F. R. Van Heerden

Phenolic variation in wild populations of Aspalathus linearis (rooibos tea)

Abstract Rooibos tea, a herbal tea derived from Aspalathus linearis (Fabaceae—tribe Crotalarieae) has become increasingly popular as a health drink. The beneficial properties are partly ascribed to the phenolic constituents in the plant, which are enzymatically modified during processing. Within the species, distinct geographical forms can be recognised, differing in habit, fire-survival strategy, vegetative and reproductive morphology, enzyme patterns and flavonoids. Several phenolic compounds are known to occur in A. linearis . The main constituent of the commercial tea type (also known as the Rocklands type or the red tea type) is the dihydrochalcone aspalathin, but the presence of other flavonoids such as nothofagin, orientin, isoorientin, vitexin, rutin and isoquercetrin has been reported. These compounds are found in the processed product, as well as the dried leaves. The relative quantities of phenolic compounds show large qualitative and quantitative differences between populations and provenances of the wild tea types. Within populations, however, the patterns are remarkably uniform. Aspalathin was found to be the main compound in processed (“fermented”) tea and also in dried leaves of several tea types. The compound is absent in some wild tea populations, where other flavonoids occur as the main phenolics, notably orientin, isoorientin and rutin. Rutin is invariably the main compound in Aspalathus pendula , a close relative of A. linearis that is rarely used to make tea. An overview of natural variation in phenolic compounds of the main wild tea types is presented.

Distribution and chemotaxonomic significance of flavonoids inAloe (Asphodelaceae)

A chemotaxonomic study of practically all the species of the genusAloe showed that flavonoids occur as major compounds in 31 out of a total of 380 species investigated. Flavanones and dihydroflavonols are present in the exudate of species inAloe ser.Rhodacanthae andSuperpositae and also in a number of the endemic species from Madagascar. Flavones occur as the only major compound in the leaf extracts of the sects.Leptoaloe andGraminialoe. In ser.Macrifoliae and inLomatophyllum, the sister genus ofAloe, isovitexin co-occurred with theC-glucosylanthrone aloin. The chemotaxonomic implication of these results are discussed together with the significance of the taxonomic and chemogeographical distribution of flavonoids inAloe. With a few rare exceptions, the leaf compounds from two different biogenetic pathways (polyketide pathway and flavonoid pathway) are mutually exclusive. Since flavonoids are restricted to the basal groups inAloe, we conclude that flavonoids are plesiomorphic characters inAloe reflecting ancient phylogenetic and biogeographic links.

Scaphopetalone and scaphopetalumate, a lignan and a triterpene ester from Scaphopetalum thonneri.

From the methanol extract of the stem bark of Scaphopetalum thonneri, two new compounds, including one lignan, named scaphopetalone, one new ester of ferulic acid, named scaphopetalumate were isolated together with three known compounds including: two coumarins (scopoletin and scopolin), and one pentacyclic triterpene (oleanolic acid). The structure of the new compounds were elucidated by means of spectroscopic analyses.

A phytochemical investigation of Craterocapsa tarsodes, a plant used for the treatment of epilepsy by the Northern Sotho people of South Africa

Craterocapsa tarsodes (Campanulaceae) is one of the plants used by the Northern Sotho people in an herbal remedy to treat epilepsy. A phytochemical investigation of this plant resulted in the isolation of three major secondary metabolites. By using NMR spectroscopy and MS spectrometry these three compounds were identified as the known acteoside (verbascoside), pinocembrin 7-β-neohesperidoside and shanzhiside methyl ester. A literature search revealed that neurosedative properties are associated with acteoside and that flavonoids related to pinocembrin interact with benzodiazepine receptors. Therefore, the presence of acteoside and pinocembrin neohesperidoside in C. tarsodes may account for the use of this plant against epilepsy.

Asebotin, a dihydrochalcone glucoside from Guibourtia tessmannii

Asebotin (1), a dihydrochalcone glucoside, was isolated from the stem bark of Guibourtia tessmanni and characterised by means of spectroscopic analysis including 1H-, 13C, MS and 1D Noe difference experiment.

A Facile Route to Steroidal 6-Deoxy-α-L-allopyranosides

Abstract The synthesis of a steroidal 6-deoxy-α-L-allopyranoside from cholestanol and rhamnose is described. The crucial steps in the reaction sequence comprised the transformation of a pseudoglycal into the more steric hindered 2,3-cis-diol via an intermediate bromohydrin.