Biplot analysis of monthly variations in essential oil concentration and chemical composition of Pittosporum tobira leaves in Mediterranean conditions

Pittosporum tobira L. (P. tobira) leaves were tested for essential oil and chemical composition monthly for 12 months. Leaves had 0.12–0.25% essential oil depending on the month. January, December, and February leaves had the most essential oil (0.25–0.23%). Low temperatures increased volatile oil content, while high temperatures decreased it. P. tobira leaf volatile oil had 45 components. Sesquiterpenes were the most abundant terpene group (34.93%), with the highest concentrations in May (38.75%) and the lowest in January (30.50%). Alkanes followed (22.1%). This group's highest values (23.81%) were again found in May. Oxygenated sesquiterpenes had the highest September values (21.32%). When analyzed separately, viridiflorol (13.34%), nonane (11.48%), undecane (9.99%), α-pinene (6.59%), and α-cubebene (6.02%) were the main components. The volatile oil of P. tobira leaves had the highest viridiflorol (18.64%) in October and the highest nonane (13.79%) in February and December. June had the highest α-pinene (8.68%) and α-cubebene (7.88%) ratios. Thus, Mediterranean-grown P. tobira leaves had different volatile oil and volatile components each month. This plant's leaves should be studied in months with the highest volatile components.