Biomedical subjects
Publications and source records attributed to B A Nagasampagi.
A new germacranolide has been isolated from the aerial parts of Artemisia pallens and the structure was established as 4,5 beta-epoxy-10 beta-hydroxy-1-en-3-one-trans-germacran-6 alpha,12-olide (1) by comparison with its 10 alpha-epimer isolated from the same plant.
Three new eudesmanoids have been isolated from Sphaeranthus indicus and their structures were established as 11alpha,13-dihydro-3alpha,7alpha-dihydroxy-4,5-epoxy-6beta,7-eudesmanolide, 11alpha,13-dihydro-7alpha-acetoxy-3beta-hydroxy-6beta,7-eudesm-4-enolide and 3-keto-beta-eudesmol by comparison of spectral data with those of other 7alpha-hydroxyeudesmanolides.
Crude neem products have earlier shown considerable promise for control of culicine mosquito vectors in rice fields as a by-product of their agricultural use as fertilizers, but suffer from disadvantages of bulkiness and lack of stability in storage. Relatively stable lipid-rich fractions of neem were shown to be as effective as good-quality crude neem products in control of breeding of culicine vectors of Japanese encephalitis, and also produced a slight but significant reduction in populations of anopheline pupae. Neem-based formulations coated over urea significantly increased grain yield, but used alone did not, whereas combining the use of neem-coated urea and water management by intermittent irrigation had a greater effect on grain yield than that of water management alone. The neem fractions were relatively cost-effective, and the combined water management and neem-coated urea strategy is acceptable to farmers, who are already aware of the benefits of the use of neem-coated urea, and of water management. This technology therefore has considerable promise as an environmentally benign method of rice-field mosquito control that could be sustainably implemented by farmers.
Applications of neem, Azadirachta indica (Meliaceae), to rice-fields were evaluated with the dual objective of controlling the culicine mosquito vectors of Japanese encephalitis virus (JEV) and enhancing the grain yield. Since crude neem products deteriorate under improper storage conditions, a laboratory bioassay was developed to screen neem cake powder against mosquito larvae, Culex quinquefasciatus. Only samples of neem giving over 90% bioassay mortality were used in field trials. When good quality neem cake powder was applied at the dose of 500 kg/ha, either alone or coated over urea, there was a striking reduction in the abundance of late instar culicine larvae and pupae. Only fourteen pupae were obtained over a period of 13 weeks in neem cake powder treated plots, and four in those treated with neem coated urea, compared with 101 in control plots. Both treatments were significantly less than the control, but on par with one another. In another field trial, neem cake coated urea was tested at 500 and 250 kg neem/ha in combination with water management practices. No reduction in efficacy was noted at the lower dose. Larval abundance in plots under water management alone did not differ significantly from the controls, but was significantly reduced when water management was combined with neem products. Two stable formulations, 'Neemrich-I' (lipid rich) and 'Neemrich-II' (azadirachtin rich), also gave good suppression of immature culicines. All the treatments with neem also gave higher grain yield than the control.(ABSTRACT TRUNCATED AT 250 WORDS)
Parthenin has been reported as the active allergen in Parthenium hysterophorus contact sensitivity. A study was carried out to test various chemical fractions of the plant for isolating and identifying the exact allergens. Two additional sesquiterpene lactones apart from parthenin have been shown to be allergenically active. Structures of these sesquiterpenoids are presented. Photopatch tests do not indicate a photosensitizing capacity for these compounds.
The increasing incidence of contact dermatitis due to the wild growth of the weed Partheium hysterophorus Linn. in many parts of India has prompted chemical analysis coupled with clinical testing to isolate the offending agent. Results are present to show that parthenin, a sesquiterpene lactone, is the major antigen which produces contact dermatitis in sensitive human beings.