Essential Oils From <i>Bougainvillea glabra</i> Stem Barks and Leaves: Chemical Profile, Biological Activity, and Computational Approaches

This study first investigates the chemical composition and biological activities of essential oils extracted from the stem barks and leaves of Bougainvillea glabra Choisy cultivated in Vietnam. The gas chromatography-mass spectrometry (GC-MS) analysis revealed cis-phytol as the major compound, especially in the leaf essential oil (75.5%). Both essential oils exhibited notable cytotoxicity against HepG2 cells, with the stem bark oil showing stronger effects. The samples also displayed significant antioxidant activity, xanthine oxidase (XO) inhibition, nitric oxide (NO) suppression, and enzyme inhibitory properties against α-glucosidase, protein tyrosine phosphatase 1B (PTP1B), and acetylcholinesterase (AChE), with the leaf oil generally outperforming the stem bark oil. B. glabra showed anti-inflammation via the inhibition of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions. Especially, the studied oils (IC₅₀ 198.43-227.18 µg/mL) are better than the standard acarbose (IC₅₀ 241.76 µg/mL) against the α-glucosidase enzyme. Antimicrobial assays revealed moderate inhibition of two samples against both Gram (+) and Gram (-) bacteria, but limited antifungal activity. The findings were further supported by computational analyses. Molecular docking and toxicity prediction of the three major oil constituents, linalool, cis-phytol, and neophytadiene, revealed notable binding affinities to α-glucosidase and favorable safety profiles.