The Essential Oil of Citrus lumia Risso and Poit. ‘Pyriformis’ Shows Promising Antioxidant, Anti-Inflammatory, and Neuromodulatory Effects

Citrus lumia Risso and Poit. ‘Pyriformis’ are horticultural varieties of Citrus lumia Risso.
The fruit is very fragrant and pear-shaped, with a bitter juice, a floral flavor, and a very thick rind.
The flavedo shows enlarged (0.74 1.16 mm), spherical and ellipsoidal secretory cavities containing
the essential oil (EO), visible using light microscopy, and more evident using scanning electron
microscopy. The GC-FID and GC-MS analyses of the EO showed a phytochemical profile characterized
by the predominance of D-limonene (93.67%). The EO showed interesting antioxidant and
anti-inflammatory activities (IC50 0.07–2.06 mg/mL), as evaluated by the in vitro cell-free enzymatic
and non-enzymatic assays. To evaluate the effect on the neuronal functional activity, the embryonic
cortical neuronal networks grown on multi-electrode array chips were exposed to non-cytotoxic concentrations
of the EO (5–200 g/mL). The spontaneous neuronal activity was recorded and the mean
firing rate, mean burst rate, percentage of spikes in a burst, mean burst durations and inter-spike intervals
within a burst parameter were calculated. The EO induced strong and concentration-dependent
neuroinhibitory effects, with IC50 ranging between 11.4–31.1 g/mL. Furthermore, it showed an
acetylcholinesterase inhibitory activity (IC50 0.19 mg/mL), which is promising for controlling some
of the key symptoms of neurodegenerative diseases such as memory and cognitive concerns.