الفهرس 
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Abstract
The present study was conducted to provide a detailed description of the biological aspects of Calotropis procera and Cynanchum acutum. Floristic features of vegetation including plant association, life-span, life-form spectra and Chorotypes of the two communities. Soil analysis to determine the soil variables controlling the abundance and distribution of both Calotropis and Cynanchum. Evaluation of the economic potentialities of C. procera and C. acutum growing naturally by investigating some bioactive metabolites (flavonoids, polyphenols and fatty acids) and detecting their antioxidant and antimicrobial activities. The floristic components of C. procera community were 33 plant, distinguished to 8 monocots and 25 dicots, belonging to 14 families. Tamarix nilotica, Alhagi graecorm, Launea murcronata, Trichodesma africanum and Hyoscyamus muticus were the most common associates. Seven life-forms spectra have been recognized, with therophytes and geophytes are the common. The majority of species are Saharo-Sindian, Saharo-Arabian and Sudano-Zambezian. The floristic composition of Cynanchum includes 45 species belonging to 17 families. Poaceae, Asteraceae and Brassicaceae were the main presented families. Five life-forms were recognized. Therophytes represented 76%. The plant assemblage of this community may be grouped into ten chorotypes. Calotropis community is confined to deep fine surface deposits, with predominance of medium sand fraction, low moisture content, nutritionally poor soil with pH slightly alkaline. Cynanchum flourished in sandy-loam texture, wet, non-saline, fertile and slightly-moderate alkaline soil. The flavonoids and polyphenols content of Cynanchum were higher than in Calotropis. Thirteen fatty acids were detected in Calotropis shoot, while only ten fatty acids of lipoidal matter of Cynanchum have been identified. Methanoil extracts of both Calotrpis and Cynanchum showed antioxidant and antimicrobial activities.