Novel indole alkaloids from the flower buds of Panax vietnamensis var. fuscidiscus: Distribution in reproductive organs and integrated biological evaluation.

BACKGROUND: While the chemical constituents of flower buds from several Panax species have been reported, the phytochemical profile of the flower buds of Vietnamese ginseng remains understudied, particularly alkaloids. This study aimed to characterize alkaloids from the flower buds of Panax vietnamensis var. fuscidiscus (PVF), investigate their distribution across reproductive plant parts, and their biological relevance. METHODS: Flower buds were extracted with methanol, then fractionated by liquid-liquid partitioning and chromatography. Structures of isolated compounds were elucidated using NMR and MS. Their distribution in flower buds and various berry stages was analysed by HPTLC, HPLC/PDA, and UPLC-QToF-MS. Anti-bacterial activity was evaluated in vitro, and molecular docking with in silico ADMET analysis was conducted to explore potential targets and pharmacokinetic characteristics. RESULTS: Two novel indole alkaloids, panaxindolic acid and pyrindolic acid, with the known alkaloid panaxindole and tryptophan, were isolated. All identified alkaloids were detected in multiple reproductive parts, indicating a broad distribution. Docking simulations predicted strong binding of the isolated alkaloids toward monoamine oxidase B (MAO-B) through hydrogen bonding and π-π stacking with key residues, including CYS172 and TYR398. Although panaxindole exhibited limited anti-bacterial activity in vitro, computational analyses suggested potential interactions with bacterial DNA gyrase and the 30S ribosomal subunit. ADMET predictions indicated favorable pharmacokinetic profiles and low toxicity. CONCLUSION: This study presents the first systematic investigation of indole alkaloids from PVF flower buds and their distribution across reproductive organs. Although in vitro anti-bacterial activity of panaxindole was limited, in silico analyses highlight potential biological relevance to neurodegenerative disease-associated targets.