Browsing by Author "Sankara G. Unnikrishnan"

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Effects of stress on alkaloid metabolism in Crinum asiaticum
(1990) Shibnath Ghosal; Sushil K. Singh; Sankara G. Unnikrishnan
The biochemical role of free and conjugated alkaloids in the fruits of Crinum asiaticum during strees (incisional injury and attack by an insect) is appraised. Wounding of C. asiaticum fruits caused almost complete hydrolysis of the alkaloidal conjugates and also produced oxidized metabolises of lycorine and its analogues. Prior treatment of fruits with anaesthetic agents, e.g. ether and lidocaine, not only protected the alkaloidal conjugates from hydrolysis but also prevented their oxidation. The qualitative and quantitative changes observed in the alkaloids, in response to the stress, suggest their role in protective and repair mechanisms of the producer plant, notably, augmentation of a 'second messenger', cAMP, in the fruits in response to injury and systemic administration of theophylline was observed. Prior administration of anaesthetic agents (ether or lidocaine), kept the concentration of cAMP significantly low despite inflicting subsequent injury. © 1990.
Phosphatidylpyrrolophenanthridine alkaloids from Zephyranthes flava
(1987) Shibnath Ghosal; Sushil K. Singh; Sankara G. Unnikrishnan
Four new alkaloidal phospholipids, 2-O-glycerophosphoryllycorine, phosphatidyllycorines, phosphatidylpseudolycorines and phosphatidyllycorinium methocation, were isolated from the flowers of Zephyranthes flava. The structures of these compounds were established by comprehensive spectral analyses, chemical transformations and synthesis, where possible. The biological profile of this novel group of alkaloidal conjugates is appraised. © 1987.