Phytochemical Analysis, Antiproliferative, Antibacterial, Antifungal, and Antiviral Activities of Bitter Orange (citrus Aurantium) Leaf Essential Oil

The young and old leaves of bitter orange (Citrus aurantium) were examined for their essential oil (EO) compositions, anticancer, antimicrobial, and antiviral activities. The EO yields were 0.77% in young leaves and 0.26% in old leaves. The EO composition showed the predominance of sabinene (37.17%), E-beta-ocimene (8.21%), delta-3-carene (7.71%), linalool (7.35%), and limonene (5.43%) in young leaves while of sabinene (47.47%), beta-sinensal (5.71%), E-beta-ocimene (4.98%), delta-3-carene (4.11%), and beta-caryophyllene (4.06%) in old leaves. The EOs of both young and old leaves showed potent cytotoxic activities against human lung carcinoma (A549) and colon adenocarcinoma (DLD-1) cells with IC50 < 0.1 g/mL. The young leaf EO had higher antibacterial activity than the old leaf EO for all bacterial strains with inhibition zones (IZ) varying from 17 to 45 and 8 to 36 mm, respectively. The EOs of both young and old leaves had strong antifungal activity against all fungal strains with IZ = 90 mm. The young leaf EO was found to be the most active in protecting cells against Herpes simplex virus type-1 (HSV-1) infection during the protection, absorption, and direct periods as compared to the untreated and treated Vero cells except the replication phase.