Major Sesquiterpenoids in <i>Psychotria laui</i> Leaf Essential oil Exhibit Anti-Inflammatory and Cytotoxic Properties

Objective: This study aims to investigate the chemical constituents and biological properties of the essential oil derived from Psychotria laui, a plant recognized for its medicinal applications, particularly in traditional Vietnamese medicine, where it is utilized for the treatment of digestive and inflammatory disorders. Methods: Fresh leaves of Psychotria laui were gathered in Quangtri, Vietnam, and subjected to hydro-distillation using a Clevenger-type apparatus to obtain the essential oil. The chemical composition of the essential oil was analyzed by gas chromatography-mass spectrometry (GC-MS). The antioxidant potential was measured using the DPPH (2,2-Diphenyl-1-picrylhydrazyl) assay, while the inhibition of nitric oxide production was tested in lipopolysaccharide-stimulated RAW264.7 cells. Cytotoxicity against the SK-LU-1 cell line (human lung adenocarcinoma) was evaluated using the sulforhodamine B (SRB) assay. Results: The essential oil from Psychotria laui contained 78 distinct constituents. The major compounds identified were spathulenol (10.4%), thujopsan-2- α-ol (9.5%), 7- epi- α-eudesmol (6.5%), 14-hydroxy-9- epi-( E)-caryophyllene (4.4%), epi- α-cadinol (3.9%), α-muurolol (3.8%), 1- epi-cubenol (3.5%), and δ-cadinene (3.2%). The essential oil showed no antioxidant activity, with an IC 50 (half-maximal inhibitory concentration) value greater than 500 µg/mL, in contrast to the positive control, L-ascorbic acid, which had an IC 50 of 7.78 ± 0.39 µg/mL in the DPPH assay. However, its anti-inflammatory activity was evident by its ability to inhibit nitric oxide production, with an IC 50 of 19.48 ± 1.53 µg/mL in lipopolysaccharide-stimulated RAW264.7 macrophages. Moreover, the essential oil exhibited potent cytotoxicity against the SK-LU-1 cancer cell line, with an IC 50 of 8.49 ± 0.73 µg/mL in the SRB assay. Conclusion: The essential oil from Psychotria laui leaves contains numerous bioactive compounds and exhibits significant anti-inflammatory and cytotoxic properties, although it lacks antioxidant activity.