Extractives from the ptaeroxylaceae and the mesembryanthemaceae.

Abstract

This work is an account of the investigations into the chemistry of two Cedrelopsis species from the Ptaeroxylaceae, Cedrelopsis grevei and Cedrelopsis microfoliata and a species from the Mesembryanthemaceae, Khadia alticola, as well as investigations into the synthesis of hydroxylated and prenylated chalcones. Cedrelopsis grevei, commonly called Katrafay, is amongst the many medicinal plants of Madagascar, being used to relieve muscle fatigue when the bark is soaked in hot water. Previous investigations of the wood and stem bark of this plant, have yielded chromones and coumarins and a recent investigation of the stem bark of a specimen collected in the north of Madagascar has yielded two novel limonoids of unusual structure, cedmilinol and cedmiline. The fruit and seed of Cedrelopsis grevei have not been studied previously and a phytochemical investigation of these plant parts was undertaken in this work. The dichloromethane extract of the fruit and seeds yielded, after column chromatography, a dihydrochalcone, uvangoletin, a flavanone, 5,7dimethoxypinocembrin, two simple chalcones, cardamonin and flavokawin Band three prenylated chalcones, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone. Three of these compounds, 2’-methoxyhelikrausichalcone, cedreprenone and cedrediprenone have not been isolated previously. Cedrelopsis microfoliata is another medicinal plant used in Madagascar. The leaves of this plant are used to prepare a decoction for woman to drink after childbirth. This is the first phytochemical investigation of Cedrelopsis microfoliata. The hexane extract of the dried stem bark yielded three compounds after column chromatography, a chalcone, microfolian and two flavanones, microfolione and (+)-agrandol. The dicholoromethane extract of this compound yielded four compounds after column chromatography, three coumarins, cedrecoumarin A, obliquin and microfolicoumarin and a sesquiterpenoid, sesquichamaenol. Four of the compounds isolated from Cedrelopsis microfoliata, microfolidione, microfolione, (+)-agrandol and microfolicoumarin have not been isolated previously. Khadia alticola is one of the species added to "Khadi", a Tswana/South Sotho name for beer brewed traditionally using the fleshy roots of a variety of taxa. Khadia is also reported to be used medicinally by the Manyika people of the Umtali district of Zimbabwe. The phytochemical investigation of the roots of Khadia alticola, which have not been studied previously, was undertaken to determine whether mesembrine type alkaloids were present in this species and thus contributing to the "potency" of the beer brewed traditionally. No mesembrine alkaloids were isolated in this work, however, a common sterol, sitosterol was isolated from the acidic chloroform fraction of the roots of this species and a flavonoid, 3,4',5,7-tetrahydroxyflavan was isolated from the basic chloroform fraction. Two chalcones, 3’,5’-dihydroxychalcone and 2’-hydroxychalcone were synthesised using the Claisen condensation. An isoprenylated acetophenone intermediate and an isoprenylated chalcone were also synthesised.