Essential oils (EOs) from Citrus sinensis (Rutaceae) possess diverse biological activities. However, a comprehensive comparison of their chemical composition and bioactivity across different plant parts has not been studied yet. The current research comparatively assesses the yield, chemical composition, chiral distribution, antioxidant properties, and larvicidal activity of EOs extracted from the peels, leaves, and flowers of C. sinensis. EOs extracted via hydro-distillation (HD) and steam distillation (SD) were analyzed by gas chromatography–mass spectrometry (GC-MS) and chiral GC-MS to explore their chemical composition and enantiomeric distribution. In addition, their larvicidal and antioxidant potentials were evaluated following standard protocols. Peels of C. sinensis exhibited significantly higher oil content (1.75–2.25%) compared to its leaves (0.75–0.78%) and flowers (0.20–0.25%). The GC-MS analysis identified around 60 compounds, including terpenoids, sesquiterpenoids, and oxygenated terpenoids in the HD and SD extractions. Higher concentrations of sabinene were found in flower extract (38.05–39.89%) and leaf extract (32.30–36.91%), while peel extract contained more than 90% limonene. The larvicidal activity of peel oil was primarily attributed to limonene, with an LC₅₀ value of 0.0031 µL/mL. The current study reports the first chiral (GC-MS) analysis in the essential oil of the leaves and flowers of C. sinensis, paving the way for authenticity and purity. Furthermore, the chemical profiling of citrus EOs, particularly from the peel, demonstrates a safe and promising candidate for diverse biological applications.

Nepal has the most unique and valuable medicinal plants, owing to its diverse climatic conditions. Plant extracts as traditional medicine provide primary health coverage for about 65-80% of the world’s population, especially in the developing world. However, very limited biological research has been done in Nepal to date. This research aims to evaluate the pharmacological activity of eight medicinal plants from Nepal namely Anaphalis triplinervis (Sims) C.B.Clarke, Chlorophytum arundinaceuum Baker, Curculigo orchioides Gaertn., Girardinia diversifolia (Link) Friis, Rhododendron anthopogon D. Don, Swertia racemosa (Griseb.) Wall. Ex C.B.Clarke and two lichen species Dolichousnea longissima (Ach.) Articus and Hypotrachyna cirrhata (Fr.) Divakar, A. Crespo, Sipman, Elix & Lumbschsp. The ethanolic extracts of these plants were prepared by cold extraction process after which acute oral toxicity, antidiarrhoeal and antiulcer activity were analysed. All laboratory works were done in Natural Products Research Laboratory, Thapathali, Kathmandu, Nepal. The acute oral toxicity study showed no morbidity, mortality, toxicity signs, or symptoms at 2000 mg kg 1 in all medicinal plants except H. cirrhata. In the anti-ulcer test, C. orchioides, D. longissima, G. diversifolia, H. cirrhata and R. anthopogon significantly reduced gastric lesions in the ethanol-induced ulcer model at 500 mg kg -1 when compared to the standard drug, sucralfate (100 mg kg -1). The antidiarrheal effect was evaluated by gastrointestinal motility test at 500 mg kg -1 body weight in mice where the extracts of H. cirrhata and S. racemosa showed considerable antidiarrheal effect by reducing GI motility significantly compared to their respective control and standard drug loperamide (2 mg kg -1).