Fate of leucine in the biosynthesis of bakuchiol, a meroterpene from Psoralea corylifolia

Significant incorporations of labelled leucine, valine and isovaleric acid into the meroterpene, bakuchiol (1) isolated from the medicinal plant, Psoralea corylifolia have been observed. Degradation experiments show that labels from these substrates find their way into both phenylpropane derived as well as terpenic part of 1 thereby indicating that none of the known pathways is operative in the case of 1. It is suggested that these substrates are metabolised to CO2 which is then incorporated into 1.     

Observations on natural breeding and larval development of the common mud-eel Amphipnous cuchia (Ham.)

Amphipnous cuchia is a rare fish in India with a spawning period confined down to peak summer. The fish lays its eggs in especially prepared nest-holes and keeps a guard on the developing young ones. The yolk reserve persists till about 22 to 24 days of development. Larvae respond to direct feeding even before yolk-absorption. The young ones feed actively on chironomus larvae. Surface breaking habit for aerial respiration apparently commences around 15th–16th day of larval life. Adult characters are almost attained in about a month's time.     

An immunologically active arabinogalactan from Tinospora cordifolia

An arabinogalactan of mean M(r) 2.2 x 10(6) has been isolated from the dried stems of Tinospora cordifolia and examined by methylation analysis, partial hydrolysis and carboxyl reduction. Purified polysaccharide showed polyclonal mitogenic activity against B-cells, their proliferation did not require macrophages.     

Post-eocene biofacies,palaeoenvironments and palaeogeography of the Bengal Basin,India

The Bengal Basin is known for the extensive development of a thick Cretaceous— Tertiary sedimentary sequence in the eastern part of India. The basin has undergone several phases of transgressions, regressions, periodic uplifts and localised negative movements throughout the period of its evolution. The sedimentation up to the end of the Eocene was largely under the influence of a major transgressive phase which was later replaced by a regressive phase on account of the uplift and resulting marine retreat. in this paper, an analysis of the microfaunal distribution, biofacies and sedimentary and tectonic history is made for reconstruction of the palaeoenvironmental conditions and palaeogeography of the Bengal Basin relating to the post-Eocene regressive phase of evolution.During the Oligocene—Early Miocene, the open marine conditions existing since the Eocene were progressively modified on account of the regression into more brackish, lagoonal and estuarine types. A typical prograding delta started to spread over a large part of the marginal area of the basin. The rocks of the Barail Group, formed under the transitional environments of the delta, are found to occur in almost all the major geo-provinces of the basin. The sedimentary environments and characteristics of the rocks were ultimately controlled by the configurations of the respective geo-provinces. The negative movements in the Miocene along certain marginal areas were associated with the marine transgressive phase giving rise to the Surma Group. This transgressive phase was, however, short lived and its impact was not equally felt in all areas. The northeastern region was still uplifted which favoured an almost continuous existence of the deltaic phase.By the end of Miocene a greater part of the basin underwent a strong tectonic upheaval which was possibly the precursor of the main Himalayan orogeny. The intermontane depressions formed in the uplifted areas were the depositional sites for the Tipam Group and younger beds in Plio-Pleistocene times. The rapidly eroded debris from the highlands spread over a wide area towards the south under the influence of the river system of the Ganga and Brahmaputra which has transformed the original basinal areas into a large modern delta complex.     

Structural and synthetic studies on the retrofractamides—amide constituents of Piper retrofractum

Two new unsaturated amides, retrofractamides A and C, were isolated from the total above-ground parts of Piper retrofractum. Retrofractamide A was shown to be N-isobutyl-9(3′,4′-methylenedioxyphenyl)2E,4E,8E-nonatrienamide from spectroscopic and chemical investigations. The structure 6 for retrofractamide C was suggested from spectroscopic and chemical studies and was confirmed by a total stereoselective synthesis. The presence of sesamin and 3,4,5-trimethoxydihydrocinnamic acid as well as two higher homologues of retrofractamide A, viz. pipericide (retrofractamide B) and retrofractamide D was demonstrated. The synthesis of pipericide was also achieved.     

Aurantiamides: A new class of modified dipeptides from Piper aurantiacum

Two new amides, aurantiamide and aurantiamide acetate, were isolated from Piper aurantiacum. Their structures were determined as N-(N′-benzoyl-S-phenylalaninyl)-S-phenylalaninol and its acetate, respectively, from chemical and spectroscopic studies. The structures and stereochemistry were confirmed by synthesis. The corresponding diastereoisomers were also synthesized and their spectroscopic properties compared with those of the natural compounds.