Comparative chemical composition, antioxidant activity and acetylcholinesterase inhibition of Citrus medica L. cv. Diamante and Citrus bergamia Risso

Cultivation of Citrus medica L. cv. Diamante and Citrus bergamia Risso species are limited to Calabria, Southern Italy. The n-hexane peel extracts of both species were analysed by GC-MS. The Diamante citron peel extract is characterized by the presence of four monoterpenes as main components: limonene, γ-terpinene, nerol and geraniol. The sesquiterpene fraction was less represented; the major constituents were β-bisabolene and α-bergamotene. The coumarin citropten was also found. C. bergamia peel was characterized by the presence of monoterpenes linalool, linalyl acetate, limonene, γ-terpinene, α-pinene and β-pinene and the coumarin bergaptene. Antioxidant activity was measured through the DPPH assay [2]. C. medica peel extract showed an IC₅₀ of 147µg/mL while low activity was found when C. bergamia peel extract was used. Inhibition of AchE was assessed by a modified colorimetric method of Ellman [4]. C. medica L. cv. Diamante peel extract exerted an interesting activity against AchE with an IC₅₀ of 621µg/mL. On the contrary the same extract obtained from C. bergamia showed less activity with IC₅₀ of 5.02mg/mL. Limonene, the most abundant compound of C. medica L. cv. Diamante peel extract, showed an inhibition of 22.6% at 1.2 mM.

References: [1] Conforti, F. et al. (2005) Biol. Pharm. Bull. 28: 1791. [2] Perry, N.S. et al. (1992) J. Pharm. Pharmacol. 52: 895.