Biological and Chemical Studies on Extracts from Natural Plants and Maillard Reaction Systems

Medicinal plant extracts that contain antioxidant acitivity have been used to treat various diseases and have received much attention in recent years. The antioxidant activity of volatile extracts of teas prepared from mulberry (Morus alba L.) Camellia sinensis L., Cudrania tricuspidata (Carr.) Burea plant, and broccoli (Brassica oleracea L.) sprouts was examined using three antioxidant assays. All extracts exhibited antioxidant activity with a clear dose response in the aldehyde/carboxylic acid, the malonaldehyde/gas chromatography (MA/GC), 1-1-diphenyl-2-picrylhydrazyl (DPPH) assay. At the level of 500 mug/mL, they inhibited hexanal oxidation by 77.02 +/- 0.51% (stems of Burea plant), 52.57 +/- 0.92% (fermented tea of Camellia and stems of Mulberry tea), and 99.48 +/- 1.49% (broccoli sprouts) in the aldehydes/carboxylic acid assay. MA formation was also inhibited by 76.17 +/- 0.27% (roots of Burea plant) to 59.32 +/- 0.27% (stems of Mulberry tea) at the level of 160 mug/mL, and by 82% (broccoli sprouts) at the level of 500 mug/mL. The antioxidant activity of the extracts obtained from mulberry ( Morus alba L.) Camellia sinensis L., Cudrania tricuspidata (Carr.) Burea plant, and broccoli (Brassica oleracea L.) sprouts was comparable to those of known antioxidants, &agr;-tocopherol and BHT. Volatile extracts were analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC/MS) to identify the principal antioxidant(s). Among volatile compounds of teas prepared from mulberry (Morus alba L.) Camellia sinensis L., Cudrania tricuspidata (Carr.) Burea plant, eugenol, 2,5-dihydroxyl acetophenone, and isoeugenol exhibited antioxidant activity comparable to that of BHT in both assays. Fraction II of volatile extracts from broccoli sprouts inhibited hexanal oxidation by 96 % for up to 30 days at the level of 100 microg/ml used in the aldehyde/carboxylic acid assay which contained high levels of 4-methylpentylisothiocyanate, 4-methylthiobutylnitrile, 5-methylthiopentylnitrile, 3-methylthiopropylisothiocyanate, and 4-methylthiobutyl-isothiocyanate. The residual aqueous solutions from the steam distillation also exhibited antioxidant activity in the DPPH assay (58% at the level of 1000 mug/ml) and in the lipid/Ma assay (74% at the level of 500 mug/ml).;All Seven fractions obtained from rhubarb were investigated to determine emodin using high-performance liquid chromatography-diode array detection (HPLC-DAD) and then examined for antioxidant activity using MA/GC assays. Among the fractions, fraction VI showed very high antioxidant activity and contains the highest level of emodin. This fraction inhibited MA formation from cod liver oil by 75.4 +/- 13.7% at the level of 50 mug/mL, 92.8 +/- 0.6% at the level of 100 mug/mL, and 93.9 +/- 1.1% at the level of 500 mug/mL. The antioxidant activity of fraction VI was comparable to those of known antioxidants, &agr;-tocopherol and BHT. The positive relationship between emodin and antioxidant activity was observed.;Caramel color is one of the oldest and most widely used colorings for variety of foods and beverages. It is well known that the major reaction that occurs in a caramel model system is Maillard reaction. Amounts of carcinogenic 4(5)-methylimidazole (MI) formed from D-glucose/ammonia /sulfite Mallard model systems were analyzed by LC/MS and GC. The amount formed ranged from 7.0 to 155.0 ppm (LC/MS) and 28.56 to 1,269.71 mug/mL (GC) under various conditions. Addition of sodium sulfide reduced formation of 4(5)-MI significantly, suggesting that sulfite plays an important role in the formation of carcinogenic 4-MI in caramel color. Glyoxal, methylglyoxal, and diacetyl known as precursors of 4(5)-MI formed from sucrose alone and from the D-glucose/ammonia /sulfite Mallard model systems were analyzed by GC. Amounts of glyoxal, methylglyoxal, and diacetyl formed in Maillard model systems ranged from 2.98 to 46.12 mug/mL, from 8.27 to 156.61 mug/mL, and from 14.94 to 1,588.45 mug/mL, respectively. Addition of sodium sulfide also reduced formation of these chemicals significantly. Total &agr;-dicarbonyl compounds in 12 commercial soft drinks ranged from 5.75 to 50.72 mug/mL. 4(5)-MI was found in levels ranging from 1.76 to 28.11 mug/mL in 10 commercial soft drinks.