Positive effect of some cannabinoids in the treatment and prophylaxis of a wide variety of oxidation-associated diseases and growing popularity of supplements containing cannabinoids, mainly cannabinoid oils (e.g. CBD oil, CBG oil), in the self-medication of humans cause a growing interest in the antioxidant properties of these compounds, especially those not showing psychotropic effects. Herein, we report the antioxidant activity of cannabigerol (CBG), cannabidiol (CBD), Δ9-tetrahydrocannabinol (Δ9-THC), cannabinol (CBN), cannabigerolic acid (CBGA), cannabinolic acid (CBDA) and Δ9-tetrahydrocannabinolic acid (Δ9-THCA) estimated by spectrophotometric methods: ABTS, DPPH, ORAC, beta-carotene CUPRAC and FRAP. The presented data prove that all the examined cannabinoids exhibit antioxidant activity manifested in their ability to scavenge free radicals, to prevent the oxidation process and to reduce metal ions. Although the intensity of these activities is not the same for the individual cannabinoids it is comparable for all of them with that of E vitamin. As results from the research, the significance of the two types of electron sources presenting in examined cannabinoids, phenolic groups and double bonds transferring electrons, depends on the type of electron-accepting species - radicals/metal ions.

Negative impact of radicals on humans and animals is responsible for growing research interest in antioxidant properties of substances, which protect living organisms from the damaging influence of these reactive species. Among numerous methods for antioxidant activity estimation, DPPH and ABTS are the most popular and commonly used ones due to their ease, speed, sensitivity and the usage of stabile radicals. The paper shows and discusses the antioxidant properties of a few compounds exhibiting different extinction of the wavelength used to monitor colored radical depletion in spectrophotometric measurements—e.g. 516 and 744 nm in DPPH and ABTS assays, respectively. As results from the presented data, the difference between true and spectrophotometrically estimated IC₅₀ values for colored antioxidants depends not only on extinction coefficient of the monitored wavelength by the antioxidant but also on its remaining concentration in the measuring system. The presented results seems to be helpful for the researches examining coloured antioxidants and plant extracts containing substances having spectra in Vis region.