GC-MS profiling and in vitro assessment of antioxidant and 5-lipoxygenase inhibitory activities of essential oils from five indigenous Hedychium species in Thailand

The genus Hedychium (Zingiberaceae) consists of rhizomatous aromatic plants widely utilized in Thai traditional medicine and cosmetic formulations. Although recognized ethnopharmacological, the phytochemistry and bioactivity of Thai Hedychium species have great potential for drug development. This study investigated the chemical profiles, in vitro antioxidant capacities, and in vittro 5-lipoxygenase (5-LOX) inhibitory activities of essential oils hydrodistilled from the fresh rhizomes of five Thai species—H. bousigonianum, H. coccineum, H. coronarium, H. ellipticum, and H. flavescens. Gas chromatography–mass spectrometry (GC–MS) analysis revealed distinct, species-specific chemotypes, characterized by α-eudesmol (37.41%) in H. bousigonianum; β-pinene (27.42% and 35.38%, respectively) in H. coccineum and H. flavescens; linalool (26.40%) in H. coronarium; and 1,8-cineole (89.36%) in H. ellipticum. The essential oils from the fresh rhizome of H. bousigonianum, H. coccineum, H. coronarium, H. ellipticum, and H. flavescens demonstrated antioxidant activity across multiple assays. Their free radical scavenging capacity was confirmed by the DPPH assay (IC₅₀ = 17.92 ± 0.62, 20.26 ± 0.53, 20.02 ± 0.89, 18.27 ± 0.60, and 22.12 ± 0.60 µg/mL, respectively) and the ABTS assay (IC₅₀ = 13.16 ± 0.95, 19.02 ± 0.43, 18.09 ± 0.34, 11.81 ± 0.67, and 19.34 ± 0.27 µg/mL, respectively). Similar trends were observed in the superoxide anion (IC₅₀ = 28.41 ± 0.64, 28.96 ± 0.51, 31.47 ± 0.58, 26.19 ± 0.61, and 29.12 ± 0.42 µg/mL, respectively) and hydroxyl radical assays (IC₅₀ = 26.67 ± 0.73, 27.98 ± 0.37, 28.92 ± 0.31, 25.34 ± 0.81, and 32.45 ± 0.55 µg/mL, respectively). Furthermore, the essential oils showed 5-LOX inhibitory activity (IC₅₀ = 57.32 ± 1.09, 67.50 ± 1.70, 60.31 ± 1.25, 55.84 ± 1.53, and 75.34 ± 2.28 µg/mL, respectively), supporting their potential anti-inflammatory properties. Notably, the essential oils from H. bousigonianum and 
H. ellipticum showed the most potent dual antioxidant and anti-inflammatory activities, highlighting their promise as natural sources of bioactive compounds for future pharmaceutical development.