In vitro 5-Lipoxygenase inhibition of polyphenolic antioxidants from undomesticated plants of South Africa

Abstract

Aqueous and methanolic extracts of 18 leafy vegetables from South Africa were investigated for their free radical scavenging activity, total phenolic content and anti-inflammatory properties. Amaranthus dubius, Amaranthus hybridus, Amaranthus spinosus, Asystasia gangetica, Bidens pilosa, Centella asiatica, Ceratotheca triloba, Chenopodium album, Cleome monophylla, Emex australis, Galinsoga parviflora, Justicia flava, Momordica balsamina, Oxygonum sinuatum, Physalis viscosa, Portulaca oleracea, Senna occidentalis and Solanum nigrum were used in this study.In the radical scavenging studies using 2,2-diphenyl-2-picrylhydrazyl hydrate(DPPH), methanolic extracts from six plants almost completely inhibited DPPH absorption (J. flava-96.6%, P. oleracea-96.5%, M. balsamina-94.7%, O. sinuatum-92.1%, S. nigrum-92.0% and A. hybridus-90.5%), whereas methanolic extracts from E. australis-78.6% and G. parviflora-76.5% showed lowest activities among the plants studied. Aqueous extracts were considerably less effective radical scavengers compared to methanolic extracts showing highest activity with J. flava-48.0% and lowest with A. gangetica-36.2%. A correlation between radical scavenging activity of extracts with total phenolic content was observed. Out of 18 plants studied for anti-inflammatory activity, methanolic extracts from eight plants showed significant inhibition of 5-lipoxygenase (5-Lox) activity. Among the plants studied Bidens pilosa (IC50 21.8 µg/ml) showed maximum anti-inflammatory activity while Emex australis (IC50 81.4 µg/ml) showed minimum inhibition of 5-Lox activity. Large amounts of phenolic compounds may contribute towards the antioxidant and anti-inflammatory properties among the plants studied. Key words: Leafy vegetables, radical scavenging, DPPH, total phenolics, 5-lipoxygenase, anti-inflammatory.