Antioxidant and Photoprotective Activity of a Lipophilic Extract Containing Neolignans from Krameria triandra Roots

Abstract

The antioxidant/photoprotective potential of a standardized Krameria triandra (KT) root extract (15 % neolignans) has been evaluated in different cell models, rat erythrocytes and human keratinocytes cell lines, exposed to chemical (cumene hydroperoxide, CuOOH) and physical (UVB radiation) free radical inducers. The extract was significantly more active (IC₅₀ 0.28 ± 0.04 μg/ml) than the typical chain-breaking antioxidant α-tocopherol (IC₅₀ = 6.37 ± 0.41 μg/ml) in inhibiting the CuOOH-induced hemolysis in rat blood cells. The KT constituent 2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran, was the most active (IC₅₀ = 0.03 ± 0.005 μg/ml), followed by eupomatenoid 6 (IC₅₀ = 0.29 ± 0.06 μg/ml) and conocarpan (IC₅₀ = 0.77 ± 0.08 μg/ml). The same order of potency was observed in red blood cells exposed to UVB irradiation in continuo, with IC₅₀ values 0.78 ± 0.08 μg/ml for KT extract, 0.18 ± 0.02 μg/ml for 2-(2,4-dihydroxyphenyl)-5-(E)-propenylbenzofuran, 0.95 ± 0.11 μg/ml for eupomatenoid 6, and 3.8 ± 0.39 μg/ml for conocarpan. In cultured human keratinocytes exposed to UVB radiation (50 mJ/cm²), KT extract (2.5-20 μg/ml) significantly and dose-dependently restrained the loss in cell viability and the intracellular oxidative damage: glutathione (GSH) depletion and the rise in dichlorofluorescein (DCF), marker of peroxide accumulation, were suppressed by 20 μg/ml KT and in parallel cell morphology maintained. The cytoprotective effect of the extract was confirmed in a more severe model of cell damage: exposure of keratinocytes to higher UVB doses (300 mJ/cm²), which induce a 50 % cell death. In keratinocyte cultures supplemented with 10 μg/ml, cell viability was almost completely preserved and more efficiently than with (-)-epigallocatechin 3-gallate and green tea. The results of this study indicate the potential use of Rhatany extracts, standardized in neolignans, as topical antioxidants/radical scavengers against skin photodamage.

Key words

Krameria triandra - Krameriaceae - Rhatany - neolignans - erythrocytes - keratinocytes cell lines - antioxidant activity - photoprotection

References

• 1 Scholz E, Rimpler H. Proanthocyanidins from Krameria triandra Roots.  Planta Medica. 1989;  55 379-84
• 2 Arnone A, Di Modugno V, Nasini G. Isolation and structure determination of new neolignans and norneolignans from Rhatany.  Gazzetta Chimica Italiana. 1988;  118 675-82
• 3 Maffei Facino R, Carini M, Aldini G, De Angelis L. A rapid screening by liquid chromatography/mass spectrometry and fast atom bombardment mass spectrometry of phenolic constituents with radical scavenging activity from Krameria triandra roots.  Rapid Communications in Mass Spectrometry. 1997;  11 1303-8
• 4 De Bellis P, Griffini A, Peterlongo F. Identification of the main neolignan constituents of Rhatany (Krameria triandra roots) by HPLC-MS and GC-MS.  Fitoterapia. 1994;  65 503-14
• 5 Maffei Facino R, Carini M, Aldini G, Calloni M T, Bombardelli E, Morazzoni P. Sparing effect of procyanidins from Vitis vinifera on vitamin E : in vitro studies.  Planta Medica. 1998;  64 343-7
• 6 Carini M, Adini G, Bombardelli E, Morazzoni P, Maffei Facino R. UVB-Induced hemolysis of rat erythrocytes: protective effect of procyanidins from grape seeds.  Life Sciences. 2000;  67 1799-814
• 7 Carini M, Aldini G, Piccone M, Maffei Facino R. Fluorescent probes as markers of oxidative stress in keratinocyte cell lines following UVB exposure.  Il Farmaco. 2000;  55 526-34
• 8 Tebbe B, Wu S, Geilen C C, Eberle J, Kodeljia V, Orfanos C E. L-Ascorbic acid inhibits UVA-induced lipid peroxidation and secretion of IL-1α and IL-6 in cultured human keratinocytes in vitro .  Journal of Investigative Dermatology. 1997;  108 302-6
• 9 Markwell M A, Haas S M, Tolbert N E, Bieber L L. Protein determination in membrane and lipoprotein samples: manual and automated procedures.  Methods in Enzymology. 1981;  72 296-303
• 10 Maffei Facino R, Carini M, Aldini G, Calloni M T. Hidroxynimesulide, the main metabolite of nimesulide, prevents hydroperoxide/hemoglobin-induced hemolysis of rat erythrocytes.  Drugs under Experimental and Clinical Research. 1997;  23 157-65
• 11 Mukhtar H, Katiyar S K, Agarwal R. Green tea and skin anticarcinogenic effects.  Journal of Investigative Dermatology. 1994;  102 3-7
• 12 Ahmad N, Mukhtar H. Green tea polyphenols and cancer: biological mechanisms and practical implications.  Nutrition Reviews. 1999;  57 78-83