الفهرس 
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Abstract
In the search for new and safe plant products for agricultural and medical purposes. A screening study was performed on leaves of 124 local plant species for their molluscicidal, antioxidant and antimicrobial potential. Of the plants screened then in vitro evaluated, Yucca desmettiana and Pittosporum tobira var.variegata exhibited the highest molluscicidal activity and they met most of the criteria proposed by WHO for viable plant molluscicides. Two new pure steroidal saponins were isolated and identified from 80% methanol extract of Yucca desmettiana leaves. The isolated two compounds Y1 and Y2 exhibited molluscicidal activity against Biomphalaria alexandrina snails with LC100 values of 8 and 11 mg.l-1 within 24h respectively.
Among the chloroform and methanolic leaf extracts of the 124 plants screened, methanolic extract of Punica granatum was the most efficient antioxidant (antiradical activity) extract with the lowest IC50 value of 18.68 μg.ml-1. Its contents of total phenolics and flavonoids were 242.26±18.65 mg tannic acid equivalent (TAE)/g extract and 54.36±5.07 mg rutin equivalent (RE)/g extract respectively.
Of the plants screened and in vitro evaluated, only methanolic extract of Lagerstroemia indica leaves proved to be active against all the tested four food-borne bacteria as well as the pathogenic fungus Candida albicans with diameter of inhibition zone between 20-30 mm and MLC values between 60-120μg.ml-1. One pure flavone glycoside was isolated from its methanolic extract and was identified by chemical and spectroscopic analyses. The isolated compound exerted potent antimicrobial activity against all tested microbial strains with MLC values of 32 µg.ml-1 for C. albicans and 16 µg.ml-1 for the four tested food-borne bacteria.
The above four most active extracts were found to be safe using experimental albino rats, suggesting that they may be utilized as a potential source of some beneficial bioactive compounds.
Key words: Molluscicidal activity- Antioxidant activity- Antimicrobial activity- Steroidal saponins- Phenolic compounds- Flavone glycosides- Yucca desmettiana- Pittosporum tobira var. variegata- Punica granatum- Lagerstroemia indica- Rats.