Both cacao and mandarin oil are known to be antioxidants!
Different scientific articles write about cocoa being is a natural antioxidant.
The antibacterial and antioxidant activities of essential oils from Bitter orange, Sweet orange, Lemon and Mandarin were investigated. Read more..
p.s.: If you wonder: the bioavailability of orally administered essential oils is very high: https://patents.google.com/patent/US5716928A/en