Abstract
Phenolic compounds were extracted from lentil seeds using three solvent systems: 80% (v/v) acetone, 80% (v/v) methanol, and 80% (v/v) ethanol. Each extract was subsequently separated into two fractions by chromatoghraphy on a column with Toyo Pearl HW-40 using water (fraction I) and methanol (fraction II) for elution. Antioxidative activity of extracts and their respective fractions were examined in a β-carotene-linoleate model system. All three extracts exhibited similar antioxidant activity. Considering the level of phenolic compounds in extracts it seems that phenolic compounds from the acetone extract were less active than those from either the methanolic and ethanolic ones. Because the content of phenolics was about 16-fold lower in fraction I of the methanolic and ethanolic extracts compared to fraction II, the phenolics in fraction I of the methanol and ethanol extracts from lentil seeds are much more active than these in fraction II. A stronger antioxidant activity of fraction I from the acetone extract compared to the crude acetone extract was observed during the latter incubation stage. The reason was a relatively high level of phenolic compounds in this fraction. UV spectra confirmed that the phenolic compounds from the acetone extract were different compared to methanolic and ethanolic extracts.
Highlights
Plant phenolics encompass a wide variety of compounds characterized by the presence of an aromatic ring with one or more hydroxyl groups and a variety of substituents
The content of total phenolic compounds in lentil seed extracts depended upon the solvent employed (Fig. 1)
Fractions I of the methanol and ethanol extracts eluted from the Toyo Pearl HW-40 column contained small amounts of phenolics whereas Fraction I of the acetone extract contained substantially more phenolics (i.e. 6.06 g/100 g of fraction I)
Summary
Plant phenolics encompass a wide variety of compounds characterized by the presence of an aromatic ring with one or more hydroxyl groups and a variety of substituents. Tsuda et al (1993) reported antioxidant activity of phenolic compounds in a bean (Phaseolus vulgaris) extract. The navy bean (Phaseolus vulgaris) hull extract was found to possess better antioxidant efficacy than a mixture of BHA-BHT when used at the same concentration (Onyeneho and Hettiarachchy, 1991). Antioxidant properties were reported for the phenolic fractions separated using Sephadex LH-20 column chromatography from the extracts of everlasting pea (Lathyrus latifolius), faba bean (Vicia faba minor) and broad bean (Vicia faba maior) (Amarowicz et al, 1996c). Antioxidative activities of quercetin and kaempferol as well as their glucuronides and rutinosides, characterized as the main flavonoids of yellow and green beans (Phaseolus vulgaris), were evaluated by an enhanced chemiluminescence (ECL) technique (Raab et al, 1996; Hempel and Bohm, 1996). Hydrophilic oxygen radical scavengers in leguminous seeds were investigated by an EPR spin traping method (Yoshiki et al, 1996)
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