Author(s)

Borice T. Tsafack¹, Cyrille L. K. Bomgning², Jonas Kühlborn³, Romuald T. Fouedjou¹, Beaudelaire K. Ponou¹, Remy B. Teponno¹, Agathe L. Fotio⁴, Luciano Barboni⁵, Till Opatz³, Télesphore B. Nguelefack^2*, Léon A. Tapondjou^1*

¹Research Unit of Applied and Environmental Chemistry, Department of Chemistry, Faculty of Science, University of Dschang, Dschang, Cameroon.
²Research Unit of Animal Physiology and Phytopharmacology, Department of Animal Biology, Faculty of Science, University of Dschang, Dschang, Cameroon.
³Institute of Organic Chemistry, Johannes Gutenberg University Mainz, Mainz, Germany.
⁴Department of Zoology and Animal Physiology, Faculty of Science, University of Buea, Buea, Cameroon.
⁵School of Science and Technology, Chemistry Division, University of Camerino, Camerino, Italy.

Lipid peroxidation plays a pivotal role in the pathogenicity and maintenance of hepatitis. Thus, substances protecting hepatocyte membranes from lipid peroxidation are of great importance in the management of hepatotoxicity and hepatitis. The present work deals with the in vitro hepatoprotective activity of the methanol extract of Desmodium uncinatum, its sub-fractions, the major isolated compounds and some of their semi-synthetic derivatives in order to study structure activity relationships. Using hydrogen peroxide (H₂O₂)-induced lipid peroxidation of hepatocyte membranes as a model, the hepatoprotective-guided phytochemical survey of the methanol extract of aerial parts of D. uncinatum was carried out by successive column chromatography. One of the most active compounds (Isovitexin) was chemically transformed to yield new semi-synthetic. The identification of isolated and semi-synthetic compounds was performed using NMR techniques, mass spectrometry and by comparison of their data with those reported in the literature. The n-butanol fraction was the most effective (IC₅₀: 22.9 μg/mL) compared to the crude methanol extract (IC₅₀: 43.6 μg/mL) and other fractions. The n-butanol sub-fractions FA (containing non-phenolic compounds) and FB (mainly containing phenolic compounds) exhibited respective IC₅₀ of 14.36 and 128.2 μg/ml. Purification of FA yielded 3-O-β-D-glucopyranosyl-β-sitosterol (1), 3-O-β-D- 2-acetyl-amino-2-deoxyglucopyranoxyloleanoic acid (2), (2S, 3S, 4R, 7R, 8Z)-1-O-β-D-glucopyranosyl-2-[(R)-2'-hydroxyarachidoylamino]-docosan-8-ene-3,4,7-triol (4), spiraeamide (5), mannitol (6), while FB afforded essentially three C-glycosylflavonoids namely isovitexin (7), vitexin (8) and vicenin-3 (9). Chemical transformations (methylation, allylation and prenylation) of isovitexin afforded five new semi-synthetic derivatives: 4',5,7-O- trimethyli-sovitexin (10), 4'-O-allylisovitexin (11), 4',7-O-diallylisovitexin (12), 4'-O-prenylisovitexin (13) and 8-C-prenyl-4',7-O-diprenylisovitexin (14). The screening of these derivatives revealed that allylation did not significantly affect the hepatoprotective activity while methylation, prenylation, number and position of sugar moieties on the A ring of flavonoids significantly reduced it. Results demonstrated that the n-butanol fraction obtained from the methanol extract of Desmdium uncinatum may possess hepatoprotective activity due to its content in C-glycosylflavonoids and cerebrosides. Hydroxyl groups in C-glycosylflavonoids are important for their lipid peroxidation inhibitory activity.

Desmodium uncinatum, Hepatoprotective Activity, Lipid Peroxidation, Hepatocyte Membranes, C-glycosylflavonoids

Tsafack, B. , Bomgning, C. , Kühlborn, J. , Fouedjou, R. , Ponou, B. , Teponno, R. , Fotio, A. , Barboni, L. , Opatz, T. , Nguelefack, T. and Tapondjou, L. (2018) Protective Effects of Extracts, Isolated Compounds from Desmodium uncinatum and Semi-Synthetic Isovitexin Derivatives against Lipid Peroxidation of Hepatocyte’s Membranes. Advances in Biological Chemistry, 8, 101-120. doi: 10.4236/abc.2018.86009.