Variation in phytochemical profiles and anti-cholinesterase activity across wild Iranian populations of Leucojum aestivum L.: a conservation perspective

Leucojum aestivum L. (Amaryllidaceae) is a perennial bulbous species of high pharmaceutical importance, primarily recognized as a natural source of the alkaloid galantamine for Alzheimer’s disease treatment. Iranian L. aestivum populations (LAPs) may contain unique alkaloids with strong acetylcholinesterase (AChE) inhibitory effects, making them a conservation priority. To investigate phytochemical diversity and bioactivity, eight natural populations including LAP1 (Chahar Deh, Astaneh Ashrafieh); LAP2 (Baz Kia Gurab, Lahijan); LAP3 (Sangar); LAP4 (Chomesghal, Ziabar); LAP5 (Pinchah, Astaneh Ashrafieh); LAP6 (Chaboksar); LAP7 (Valiseh, Rudsar); and LAP8 (Vali Abad, Tonkabon) were sampled during the flowering stage. Galantamine, lycorine, total phenolic content (TPC), total flavonoid content (TFC), antioxidant capacity (FRAP and DPPH), and AChE inhibitory activity were quantified in bulbs and leaves. The highest AChE inhibition was recorded in bulbs of LAP6 (IC50: 95.57 µg/ml) and LAP7 (IC50: 102.38 µg/ml), corresponding to elevated galantamine levels (20.31 and 24.92 mg/g dry extract, respectively), which showed a strong positive correlation (r = 0.880, p < 0.01). In contrast, LAP8 contained no detectable galantamine in bulbs but exhibited exceptionally high leaf lycorine content (107.91 mg galanthamine equivalent/g dry extract) and antioxidant capacity (FRAP: 90.71 µmol Fe²⁺/g DW; DPPH, IC₅₀: 95.10 µg/ml), alongside moderate AChE inhibition (IC50: 150.80 µg/ml in bulbs, 231.63 µg/ml in leaves). Leaf TPC (8.57–13.39 mg GAE/g DW) consistently exceeded bulb TPC (0.18–7.59 mg GAE/g DW). Cluster analysis grouped populations into three distinct classes: balanced alkaloid levels and antioxidant power (LAP1, LAP5, LAP6), lower alkaloid levels (LAP2, LAP3, LAP4), and high phenolic content and antioxidant power with relatively elevated alkaloid levels (LAP7, LAP8). These findings demonstrated a strong linkage between alkaloid composition and bioactivity, highlighting the pharmaceutical potential of specific chemotypes and emphasizing the necessity of in situ conservation and ex situ cultivation for sustainable utilization and drug development targeting cholinesterase inhibition and antioxidant activity.