From waste to bioactive resource: Differences in chemical composition and antimicrobial activity of cultivated Citrus sinensis (L.) Osbeck according to harvest period and extraction method

Globally, scientific studies focusing on the valorization of medicinal plant residues, including agricultural by-products, have received increasing attention. Citrus species are among the most widely cultivated and economically important plants due to their rich chemical composition and the broad range of biological activities. In this study, the chemical composition, yields, and biological activities of essential oils and extracts obtained from the leaves and branch tips of Citrus sinensis collected during two different periods were comparatively characterized using hydrodistillation and supercritical CO2 extraction, and the observed differences among the samples were described. The hydrodistillation yield of samples collected during the fruiting period (CMH) was 0.1%, whereas the supercritical CO2 extract (CMS) yield reached 0.5%. For pruning-period samples, the hydrodistillation yield (CBH) was 0.1%, while the supercritical extract (CBS) yield was 0.2%. GC–MS analysis showed that CMH mainly contained β-sinensal (20.9%), phytol (10.9%), β-caryophyllene (9.3%), and linalool (7.5%). CMS was rich in α-tocopherol (10.2%), α-amyrin (9.1%), β-sitosterol (6.9%), and phytol (5.2%). CBH was characterized by high amounts of sabinene (29.5%) and limonene (15.6%), whereas CBS predominantly contained α-amyrin (19.6%), α-tocopherol (10.0%), lupeol (8.0%), and phytol (7.7%). Minimum inhibitory concentration (MIC) analysis demonstrated that CMH and CMS exhibited better antimicrobial activity against the tested strains. While the CMH and CMS samples displayed the highest efficacy, the CBH and CBS also showed notable activity. Overall, the findings indicate that these agricultural waste materials have considerable potential for medicinal, industrial, and food-related applications due to their yield and chemical composition.