Abubidentin A, New Oleanane-type Triterpene Ester from Abutilon bidentatum and its antioxidant, cholinesterase and antimicrobial activities

Background: This work describes the phytochemical and biological investigation of aerial parts of Abutilon bidentatum Hochst. Of Saudi origin.

Methodology: Petroleum ether fraction of ethanolic extract A. bidentatum was fractionated on a silica gel column and further purified with different chromatographic procedures for the isolation of chemical compounds. The chemical structures of all the pure isolated compounds were elucidated by the interpretation of their spectral data using IR, UV, ¹H, ¹³C NMR, and MS spectroscopy and chemical methods (alkaline hydrolysis) as well as comparison with data reported in the literature. The extract and isolated compounds were evaluated for antioxidant, cholinesterase inhibitory, and antimicrobial activities.

Results: A new oleanane-type triterpene ester, namely abubidentin A (3) (α, 3β, 30-trihydroxy-29-carboxy-olean-9(11), 12-diene-3-dotriacontanoate), along with two known compounds: 2-hydroxydocosanoic acid (1) and stigmasta-22-ene-3-β-ol (2) were isolated from the aerial parts of Abutilon bidentatum Hochst. (Malvaceae). Concerning the biological potential, the abubidentinA displayed antioxidant, cholinesterase inhibitory and antimicrobial activities. AbubidentinA possessed strong antioxidant activity against DPPH and ABTS⁺ radical scavenging assays. This new triterpene exhibited high inhibition against acetylcholinesterase (IC₅₀ 38.13 ± 0.07 µgmL^-1) and butyrylcholinesterase (IC₅₀ 32.68 ± 0.37 µgmL^-1). Abubidentin A displayed promising antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus (125-150 µgmL^-1).

Conclusion: These findings suggest A. bidentatum can contribute as a source of new biologically active compounds, especially antioxidants and antimicrobial agents.