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Alkenyl cyclohexanone derivatives from Lannea rivae and Lannea schweinfurthii

Yaouba, Souaibou, Koch, Andreas, Guantai, Eric M., Derese, Solomon, Irungu, Beatrice, Heydenreich, Matthias, Yenesew, Abiy
Phytochemistry letters 2018 v.23 pp. 141-148
Escherichia coli, Lannea, Staphylococcus aureus, antibacterial properties, bark, beta-sitosterol, catechin, cell lines, cyclohexanones, cytotoxicity, epicatechin, inflammation, lupeol, mammals, mass spectrometry, nuclear magnetic resonance spectroscopy, phenols, prostatic neoplasms, roots
Phytochemical investigation of the CH2Cl2/MeOH (1:1) extract of the roots of Lannea rivae (Chiov) Sacleux (Anacardiaceae) led to the isolation of a new alkenyl cyclohexenone derivative: (4R,6S)-4,6-dihydroxy-6-((Z)-nonadec-14′-en-1-yl)cyclohex-2-en-1-one (1), and a new alkenyl cyclohexanol derivative: (2S*,4R*,5S*)-2,4,5-trihydroxy-2-((Z)-nonadec-14′-en-1-yl)cyclohexanone (2) along with four known compounds, namely epicatechin gallate, taraxerol, taraxerone and β-sitosterol; while the stem bark afforded two known compounds, daucosterol and lupeol. Similar investigation of the roots of Lannea schweinfurthii (Engl.) Engl. led to the isolation of four known compounds: 3-((E)-nonadec-16′-enyl)phenol, 1-((E)-heptadec-14′-enyl)cyclohex-4-ene-1,3-diol, catechin, and 1-((E)-pentadec-12′-enyl)cyclohex-4-ene-1,3-diol. The structures of the isolated compounds were determined by NMR spectroscopy and mass spectrometry. The absolute configuration of compound 1 was established by quantum chemical ECD calculations. In an antibacterial activity assay using the microbroth kinetic method, compound 1 showed moderate activity against Escherichia coli while compound 2 exhibited moderate activity against Staphylococcus aureus. Compound 1 also showed moderate activity against E. coli using the disc diffusion method. The roots extract of L. rivae was notably cytotoxic against both the DU-145 prostate cancer cell line and the Vero mammalian cell line (CC50=5.24 and 5.20μg/mL, respectively). Compound 1 was also strongly cytotoxic against the DU-145 cell line (CC50=0.55μg/mL) but showed no observable cytotoxicity (CC50>100μg/mL) against the Vero cell line. The roots extract of L. rivae and L. schweinfurthii, epicatechin gallate as well as compound 1 exhibited inhibition of carageenan-induced inflammation.