Annual variation in yield, chemical composition, antioxidant and antibacterial activity of rockrose (Cistus ladanifer L.) essential oils

The fluctuation in yield, composition, antibacterial and antioxidant activity of the essential oil (EO) of rockrose (Cistus ladanifer L.) obtained from two locations in central Spain was analysed and compared over the course of one year. Fifteen kilograms of C. ladanifer, collected monthly or fortnightly from two sites with different plant age (7 and 12 years), underwent steam-distillation. GC (FID)-MS analyses were done to determine the volatile profile of EOs. Obtained EO yields varied significantly (P < 0.001) throughout the year, ranging between 0.03 and 0.19% w/d.w. (±0.05) with the highest yields (>0.1%) observed from September to February. The younger population exhibited higher EO yields that the older one. Both rockrose populations displayed a high content of α-pinene (40.4–62.0%); the other predominant constituents included allo-aromadendrene + trans-pinocarveol, limonene, bornyl acetate and viridiflorol. The higher EO yields coincided with a higher content of α-pinene and a lower content of the other components. Furthermore, EOs' antibacterial potential was tested against Bacillus cereus. Only a weak antibacterial potency (512–1024 μg/mL) was revealed, with stronger potency in case of older rockrose population. In vitro antioxidant capacity, evaluated by ORAC method, showed similar results for both populations, with its stronger potential between February and May.