Dominic A. Okorie

The limonoid chemistry of the genus Khaya (meliaceae)

The six species of the genus Khaya have been examined, and tables are given showing the limonoids isolated. The results are discussed in relation to the taxonomy of the genus.

Chromones and limonoids from Harrisonia abyssinica

Abstract Examination of the roots of Harrisonia abyssinica yielded three known chromones, alloptaeroxylin, peucenin, O -methylalloptaeroxylin and two kno

New benzyldihydrochalcones from Uvaria chamae

Abstract Two new benzyldihydrochalcones have been identified in the roots of Uvaria chamae . They are accompanied by the known benzyl benzoate.

Limonoids from Swietenia humilis

Abstract Two new limonoids have been isolated from the seed of Swietenia humilis . They have been identified as methyl 2-hydroxy-3-isobutyryloxymeliac-8(30)-enate (present as a mixture with the 3-tiglate) and its 8(30) oxide.

Myrianthic acid: a triterpene acid from the rootwood of Myrianthus arboreus

Abstract Arjunolic acid and a new triterpene acid, myrianthic acid, were isolated from the rootwood of Myrianthus arboreus . The structures of the two compounds were elucidated by IR, 1 H NMR and mass spectroscopy.

A new class of indolosesquiterpene alkaloids from polyathia suaveolens

Abstract Three new alkaloids, polyavolensin, polyavolensinol and polyavolensinone, isolated from the stem of Polyathia suaveolens are shown to belong to a new class of indolosesquiterpenes with structures 4, 5, 6 respectively by PMR, CMR and mass spectrometry. They have also been interrelated by chemical reactions.

Structure-activity relationship in the toxicity of some naturally occuring coumarins-chalepin, imperatorin and oxypeucedanine

Imperatorin, oxypeucedanine and chalepin are furanocoumarins isolated from Clausena anisata a medicinal plant common in West Africa. Only chalepin is found to have anticoagulant activity when administered to rats at a single dose. Aniline hydroxylase activity was appreciably depressed by each of the substances. Ethylmorphine demethylase, hepatic DNA, reduced glutathione and glucose-6-phosphatase were unaffected by these compounds when administered at a dose of 50 mg/kg for 3 days prior to sacrifice. Under similar conditions only chalepin treatment resulted in alpha-1-globulin increase and a decrease in beta-globulin content of the serum. Intraperitoneal treatment with chalepin (100 mg/kg) for 2 days resulted in the death of 4 rats out of 10 within a 48 h of treatment. Livers of dead rats showed generalized necrosis of hepatocytes. No deaths were recorded for imperatorin and oxypeucedanine. Rats surviving after 8 weeks showed no changes in hepatic enzyme activity, reduced glutathione and DNA concentrations. However, chalepin and imperatorin induced alterations in the serum protein pattern within this period. Liver lesions were observed in chalepin treated animals and were characterized by very mild necrosis of hepatocytes. No lesions were observed in the livers of rats treated with imperatorin and oxypeucedanine.

Polyavolinamide, an indolosesquiterpene alkaloid from Polyathia suaveolens

Abstract A new indolosesquiterpene alkaloid, polyavolinamide, has been identified in the stem of Polyathia suaveolens accompanied by the three previously isolated indolosesquiterpene alkaloids, polyavolensin, polyavolensinol, polyavolensinone, as well as an unidentified triterpene and an aporhine alkaloids. Polyavolinamide was also the major component of the root bark. Its structure was assigned on the basis of 11 H and 13 C NMR, and mass spectrometry.

Revised structure and synthesis of piperolein acids, guineensine and wisanine from Piper guineense

Abstract The structures of piperolein acids guineensine and wisanine have been confirmed by synthesis, UV irradiation of trans piperolein B acid ester gave the cis-isomer reported in the literature as the trans-isomer. The trans-2, trans-4 ethylenic bonds in guineensine and wisanine were introduced by reacting piperolein B aldehyde and 2-methoxy piperonal with the appropriate Wittig or Reformatsky reagent.

Revised structure of polyavolensin and its analogues

Abstract The structure of polyavolensin (4) has been determined by X-ray crystallography and the recently published structure needs revision.