Five decades in the study of natural products

This paper describes the five-decade long fascinating journey taken by Prof. T R Govindachari towards the study of the natural products of India. A variety of Indian plants were investigated by him for the study of their constituent alkaloids and terpenoids. The concluding part of the paper summarizes the isolation and identification of the constituents of the neem kernel, which eventually led to the first X-ray structure determination of azadirachtin A

Chemical examination of Cardanthera uliginosa

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Insect antifeedant and growth regulating activities of neem seed oil- the role of major tetranortriterpenoids

An attempt was made to correlate insect antifeedant and growth regulatory activities of neem (Azadirachta indica) seed oil with the major tetranortriterpenoids. Selective elimination of triterpenoids by preparative high-performance liquid chromatography, incorporation of the eliminated compounds in defined concentrations and bioassaying the resultant fractions against Spodoptera litura indicated the necessity to quantify major triterpenoids for correlation of bioactivity of neem oil

Studies in the isoquinoline series Part III. synthesis of some 5:6- and 5: 8-dimethoxyisoquinolines

A series of 3:4-dihydro-5:6-dimethoxy and 3:4-dihydro-5:8-di-methoxyisoquinolines are repoited. These have been dehydro genated to the corresponding isoquinoline derivatives

Insect antifeedant and growth-regulating activities of salannin and other c-seco limonoids from neem oil in relation to azadirachtin

The antifeedant and insect growth-regulating activities of salannin, nimbin, and 6-deacetylnimbin, in comparison with azadirachtin-A, have been studied against Spodoptera litura, Pericallia ricini, and Oxya fuscovittata. Salannin deterred feeding, delayed molt by increasing larval duration, caused larval and pupal mortalities, and decreased pupal weights in the two lepidopterans. Salannin also caused molt delays and nymphal mortalities in Oxya fuscovittata. The role of salannin and other compounds in conferring bioactivity, along with azadirachtin-A, to neem oil/neem seed extracts is emphasized

Addition of dinitrogentrioxide to Δ<SUP>1</SUP>-arylcyclohexenes

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Structure of tylophorine

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Studies in protoberberine alkaloids: Part III. Stereochemistry of 13-Methylprotoberberines

NMR spectral analysis has been used to deduce conformational structure la for thalic-tricavine and Vic for meso-thalictricavine

Chemical investigation of some Indian plants. Part VI

Several known compounds belonging to the class of acids, alcohols, alkaloids, anthraquinones, carbohydrates, coumarins, isocoumarins, steroids, triterpenoids and xanthones have been isolated from a number of Indian plants