N. Raman

Synthesis, antimicrobial and antifungal activity of a new class of spiro pyrrolidines.

A new class of spiro pyrrolidines, dispiro[oxindole-cyclohexanone]pyrrolidines, dispiro[oxindole-tetrahydronaphthalen-1-one]pyrrolidines, dispiro[oxindole-arylidene-cyclohexanone]pyrrolidines, dispiro[oxindole-hexahydro-indazole]pyrrolidines, and spiro[butenolide]pyrrolidines, have been screened for their antibacterial and antifungal activity against ten human pathogenic bacteria and four dermatophytic fungi. They were found to have antimicrobial and antifungal activity compounds against various pathogens except Bacillus subtilis. The spiro pyrrolidinines were synthesized by the regioselective 1,3-dipolar cycloaddition reaction of azomethine ylides generated either from isatin and sarcosine or from aziridine. The azomethine ylide so generated reacted with various dipolarophiles such as 2-arylidene-cyclohexanones, 2-arylidene-tetrahydronapthalen-1-ones, 2,6-bis(arylmethylidene)cyclohexanones and 3-arylidene-5-phenyl- butenolides.

Mycorrhizal status of plant species colonizing a magnesite mine spoil in India

SummaryThe present study reports the vesicular arbuscular mycorrhizal fungal association with 14 plant species colonizing a magnesite mine spoil in Salem, Tamil Nadu state, India. The soil was poor in Olsen-available P (5–45 kg/ha-1). Hyphal, arbuscular and vesicular infection was noticed. Infection ranged from 32 to 82%. Thirteen VAM fungal species were identified. Spores of Glomus fasciculatum and Gigaspora gigantea were commonly found in the magnesite mine spoil.

Mycorrhizal research — a priority in agriculture

The vesicular arbuscular mycorrhizae (VAM) help in conversion of arid soil to fertile and productive soil. VAM fungi increase plant growth through enhanced nutrient uptake and cycling of phosphorus, nitrogen, carbon, zinc, copper and other minerals. The bacteria associated with mycorrhizal fungi solubilize P which is transported through the mycorrhizal fungi to plant. Mycorrhizal fungal hyphae produce phosphatases and organic acids that enhance the availability of soil P by weathering P from the clay matrix and maintaining the solution P by binding Ca with the secreted oxalates. There are reports that N fixed by one plant has been transported to an adjacent, non-fixing plant through mycorrhizal fungal hyphae. Mycorrhizal hyphae form aggregates by directly binding soil particles possibly by producing polysaccharides. These aggregates are a major input into systems with low organic matter. Apart from nutrient uptake, mycorrhizae also enhance the transport of water from soil to plant. VAM fungal inoculated plants exhibit increased drought resistance and resistance to fungal root diseases and nematode diseases. VAM fungi initiate host defence response in roots by increasing phenols, peroxidases, phytoalexins etc. VAM fungi by synergistic action with nitrogen fixing nodulating organisms enhance mineral nutrition and growth of crop plants. Agricultural practices such as fallowing, tillage, top soil removal, fires, water logging and the use of chemicals like pesticides and fertilizers can influence VAM inoculum potential. Large differences exist between plant species in their dependence of VAM fungi for uptake and growth. The selection of VAM fungi, inoculum production and inoculation techniques are important factors which play a major role in favouring good results of VAM fungi for agricultural systems. The benefits of VAM fungi for sustainable agriculture are immense.

Bioactive Molecules fromCynodon dactylon of Indian Biodiversity

Cynodon dactylon(L.) Pers. (Gramineae), called Bermuda grass (English) is widely distributed in the tropics and the wanner areas of the temperate regions and used in traditional medicine for diarrhoea, leprosy, scabies, haemoptysis, haematuria, cephalalgia, catarrhal opthalmia, epileptic seizures, skin diseases, erysipelas, dropsy and anasarca and as a diuretic1. Eventhough the plant has been phytochemically investigated for the presence of flavonoids2triterpenoids3and streoids there are no reports on the presence of alkaloids (NAPRALERT). This is the first report on the isolation and structural elucidation of alkaloids (tryptamine, tyramine and gramme) from the aerial parts of C. dactylonof Gramineae from a 1996 collection. The structure of the alkaloids was proposed on the basis of UV, MS, IR and NMR (1H and13C) spectral data. The antimicrobial activity of the crude extract and the alkaloids against human pathogenic bacteria and dermatophytes was reported for the first time.