), and eucalyptus-oil (1,8-cineole: TRPM8 agonist, TRPA1 antagonist) [41,42].…”

Possible Use of Phytochemicals for Recovery from COVID-19-Induced Anosmia and Ageusia

“…For example, TRPA1 (transient potential channel ankyrin 1) (curcumin, cinnamaldehyde, nicotine, linalool, eugenol, and others), TRPV1 (transient potential channel vanilloid 1) (capsaicin, eugenol, camphor, gingerol, vanillin and others), TRPM8 (transient receptor potential melastatin) (1,8-cineole (eucalyptol), menthol), and TRPC6 (transient receptor potential canonical) (hyperforin) are activated by the chemical compounds shown here in parentheses [296]. The essential oil of Citrus aurantium (bitter orange, or daidai) activates TRPA1 [297]. Of the ten major chemical constituents, (+)-Limonene was included the most (over 95%), and osthole had the strongest effect in activating TRPA1.…”

“…Of the ten major chemical constituents, (+)-Limonene was included the most (over 95%), and osthole had the strongest effect in activating TRPA1. Other major chemical constituents were linalyl acetate, linalool, (+)-carvone, (−)-carvone, geranyl acetate, osthole, geranyl propionate, neryl acetate, and citral, and they all activated TRPA1 although not as strongly as osthole [297]. TRPA1 (transient receptor potential Ankyrin 1) is the only member of the TRPA sub-family of TRPA subfamily, and it is expressed in both the central and peripheral nervous systems as well as in various extra-neuronal tissues [298].…”

TRPA1 in obesity and insulin resistance

“…For example, sesquiterpene isovelleral, polygodial, miogadial and miogatrial activates TRPA1. α-, β-eudesmol and γ-eudesmol are nonelectrophilic sesquiterpenes which also activates TRPA1 channel (Escalera, Von Hehn et al, 2008;Ohara et al, 2017;Terada et al, 2019). In a recent report by Terada et al .…”

“…Out of the total 10 terpenes tested, they found that 5 of them (linalyl acetate, geranyl acetate, osthole, geranyl propionate, and neryl acetate) activate human TRPA1 but not TRPV1 or TRPM8. This study was done using transfected cell line which requires further validation (Terada et al. 2019).…”