S. Rosendal Jensen

Isolation of an Angiotensin Converting Enzyme (ACE) inhibitor from Olea europaea and Olea lancea

The aqueous extract of the leaves of Olea europaea and Olea lancea both inhibited Angiotensin Converting Enzyme (ACE) in vitro. A bioassay-directed fractionation resulted in the isolation of a strong ACE-inhibitor namely the secoiridoid 2-(3,4-dihydroxyphenyl)ethyl 4-formyl-3-(2-oxoethyl)-4 E-hexenoate (oleacein) (IC(50) = 26 μM). Five secoiridoid glycosides (oleuropein, ligstroside, excelcioside, oleoside 11-methyl ester, oleoside) isolated from Oleaceous plants showed no significant ACE-inhibition whereas, after enzymatic hydrolysis, the ACE-inhibition at 0.33 mg/ml was between 64% to 95%. Secoiridoids have not been described previously in the literature as inhibitors of ACE. Oleacein showed a low toxicity in the brine shrimp (Artemia satina) lethality test (LC(50) (24 h) = 969 ppm).

Phytochemical interrelationships in the Cornaceae

Abstract The distribution of iridoids, ellagitannins, proanthocyanidins and other compounds in the Cornaceae and related families is discussed in relation to the various taxonomic treatments. Analysis of the chemical data indicates that: (a) Benthamia and Cynoxylon are the most primitive sub-genera in Cornus, (b) Corokia possesses a chemical pattern consistent with that of the Cornaceae, but Helwingia might better be elevated to family rank, (c) Alangiaceae, Davidiaceae, Garryaceae and Nyssaceae broadly fall into the same pattern as the Cornaceaa and can be placed in a restricted order, Cornales, which excludes Araliaceae, Umbelliferae and Rhizophoraceae, and (d) the Cornales shows affinities to the Saxifragales and the Dipsacales.

The genus Comus: Non-flavonoid glucosides as taxonomic markers

Previous proposals for subdivision of the genus Cornus are reviewed. Twenty-seven authenticated Cornus species have been studied for their content of non-flavonoid glucosides. Two distinct groups of taxa can be distinguished on this basis: one, containing a hydroxycyclohexadienone glucoside, along with salidroside, its reduced counterpart, and the second, characterized by containing various iridoid glucosides. The two types of glucosides are apparently mutually exclusive.

Application of 2H n.m.r. spectroscopy to a study of the biosynthesis of the iridoid glucoside cornin in Verbena officinalis

2 H N.m.r. spectroscopy has been used to demonstrate that in specifically labelled deoxyloganin, the label at C-8 is retained during its conversion into cornin in Verbena officinalis, suggesting that the 6-oxo group is produced by oxidation in an unactivated position.