Targeted Discovery of Anthranilic Acid-Based Alkaloids with Neuroprotective and Acetylcholinesterase Inhibitory Effects from Natural Indigo Plant (persicaria Tinctoria) Using DeepSAT Technology

Persicaria tinctoria, a commercially significant cultivated plant, represents the principal source of natural indigo dye and produces the pharmaceutically active metabolite indirubin. Herein, four undescribed anthranilic acid- based alkaloids, (+/-)-persicaritinctories A-C (1a/1b, 3 and 4) and six undescribed natural products (5-9 and 11), along with four known compounds (2, 10, 12 and 13), have been isolated from the leaves of Persicaria tinctoria under the guidance of HSQC-based DeepSAT technology. We elucidated these structures through comprehensive spectroscopic analyses, computer-assisted structure elucidation (CASE) with density functional theory (DFT) calculations, single-crystal X-ray diffraction analysis, and comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Furthermore, the plausible biosynthetic pathways for compounds 1a/1b and 3 were proposed. The isolated alkaloids were subsequently evaluated for their neuroprotective effects and acetylcholinesterase inhibitory activities. These findings not only enhance our understanding of the neuroprotective activity of anthranilic acid alkaloids but also highlight the potential of P. tinctoria for further pharmacological investigation and application development.