BackgroundRecent years have witnessed that there is a revival of interest in drug discovery from medicinal plants for the maintenance of health in all parts of the world. The aim of this work was to investigate 26 plants belonging to 17 families collected from a unique place in Yemen (Soqotra Island) for their in vitro anticancer, antimicrobial and antioxidant activities.MethodsThe 26 plants were extracted with methanol and hot water to yield 52 extracts. Evaluation for in vitro anticancer activity was done against three human cancer cell lines (A-427, 5637 and MCF-7) by using an established microtiter plate assay based on cellular staining with crystal violet. Antimicrobial activity was tested against three Gram-positive bacteria, two Gram-negative bacteria, one yeast species and three multiresistant Staphylococcus strains by using an agar diffusion method and the determination of MIC against three Gram-positive bacteria with the broth micro-dilution assay. Antioxidant activity was investigated by measuring the scavenging activity of the DPPH radical. Moreover, a phytochemical screening of the methanolic extracts was done.ResultsNotable cancer cell growth inhibition was observed for extracts from Ballochia atro-virgata, Eureiandra balfourii and Hypoestes pubescens, with IC50 values ranging between 0.8 and 8.2 μg/ml. The methanol extracts of Acanthospermum hispidum, Boswellia dioscorides, Boswellia socotrana, Commiphora ornifolia and Euphorbia socotrana also showed noticeable antiproliferative potency with IC50 values < 50 μg/ml. The greatest antimicrobial activity was exhibited by extracts from Acacia pennivenia, Boswellia dioscorides, Boswellia socotrana, Commiphora ornifolia, Euclea divinorum, Euphorbia socotrana, Leucas samhaensis, Leucas virgata, Rhus thyrsiflora, and Teucrium sokotranum with inhibition zones > 15 mm and MIC values ≤ 250 μg/ml. In addition, the methanolic extracts of Acacia pennivenia, Boswellia dioscorides, Boswellia socotrana and Commiphora ornifolia showed good antioxidant potential at low concentrations (more than 80% at 50 μg/ml).ConclusionOur results show once again that medicinal plants can be promising sources of natural products with potential anticancer, antimicrobial and antioxidative activity. The results will guide the selection of some plant species for further pharmacological and phytochemical investigations.

Activity. -A variety of novel title guanidine derivatives such as (III), (V) and (VII) are synthesized via reaction of cyanamide potassium salts (I) with hydrazine derivatives and evaluated for their cytotoxic activity. The highest in vitro cytotoxic activities are found for compounds (Vb) and (Vc). The molecular orbital calculation of the possible tautomeric forms of the benzenesulfonylguanidine derivatives are also presented. -(SLAWINSKI*, J.; BEDNARSKI, P.; GRUENERT, R.; RESZKA, P.; Pol. J. Chem. 77 (2003) 1, 53-64; Dep. Chem. Technol. Drugs, Med. Univ. Gdansk, PL-80-416 Gdansk, Pol.; Eng.) -M. Kowall 25-114

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Fused pyridine derivatives R 0450 Unexpected Formation of Pyridodiindole Derivatives with Cytotoxic Activity via Double Nenitzescu Reaction. -The reaction of triamine (II) with 2 equivalents of 1,4-benzoquinone (III) leads unexpectedly to a mixture of 1:1-adduct (IV) and 1:2-adducts (V)/(VI) [some yields not given]. Derivatives (V) and (VI) demonstrate cytotoxic activity against several human cancer cell lines. -(WILLEMANN, C.; WAIBEL, R.; GRUENERT, R.; BEDNARSKI, P.; TROSCHUETZ*, R.; J. Heterocycl. Chem. 45