IN SILICO SCREENING OF SUNFLOWER (HELIANTHUS ANNUUS L.) BY- PRODUCT METABOLITES AGAINST HUMAN ACETYLCHOLINESTERASE AND BUTYRYLCHOLINESTERASE

VIII. INTERNATIONAL AGRICULTURAL, BIOLOGICAL, LIFE SCIENCE CONFERENCE, İstanbul, Türkiye, 7 - 09 Eylül 2026, ss.798-799, (Özet Bildiri)

Sunflower (Helianthus annuus L.) is the principal oilseed crop of the Thrace region, and its

leaves, stems and receptacles are discarded during oil extraction although they contain a range

of phenolic and terpenoid metabolites. This study screened sunflower by-product metabolites

for binding to human acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and

examined their physicochemical suitability for central nervous system exposure. Eighteen

metabolites with documented occurrence in sunflower by-product tissues were selected from

the published phytochemical literature: receptacle flavones (hispidulin, jaceosidin, cirsiliol,

pectolinarigenin, scrophulein, isoquercitrin), leaf sesquiterpenoids (heliannuols A, C and D),

diterpene acids (kaurenoic, grandifloric and trachylobanoic acids), caffeoylquinic acids (3,4-

and 3,5-di-O-caffeoylquinic acids, cynarin), tambulin, β-amyrin and stigmasterol. Structures

were retrieved by PubChem CID, verified by InChIKey and assigned ionisation states at pH

7.4. Five reference cholinesterase inhibitors were included as scale references. Docking was

performed with AutoDock Vina 1.2.7 (exhaustiveness 32, three independent seeds) against

AChE (PDB 4EY7, 2.35 Å) and BChE (4BDS, 2.10 Å). To keep the two search spaces

comparable, the enzymes were superimposed (53.5% sequence identity; 1.01 Å RMSD over

493 Cα) and the crystallographic donepezil centroid of 4EY7 was transformed into the BChE

coordinate frame; the transferred centre lay 5.6 Å from the crystallographic tacrine of 4BDS.

Redocking reproduced the tacrine pose in BChE as the top-ranked solution (0.50 Å RMSD);

for donepezil in AChE the near-native pose was sampled but ranked third (1.55 Å). Predicted

binding energies for the sunflower metabolites ranged from −6.59 to −11.68 kcal/mol at AChE

and from −6.12 to −10.76 kcal/mol at BChE, with seed-to-seed variation not exceeding 0.32

kcal/mol. The strongest predicted binding at AChE was obtained for 3,5-di-O-caffeoylquinic

acid (−11.68), cynarin (−10.88) and pectolinarigenin (−10.75); the reference drug donepezil

scored −11.85. Physicochemical assessment using criteria for central nervous system exposure,

under which four of the five reference drugs qualified, admitted five of the eighteen metabolites:

pectolinarigenin, scrophulein and heliannuols A, C and D. The anionic diterpene and

caffeoylquinic acids, the glycosylated flavonol isoquercitrin, and the triterpene and phytosterol

fractions fell outside these criteria, as did the more hydroxylated receptacle flavones. The five

qualifying metabolites occupied positions 3, 8, 16, 17 and 18 of eighteen in the affinity ranking,

pectolinarigenin combining the third strongest predicted binding with a profile within the

applied limits. Differences between AChE and BChE scores were negative for sixteen of

eighteen metabolites and showed no dependence on molecular weight (r² = 0.027). Within these

limits, predicted binding strength and physicochemical suitability were distributed differently

across the compound classes examined, and the methylated receptacle flavones,

pectolinarigenin in particular, merit further evaluation.

Keywords: Helianthus annuus L., sunflower by-products, molecular docking, cholinesterases,

pectolinarigenin